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ckpts/universal/global_step120/zero/17.attention.query_key_value.weight/exp_avg.pt

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+version https://git-lfs.github.com/spec/v1
+oid sha256:91cf845b100cc8fd139d8148727274a6239222275c34f11b14b9b2b53b2c3c45
+size 50332828

ckpts/universal/global_step120/zero/17.attention.query_key_value.weight/fp32.pt

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+version https://git-lfs.github.com/spec/v1
+oid sha256:8ae855954f7aff680421fa2f9ce5d93710e462a53c85aa29d7b1df053fa2c766
+size 50332749

venv/lib/python3.10/site-packages/torch/distributed/_shard/__init__.py

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+from .api import (
+    _shard_tensor,
+    load_with_process_group,
+    shard_module,
+    shard_parameter,
+)

venv/lib/python3.10/site-packages/torch/distributed/_shard/_utils.py

@@ -0,0 +1,28 @@
+import torch
+from torch.distributed._shard.metadata import ShardMetadata
+from typing import Sequence
+
+DEPRECATE_MSG = "Please use DTensor instead and we are deprecating ShardedTensor."
+
+def narrow_tensor_by_index(tensor: torch.Tensor, offsets: Sequence[int], sizes: Sequence[int]) -> torch.Tensor:
+    """
+    Narrow the tensor according to ``offsets`` and ``sizes``.
+    """
+    narrowed_tensor = tensor
+    for idx, (offset, size) in enumerate(zip(offsets, sizes)):
+        if size < tensor.size(idx):
+            # Reshape to get shard for this rank and we don't want autograd
+            # recording here for the narrow op and 'local_shard' should be a
+            # leaf variable in the autograd graph.
+            narrowed_tensor = narrowed_tensor.narrow(
+                idx,
+                offset,
+                size
+            )
+    return narrowed_tensor
+
+def narrow_tensor(tensor: torch.Tensor, metadata: ShardMetadata) -> torch.Tensor:
+    """
+    Narrow the tensor according to the metadata
+    """
+    return narrow_tensor_by_index(tensor, metadata.shard_offsets, metadata.shard_sizes)

venv/lib/python3.10/site-packages/torch/distributed/_shard/api.py

@@ -0,0 +1,290 @@
+from contextlib import contextmanager
+from typing import Optional
+import torch
+import torch.distributed as dist
+import torch.nn as nn
+from torch.distributed import distributed_c10d
+from torch.distributed._shard.sharded_tensor import (
+    ShardedTensor,
+)
+from .sharding_spec import (
+    ShardingSpec,
+    ChunkShardingSpec
+)
+from .sharding_plan import (
+    ShardingPlan
+)
+from .sharder import Sharder
+
+def _shard_tensor(
+    tensor: torch.Tensor, sharding_spec: ShardingSpec, src_rank=0, process_group=None
+) -> ShardedTensor:
+    """
+    Given a :class:`torch.Tensor`, it shards that tensor according to the provided
+    ``sharding_spec``. ``src_rank`` denotes the source rank which would be
+    used as the ground truth of the data which would be scattered as shards
+    across the rest of the ranks.
+
+    Args:
+        tensor (:class:`torch.Tensor`): Tensor needs to be sharded.
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+
+    Keyword args:
+        src_rank (int, optional): The source rank which is used as the ground truth of
+            the data for the parameter that would be sharded and scattered
+            across the rest of the ranks.
+            Default: 0.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+
+    Returns:
+        A :class:`ShardedTensor` sharded from the given tensor.
+
+    .. warning::
+        Only :class:`torch.distributed._shard.sharding_spec.ChunkShardingSpec` is
+        currently supported as the ``sharding_spec``.
+    """
+    if not tensor.is_contiguous():
+        raise ValueError('input tensor is not a contiguous Tensor')
+
+    pg = process_group if process_group is not None else distributed_c10d._get_default_group()
+    world_size = dist.get_world_size(pg)
+    current_rank = dist.get_rank(pg)
+
+    # Validate src_rank and sharding_spec are same across all ranks.
+    gathered_list = [None] * world_size
+    dist.all_gather_object(gathered_list, (src_rank, sharding_spec), group=pg)
+
+    for idx, entry in enumerate(gathered_list):
+        if src_rank != entry[0]:  # type: ignore[index]
+            raise ValueError(
+                f'src_rank={src_rank} on rank: {current_rank} does not '  # type: ignore[index]
+                f'match with src_rank={entry[0]} on rank: {idx}')
+        if sharding_spec != entry[1]:  # type: ignore[index]
+            raise ValueError(
+                f'sharding_spec={sharding_spec} on rank: {current_rank} does not '  # type: ignore[index]
+                f'match with sharding_spec={entry[1]} on rank: {idx}')
+
+    st = sharding_spec.shard(tensor, src_rank=src_rank, process_group=process_group)
+
+    return st
+
+def shard_parameter(
+        module: torch.nn.Module,
+        param_name: str,
+        sharding_spec: ShardingSpec,
+        src_rank=0,
+        process_group=None):
+    """
+    Given a :class:`torch.nn.Module`, a ``param_name`` for a parameter in that
+    module, it shards that parameter according to the provided
+    ``sharding_spec``. ``src_rank`` denotes the source rank which would be
+    used as the ground truth of the data which would be scattered as shards
+    across the rest of the ranks.
+
+    This method replaces ``module.param_name`` with a
+    :class:`torch.distributed._sharded_tensor.ShardedTensor`
+
+    Args:
+        module (:class:`torch.nn.Module`): Module whose parameter needs to be sharded.
+        param_name (str): Name of the parameter of ``module`` that needs to be sharded.
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+
+    Keyword args:
+        src_rank (int, optional): The source rank which is used as the ground truth of
+            the data for the parameter that would be sharded and scattered
+            across the rest of the ranks.
+            Default: 0.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+
+    .. warning::
+        Only :class:`torch.distributed._shard.sharding_spec.ChunkShardingSpec` is
+        currently supported as the ``sharding_spec``.
+    """
+    # Perform some validation first.
+    if not hasattr(module, param_name):
+        raise AttributeError(f'{module._get_name()} has no attribute `{param_name}`')
+
+    tensor = getattr(module, param_name)
+    if not isinstance(tensor, torch.Tensor):
+        raise ValueError(f'Expected {type(module).__name__}.{param_name} to be a Tensor, but found {type(tensor).__name__}')
+
+    if not tensor.is_contiguous():
+        raise ValueError(f'param: {param_name} is not a contiguous Tensor')
+
+    st = _shard_tensor(tensor, sharding_spec, src_rank, process_group)
+
+    # Replace param with ShardedTensor.
+    module.register_parameter(param_name, nn.Parameter(st))
+
+# Tracks the current process group in the load context manager.
+_CURRENT_PROCESS_GROUP: Optional[dist.ProcessGroup] = None
+
+@contextmanager
+def load_with_process_group(process_group):
+    """
+    Context manager to set the process group with which to load a ShardedTensor.
+    """
+    global _CURRENT_PROCESS_GROUP
+    if _CURRENT_PROCESS_GROUP is not None:
+        raise RuntimeError(
+            'ProcessGroup already set by previous "load_with_process_group" '
+            'context manager')
+    _CURRENT_PROCESS_GROUP = process_group
+    try:
+        yield process_group
+    finally:
+        _CURRENT_PROCESS_GROUP = None
+
+def _get_current_process_group():
+    """
+    Retrieves the current process group set by ``load_with_process_group``.
+    If not set, it just returns the default group.
+    """
+    global _CURRENT_PROCESS_GROUP
+    if _CURRENT_PROCESS_GROUP is None:
+        return distributed_c10d._get_default_group()
+    else:
+        return _CURRENT_PROCESS_GROUP
+
+def _reshard_output(
+        module: torch.nn.Module,
+        resharding_spec: ShardingSpec) -> torch.nn.Module:
+    """
+    Hook a module with output resharding in the forward pass according
+    to the given ``resharding_spec``.
+
+    Args:
+        module (:class:`torch.nn.Module`): Module whose output needs to be resharded.
+        resharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`):
+            The specification describing how the output of the module will be resharded.
+
+    Returns:
+        A :class:`torch.nn.Module` object with reshard API hooked.
+    """
+    def hook_func(_module, _input, output):
+        if isinstance(output, ShardedTensor):
+            return output.reshard(resharding_spec)
+        return output
+    module.register_forward_hook(hook_func)
+    return module
+
+def _collect_local_shard(module: torch.nn.Module) -> torch.nn.Module:
+    """
+    Hook a module with local shards collection in the forward pass.
+
+    This API is typically used to convert a sharded representation back to data parallel
+    representation. In particular, it returns the local tensor for this Shard. If the
+    size along the sharding dimension for the local tensor is 1, this dimension is removed
+    from the final result. For example a [4, 16] ShardedTensor across 4 ranks is typically
+    a local Tensor of size [16] across each rank and not [1, 16] across each rank.
+
+    Args:
+        module (:class:`torch.nn.Module`): Module whose output is ShardedTensor and the
+            local tensor value needs to be returned.
+
+    Returns:
+        A :class:`torch.nn.Module` object with collection API hooked.
+    """
+
+    def hook_func(_module, _input, output):
+        if isinstance(output, ShardedTensor):
+            local_tensor = output.local_tensor()
+            # Squeeze the # of dimensions manually, only applicable to ChunkShardingSpec
+            sharding_spec = output._sharding_spec
+            if isinstance(sharding_spec, ChunkShardingSpec) \
+               and local_tensor.size(sharding_spec.dim) == 1:  # type: ignore[attr-defined, arg-type]
+                local_tensor = local_tensor.squeeze(
+                    output._sharding_spec.dim  # type: ignore[attr-defined]
+                )
+            return local_tensor
+    module.register_forward_hook(hook_func)
+    return module
+
+def shard_module(
+    module: nn.Module,
+    plan: ShardingPlan,
+    src_rank=0,
+    process_group=None
+):
+    """
+    Shards a given module according to the provided sharding `plan`. This method
+    first shards all the parameters according to the given sharding `plan`. Then if
+    `output_plan` and `return_local_tensor` are specified in the sharding `plan`, it
+    will tag the output of modules according `output_plan`, convert the module's
+    output back to data parallel according to `return_local_tensor`.
+
+    Needs to be called on all ranks in an SPMD fashion.
+
+    Args:
+        module (:class:`torch.nn.Module`): The module to apply sharding to
+        plan (:class:`torch.distributed._shard.sharding_plan.ShardingPlan`):
+            The ShardingPlan which specified param name to ShardingSpec to apply to
+            each parameter.
+
+    Keyword args:
+         src_rank (int, optional): The source rank which is used as the ground truth of
+            the data for the module that would be sharded and scattered across the rest
+            of the ranks.
+            Default: 0.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+    """
+    # record Sharder paths for sanity check on the plan to ensure items in the plan
+    # does not conflict with the submodule tree that the Sharder is working with
+    sharder_paths = []
+    for name, spec in plan.plan.items():
+        if isinstance(spec, Sharder):
+            sharder_paths.append(name)
+
+    # shard the parameter according to the ShardingPlan
+    for name, spec in plan.plan.items():
+        if isinstance(spec, ShardingSpec):
+            # if found a sharding spec, try to shard the parameter
+            module_path, _, param_name = name.rpartition(".")
+
+            for sharder_path in sharder_paths:
+                if module_path.startswith(sharder_path):
+                    raise RuntimeError(f"ShardingPlan is in-valid, trying to shard a parameter: {name},"
+                                       f" but there's already a Sharder entry for module {sharder_path},"
+                                       f" parameter sharding should not conflict with the submodule tree"
+                                       f" that a Sharder is working with!")
+
+            mod = module.get_submodule(module_path)
+            shard_parameter(
+                mod,
+                param_name,
+                spec,
+                src_rank=src_rank,
+                process_group=process_group
+            )
+        elif isinstance(spec, Sharder):
+            parent_mod_path, _, mod_name = name.rpartition(".")
+            if name == "":
+                raise KeyError("Module path must not be empty for custom sharder!")
+            mod = module.get_submodule(name)
+            parent_mod = module.get_submodule(parent_mod_path)
+            sharded_mod = spec.shard(mod)
+            # swap this submodule with the sharded module
+            parent_mod.mod_name = sharded_mod
+        else:
+            raise TypeError(f"Only `ShardingSpec` and `Sharder` are supported to shard '{name}'")
+
+    # reshard output if there's an entry in `reshard_output` for this module
+    if plan.output_plan is not None:
+        for module_path, output_spec in plan.output_plan.items():
+            if isinstance(output_spec, ShardingSpec):
+                mod = module.get_submodule(module_path)
+                _reshard_output(mod, output_spec)
+            else:
+                raise TypeError(f"Only `ShardingSpec` is supported as output_plan for '{module_path}'")
+    # convert the output back to data parallel for the modules appears in
+    # `return_local_tensor` of the plan, we will call `_collect_local_shard`
+    # to collect the local tensor for output of modules
+    if plan.return_local_tensor is not None:
+        for module_path in plan.return_local_tensor:
+            mod = module.get_submodule(module_path)
+            _collect_local_shard(mod)

venv/lib/python3.10/site-packages/torch/distributed/_shard/common_op_utils.py

@@ -0,0 +1,61 @@
+import torch
+from torch.utils import _pytree as pytree
+from typing import Optional
+
+def _basic_validation(op, args=(), kwargs=None):
+    """
+    Common validation across all ops go in here.
+    """
+    from torch.distributed._shard.sharded_tensor import ShardedTensor
+
+    if len(args) == 0 and (kwargs is None or len(kwargs) == 0):
+        raise ValueError(f" No input for '{op.__name__}'!")
+
+    # Validate types
+    has_distributed_tensor = False
+
+    def is_distributed_tensor(e):
+        nonlocal has_distributed_tensor
+        if isinstance(e, ShardedTensor):
+            has_distributed_tensor = True
+
+    pytree.tree_map_(is_distributed_tensor, args)
+    pytree.tree_map_(is_distributed_tensor, kwargs)
+
+    if not has_distributed_tensor:
+        raise TypeError(
+            f"torch function '{op.__name__}', with args: {args} and "
+            f"kwargs: {kwargs} are called without any distributed tensor!"
+        )
+
+    # Validate all distributed tensors use the same PG.
+    cur_pg: Optional[torch.distributed.ProcessGroup] = None
+
+    def validate_pg(e):
+        nonlocal cur_pg
+        if isinstance(e, ShardedTensor):
+            if cur_pg is not None and e._process_group is not cur_pg:
+                raise RuntimeError(
+                    'All distributed tensors should use the '
+                    'same ProcessGroup if used together in an op.'
+                )
+            cur_pg = e._process_group
+
+    pytree.tree_map_(validate_pg, args)
+    pytree.tree_map_(validate_pg, kwargs)
+
+def _register_default_op(op, decorator):
+    @decorator(op)
+    def tensor_default_op(types, args=(), kwargs=None, pg=None):
+        """
+        Handles ``__torch_function__`` dispatch for the default tensor ops that
+        behave the same as ``torch.Tensor`` such as ``torch.Tensor.shape`` or
+        ``torch.Tensor.dtype``. We simply lower to the real op call with
+        DisableTorchFunctionSubclass context like ``torch.Tensor.__torch_function__``
+        to avoid recursions.
+        """
+        if kwargs is None:
+            kwargs = {}
+
+        with torch._C.DisableTorchFunctionSubclass():
+            return op(*args, **kwargs)

venv/lib/python3.10/site-packages/torch/distributed/_shard/metadata.py

@@ -0,0 +1,61 @@
+from dataclasses import dataclass
+from typing import List, Union, Optional
+from functools import reduce
+
+from torch.distributed.remote_device import _remote_device
+
+@dataclass
+class ShardMetadata:
+    """
+    Represents a shard of the overall Tensor including its
+    offsets, lengths and device placement.
+
+    Args:
+        shard_offsets(List[int]): Offsets in the original tensor indicating
+            the start offsets for this shard. Should have the same rank as
+            the original tensor.
+        shard_sizes(List[int]): Integers indicating the size of each
+            dimension for this shard. Should have the same rank as the
+            original tensor.
+        placement(:class:`torch.distributed._remote_device`):
+            Specifies the placement of this shard.
+    """
+
+    __slots__ = ['shard_offsets', 'shard_sizes', 'placement']
+
+    shard_offsets: List[int]
+    shard_sizes: List[int]
+    placement: Optional[_remote_device]
+
+    def __init__(
+        self,
+        shard_offsets: List[int],
+        shard_sizes: List[int],
+        placement: Optional[Union[str, _remote_device]] = None
+    ):
+        self.shard_offsets = shard_offsets
+        self.shard_sizes = shard_sizes
+        if isinstance(placement, str):
+            self.placement = _remote_device(placement)
+        else:
+            self.placement = placement
+        if len(self.shard_offsets) != len(self.shard_sizes):
+            raise ValueError(
+                f'shard_offsets and shard_sizes should have '
+                f'the same number of elements, found {len(self.shard_offsets)} '
+                f'and {self.shard_sizes} respectively')
+
+        for i in range(len(self.shard_offsets)):
+            if self.shard_offsets[i] < 0:
+                raise ValueError('shard_offsets should be >=0')
+            if self.shard_sizes[i] < 0:
+                raise ValueError('shard_sizes should be >= 0')
+
+    def __hash__(self):
+        def _hash_reduce(a, b):
+            return (a << 8) + hash(b)
+
+        res = reduce(_hash_reduce, self.shard_offsets, 37)
+        res = reduce(_hash_reduce, self.shard_sizes, res)
+        res = _hash_reduce(res, self.placement)
+        return res

venv/lib/python3.10/site-packages/torch/distributed/_shard/op_registry_utils.py

@@ -0,0 +1,35 @@
+import functools
+from inspect import signature
+from .common_op_utils import _basic_validation
+
+"""
+Common utilities to register ops on ShardedTensor
+and PartialTensor.
+"""
+
+def _register_op(op, func, op_table):
+    """
+    Performs basic validation and registers the provided op in the given
+    op_table.
+    """
+    if len(signature(func).parameters) != 4:
+        raise TypeError(
+            f'Custom sharded op function expects signature: '
+            f'(types, args, kwargs, process_group), but received '
+            f'signature: {signature(func)}')
+
+    op_table[op] = func
+
+def _decorator_func(wrapped_func, op, op_table):
+    """
+    Decorator function to register the given ``op`` in the provided
+    ``op_table``
+    """
+
+    @functools.wraps(wrapped_func)
+    def wrapper(types, args, kwargs, process_group):
+        _basic_validation(op, args, kwargs)
+        return wrapped_func(types, args, kwargs, process_group)
+
+    _register_op(op, wrapper, op_table)
+    return wrapper

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/__init__.py

@@ -0,0 +1,469 @@
+import functools
+from typing import List, TYPE_CHECKING
+
+import torch
+
+if TYPE_CHECKING:
+    from torch.distributed._shard.sharding_spec import ShardingSpec
+else:
+    ShardingSpec = "ShardingSpec"
+
+from .api import (
+    _CUSTOM_SHARDED_OPS,
+    _SHARDED_OPS,
+    Shard,
+    ShardedTensorBase,
+    ShardedTensor,
+    ShardedTensorMetadata,
+    TensorProperties,
+)
+from .metadata import ShardMetadata  # noqa: F401
+from torch.distributed._shard.op_registry_utils import _decorator_func
+
+
+def empty(sharding_spec: ShardingSpec,
+          *size,
+          dtype=None,
+          layout=torch.strided,
+          requires_grad=False,
+          pin_memory=False,
+          memory_format=torch.contiguous_format,
+          process_group=None,
+          init_rrefs=False) -> ShardedTensor:
+    """
+    Returns a :class:`ShardedTensor` filled with uninitialized data.
+        Needs to be called on all ranks in an SPMD fashion.
+
+    Args:
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+        size (int...): a sequence of integers defining the shape of the output
+            tensor. Can be a variable number of arguments or a collection like a list or tuple.
+
+    Keyword args:
+        dtype (:class:`torch.dtype`, optional): the desired data type of returned tensor.
+            Default: if ``None``, uses a global default (see :func:`torch.set_default_dtype`).
+        layout (:class:`torch.layout`, optional): the desired layout of returned Tensor.
+            Default: ``torch.strided``.
+        requires_grad (bool, optional): If autograd should record operations on the
+            returned tensor. Default: ``False``.
+        pin_memory (bool, optional): If set, returned tensor would be allocated in
+            the pinned memory. Works only for CPU tensors. Default: ``False``.
+        memory_format (:class:`torch.memory_format`, optional): the desired memory format of
+            returned Tensor. Default: ``torch.contiguous_format``.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+        init_rrefs (bool, optional): Whether or not to initialize
+            :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+            Need to initialize the RPC Framework if specified as ``True``.
+            Default: ``False``.
+
+    Returns:
+        A :class:`ShardedTensor` object on each rank
+    """
+    return ShardedTensor(
+        sharding_spec,
+        *size,
+        dtype=dtype,
+        layout=layout,
+        requires_grad=requires_grad,
+        pin_memory=pin_memory,
+        memory_format=memory_format,
+        process_group=process_group,
+        init_rrefs=init_rrefs,
+    )
+
+def ones(sharding_spec: ShardingSpec,
+         *size,
+         dtype=None,
+         layout=torch.strided,
+         requires_grad=False,
+         pin_memory=False,
+         memory_format=torch.contiguous_format,
+         process_group=None,
+         init_rrefs=False) -> ShardedTensor:
+    """
+    Returns a :class:`ShardedTensor` with the scalar value 1.
+        Needs to be called on all ranks in an SPMD fashion.
+
+    Args:
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+        size (int...): a sequence of integers defining the shape of the output
+            tensor. Can be a variable number of arguments or a collection like a list or tuple.
+
+    Keyword args:
+        dtype (:class:`torch.dtype`, optional): the desired data type of returned tensor.
+            Default: if ``None``, uses a global default (see :func:`torch.set_default_dtype`).
+        layout (:class:`torch.layout`, optional): the desired layout of returned Tensor.
+            Default: ``torch.strided``.
+        requires_grad (bool, optional): If autograd should record operations on the
+            returned tensor. Default: ``False``.
+        pin_memory (bool, optional): If set, returned tensor would be allocated in
+            the pinned memory. Works only for CPU tensors. Default: ``False``.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+        init_rrefs (bool, optional): Whether or not to initialize
+            :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+            Need to initialize the RPC Framework if specified as ``True``.
+            Default: ``False``.
+
+    Returns:
+        A :class:`ShardedTensor` object on each rank
+    """
+    return full(
+        sharding_spec,
+        size,
+        fill_value=1,
+        dtype=dtype,
+        layout=layout,
+        requires_grad=requires_grad,
+        pin_memory=pin_memory,
+        memory_format=memory_format,
+        process_group=process_group,
+        init_rrefs=init_rrefs
+    )
+
+def zeros(sharding_spec: ShardingSpec,
+          *size,
+          dtype=None,
+          layout=torch.strided,
+          requires_grad=False,
+          pin_memory=False,
+          memory_format=torch.contiguous_format,
+          process_group=None,
+          init_rrefs=False) -> ShardedTensor:
+    """
+    Returns a :class:`ShardedTensor` filled with the scalar value 0.
+        Needs to be called on all ranks in an SPMD fashion.
+
+    Args:
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+        size (int...): a sequence of integers defining the shape of the output
+            tensor. Can be a variable number of arguments or a collection like a list or tuple.
+
+    Keyword args:
+        dtype (:class:`torch.dtype`, optional): the desired data type of returned tensor.
+            Default: if ``None``, uses a global default (see :func:`torch.set_default_dtype`).
+        layout (:class:`torch.layout`, optional): the desired layout of returned Tensor.
+            Default: ``torch.strided``.
+        requires_grad (bool, optional): If autograd should record operations on the
+            returned tensor. Default: ``False``.
+        pin_memory (bool, optional): If set, returned tensor would be allocated in
+            the pinned memory. Works only for CPU tensors. Default: ``False``.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+        init_rrefs (bool, optional): Whether or not to initialize
+            :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+            Need to initialize the RPC Framework if specified as ``True``.
+            Default: ``False``.
+
+    Returns:
+        A :class:`ShardedTensor` object on each rank
+    """
+    return full(
+        sharding_spec,
+        size,
+        fill_value=0,
+        dtype=dtype,
+        layout=layout,
+        requires_grad=requires_grad,
+        pin_memory=pin_memory,
+        memory_format=memory_format,
+        process_group=process_group,
+        init_rrefs=init_rrefs
+    )
+
+def full(sharding_spec: ShardingSpec,
+         size,
+         fill_value,
+         *,
+         dtype=None,
+         layout=torch.strided,
+         requires_grad=False,
+         pin_memory=False,
+         memory_format=torch.contiguous_format,
+         process_group=None,
+         init_rrefs=False) -> ShardedTensor:
+    """
+    Creates a :class:`ShardedTensor` filled with fill_value. The tensor’s dtype
+        is inferred from fill_value. If dtype is specified, it will override the
+        inferred type from fill_value. Needs to be called on all ranks in an SPMD fashion.
+    Args:
+        sharding_spec (:class:`torch.distributed._sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+        size (int...):  a list, tuple, or `torch.Size` of integers defining the shape of the
+            output tensor.
+        fill_value (Scalar) – the value to fill the output tensor with.
+    Keyword args:
+        dtype (:class:`torch.dtype`, optional): the desired data type of returned tensor.
+            Default: if ``None``, uses a global default (see :func:`torch.set_default_dtype`).
+        layout (:class:`torch.layout`, optional): the desired layout of returned Tensor.
+            Default: ``torch.strided``.
+        requires_grad (bool, optional): If autograd should record operations on the
+            returned tensor. Default: ``False``.
+        pin_memory (bool, optional): If set, returned tensor would be allocated in
+            the pinned memory. Works only for CPU tensors. Default: ``False``.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+        init_rrefs (bool, optional): Whether or not to initialize
+            :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+            Need to initialize the RPC Framework if specified as ``True``.
+            Default: ``False``.
+    Returns:
+        A :class:`ShardedTensor` object on each rank
+    """
+    sharded_tensor = ShardedTensor(
+        sharding_spec,
+        *size,
+        dtype=dtype,
+        layout=layout,
+        requires_grad=requires_grad,
+        pin_memory=pin_memory,
+        memory_format=memory_format,
+        process_group=process_group,
+        init_rrefs=init_rrefs,
+    )
+    torch.nn.init.constant_(sharded_tensor, fill_value)  # type: ignore[arg-type]
+    return sharded_tensor
+
+def rand(sharding_spec: ShardingSpec,
+         *size,
+         dtype=None,
+         layout=torch.strided,
+         requires_grad=False,
+         pin_memory=False,
+         memory_format=torch.contiguous_format,
+         process_group=None,
+         init_rrefs=False) -> ShardedTensor:
+    """
+    Creates a :class:`ShardedTensor` filled with random numbers from a uniform distribution
+        on the interval :math:`[0, 1)`. The shape of the tensor is defined by the
+        variable argument `size`. Needs to be called on all ranks in an SPMD fashion.
+
+    Args:
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+        size (int...):  a list, tuple, or `torch.Size` of integers defining the shape of the
+            output tensor.
+
+    Keyword args:
+        dtype (:class:`torch.dtype`, optional): the desired data type of returned tensor.
+            Default: if ``None``, uses a global default (see :func:`torch.set_default_dtype`).
+        layout (:class:`torch.layout`, optional): the desired layout of returned Tensor.
+            Default: ``torch.strided``.
+        requires_grad (bool, optional): If autograd should record operations on the
+            returned tensor. Default: ``False``.
+        pin_memory (bool, optional): If set, returned tensor would be allocated in
+            the pinned memory. Works only for CPU tensors. Default: ``False``.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+        init_rrefs (bool, optional): Whether or not to initialize
+            :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+            Need to initialize the RPC Framework if specified as ``True``.
+            Default: ``False``.
+
+    Returns:
+        A :class:`ShardedTensor` object on each rank
+    """
+    sharded_tensor = ShardedTensor(
+        sharding_spec,
+        *size,
+        dtype=dtype,
+        layout=layout,
+        requires_grad=requires_grad,
+        pin_memory=pin_memory,
+        memory_format=memory_format,
+        process_group=process_group,
+        init_rrefs=init_rrefs,
+    )
+    torch.nn.init.uniform_(sharded_tensor, 0, 1)  # type: ignore[arg-type]
+    return sharded_tensor
+
+def randn(sharding_spec: ShardingSpec,
+          *size,
+          dtype=None,
+          layout=torch.strided,
+          requires_grad=False,
+          pin_memory=False,
+          memory_format=torch.contiguous_format,
+          process_group=None,
+          init_rrefs=False) -> ShardedTensor:
+    """
+    Creates a :class:`ShardedTensor` filled with random numbers from a uniform distribution
+        with mean `0` and variance `1` (also called standard normal distribution). The shape
+        of the tensor is defined by the variable argument `size`. Needs to be called on all ranks
+        in an SPMD fashion.
+
+    Args:
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+        size (int...):  a list, tuple, or `torch.Size` of integers defining the shape of the
+            output tensor.
+
+    Keyword args:
+        dtype (:class:`torch.dtype`, optional): the desired data type of returned tensor.
+            Default: if ``None``, uses a global default (see :func:`torch.set_default_dtype`).
+        layout (:class:`torch.layout`, optional): the desired layout of returned Tensor.
+            Default: ``torch.strided``.
+        requires_grad (bool, optional): If autograd should record operations on the
+            returned tensor. Default: ``False``.
+        pin_memory (bool, optional): If set, returned tensor would be allocated in
+            the pinned memory. Works only for CPU tensors. Default: ``False``.
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+        init_rrefs (bool, optional): Whether or not to initialize
+            :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+            Need to initialize the RPC Framework if specified as ``True``.
+            Default: ``False``.
+
+    Returns:
+        A :class:`ShardedTensor` object on each rank
+    """
+    sharded_tensor = ShardedTensor(
+        sharding_spec,
+        *size,
+        dtype=dtype,
+        layout=layout,
+        requires_grad=requires_grad,
+        pin_memory=pin_memory,
+        memory_format=memory_format,
+        process_group=process_group,
+        init_rrefs=init_rrefs,
+    )
+    torch.nn.init.normal_(sharded_tensor, 0, 1)  # type: ignore[arg-type]
+    return sharded_tensor
+
+def init_from_local_shards(
+        local_shards: List[Shard],
+        *global_size,
+        process_group=None,
+        init_rrefs=False) -> ShardedTensor:
+    """
+    Creates an :class:`ShardedTensor` from local shards and the global metadata.
+    Needs to be called on all ranks in an SPMD fashion.
+
+    Args:
+        local_shards (List[:class `torch.distributed._shard.sharded_tensor.Shard`]): A list
+            of shards that represent the local shards on this rank.
+        global_size (int...):  a list, tuple, or `torch.Size` of integers defining the
+            shape of the overall sharded tensor.
+
+    Keyword args:
+        process_group (ProcessGroup, optional): The process group to work on. If None,
+            the default process group will be used.
+        init_rrefs (bool, optional): Whether or not to initialize
+            :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+            Need to initialize the RPC Framework if specified as ``True``.
+            Default: ``False``.
+
+    Returns:
+        A :class:`ShardedTensor` object handle on this rank
+
+
+    Examples:
+        Suppose we want construct a sharded tensor on two ranks, global size = (10, 5),
+        each shard have a (5, 5) local tensor, we can do it like below:
+
+        on rank 0:
+        >>> # xdoctest: +SKIP("not distributed")
+        >>> local_shard_metadata = ShardMetadata(
+        >>>     shard_offsets=[0, 0],
+        >>>     shard_lengths=[5, 5],
+        >>>     placement="rank:0/cuda:0"
+        >>> )
+        >>> local_shards = [Shard(torch.randn(5, 5), local_shard_metadata)]
+        >>> sharded_tensor = init_from_local_shards(local_shards, [10, 5])
+
+        on rank 1:
+        >>> # xdoctest: +SKIP("not distributed")
+        >>> local_shard_metadata = ShardMetadata(
+        >>>     shard_offsets=[5, 0],
+        >>>     shard_lengths=[5, 5],
+        >>>     placement="rank:1/cuda:1"
+        >>> )
+        >>> local_shards = [Shard(torch.randn(5, 5), local_shard_metadata)]
+        >>> sharded_tensor = init_from_local_shards(local_shards, [10, 5])
+    """
+    return ShardedTensor._init_from_local_shards(
+        local_shards,
+        *global_size,
+        process_group=process_group,
+        init_rrefs=init_rrefs
+    )
+
+def state_dict_hook(module, destination, prefix, local_metadata):
+    """
+    Hook to add ShardedTensor to Module's ``state_dict``. Needs to be
+    registered to the Module using
+    :meth:`torch.nn.Module._register_state_dict_hook`.
+    """
+    for submodule_name, submodule in module.named_modules():
+        for attr_name, attr in submodule.__dict__.items():
+            if isinstance(attr, ShardedTensor):
+                mod_prefix = prefix + submodule_name
+                key = mod_prefix + ('.' if mod_prefix else '') + attr_name
+                destination[key] = attr
+
+def pre_load_state_dict_hook(module, state_dict, prefix, local_metadata, strict, missing_keys, unexpected_keys, error_msgs):
+    """
+    Pre-load state dict hook to add ShardedTensor to the module.
+    """
+    for submodule_name, submodule in module.named_modules():
+        for attr_name in submodule.__dict__.keys():
+            mod_prefix = prefix + submodule_name
+            key = mod_prefix + ('.' if mod_prefix else '') + attr_name
+            if key in state_dict:
+                if isinstance(state_dict[key], ShardedTensor):
+                    setattr(submodule, attr_name, state_dict[key])
+
+def custom_sharded_op_impl(func):
+    """
+    Provides a way for users to write their own custom sharded operator. This
+    can be used to override existing ShardedTensor operators or write a new
+    one not supported by ShardedTensor. If the operator in question is covered
+    by ``__torch_function__`` dispatch and has a ShardedTensor as any of its
+    parameters, the function provided will be invoked for that operator.
+
+    Example::
+        >>> # xdoctest: +SKIP
+        >>> @custom_sharded_op_impl(torch.nn.functional.linear)
+        >>> def my_custom_sharded_linear(types, args, kwargs, process_group):
+        >>>     ...
+        >>> # xdoctest: +SKIP("Undefined variables")
+        >>> input = torch.rand(10, 32)
+        >>> weight = sharded_tensor.rand(32, 16)
+        >>> bias = torch.rand(16)
+        >>> # This will call 'my_custom_sharded_linear'
+        >>> torch.nn.functional.linear(input, weight, bias)
+
+    The types, args and kwargs parameters are the same parameters that are
+    passed to ``__torch_function__`` dispatch API
+    (https://pytorch.org/docs/stable/notes/extending.html#extending-torch).
+    There is an additional ``process_group`` parameter which is the
+    process_group used for the ShardedTensor and can be used by
+    implementations for communications within a sharded implementation.
+
+    Args:
+        func(Callable): Torch function for which we want to provide a sharded
+            implementation (ex: torch.nn.functional.linear)
+    """
+    return functools.partial(
+        _decorator_func,
+        op=func,
+        op_table=_CUSTOM_SHARDED_OPS
+    )
+
+def _sharded_op_impl(func):
+    """
+    Decorator to register a default sharded op.
+    """
+    return functools.partial(
+        _decorator_func,
+        op=func,
+        op_table=_SHARDED_OPS
+    )
+
+# Import all builtin sharded ops
+from ._ops import *  # noqa: F403

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/_ops/__init__.py

@@ -0,0 +1,9 @@
+import torch.distributed._shard.sharded_tensor._ops.misc_ops
+import torch.distributed._shard.sharded_tensor._ops.tensor_ops
+
+from .binary_cmp import equal, allclose
+from .init import kaiming_uniform_, normal_, uniform_, constant_
+
+# Import all ChunkShardingSpec ops
+from torch.distributed._shard.sharding_spec.chunk_sharding_spec_ops.embedding import sharded_embedding
+from torch.distributed._shard.sharding_spec.chunk_sharding_spec_ops.embedding_bag import sharded_embedding_bag

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/_ops/_common.py

@@ -0,0 +1,107 @@
+import functools
+from torch.distributed._shard.sharded_tensor import (
+    _sharded_op_impl,
+    Shard,
+    ShardedTensor,
+)
+from torch.distributed._shard.common_op_utils import _basic_validation
+
+def _sharded_op_common(op, early_stop_func, extra_check):
+    """
+    Inject sharded tensor op registration with common logics executed before
+    different behaviors are done on either local shards or a local tensor.
+
+    Example::
+        >>> # xdoctest: +SKIP("Undefined variables")
+        >>> op = torch.transpose
+        >>> @_sharded_op_impl(op)
+        >>> @_sharded_op_common(op, early_stop_func, extra_check)
+        >>> def sharded_tensor_op(types, args, kwargs, process_group):
+        >>>   ...
+        >>>
+        >>> st = sharded_tensor.rand(32, 16)
+        >>> st.transpose(1, 2)
+        >>> # This will call '_sharded_op_common'
+
+    Args:
+        op: The op to be registered and applied to all shards of the st.
+        early_stop_func (Callable, optional): the func for early stop.
+            Default: if ``None``, no early stop.
+        extra_check (Callable, optional): the func for extra condition check.
+            Default: if ``None``, no extra check.
+
+    Return:
+        func (Callable): Torch function for which we want to provide a sharded
+            implementation (ex: torch.transpose)
+    """
+    def decorator_sharded_func(wrapped_func):
+        @functools.wraps(wrapped_func)
+        def wrapper(types, args=(), kwargs=None, pg=None):
+            _basic_validation(op, args, kwargs)
+
+            st = args[0]
+            if kwargs is None:
+                kwargs = {}
+            if extra_check:
+                extra_check(*args, **kwargs)
+            if early_stop_func:
+                early_stop = early_stop_func(*args, **kwargs)
+                if early_stop:
+                    return st
+            return wrapped_func(types, args, kwargs, pg)
+
+        return wrapper
+
+    return decorator_sharded_func
+
+def _register_sharded_op_on_local_shards(
+    op, early_stop_func=None, extra_check=None, customized_func=None
+):
+    """
+    Handles ``__torch_function__`` dispatch for ops which are performed on
+    each shard of the sharded tensor such as elementwise op like
+    ``torch.nn.functional.gelu`` or ``torch.nn.functional.relu``.
+
+    For more complicated ops, a customized func can be used to generate
+    the new shards and sharded tensor size.
+
+    This function expects that the original ShardingSpec for the ShardedTensor
+    is preserved irrespective of whether or not a customized function is used.
+
+    Args:
+        op: The op to be registered and applied to all shards of the st.
+        early_stop_func (Callable, optional): the func for early stop.
+            Default: if ``None``, no early stop.
+        extra_check (Callable, optional): the func for extra condition check.
+            Default: if ``None``, no extra check.
+        customized_func (Callable, optional): the func for customized logic
+            to generate new shards and sharded tensor size.
+            Default: if ``None``, we simply lower to the real op call with
+                all local shards of the st.
+
+    Return:
+        func (Callable): registered implementation for sharded op for
+        ``__torch_function__`` dispatch.
+    """
+    @_sharded_op_impl(op)
+    @_sharded_op_common(op, early_stop_func, extra_check)
+    def sharded_tensor_op_on_local_shards(types, args=(), kwargs=None, pg=None):
+        st = args[0]
+        st_metadata = st.metadata()
+        local_shards = st.local_shards()
+        local_shards_new = []
+        if customized_func:
+            local_shards_new, st_metadata = customized_func(args, kwargs, pg)
+        else:
+            for local_shard in local_shards:
+                args = (local_shard.tensor, *args[1:])
+                local_shards_new.append(
+                    Shard(op(*args, **kwargs), local_shard.metadata)
+                )
+        return ShardedTensor._init_from_local_shards_and_global_metadata(
+            local_shards_new,
+            st_metadata,
+            process_group=pg,
+            init_rrefs=st._init_rrefs,
+            sharding_spec=st.sharding_spec()
+        )

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/_ops/binary_cmp.py

@@ -0,0 +1,68 @@
+import torch
+import torch.distributed as dist
+import torch.distributed.distributed_c10d as distributed_c10d
+from torch.distributed._shard.sharded_tensor import (
+    ShardedTensor,
+    _sharded_op_impl
+)
+
+def _communicate_result(result, pg):
+    # Gather results from all ranks.
+    if result:
+        result_tensor = torch.ones(1, device=torch.device(torch.cuda.current_device()))
+    else:
+        result_tensor = torch.zeros(1, device=torch.device(torch.cuda.current_device()))
+
+    dist.all_reduce(result_tensor, group=pg)
+
+    expected_result = torch.ones(1, device=torch.device(torch.cuda.current_device())) * dist.get_world_size(pg)
+
+    return torch.equal(result_tensor, expected_result)
+
+def binary_cmp(cmp_fun, types, args, kwargs=None, process_group=None):
+    if len(args) != 2:
+        raise ValueError(f'Expected two arguments for torch.{cmp_fun.__name__}')
+
+    result = True
+    st1 = args[0]
+    st2 = args[1]
+    if not (isinstance(st1, ShardedTensor) and isinstance(st2, ShardedTensor)):
+        raise TypeError(f'Both arguments to torch.{cmp_fun.__name__} need to be of type ShardedTensor')
+
+    # Verify same PG
+    if st1._process_group != st2._process_group:
+        return False
+
+    if distributed_c10d._rank_not_in_group(st1._process_group) or distributed_c10d._rank_not_in_group(st2._process_group):
+        return distributed_c10d._rank_not_in_group(st1._process_group) == distributed_c10d._rank_not_in_group(st2._process_group)
+
+    # Verify metadata
+    if st1.metadata() != st2.metadata():
+        return _communicate_result(False, st1._process_group)
+
+    # Verify number of local shards
+    st1_local_shards = st1.local_shards()
+    st2_local_shards = st2.local_shards()
+    if len(st1_local_shards) != len(st2_local_shards):
+        return _communicate_result(False, st1._process_group)
+
+    # kwargs must be dict-like
+    if kwargs is None:
+        kwargs = {}
+    # Verify each local shard
+    for idx in range(len(st1_local_shards)):
+        if st1_local_shards[idx].metadata != st2_local_shards[idx].metadata:
+            return _communicate_result(False, st1._process_group)
+        if not cmp_fun(st1_local_shards[idx].tensor, st2_local_shards[idx].tensor, **kwargs):
+            return _communicate_result(False, st1._process_group)
+
+
+    return _communicate_result(True, st1._process_group)
+
+@_sharded_op_impl(torch.equal)
+def equal(types, args, kwargs, process_group):
+    return binary_cmp(torch.equal, types, args, kwargs, process_group)
+
+@_sharded_op_impl(torch.allclose)
+def allclose(types, args, kwargs, process_group):
+    return binary_cmp(torch.allclose, types, args, kwargs, process_group)

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/_ops/init.py

@@ -0,0 +1,143 @@
+import torch
+import torch.distributed._shard.sharded_tensor as sharded_tensor
+from torch.distributed._shard.sharded_tensor import (
+    _sharded_op_impl,
+)
+
+def validate_param(param, param_name):
+    if param is None:
+        raise ValueError(f"param: {param_name} shouldn't be None!")
+
+@_sharded_op_impl(torch.nn.init.uniform_)
+def uniform_(types, args=(), kwargs=None, pg=None):
+    r"""
+    Fills the Tensor in tensor.local_shards with values drawn from the uniform
+    distribution :math:`\mathcal{U}(a, b)`.
+    Args:
+        tensor: tensor sharded across devices
+        a: the lower bound of the uniform distribution
+        b: the upper bound of the uniform distribution
+    """
+    validate_param(kwargs, "kwargs")
+    sharded_tensor = kwargs["tensor"]
+    validate_param(sharded_tensor, "tensor")
+    a = kwargs['a']
+    validate_param(a, "a")
+    b = kwargs['b']
+    validate_param(b, "b")
+
+    for shard in sharded_tensor.local_shards():
+        torch.nn.init.uniform_(shard.tensor, a=a, b=b)
+    return sharded_tensor
+
+@_sharded_op_impl(torch.nn.init.normal_)
+def normal_(types, args=(), kwargs=None, pg=None):
+    r"""
+    Fills the Tensors in tensor.local_shards with values drawn from the normal
+    distribution :math:`\mathcal{N}(\text{mean}, \text{std}^2)`.
+    Args:
+        tensor: tensor sharded across devices
+        mean: the mean of the normal distribution
+        std: the standard deviation of the normal distribution
+    """
+    validate_param(kwargs, "kwargs")
+    sharded_tensor = kwargs["tensor"]
+    validate_param(sharded_tensor, "tensor")
+    mean = kwargs['mean']
+    validate_param(mean, "mean")
+    std = kwargs['std']
+    validate_param(std, "std")
+
+    for shard in sharded_tensor.local_shards():
+        torch.nn.init.normal_(shard.tensor, mean=mean, std=std)
+    return sharded_tensor
+
+@_sharded_op_impl(torch.nn.init.kaiming_uniform_)
+def kaiming_uniform_(types, args=(), kwargs=None, pg=None):
+    r"""
+    Fills the Tensors in tensor.local_shards with values according to the method
+    described in `Delving deep into rectifiers: Surpassing human-level
+    performance on ImageNet classification` - He, K. et al. (2015), using a
+    uniform distribution. The resulting tensor will have values sampled from
+    :math:`\mathcal{U}(-\text{bound}, \text{bound})` where
+    .. math::
+        \text{bound} = \text{gain} \times \sqrt{\frac{3}{\text{fan\_mode}}}
+    Also known as He initialization.
+    Args:
+        tensor: tensor sharded across devices
+        a: the negative slope of the rectifier used after this layer (only
+            used with ``'leaky_relu'``)
+        mode: either ``'fan_in'`` (default) or ``'fan_out'``. Choosing ``'fan_in'``
+            preserves the magnitude of the variance of the weights in the
+            forward pass. Choosing ``'fan_out'`` preserves the magnitudes in the
+            backwards pass.
+        nonlinearity: the non-linear function (`nn.functional` name),
+            recommended to use only with ``'relu'`` or ``'leaky_relu'`` (default).
+    """
+    validate_param(kwargs, "kwargs")
+    sharded_tensor = kwargs["tensor"]
+    validate_param(sharded_tensor, "tensor")
+    a = kwargs['a']
+    validate_param(a, "a")
+    mode = kwargs['mode']
+    validate_param(mode, "mode")
+    nonlinearity = kwargs['nonlinearity']
+    validate_param(nonlinearity, "nonlinearity")
+
+    for shard in sharded_tensor.local_shards():
+        torch.nn.init.kaiming_uniform_(shard.tensor, a=a, mode=mode, nonlinearity=nonlinearity)
+    return sharded_tensor
+
+@_sharded_op_impl(torch.nn.init.constant_)
+def constant_(types, args=(), kwargs=None, pg=None):
+    r"""
+    Fills the input ShardedTensor with the value \text{val}val.
+    Args:
+        tensor: tensor sharded across devices
+        val: the value to fill the tensor with
+    """
+    validate_param(kwargs, "kwargs")
+    sharded_tensor = kwargs["tensor"]
+    validate_param(sharded_tensor, "tensor")
+    val = kwargs['val']
+    validate_param(val, "val")
+    for shard in sharded_tensor.local_shards():
+        torch.nn.init.constant_(shard.tensor, val=val)
+    return sharded_tensor
+
+tensor_like_creation_op_map = {
+    torch.full_like: sharded_tensor.full,
+    torch.empty_like: sharded_tensor.empty,
+    torch.zeros_like: sharded_tensor.zeros,
+    torch.ones_like: sharded_tensor.ones,
+    torch.rand_like: sharded_tensor.rand,
+    torch.randn_like: sharded_tensor.randn,
+}
+
+# tensor ops that behave the same as the default tensor
+def register_tensor_creation_op(op):
+    @_sharded_op_impl(op)
+    def tensor_creation_op(types, args=(), kwargs=None, pg=None):
+        """
+        Handles ``__torch_function__`` dispatch for tensor creation ops that
+        takes a ShardedTensor as argument, such as ``torch.zeros_like`` or
+        ``torch.full_like``.
+        """
+        creation_op = tensor_like_creation_op_map.get(op, None)
+        if creation_op is None:
+            raise RuntimeError(f"Tensor creation {op} not supported!")
+        if kwargs is None:
+            kwargs = {}
+
+        st = args[0]
+
+        new_st = creation_op(st.sharding_spec(), st.size(), *args[1:], **kwargs)  # type: ignore[operator]
+        return new_st
+
+
+register_tensor_creation_op(torch.full_like)
+register_tensor_creation_op(torch.empty_like)
+register_tensor_creation_op(torch.zeros_like)
+register_tensor_creation_op(torch.ones_like)
+register_tensor_creation_op(torch.rand_like)
+register_tensor_creation_op(torch.randn_like)

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/_ops/misc_ops.py

@@ -0,0 +1,12 @@
+import torch
+from torch.distributed._shard.sharded_tensor import (
+    _sharded_op_impl,
+)
+
+# This is used by `_apply()` within module.py to set new
+# parameters after apply a certain method, we should follow
+# the future behavior of overwriting the existing tensor
+# instead of doing in-place change using `.data = `.
+@_sharded_op_impl(torch._has_compatible_shallow_copy_type)
+def tensor_has_compatible_shallow_copy_type(types, args=(), kwargs=None, pg=None):
+    return False

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/_ops/tensor_ops.py

@@ -0,0 +1,215 @@
+import copy
+import torch
+from torch.distributed._shard.sharded_tensor import (
+    _sharded_op_impl,
+    Shard,
+    ShardedTensor,
+)
+from ._common import (
+    _register_sharded_op_on_local_shards,
+)
+from torch.distributed._shard.common_op_utils import _register_default_op
+
+
+# Tensor properties access
+_register_default_op(torch.Tensor.shape.__get__, _sharded_op_impl)  # type: ignore[attr-defined]
+_register_default_op(torch.Tensor.dtype.__get__, _sharded_op_impl)  # type: ignore[attr-defined]
+_register_default_op(torch.Tensor.layout.__get__, _sharded_op_impl)  # type: ignore[attr-defined]
+_register_default_op(torch.Tensor.size, _sharded_op_impl)
+_register_default_op(torch.Tensor.dim, _sharded_op_impl)
+_register_default_op(torch.Tensor.ndim.__get__, _sharded_op_impl)  # type: ignore[attr-defined]
+_register_default_op(torch.Tensor.is_contiguous, _sharded_op_impl)
+_register_default_op(torch.Tensor.contiguous, _sharded_op_impl)
+_register_default_op(torch.Tensor.is_floating_point, _sharded_op_impl)
+
+# __reduce_ex__ to dispatch to get_state/set_state
+_register_default_op(torch.Tensor.__reduce_ex__, _sharded_op_impl)
+
+# autograd related properties
+_register_default_op(torch.Tensor.requires_grad.__get__, _sharded_op_impl)  # type: ignore[attr-defined]
+# TODO: set grad with a ShardedTensor that consists of all local grads
+_register_default_op(torch.Tensor.grad.__get__, _sharded_op_impl)  # type: ignore[union-attr]
+_register_default_op(torch.Tensor.grad_fn.__get__, _sharded_op_impl)  # type: ignore[union-attr]
+_register_default_op(torch.Tensor.is_leaf.__get__, _sharded_op_impl)  # type: ignore[attr-defined]
+
+# device property is ambiguous as from a global prospective,
+# ShardedTensor.device consists of multiple devices (might even across hosts)
+# We choose to return the current device of the local tensor to represent
+# the device property on each rank
+@_sharded_op_impl(torch.Tensor.device.__get__)
+def tensor_device(types, args=(), kwargs=None, pg=None):
+    self_st = args[0]
+    # Validate types
+    if not isinstance(self_st, ShardedTensor):
+        raise TypeError("input needs to be a ShardedTensor")
+    dev: torch.device
+    if self_st._local_shards:
+        dev = self_st._local_shards[0].tensor.device
+    elif pg and pg._get_backend_name() == "gloo":
+        dev = torch.device("cpu")
+    else:
+        dev = torch.device(torch.cuda.current_device())
+    return dev
+
+@_sharded_op_impl(torch.Tensor.is_meta.__get__)  # type: ignore[attr-defined]
+def st_is_meta(types, args=(), kwargs=None, pg=None):
+    return args[0].local_tensor().is_meta
+
+
+def sharded_type_as_check(*args, **kwargs):
+    """
+    Perform extra checks for the sharded_type_as op such as the input needs to
+    be either a Tensor or ShardedTensor.
+
+    Args: same as ``torch.Tensor.type_as``.
+
+    Return: None
+    """
+    if len(args) < 2:
+        raise ValueError("Needs to give a tensor to cast type as!")
+    if not isinstance(args[1], torch.Tensor) and not isinstance(args[1], ShardedTensor):
+        raise ValueError("Needs to give a Tensor or ShardedTensor to cast type as!")
+
+
+def same_dtype(*args, **kwargs):
+    """
+    When the dtype is the same, return the original ShardedTensor.
+
+    Args: same as ``torch.Tensor.type_as``.
+
+    Return (bool): Whether to return early or not.
+    """
+    return args[0].dtype == args[1].dtype
+
+
+def sharded_type_as(args, kwargs, pg):
+    """
+    Handles ``__torch_function__`` dispatch for the ``torch.Tensor.type_as`` op.
+
+    Args: same as ``torch.Tensor.type_as``.
+
+    Return:
+        new_local_shards (List[Shard]): Local shards for the new sharded tensor.
+        st_meta (ShardedTensorMetadata): Metadata of the new sharded tensor.
+    """
+    st = args[0]
+    tensor = args[1]
+    if isinstance(tensor, ShardedTensor):
+        tensor = tensor.local_tensor()
+    new_local_shards = []
+    for shard in st.local_shards():
+        new_local_shards.append(Shard(shard.tensor.type_as(tensor), shard.metadata))
+    st_meta = copy.deepcopy(st._metadata)
+    st_meta.tensor_properties.dtype = tensor.dtype
+    return new_local_shards, st_meta
+
+
+_register_sharded_op_on_local_shards(
+    torch.Tensor.type_as,
+    early_stop_func=same_dtype,
+    extra_check=sharded_type_as_check,
+    customized_func=sharded_type_as,
+)
+
+
+def sharded_deepcopy(args, kwargs, pg):
+    # NOTE: we directly implement deepcopy magic method
+    # instead of using the default tensor.__deepcopy__
+    # and implement clone(). This is because the default
+    # tensor deepcopy copies every attribute, but the
+    # process_group in ShardedTensor cannot be deep copied.
+    self_st = args[0]
+    new_local_shards = copy.deepcopy(self_st.local_shards())
+    new_metadata = copy.deepcopy(self_st.metadata())
+    return new_local_shards, new_metadata
+
+
+_register_sharded_op_on_local_shards(
+    torch.Tensor.__deepcopy__,
+    customized_func=sharded_deepcopy,
+)
+
+
+@_sharded_op_impl(torch.Tensor.copy_)
+def sharded_inplace_copy(types, args, kwargs, pg):
+    # NOTE: inplace op don't need to rewrap
+    kwargs = {} if kwargs is None else kwargs
+    self_st = args[0]
+    new_st = args[1]
+    nonblocking = kwargs.get("non_blocking", False)
+    for local_shard, new_shard in zip(self_st.local_shards(), new_st.local_shards()):
+        if local_shard.metadata != new_shard.metadata:
+            raise RuntimeError(
+                "inplace copy can only happen between two ShardedTensor with same metadata!"
+            )
+    for local_shard, new_shard in zip(self_st.local_shards(), new_st.local_shards()):
+        local_shard.tensor.copy_(new_shard.tensor, nonblocking)
+
+    return self_st
+
+
+def sharded_clone(args, kwargs, pg):
+    self_st = args[0]
+    desire_memory_format = kwargs.get("memory_format", None)
+    if desire_memory_format and desire_memory_format != torch.preserve_format:
+        raise RuntimeError("Only support torch.preserve_format for ShardedTensor!")
+    cloned_local_shards = [
+        Shard(
+            local_shard.tensor.clone(memory_format=desire_memory_format),
+            metadata=copy.deepcopy(local_shard.metadata),
+        )
+        for local_shard in self_st.local_shards()
+    ]
+    new_metadata = copy.deepcopy(self_st.metadata())
+    return cloned_local_shards, new_metadata
+
+
+_register_sharded_op_on_local_shards(
+    torch.Tensor.clone,
+    customized_func=sharded_clone,
+)
+
+
+def sharded_detach(args, kwargs, pg):
+    self_st = args[0]
+    detached_local_shards = [
+        Shard(
+            local_shard.tensor.detach(),
+            metadata=copy.deepcopy(local_shard.metadata),
+        )
+        for local_shard in self_st.local_shards()
+    ]
+    new_metadata = copy.deepcopy(self_st.metadata())
+    new_metadata.tensor_properties.requires_grad = False
+    return detached_local_shards, new_metadata
+
+
+_register_sharded_op_on_local_shards(
+    torch.Tensor.detach,
+    customized_func=sharded_detach,
+)
+
+
+@_sharded_op_impl(torch.Tensor.requires_grad_)
+def tensor_requires_grad_set(types, args=(), kwargs=None, pg=None):
+    self_st = args[0]
+    # Validate types
+    if not isinstance(self_st, ShardedTensor):
+        raise TypeError("input needs to be a ShardedTensor")
+
+    if kwargs is None:
+        kwargs = {}
+
+    requires_grad = args[1] if len(args) > 1 else kwargs.get("requires_grad", True)
+    if requires_grad == self_st.requires_grad:
+        return self_st
+
+    for local_shard in self_st.local_shards():
+        local_shard.tensor.requires_grad_(requires_grad)
+
+        # update the wrapper class property
+    with torch._C.DisableTorchFunctionSubclass():
+        self_st.requires_grad_(requires_grad)
+    # update the metadata in the meanwhile
+    self_st._metadata.tensor_properties.requires_grad = requires_grad
+    return self_st

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/api.py

@@ -0,0 +1,1253 @@
+from __future__ import annotations  # type: ignore[attr-defined]
+from dataclasses import dataclass
+from typing import (
+    Callable,
+    Dict,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    cast,
+)
+import copy
+import warnings
+from functools import reduce
+import weakref
+
+import threading
+import torch
+import torch.distributed as dist
+from torch.distributed import rpc
+from torch.distributed import distributed_c10d
+from torch.distributed._shard.metadata import ShardMetadata
+import torch.distributed._shard.sharding_spec as shard_spec
+from torch.distributed._shard.sharding_spec.api import (
+    _dispatch_custom_op,
+    _has_custom_op,
+)
+from torch.distributed._shard.sharding_spec._internals import (
+    check_tensor,
+    validate_non_overlapping_shards_metadata,
+)
+from torch.distributed._shard._utils import (
+    DEPRECATE_MSG,
+)
+
+from .metadata import TensorProperties, ShardedTensorMetadata
+from .shard import Shard
+from .reshard import reshuffle_local_shard, reshard_local_shard
+from .utils import (
+    _flatten_tensor_size,
+    _parse_and_validate_remote_device,
+    _validate_output_tensor_for_gather,
+    build_metadata_from_local_shards,
+    build_global_metadata
+)
+from torch.distributed.remote_device import _remote_device
+from torch.utils import _pytree as pytree
+import operator
+
+# Tracking for sharded tensor objects.
+_sharded_tensor_lock = threading.Lock()
+_sharded_tensor_current_id = 0
+_sharded_tensor_map: Dict[int, weakref.ReferenceType[ShardedTensor]] = {}
+
+# Default sharded ops
+_SHARDED_OPS: Dict[Callable, Callable] = {}
+
+# Customized user ops
+_CUSTOM_SHARDED_OPS: Dict[Callable, Callable] = {}
+
+def _register_remote_shards(sharded_tensor_id: int, rrefs: List[rpc.RRef[Shard]], rpc_rank: int):
+    with _sharded_tensor_lock:
+        if sharded_tensor_id not in _sharded_tensor_map:
+            raise RuntimeError(
+                f'Could not find sharded_tensor_id: {sharded_tensor_id} in map: {_sharded_tensor_map.keys()}')
+
+        sharded_tensor = _sharded_tensor_map[sharded_tensor_id]()
+        if sharded_tensor is None:
+            raise RuntimeError('ShardedTensor weakref has been deallocated')
+        else:
+            sharded_tensor._register_remote_shards(rrefs, rpc_rank)
+
+class ShardedTensorBase(torch.Tensor):
+    _sharding_spec: shard_spec.ShardingSpec
+    _metadata: ShardedTensorMetadata
+    _local_shards: List[Shard]
+
+    def __new__(cls, sharding_spec: shard_spec.ShardingSpec, *size, **kwargs):
+        # Use __new__ to construct a wrapper tensor, for recording tensor
+        # properties and logging purposes.
+        torch._C._log_api_usage_once("torch.distributed._shard.sharded_tensor")
+
+        # check sharding spec and build sharded tensor metadata
+        if not isinstance(sharding_spec, shard_spec.ShardingSpec):
+            raise ValueError(f"Expecting ShardingSpec but got: {type(sharding_spec)}")
+
+        sizes = _flatten_tensor_size(size)
+        dtype = kwargs["dtype"]
+        layout = kwargs["layout"]
+        pin_memory = kwargs["pin_memory"]
+        requires_grad = kwargs["requires_grad"]
+
+        if dtype is None:
+            dtype = torch.get_default_dtype()
+
+        tensor_properties = TensorProperties(
+            dtype, layout, requires_grad, pin_memory=pin_memory
+        )
+        sharded_tensor_metadata = sharding_spec.build_metadata(
+            sizes, tensor_properties=tensor_properties
+        )
+
+        r = torch.Tensor._make_wrapper_subclass(  # type: ignore[attr-defined]
+            cls,
+            sizes,
+            dtype=dtype,
+            layout=layout,
+            pin_memory=pin_memory,
+            requires_grad=requires_grad,
+        )
+        # set sharding spec
+        r._sharding_spec = sharding_spec
+        # set metadata
+        r._metadata = sharded_tensor_metadata
+        # set local shards
+        r._local_shards = []
+        return r
+
+    def metadata(self) -> ShardedTensorMetadata:
+        """
+        Returns a :class:`ShardedTensorMetadata` object corresponding to the
+        metadata for the entire tensor.
+        """
+        return self._metadata
+
+    def local_shards(self) -> List[Shard]:
+        """
+        Returns a list of :class:`Shard' corresponding to the
+        local shards for this rank. Returns an empty list if the current rank
+        does not host any shards for this Tensor.
+        """
+        return self._local_shards
+
+    @classmethod
+    def _init_from_local_shards_and_global_metadata(
+        cls,
+        local_shards: List[Shard],
+        sharded_tensor_metadata: ShardedTensorMetadata,
+        sharding_spec=None,
+    ) -> ShardedTensorBase:
+        """
+        Initialize a ShardedTensorBase with local shards and a global
+        ShardedTensorMetadata built on each rank.
+        Warning: This API is experimental and subject to change. It does
+                 not do cross rank validations, and fully rely on the user
+                 for the correctness of sharded_tensor_metadata on each rank
+        """
+        shards_metadata = sharded_tensor_metadata.shards_metadata
+        tensor_properties = sharded_tensor_metadata.tensor_properties
+
+        if len(shards_metadata) == 0:
+            raise ValueError("shards_metadata must not be empty!")
+
+        if tensor_properties.layout != torch.strided:
+            raise ValueError("Only torch.strided layout is currently supported")
+
+        if sharding_spec is None:
+            spec = shard_spec._infer_sharding_spec_from_shards_metadata(shards_metadata)
+        else:
+            spec = sharding_spec
+
+        sharded_tensor_base = ShardedTensorBase.__new__(
+            ShardedTensor,
+            spec,
+            sharded_tensor_metadata.size,
+            dtype=tensor_properties.dtype,
+            layout=tensor_properties.layout,
+            pin_memory=tensor_properties.pin_memory,
+            requires_grad=tensor_properties.requires_grad,
+        )
+
+        # check if shards_metadata have overlap shards
+        validate_non_overlapping_shards_metadata(shards_metadata)
+
+        # check if the shards_metadata is compatible with overall size of the sharded tensor.
+        check_tensor(shards_metadata, list(sharded_tensor_metadata.size))
+
+        # done validation, add local_shards
+        sharded_tensor_base._local_shards = local_shards
+        return sharded_tensor_base
+
+    @classmethod
+    def __torch_dispatch__(cls, func, types, args=(), kwargs=None):
+        raise RuntimeError(
+            f"A {cls.__name__} object is being used from c++ while calling {func.__module__}.{func.__name__} "
+            "but the there is no custom __torch_dispatch__ implementation for it."
+        )
+
+class ShardedTensor(ShardedTensorBase):
+    """
+    ShardedTensor is an torch.Tensor subclass to represent Tensors that are sharded
+    across multiple devices and multiple processes.
+
+    ShardedTensor is initialized in an SPMD like fashion where each rank
+    initializes the ShardedTensor. The ShardedTensor object on each rank
+    then only stores the local shard for the Tensor and provides global
+    metadata for all the shards.
+
+    ShardedTensor doesn't provide any Tensor like operations but is a wrapper
+    providing the Tensor representing the local shard and the global metadata.
+    Using these, users can build their custom distributed._sharded computations
+    on top of this primitive. The local shards are all initialized using the
+    create_op specified by tensor_init_params.create_op, e.g., torch.ones, or
+    torch.empty
+
+    Args:
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The specification
+            describing how to shard the Tensor.
+        size (int...): a sequence of integers defining the shape of the output
+            tensor. Can be a variable number of arguments or a collection like a list or tuple.
+
+    Keyword args:
+        dtype (:class:`torch.dtype`, optional): the desired data type of returned tensor.
+                Default: if ``None``, uses a global default (see :func:`torch.set_default_dtype`).
+        layout (:class:`torch.layout`, optional): the desired layout of returned Tensor.
+            Default: ``torch.strided``.
+        requires_grad (bool, optional): If autograd should record operations on the
+            returned tensor. Default: ``False``.
+        pin_memory (bool, optional): If set, returned tensor would be allocated in
+            the pinned memory. Works only for CPU tensors. Default: ``False``.
+        memory_format (:class:`torch.memory_format`, optional): the desired memory format of
+            returned Tensor. Default: ``torch.contiguous_format``.
+        init_rrefs (bool, optional): Whether or not to initialize
+            :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+            Need to initialize the RPC Framework if specified as ``True``.
+            Default: ``False``.
+
+    .. note:: ShardedTensor uses collectives to do various operations, i.e. it
+        uses all_gather to do cross rank validations. For NCCL-based process
+        groups, internal tensor representations of objects must be moved to the
+        GPU device before communication takes place. In this case, the device
+        used is given by ``torch.cuda.current_device()`` and it is the user's
+        responsibility to ensure that this is set so that each rank has an
+        individual GPU, via ``torch.cuda.set_device()``
+
+    """
+    def __new__(cls, sharding_spec: shard_spec.ShardingSpec, *size, **kwargs):
+        self = super().__new__(cls, sharding_spec, *size, **kwargs)
+        return self
+
+    def __init__(
+        self,
+        sharding_spec: shard_spec.ShardingSpec,
+        *size,
+        dtype=None,
+        layout=torch.strided,
+        requires_grad=False,
+        pin_memory=False,
+        memory_format=torch.contiguous_format,
+        process_group=None,
+        init_rrefs=False,
+    ):
+        # prepare initialization, initialize fields like
+        # _process_group, _local_shards, etc.
+        self._prepare_init(process_group=process_group, init_rrefs=init_rrefs)
+
+        if layout != torch.strided:
+            raise ValueError('Only torch.strided layout is currently supported')
+
+        if memory_format != torch.contiguous_format:
+            raise ValueError('Only torch.contiguous_format memory_format is currently supported')
+
+        self._metadata.tensor_properties.memory_format = memory_format
+
+        current_rank = dist.get_rank(self._process_group)
+
+        for shard_metadata in self._metadata.shards_metadata:
+            rank, device = _parse_and_validate_remote_device(self._process_group, shard_metadata.placement)
+            if rank == current_rank:
+                local_tensor = _create_tensor_from_params(
+                    shard_metadata.shard_sizes,
+                    local_device=device,
+                    tensor_properties=self._metadata.tensor_properties
+                )
+                self._local_shards.append(Shard(local_tensor, shard_metadata))
+
+        # do post initialization (i.e. register sharded_tensor_id, initialize_rpc)
+        self._post_init()
+
+    def _prepare_init(self, process_group=None, init_rrefs=False):
+        self._init_rrefs = init_rrefs
+        self._sharded_tensor_id = None
+
+        self._process_group = (
+            process_group
+            if process_group is not None
+            else distributed_c10d._get_default_group()
+        )
+
+        self._remote_shards: Dict[int, List[rpc.RRef[Shard]]] = {}
+
+    def _post_init(self):
+        # Initialize RPC if available.
+        if self._init_rrefs:
+            with _sharded_tensor_lock:
+                global _sharded_tensor_current_id, _sharded_tensor_map
+                self._sharded_tensor_id = _sharded_tensor_current_id
+                _sharded_tensor_map[self._sharded_tensor_id] = weakref.ref(self)
+                _sharded_tensor_current_id += 1
+
+            if not rpc._is_current_rpc_agent_set():
+                raise RuntimeError(
+                    'RPC Framework needs to be initialized using'
+                    ' torch.distributed.rpc.init_rpc if init_rrefs is set to True')
+            self._init_rpc()
+
+    def __del__(self):
+        # Clean up the global map.
+        with _sharded_tensor_lock:
+            global _sharded_tensor_current_id, _sharded_tensor_map
+            if (
+                hasattr(self, "_sharded_tensor_id")
+                and self._sharded_tensor_id in _sharded_tensor_map
+            ):
+                _sharded_tensor_map.pop(self._sharded_tensor_id)  # type: ignore[call-overload]
+
+    def _init_rpc(self):
+        # Validate PG and RPC ranks match.
+        pg_rank = dist.get_rank()
+        rpc_rank = rpc.get_worker_info().id
+        if pg_rank != rpc_rank:
+            raise ValueError(
+                f'Default ProcessGroup and RPC ranks must be '
+                f'the same for ShardedTensor, found process group rank: '
+                f'{pg_rank} and RPC rank: {rpc_rank}'
+            )
+
+        self._remote_shards = {}
+
+        # Gather all the sharded tensor ids.
+        worker_infos = rpc._get_current_rpc_agent().get_worker_infos()
+        rank_to_name = {}
+        name_to_rank = {}
+
+        for worker_info in worker_infos:
+            rank_to_name[worker_info.id] = worker_info.name
+            name_to_rank[worker_info.name] = worker_info.id
+
+        all_tensor_ids = rpc.api._all_gather(self._sharded_tensor_id)
+
+        # Share the local shards to the entire world.
+        futs = []
+        rpc_rank = rpc.get_worker_info().id
+        for rank in range(dist.get_world_size()):
+            # Skip self.
+            if rank == dist.get_rank():
+                continue
+
+            if len(self.local_shards()) != 0:
+                rrefs: List[rpc.RRef[Shard]] = [rpc.RRef(shard) for shard in self.local_shards()]
+                fut = rpc.rpc_async(
+                    rank,
+                    _register_remote_shards,
+                    args=(all_tensor_ids[rank_to_name[rank]], rrefs, rpc_rank))
+                futs.append(fut)
+
+        torch.futures.wait_all(futs)
+
+        # Barrier for all RPCs to finish on all ranks.
+        rpc.api._all_gather(None)
+
+    def _get_preferred_device(self) -> torch.device:
+        """
+        Return the preferred device to be used when creating tensors for collectives.
+        This method takes into account the associated process group
+        """
+        if dist.get_backend(self._process_group) == dist.Backend.NCCL:
+            return torch.device(torch.cuda.current_device())
+        return torch.device("cpu")
+
+    def gather(  # type: ignore[override]
+        self,
+        dst: int = 0,
+        out: Optional[torch.Tensor] = None,
+        enforce_dtype: bool = False,
+        dtype: Optional[torch.dtype] = None,
+    ) -> None:
+        """
+        Creates a full :class:`Tensor` on rank ``dst`` by gathering all shards of the
+        sharded tensor.
+
+        The API needs to be called on all ranks in SPMD fashion. All ranks should have
+        the same ``dst``. ``out`` should be a tensor of the same size as the overall
+        size of the sharded tensor on ``dst`` and ``None`` on all other ranks.
+
+        Args:
+            dst(int): The rank where full tensor is constructed.
+                Default: 0
+            out (:class `torch.Tensor`, optional): The output full tensor.
+                Must to be provided ONLY on ``dst`` rank.
+                Default: ``None``
+            enforce_dtype (bool): Deprecated, please use dtype instead.  Force the
+                gathered tensors to be the same type as input and output.
+            dtype (torch.dtype): Force the gathered tensors to be this dtype.
+                Default: ``None``
+        """
+        def shard_size(shard_md):
+            return reduce(operator.mul, shard_md.shard_sizes)  # type: ignore[attr-defined]
+
+        if enforce_dtype:
+            warnings.warn("enforce_dtype is deprecated.  Please use dtype instead.")
+
+        rank = dist.get_rank(self._process_group)
+        full_size = self.metadata().size
+        _validate_output_tensor_for_gather(rank, dst, full_size, out)
+
+        local_shards = self.local_shards()
+        world_size = dist.get_world_size(self._process_group)
+        rank_sizes = [0 for _ in range(world_size)]
+        max_rank_size = 0
+        shard_placement: Dict[ShardMetadata, Tuple[int, int]] = {}
+        # collect sizes
+        for shard_md in self.metadata().shards_metadata:
+            shard_rank = cast(_remote_device, shard_md.placement).rank()
+            assert shard_rank is not None
+
+            shard_placement[shard_md] = (shard_rank, rank_sizes[shard_rank])
+            rank_sizes[shard_rank] += shard_size(shard_md)
+            max_rank_size = max(max_rank_size, rank_sizes[shard_rank])
+
+        gather_list: Optional[List[torch.Tensor]]
+        if rank == dst:
+            assert out is not None
+            if enforce_dtype:
+                # enforce_dtype is deprecated.  Do it for backward compatibility.
+                dtype = out.dtype
+            # TODO make it as a view of out tensor
+            gather_list = [torch.empty((max_rank_size,), device=out.device, dtype=dtype) for _ in range(world_size)]
+        else:
+            gather_list = None
+
+        with torch.no_grad():
+            if enforce_dtype and len(local_shards) > 0:
+                # enforce_dtype is deprecated.  Do it for backward compatibility.
+                dtype = local_shards[0].tensor.dtype
+            data = torch.empty(max_rank_size, device=self._get_preferred_device(), dtype=dtype)
+
+            for shard in local_shards:
+                src = shard.tensor.flatten()
+                if src.nelement() == 0 :
+                    warnings.warn("Gathering a tensor with zero elements on rank " + str(rank))
+                    return
+                shard_offset = shard_placement[shard.metadata][1]
+                data[shard_offset: shard_offset + src.numel()].copy_(src)
+
+        dist.gather(
+            tensor=data,
+            gather_list=gather_list,
+            dst=dst,
+            group=self._process_group,
+        )
+        if rank != dst:
+            return
+        # In _validate_output_tensor_for_gather, we raise if out == None and rank == dst
+        out = cast(torch.Tensor, out)
+        assert gather_list is not None
+
+        full_size = self.metadata().size
+        dims = len(full_size)
+        for shard_md in self.metadata().shards_metadata:
+            rank, rank_offset = shard_placement[shard_md]
+            tensor = gather_list[rank]
+            tensor = tensor[rank_offset : rank_offset + shard_size(shard_md)]
+            tensor = tensor.view(shard_md.shard_sizes)
+
+            out_narrow_view = out
+            for dim in range(dims):
+                out_narrow_view = out_narrow_view.narrow(
+                    dim,
+                    shard_md.shard_offsets[dim],
+                    shard_md.shard_sizes[dim],
+                )
+
+            out_narrow_view.copy_(tensor)
+
+    def cpu(
+        self,
+        memory_format=torch.preserve_format,
+        process_group=None
+    ) -> ShardedTensor:
+        """
+        Returns a copy of this object in CPU memory.
+
+        If this ShardedTensor is already on CPU memory, then no copy is
+        performed and original object is returned.
+
+        .. note:: When moving a ShardedTensor from GPU to CPU, the ShardedTensor might
+            need to be managed by a different type of ProcessGroup(i.e. ProcessGroupGloo),
+            it is the user's responsiblity to explicitly pass in a new process_group that
+            is compatible with CPU.
+        """
+        # TODO: make this a __torch_function__ op once ShardedTensor becomes a
+        # torch.Tensor subclass, see https://github.com/pytorch/pytorch/issues/75402
+        if memory_format != torch.preserve_format and \
+                memory_format != torch.contiguous_format:
+            raise RuntimeError("Only `torch.contiguous_format` or "
+                               "`torch.preserve_format` is supported!")
+        all_on_cpu = True
+        for meta in self.metadata().shards_metadata:
+            all_on_cpu &= (meta.placement.device().type == "cpu")  # type: ignore[union-attr]
+
+        # if every shard is already on CPU, return the original object
+        if all_on_cpu:
+            return self
+
+        # if not, returns a copy of this object on CPU
+        list_shards: List[Shard] = []
+        # move all local shards to cpu, and change metadata
+        for shard in self._local_shards:
+            cpu_tensor = shard.tensor.cpu(memory_format=memory_format)  # type: ignore[call-arg]
+            metadata = copy.deepcopy(shard.metadata)
+            metadata.placement._device = torch.device("cpu")  # type: ignore[union-attr]
+            list_shards.append(
+                Shard(cpu_tensor, metadata)
+            )
+
+        st_meta = copy.deepcopy(self.metadata())
+        for meta in st_meta.shards_metadata:
+            if meta.placement.device().type != "cpu":  # type: ignore[union-attr]
+                meta.placement._device = torch.device("cpu")  # type: ignore[union-attr]
+
+        pg = self._process_group if process_group is None else process_group
+        st_cpu = ShardedTensor._init_from_local_shards_and_global_metadata(
+            list_shards,
+            sharded_tensor_metadata=st_meta,
+            process_group=pg,
+            init_rrefs=self._init_rrefs
+        )
+        return st_cpu
+
+    def cuda(
+        self,
+        device=None,
+        non_blocking=False,
+        memory_format=torch.preserve_format,
+        process_group=None
+    ) -> ShardedTensor:
+        """
+        Returns a copy of this object in CUDA memory, if the original ShardedTensor
+        is on CPU, we will move the local shard to the current GPU device of each
+        process in a SPMD fashion.
+        If this ShardedTensor is already on CUDA memory and local shards on each rank are
+        already on current device, we still returns a new ShardedTensor object with new
+        metadata, but no underlying data movements are performed.
+        .. note:: When moving a ShardedTensor from CPU to GPU, the ShardedTensor might
+            need to be managed by a different type of ProcessGroup(i.e. ProcessGroupNCCL),
+            it is the user's responsiblity to explicitly pass in a new process_group that
+            is compatible with GPU.
+        """
+        if memory_format != torch.preserve_format and \
+                memory_format != torch.contiguous_format:
+            raise RuntimeError("Only `torch.contiguous_format` or "
+                               "`torch.preserve_format` is supported!")
+
+        if device is not None:
+            device = torch.device(device) if isinstance(device, str) else device
+            assert isinstance(device, torch.device) and device.index == torch.cuda.current_device(), \
+                '''Only device without device id (e.g. "cpu" or "cuda") is expected for ShardedTensor!'''
+
+        current_device = torch.device(torch.cuda.current_device())
+        # returns a copy of ShardedTensor on CUDA current device
+        list_shards: List[Shard] = []
+        # move all local shards to current device, and change metadata
+        # if local shards already on the current device, there's no
+        # real data movement, only the metadata are copied.
+        for shard in self._local_shards:
+            cuda_tensor = shard.tensor.cuda(
+                device=current_device,
+                non_blocking=non_blocking,
+                memory_format=memory_format
+            )  # type: ignore[call-arg]
+            metadata = copy.deepcopy(shard.metadata)
+            metadata.placement._device = current_device  # type: ignore[union-attr]
+
+            list_shards.append(
+                Shard(cuda_tensor, metadata)
+            )
+
+        st_meta = copy.deepcopy(self.metadata())
+        for meta in st_meta.shards_metadata:
+            if meta.placement.device().type != "cuda":  # type: ignore[union-attr]
+                meta.placement._device = current_device  # type: ignore[union-attr]
+
+        pg = self._process_group if process_group is None else process_group
+        # we need to use `init_from_local_shards` to communicate between ranks
+        # and update the sharding spec/shards metadata.
+        st_cuda = ShardedTensor._init_from_local_shards_and_global_metadata(
+            list_shards,
+            sharded_tensor_metadata=st_meta,
+            process_group=pg,
+            init_rrefs=self._init_rrefs
+        )
+        return st_cuda
+
+    def to(self, *args, **kwargs) -> ShardedTensor:
+        current_device: torch.device
+        if self._local_shards:
+            current_device = self._local_shards[0].tensor.device
+        elif self._process_group._get_backend_name() == "gloo":
+            current_device = torch.device("cpu")
+        else:
+            current_device = torch.device(torch.cuda.current_device())
+        current_dtype = self.dtype
+        device_to = current_device
+        dtype_to = current_dtype
+        if len(args) == 1:
+            if isinstance(args[0], torch.dtype):
+                dtype_to = args[0]
+            elif isinstance(args[0], torch.device):
+                device_to = args[0]
+            elif isinstance(args[0], (str, int)):
+                device_to = torch.device(args[0])
+            elif isinstance(args[0], torch.Tensor):
+                dtype_to = args[0].dtype
+                device_to = args[0].device
+            else:
+                raise RuntimeError(f"ShardedTensor.to() have wrong arguments: {args}")
+        elif len(args) == 2:
+            device_to, dtype_to = args
+        else:
+            dtype_to = kwargs.get("dtype", current_dtype)
+            device_to = kwargs.get("device", current_device)
+
+        device_to = torch.device(device_to) if isinstance(device_to, (str, int)) else device_to
+
+        if device_to.type == "cuda":
+            # if device_to set to cuda, set to current device even
+            # if user specify the device index.
+            current_idx = torch.cuda.current_device()
+            if device_to.index != current_idx:
+                warnings.warn("ShardedTensor.to only move tensor to its current device"
+                              "If you want to put to different device, use `reshard` instead.")
+            device_to = torch.device(current_idx)
+
+        copy_tensor = kwargs.get("copy", False)
+        non_blocking = kwargs.get("non_blocking", False)
+        memory_format = kwargs.get("memory_format", torch.preserve_format)
+        process_group = kwargs.get("process_group", None)
+
+        if not copy_tensor and dtype_to == current_dtype and device_to == current_device:
+            # already have correct dtype and device, return itself
+            return self
+
+        # returns a copy of ShardedTensor on CUDA current device
+        list_shards: List[Shard] = []
+
+        for shard in self._local_shards:
+            new_tensor = shard.tensor.to(  # type: ignore[call-overload]
+                device=device_to,
+                dtype=dtype_to,
+                non_blocking=non_blocking,
+                copy=copy_tensor,
+                memory_format=memory_format
+            )
+            metadata = copy.deepcopy(shard.metadata)
+            if metadata.placement is not None:
+                metadata.placement._device = device_to
+            list_shards.append(Shard(new_tensor, metadata))
+
+        # update metadata
+        st_meta = copy.deepcopy(self.metadata())
+        st_meta.tensor_properties.dtype = dtype_to
+        for meta in st_meta.shards_metadata:
+            meta.placement._device = device_to  # type: ignore[union-attr]
+
+        pg = self._process_group if process_group is None else process_group
+        # we need to use `init_from_local_shards` to communicate between ranks
+        # and update the sharding spec/shards metadata.
+        st_to = ShardedTensor._init_from_local_shards_and_global_metadata(
+            list_shards,
+            sharded_tensor_metadata=st_meta,
+            process_group=pg,
+            init_rrefs=self._init_rrefs
+        )
+        return st_to
+
+
+    @classmethod
+    def _init_from_local_shards(
+        cls,
+        local_shards: List[Shard],
+        *global_size,
+        process_group=None,
+        init_rrefs=False,
+    ):
+        # STEP 1: Validate the Shardmetadatas locally
+        process_group = (
+            process_group
+            if process_group is not None
+            else distributed_c10d._get_default_group()
+        )
+        current_rank = dist.get_rank(process_group)
+        world_size = dist.get_world_size(process_group)
+
+        local_sharded_tensor_metadata: Optional[ShardedTensorMetadata] = None
+        global_tensor_size = _flatten_tensor_size(global_size)
+
+        if len(local_shards) > 0:
+            local_sharded_tensor_metadata = \
+                build_metadata_from_local_shards(local_shards, global_tensor_size, current_rank, process_group)
+
+        # STEP 2. Validate metadata across ranks, and build a global sharded tensor
+        # metadata by gathering local ShardedTensorMetadata
+        gathered_metadatas: List[Optional[ShardedTensorMetadata]] = []
+        if world_size > 1:
+            gathered_metadatas = [None for _ in range(world_size)]
+
+            dist.all_gather_object(
+                gathered_metadatas,
+                local_sharded_tensor_metadata,
+                group=process_group
+            )
+        else:
+            gathered_metadatas = [local_sharded_tensor_metadata]
+
+        global_sharded_tensor_metadata = build_global_metadata(gathered_metadatas)
+        tensor_properties = global_sharded_tensor_metadata.tensor_properties
+
+        # STEP 3: Validation done, create the actual ShardedTensor and populate fields
+        # prepare initialization
+        spec = shard_spec._infer_sharding_spec_from_shards_metadata(
+            global_sharded_tensor_metadata.shards_metadata
+        )
+        sharded_tensor = cls.__new__(cls,
+                                     spec,
+                                     global_sharded_tensor_metadata.size,
+                                     dtype=tensor_properties.dtype,
+                                     layout=tensor_properties.layout,
+                                     pin_memory=tensor_properties.pin_memory,
+                                     requires_grad=tensor_properties.requires_grad)
+        sharded_tensor._prepare_init(process_group=process_group, init_rrefs=init_rrefs)
+
+        # attach local_shards to the ShardedTensor created
+        sharded_tensor._local_shards = local_shards
+
+        # run post initialization, i.e. map registration, rpc initialization
+        sharded_tensor._post_init()
+        return sharded_tensor
+
+    @classmethod
+    def _init_from_local_tensor(
+        cls,
+        local_tensor: torch.Tensor,
+        sharding_spec: shard_spec.ShardingSpec,
+        *global_size: Sequence[int],
+        process_group: Optional[dist.ProcessGroup] = None,
+        init_rrefs=False,
+    ) -> ShardedTensor:
+        """
+        Initialize a ShardedTensor given only one local tensor, global sharded tensor
+        size and sharding spec on each rank.
+
+        Args:
+            local_tensor (Tensor): Single tensor of local shard stored in each rank.
+            sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`):
+                The specification describing how to shard the Tensor.
+            global_size (Sequence[int]): Size of the sharded tensor.
+            process_group (ProcessGroup, optional): The process group to aggregate on.
+                Default: None
+            init_rrefs (bool, optional): Whether or not to initialize
+                :class:`torch.distributed.rpc.RRef`s pointing to remote shards.
+                Need to initialize the RPC Framework if specified as ``True``.
+                Default: ``False``.
+
+        Returns:
+            A :class:`ShardedTensor` sharded based on the given sharding_spec with local
+                tensor stored in the current rank.
+
+        Examples:
+            >>> # xdoctest: +SKIP
+            >>> # All tensors below are of torch.int64 type.
+            >>> # We have 2 process groups, 2 ranks.
+            >>> tensor = torch.arange(2, dtype=torch.int64) + 1 + 2 * rank
+            >>> local_tensor = torch.unsqueeze(torch.cat([tensor, tensor + 2]))
+            >>> local_tensor
+            tensor([[1, 2, 3, 4]]) # Rank 0
+            tensor([[3, 4, 5, 6]]) # Rank 1
+            >>> sharding_dim = 0
+            >>> sharding_spec = ChunkShardingSpec(
+                    dim=sharding_dim,
+                    placements=[
+                        "rank:0/cuda:0",
+                        "rank:1/cuda:1",
+                    ],
+                )
+            >>> st = ShardedTensor._init_from_local_tensor(local_tensor, sharding_spec, [2, 4])
+            >>> st
+            ShardedTensor(
+                ShardedTensorMetadata(
+                    shards_metadata=[
+                        ShardMetadata(shard_offsets=[0, 0], shard_sizes=[1, 4], placement=rank:0/cuda:0),
+                        ShardMetadata(shard_offsets=[1, 0], shard_sizes=[1, 4], placement=rank:1/cuda:1),
+                    ],
+                    size=torch.Size([2, 4])
+            )
+            >>> st.local_tensor()
+            tensor([1, 2, 3, 4]) # Rank 0
+            tensor([3, 4, 5, 6]) # Rank 1
+
+        Warning: This API is experimental and subject to change. It lacks of a fully across
+                 rank validations, and we only validate the local shard on the current rank.
+                 We fully rely on the user to ensure local tensor is sharded based on the
+                 sharding spec.
+        """
+        warnings.warn(DEPRECATE_MSG)
+
+        if not local_tensor.is_contiguous():
+            raise ValueError('local_tensor is not a contiguous Tensor.')
+
+        global_tensor_size = _flatten_tensor_size(global_size)
+        tensor_properties = TensorProperties(
+            dtype=local_tensor.dtype,
+            layout=local_tensor.layout,
+            requires_grad=local_tensor.requires_grad,
+            memory_format=torch.contiguous_format,
+            pin_memory=local_tensor.is_pinned())
+        sharded_tensor_metadata = sharding_spec.build_metadata(
+            global_tensor_size,
+            tensor_properties
+        )
+
+        process_group = (
+            process_group
+            if process_group is not None
+            else distributed_c10d._get_default_group()
+        )
+        current_rank = dist.get_rank(process_group)
+
+        local_shards: List[Shard] = []
+        for shard_metadata in sharded_tensor_metadata.shards_metadata:
+            rank, device = _parse_and_validate_remote_device(process_group, shard_metadata.placement)
+            if rank == current_rank:
+                local_shards.append(Shard(local_tensor, shard_metadata))
+
+        # TODO: figure out what the API should behave when some rank have no shard
+        # see https://github.com/pytorch/pytorch/issues/7313
+        return ShardedTensor._init_from_local_shards_and_global_metadata(
+            local_shards,
+            sharded_tensor_metadata,
+            process_group=process_group,
+            init_rrefs=init_rrefs,
+            sharding_spec=sharding_spec,
+        )
+
+    @classmethod
+    def _init_from_local_shards_and_global_metadata(  # type: ignore[override]
+        cls,
+        local_shards: List[Shard],
+        sharded_tensor_metadata: ShardedTensorMetadata,
+        process_group=None,
+        init_rrefs=False,
+        sharding_spec=None,
+    ) -> ShardedTensor:
+        """
+        Initialize a ShardedTensor with local shards and a global
+        ShardedTensorMetadata built on each rank.
+
+        Warning: This API is experimental and subject to change. It does
+                 not do cross rank validations, and fully rely on the user
+                 for the correctness of sharded_tensor_metadata on each rank
+        """
+        process_group = (
+            process_group
+            if process_group is not None
+            else distributed_c10d._get_default_group()
+        )
+        current_rank = dist.get_rank(process_group)
+
+        shards_metadata = sharded_tensor_metadata.shards_metadata
+
+        local_shard_metadatas = []
+
+        # collect local shard metadatas from the global sharded_tensor_metadata
+        for shard_metadata in shards_metadata:  # type: ignore[attr-defined]
+            rank, local_device = _parse_and_validate_remote_device(process_group, shard_metadata.placement)
+
+            if current_rank == rank:
+                local_shard_metadatas.append(shard_metadata)
+
+        if len(local_shards) != len(local_shard_metadatas):
+            raise RuntimeError(
+                f'Number of local shards ({len(local_shards)}) does not match number of local '
+                f'shards metadata in sharded_tensor_metadata ({len(local_shard_metadatas)}) '
+                f'on rank ({current_rank}) '
+            )
+
+        shards_metadata = sharded_tensor_metadata.shards_metadata
+        tensor_properties = sharded_tensor_metadata.tensor_properties
+
+        if len(shards_metadata) == 0:
+            raise ValueError("shards_metadata must not be empty!")
+
+        if tensor_properties.layout != torch.strided:
+            raise ValueError("Only torch.strided layout is currently supported")
+
+        if sharding_spec is None:
+            spec = shard_spec._infer_sharding_spec_from_shards_metadata(shards_metadata)
+        else:
+            spec = sharding_spec
+
+        sharded_tensor = ShardedTensor.__new__(
+            ShardedTensor,
+            spec,
+            sharded_tensor_metadata.size,
+            dtype=tensor_properties.dtype,
+            layout=tensor_properties.layout,
+            pin_memory=tensor_properties.pin_memory,
+            requires_grad=tensor_properties.requires_grad,
+        )
+
+        def _raise_if_mismatch(expected, actual, prop_name, rank, is_property=False):
+            tensor_property_or_metadata = (
+                "tensor property" if is_property else "local ShardMetadata"
+            )
+            if expected != actual:
+                raise ValueError(
+                    f"Local shards' tensor {prop_name} property is incompatible with "
+                    f"{tensor_property_or_metadata} on rank {rank}: "
+                    f"{tensor_property_or_metadata} {prop_name}={expected}, "
+                    f"local shard tensor {prop_name}={actual}."
+                )
+
+        for shard in local_shards:
+            shard_meta = shard.metadata
+            local_shard_tensor = shard.tensor
+            placement = shard_meta.placement
+            assert placement is not None, "Must specify placement for `Shard`!"
+            rank = placement.rank()
+            local_device = placement.device()
+
+            _raise_if_mismatch(
+                tensor_properties.layout,
+                local_shard_tensor.layout,
+                "layout",
+                rank,
+                True,
+            )
+            if not local_shard_tensor.is_contiguous():
+                raise ValueError(
+                    "Only torch.contiguous_format memory_format is currently supported"
+                )
+
+            _raise_if_mismatch(
+                shard_meta.shard_sizes,
+                list(local_shard_tensor.size()),
+                "size",
+                rank,
+            )
+            _raise_if_mismatch(
+                tensor_properties.pin_memory,
+                local_shard_tensor.is_pinned(),
+                "pin_memory",
+                rank,
+                True,
+            )
+            _raise_if_mismatch(local_device, local_shard_tensor.device, "device", rank)
+            _raise_if_mismatch(
+                tensor_properties.dtype,
+                local_shard_tensor.dtype,
+                "dtype",
+                rank,
+                True,
+            )
+            _raise_if_mismatch(
+                tensor_properties.requires_grad,
+                local_shard_tensor.requires_grad,
+                "requires_grad",
+                rank,
+                True,
+            )
+
+        # check if shards_metadata have overlap shards
+        validate_non_overlapping_shards_metadata(shards_metadata)
+
+        # check if the shards_metadata is compatible with overall size of the sharded tensor.
+        check_tensor(shards_metadata, list(sharded_tensor_metadata.size))
+
+        # done validation, add local_shards
+        sharded_tensor._local_shards = local_shards
+        sharded_tensor._prepare_init(process_group=process_group, init_rrefs=init_rrefs)
+
+        # run post initialization, i.e. map registration, rpc initialization
+        sharded_tensor._post_init()
+        return sharded_tensor
+
+    def sharding_spec(self) -> shard_spec.ShardingSpec:
+        """
+        Returns the ShardingSpec for the tensor.
+        """
+        return self._sharding_spec
+
+    def reshard(self, resharding_spec: shard_spec.ShardingSpec) -> ShardedTensor:
+        """
+        Reshard a sharded tensor given the ``resharding_spec``. For now, we only support
+        single local shard.
+
+        If ``resharding_spec`` is same as the original one, this becomes a no-op.
+        If only ``resharding_spec`` shares the same sharding dim with the original one,
+        we swap local shards directly.
+        For more generic cases, we merge different shards across different ranks and split
+        the local shards based on the ``resharding_spec`` via `all_to_all` collective API.
+
+        Args:
+            resharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The
+                specification describing how the tensor is sharded.
+
+        Returns:
+            A :class:`ShardedTensor` object whose local shards are resharded.
+
+        Examples:
+            >>> # xdoctest: +SKIP
+            >>> # We have 2 process groups, 2 ranks.
+            >>> tensor = torch.arange(4, dtype=torch.int64) + 1 + 2 * rank
+            >>> tensor = torch.stack([tensor, tensor])
+            >>> tensor
+            tensor([[1, 2, 3, 4], [1, 2, 3, 4]]) # Rank 0
+            tensor([[3, 4, 5, 6], [3, 4, 5, 6]]) # Rank 1
+            tensor([[5, 6, 7, 8], [5, 6, 7, 8]]) # Rank 2
+            tensor([[7, 8, 9, 10], [7, 8, 9, 10]]) # Rank 3
+            >>> sharding_dim = 0
+            >>> spec = ChunkShardingSpec(
+                    dim=sharding_dim,
+                    placements=[
+                        "rank:0/cuda:0",
+                        "rank:1/cuda:1",
+                        "rank:2/cuda:2",
+                        "rank:3/cuda:3",
+                    ],
+                )
+            >>> current_offsets = [0] * 2
+            >>> current_offsets[0] = rank * 2
+            >>> shard_metadata = ShardMetadata(
+                    shard_offsets=copy.deepcopy(current_offsets),
+                    shard_sizes=tensor.size(),
+                    placement=spec.placements[rank],
+                )
+            >>> local_shards = [
+                    Shard(
+                        tensor=tensor,
+                        metadata=shard_metadata,
+                    )
+                ]
+            >>> st = ShardedTensor._init_from_local_shards(local_shards, tensor.size())
+            >>> sharding_dim = 1
+            >>> resharding_spec = ChunkShardingSpec(
+                    dim=sharding_dim,
+                    placements=[
+                        "rank:0/cuda:0",
+                        "rank:1/cuda:1",
+                        "rank:2/cuda:2",
+                        "rank:3/cuda:3",
+                    ],
+                )
+            >>> st.reshard(resharding_spec)
+            >>> tensor = st.local_shards()[0].tensor
+            >>> tensor
+            tensor([[1], [1], [3], [3], [5], [5], [7], [7]]) # Rank 0
+            tensor([[2], [2], [4], [4], [6], [6], [8], [8]]) # Rank 1
+            tensor([[3], [3], [5], [5], [7], [7], [9], [9]]) # Rank 2
+            tensor([[4], [4], [6], [6], [8], [8], [10], [10]]) # Rank 3
+        """
+        warnings.warn(DEPRECATE_MSG)
+
+        if (
+            not isinstance(resharding_spec, shard_spec.ChunkShardingSpec) or
+            not isinstance(self._sharding_spec, shard_spec.ChunkShardingSpec)
+        ):
+            raise NotImplementedError("Only ChunkShardingSpec supported for reshard.")
+        if (len(self.local_shards()) != 1):
+            raise NotImplementedError("Only single local shard supported for reshard.")
+
+        if self._sharding_spec.dim == resharding_spec.dim:  # type: ignore[attr-defined]
+            if self._sharding_spec.placements == resharding_spec.placements:  # type: ignore[attr-defined]
+                return self
+            else:
+                local_shards, shards_metadata = reshuffle_local_shard(
+                    self.local_tensor(),
+                    self.size(),  # type: ignore[arg-type]
+                    self._sharding_spec,
+                    resharding_spec,
+                    self._process_group,
+                )
+        else:
+            local_shards, shards_metadata = reshard_local_shard(
+                self.local_tensor(),
+                self.size(),  # type: ignore[arg-type]
+                self._sharding_spec,
+                resharding_spec,
+                self._process_group,
+            )
+        self._local_shards = local_shards
+        self._metadata.shards_metadata = shards_metadata
+        self._sharding_spec = resharding_spec
+        return self
+
+    def local_tensor(self) -> torch.Tensor:
+        """
+        Return local tensor for a sharded_tensor. For now we only support single local shard.
+
+        Returns:
+            A :class:`torch.Tensor` of the local shard.
+        """
+        if len(self.local_shards()) != 1:
+            raise NotImplementedError("Only single local shard is supported.")
+        return self.local_shards()[0].tensor
+
+    @classmethod
+    def __torch_function__(cls, func, types, args=(), kwargs=None):
+        def dispatch(st: ShardedTensor, func: Callable):
+            # Dispatch to custom user provided op first if it exists.
+            if func in _CUSTOM_SHARDED_OPS:
+                return _CUSTOM_SHARDED_OPS[func](types, args, kwargs, st._process_group)
+
+            # Dispatch to custom sharding spec op if it has one.
+            if _has_custom_op(st._sharding_spec, func):
+                return _dispatch_custom_op(
+                    st._sharding_spec,
+                    func,
+                    types,
+                    args,
+                    kwargs,
+                    st._process_group
+                )
+
+            if func in _SHARDED_OPS:
+                return _SHARDED_OPS[func](types, args, kwargs, st._process_group)
+
+            raise RuntimeError(
+                f"torch function '{func.__name__}', with args: {args} and "
+                f"kwargs: {kwargs} not supported for ShardedTensor!")
+
+        warnings.warn(DEPRECATE_MSG)
+        # Find ShardedTensor instance to get process_group and sharding_spec.
+        st_instance = None
+
+        def find_sharded_tensor(e):
+            nonlocal st_instance
+            if st_instance is None and isinstance(e, ShardedTensor):
+                st_instance = e
+
+        pytree.tree_map_(find_sharded_tensor, args)
+        pytree.tree_map_(find_sharded_tensor, kwargs)
+
+        if st_instance is not None:
+            return dispatch(st_instance, func)
+
+        raise RuntimeError(
+            f"torch function '{func.__name__}', with args: {args} and "
+            f"kwargs: {kwargs} not supported for ShardedTensor!")
+
+    def is_pinned(self) -> bool:  # type: ignore[override]
+        """
+        Returns True if the sharded tensor (each local shard) resides in pinned memory.
+        """
+        return self._metadata.tensor_properties.pin_memory
+
+    def _register_remote_shards(self, remote_shards: List[rpc.RRef[Shard]], rpc_rank: int):
+        self._remote_shards[rpc_rank] = remote_shards
+
+    def remote_shards(self) -> Dict[int, List[rpc.RRef[Shard]]]:
+        """
+        Returns a Dict[int, RRef] with keys being the RPC rank and values
+        being RRefs to shards on that rank. Need to initialize the
+        RPC framework for this functionality.
+
+        Raises an exception if ShardedTensor was created with ``init_rrefs=False``
+        """
+        if not self._init_rrefs:
+            raise RuntimeError(
+                'ShardedTensor created with init_rrefs=False, no RRefs to remote shards available'
+            )
+        return self._remote_shards
+
+    def __hash__(self):
+        return id(self)
+
+    def __repr__(self):
+        return f'ShardedTensor({self._metadata})'
+
+    @dataclass
+    class ProcessGroupState:
+        """
+        State for ser-de of process group
+        """
+        local_rank: int
+        global_rank: int
+        local_world_size: int
+        global_world_size: int
+
+    def __getstate__(self):
+        pg_state = ShardedTensor.ProcessGroupState(
+            distributed_c10d.get_rank(self._process_group),
+            distributed_c10d.get_rank(),
+            distributed_c10d.get_world_size(self._process_group),
+            distributed_c10d.get_world_size(),
+        )
+
+        return self._local_shards, self._metadata, pg_state, self._sharding_spec, self._init_rrefs
+
+    def __setstate__(self, state):
+        self._sharded_tensor_id = None
+        if not distributed_c10d.is_initialized():
+            raise RuntimeError(
+                'Need to initialize default process group using '
+                '"init_process_group" before loading ShardedTensor')
+
+        self._local_shards, self._metadata, pg_state, self._sharding_spec, self._init_rrefs = state
+
+        # Setup process group
+        from torch.distributed._shard.api import _get_current_process_group
+        self._process_group = _get_current_process_group()
+
+        # Validate process group.
+        local_rank = distributed_c10d.get_rank(self._process_group)
+        if pg_state.local_rank != local_rank:
+            raise RuntimeError(
+                f'Local rank at save time was {pg_state.local_rank}, but at '
+                f'load time was {local_rank}')
+
+        global_rank = distributed_c10d.get_rank()
+        if pg_state.global_rank != global_rank:
+            raise RuntimeError(
+                f'Global rank at save time was {pg_state.global_rank}, but at '
+                f'load time was {global_rank}')
+
+        local_world_size = distributed_c10d.get_world_size(self._process_group)
+        if pg_state.local_world_size != local_world_size:
+            raise RuntimeError(
+                f'Local world size at save time was {pg_state.local_world_size}, '
+                f'but at load time was {local_world_size}')
+
+        global_world_size = distributed_c10d.get_world_size()
+        if pg_state.global_world_size != global_world_size:
+            raise RuntimeError(
+                f'Global world size at save time was {pg_state.global_world_size}, '
+                f'but at load time was {global_world_size}')
+
+        self._post_init()
+
+
+def _create_tensor_from_params(*size, local_device, tensor_properties: TensorProperties):
+    """ Helper to construct tensor from size, device and common params. """
+    dtype = tensor_properties.dtype
+    layout = tensor_properties.layout
+    requires_grad = tensor_properties.requires_grad
+    memory_format = tensor_properties.memory_format
+    pin_memory = tensor_properties.pin_memory
+
+    return torch.empty(
+        *size, dtype=dtype, layout=layout,
+        device=local_device, requires_grad=requires_grad,
+        memory_format=memory_format, pin_memory=pin_memory
+    )

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/logger.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+
+# Copyright (c) Facebook, Inc. and its affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+import logging
+from typing import List, Tuple
+
+from torch.distributed._shard.sharded_tensor.logging_handlers import (
+    _log_handlers,
+)
+
+__all__: List[str] = []
+
+
+def _get_or_create_logger() -> logging.Logger:
+    logging_handler, log_handler_name = _get_logging_handler()
+    logger = logging.getLogger(f"sharding-spec-{log_handler_name}")
+    logger.setLevel(logging.DEBUG)
+    formatter = logging.Formatter(
+        "%(asctime)s %(filename)s:%(lineno)s %(levelname)s p:%(processName)s t:%(threadName)s: %(message)s"
+    )
+    logging_handler.setFormatter(formatter)
+    logger.propagate = False
+    logger.addHandler(logging_handler)
+    return logger
+
+
+def _get_logging_handler(
+    destination: str = "default",
+) -> Tuple[logging.Handler, str]:
+    log_handler = _log_handlers[destination]
+    log_handler_name = type(log_handler).__name__
+    return (log_handler, log_handler_name)

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/logging_handlers.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+
+# Copyright (c) Facebook, Inc. and its affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+import logging
+from typing import Dict, List
+
+__all__: List[str] = []
+
+_log_handlers: Dict[str, logging.Handler] = {
+    "default": logging.NullHandler(),
+}

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/metadata.py

@@ -0,0 +1,82 @@
+from dataclasses import dataclass, field
+from enum import Enum
+from typing import List
+
+import torch
+from torch.distributed._shard.metadata import ShardMetadata
+
+class MEM_FORMAT_ENCODING(Enum):
+    TORCH_CONTIGUOUS_FORMAT = 0
+    TORCH_CHANNELS_LAST = 1
+    TORCH_PRESERVE_FORMAT = 2
+
+@dataclass
+class TensorProperties:
+    """ Properties used to create :class:`Tensor` """
+
+    # Regular tensor fields
+    dtype: torch.dtype = field(default=torch.get_default_dtype())
+    layout: torch.layout = field(default=torch.strided)
+    requires_grad: bool = False
+    memory_format: torch.memory_format = field(default=torch.contiguous_format)
+    pin_memory: bool = False
+
+    def __getstate__(self):
+        # Since torch.memory_format cannot be pickled!
+        memory_format = self.memory_format
+        if memory_format == torch.contiguous_format:
+            mem_format_encoding = MEM_FORMAT_ENCODING.TORCH_CONTIGUOUS_FORMAT
+        elif memory_format == torch.channels_last:
+            mem_format_encoding = MEM_FORMAT_ENCODING.TORCH_CHANNELS_LAST
+        elif memory_format == torch.preserve_format:
+            mem_format_encoding = MEM_FORMAT_ENCODING.TORCH_PRESERVE_FORMAT
+        else:
+            raise RuntimeError(f'Invalid torch.memory_format: {memory_format}')
+
+        return (
+            self.dtype,
+            self.layout,
+            self.requires_grad,
+            mem_format_encoding,
+            self.pin_memory,
+        )
+
+    def __setstate__(
+        self,
+        state,
+    ):
+        (self.dtype, self.layout, self.requires_grad, mem_format_encoding, self.pin_memory) = state
+
+        if mem_format_encoding == MEM_FORMAT_ENCODING.TORCH_CONTIGUOUS_FORMAT:
+            memory_format = torch.contiguous_format
+        elif mem_format_encoding == MEM_FORMAT_ENCODING.TORCH_CHANNELS_LAST:
+            memory_format = torch.channels_last
+        elif mem_format_encoding == MEM_FORMAT_ENCODING.TORCH_PRESERVE_FORMAT:
+            memory_format = torch.preserve_format
+        else:
+            raise RuntimeError(f'Invalid torch.memory_format encoding: {mem_format_encoding}')
+
+        self.memory_format = memory_format
+
+    @staticmethod
+    def create_from_tensor(tensor: torch.Tensor) -> "TensorProperties":
+        return TensorProperties(
+            dtype=tensor.dtype,
+            layout=tensor.layout,
+            requires_grad=tensor.requires_grad,
+            memory_format=torch.contiguous_format,
+            pin_memory=tensor.is_pinned()
+        )
+@dataclass
+class ShardedTensorMetadata:
+    """
+    Represents metadata for :class:`ShardedTensor`
+    """
+
+    # Metadata about each shard of the Tensor
+    shards_metadata: List[ShardMetadata] = field(default_factory=list)
+
+    # Size of each dim of the overall Tensor.
+    size: torch.Size = field(default=torch.Size([]))
+
+    tensor_properties: TensorProperties = field(default_factory=TensorProperties)

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/reshard.py

@@ -0,0 +1,248 @@
+import copy
+from typing import List, Tuple
+
+import torch
+import torch.distributed as dist
+from torch._C._distributed_c10d import (
+    ProcessGroup,
+)
+import torch.distributed._shard.sharding_spec as shard_spec
+from torch.distributed._shard.sharding_spec._internals import (
+    get_split_size,
+    get_chunked_dim_size,
+)
+from torch.distributed.nn.functional import (
+    all_to_all,
+    all_to_all_single,
+)
+from torch.distributed._shard.metadata import ShardMetadata
+
+from .shard import Shard
+
+
+def get_idx_from_placements(placements, current_rank) -> int:
+    """
+    Return the position of the current rank in the given placements.
+
+    Args:
+        placements(List[Union[_remote_device, str]]):
+            Specifies the placement of each shard of the Tensor. The size of
+            the list represents the number of shards to be created. This could
+            be a list of
+            :class:`torch.distributed._remote_device`'s. This list
+            could also contain a string which represents remote
+            device as accepted by
+            :class:`torch.distributed._remote_device`
+        current_rank (int): number of current device.
+
+    Returns:
+        A int which contains the position of current device in the placement list.
+    """
+    for idx, placement in enumerate(placements):  # type: ignore[attr-defined]
+        if current_rank == placement.rank():  # type: ignore[union-attr]
+            return idx
+    raise RuntimeError('current_rank not in the placement.')
+
+
+def build_reshard_metadata(
+    st_size: torch.Size,
+    sharding_spec: shard_spec.ShardingSpec,
+    world_size: int,
+) -> Tuple[List[ShardMetadata], List[int]]:
+    """
+    Based the given sharding spec, we calculate the offset and local shard size.
+    We then build a ShardMetadata on top of the calculation result.
+
+    Args:
+        st_size (torch.Size): The size of the sharded tensor.
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The
+            specification describing how the tensor is sharded.
+        world_size (int): number of ranks.
+
+    Returns:
+        A Tuple of the followings:
+            A List[`ShardMetadata`] which contains the metadata for the shard, including
+                offsets, lengths and device placement.
+            A List[int] which contains the ranks in the order of placement.
+    """
+    shard_dim = int(sharding_spec.dim)  # type: ignore[attr-defined]
+    shards_metadata = [None] * world_size
+    ranks = []
+    offsets = [0] * len(st_size)
+    split_size = get_split_size(st_size[shard_dim], world_size)
+    for idx, placement in enumerate(sharding_spec.placements):  # type: ignore[attr-defined]
+        ranks.append(placement.rank())
+        sharded_dim_size = get_chunked_dim_size(st_size[shard_dim], split_size, idx)
+        local_tensor_size = list(st_size)
+        local_tensor_size[shard_dim] = sharded_dim_size
+        shards_metadata[placement.rank()] = ShardMetadata(  # type: ignore[call-overload]
+            shard_offsets=copy.deepcopy(offsets),
+            shard_sizes=local_tensor_size,
+            placement=placement,
+        )
+        offsets[shard_dim] += sharded_dim_size
+    return shards_metadata, ranks  # type: ignore[return-value]
+
+
+def reshuffle_local_shard(
+    local_shard: torch.Tensor,
+    st_size: torch.Size,
+    sharding_spec: shard_spec.ShardingSpec,
+    resharding_spec: shard_spec.ShardingSpec,
+    pg: ProcessGroup,
+) -> Tuple[List[Shard], List[ShardMetadata]]:
+    """
+    Reshuffle the local shard directly when the reshard dim is same as the original
+    sharding dim. Logically we do this in two step:
+    1. To collect all shards based on original sharding spec.
+    2. Reshard the tensor based on the given resharding spec.
+
+    In reality, we consolidate the two steps into one by sending the local tensor to
+    the new shard directly based on the resharding spec.
+
+    Args:
+        local_shard (Tensor): Local tensor stored in the current rank.
+        st_size (torch.Size): The size of the sharded tensor.
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The
+            specification describing how the tensor is sharded originally.
+        resharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The
+            specification describing how the tensor will be resharded.
+        pg (ProcessGroup): The process group to aggregate on.
+
+    Returns:
+        A Tuple of the followings:
+            A List[`Shard`] which contains the local tensor and its metadata.
+            A List[`ShardMetadata`] which contains the metadata for the shard, including
+                offsets, lengths and device placement.
+    """
+    current_rank = dist.get_rank(pg)
+    world_size = dist.get_world_size(pg)
+    # Build shards_metadata first.
+    shards_metadata, ranks = build_reshard_metadata(
+        st_size, resharding_spec, world_size
+    )
+    # Get input split size for all2all.
+    reshard_dim = int(resharding_spec.dim)  # type: ignore[attr-defined]
+    split_size = get_split_size(st_size[reshard_dim], world_size)
+    input_split_sizes = [0] * world_size
+    idx = get_idx_from_placements(sharding_spec.placements, current_rank)  # type: ignore[attr-defined]
+    new_rank = resharding_spec.placements[idx].rank()  # type: ignore[union-attr, attr-defined]
+    input_split_sizes[new_rank] = local_shard.size(reshard_dim)
+    # Get output split size for all2all.
+    output_split_sizes = [0] * world_size
+    new_idx = ranks.index(current_rank)
+    sharded_dim_size = get_chunked_dim_size(st_size[reshard_dim], split_size, new_idx)
+    output_split_sizes[new_rank] = sharded_dim_size
+    # Get gathered_input for all2all.
+    local_shard = local_shard.transpose(0, reshard_dim).contiguous()
+    gathered_input_size = list(local_shard.size())
+    gathered_input_size[0] = sharded_dim_size
+    gathered_input = torch.empty(gathered_input_size, device=local_shard.device, dtype=local_shard.dtype)
+    # all2all.
+    local_shard = all_to_all_single(
+        gathered_input,
+        local_shard,
+        input_split_sizes=input_split_sizes,
+        output_split_sizes=output_split_sizes,
+        group=pg,
+    )
+    local_tensor = local_shard.transpose(0, reshard_dim).contiguous()
+    local_shards = [Shard(local_tensor, shards_metadata[current_rank])]
+    return local_shards, shards_metadata
+
+
+def reshard_local_shard(
+    local_tensor: torch.Tensor,
+    st_size: torch.Size,
+    sharding_spec: shard_spec.ShardingSpec,
+    resharding_spec: shard_spec.ShardingSpec,
+    pg: ProcessGroup,
+) -> Tuple[List[Shard], List[ShardMetadata]]:
+    """
+    Reshard a sharded tensor given the ``resharding_spec``. When the reshard dim is
+    different from the original sharding dim, we need to do two steps logically:
+    1. To collect all shards based on original sharding spec.
+    2. Reshard the tensor based on the given resharding spec.
+
+    In reality, we consolidate the two steps into one by sending each rank the new
+    shard based on the resharding spec.
+
+    Args:
+        local_tensor (Tensor): Local tensor stored in the current rank.
+        st_size (torch.Size): The size of the sharded tensor.
+        sharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The
+            specification describing how the tensor is sharded originally.
+        resharding_spec (:class:`torch.distributed._shard.sharding_spec.ShardingSpec`): The
+            specification describing how the tensor will be resharded.
+        pg (ProcessGroup): The process group to aggregate on.
+
+    Returns:
+        A Tuple of the followings:
+            A List[`Shard`] which contains the local tensor and its metadata.
+            A List[`ShardMetadata`] which contains the metadata for the shard, including
+                offsets, lengths and device placement.
+    """
+    current_rank = dist.get_rank(pg)
+    world_size = dist.get_world_size(pg)
+    current_sharding_dim = int(sharding_spec.dim)  # type: ignore[attr-defined]
+    reshard_dim = int(resharding_spec.dim)  # type: ignore[attr-defined]
+
+    # Build shards_metadata first.
+    shards_metadata, ranks = build_reshard_metadata(
+        st_size, resharding_spec, world_size
+    )
+
+    # Compute expected size
+    input_split_sizes = []
+    for metadata in shards_metadata:
+        input_split_sizes.append(metadata.shard_sizes[reshard_dim])
+    rearrange_input = any(ranks[i] > ranks[i + 1] for i in range(len(ranks) - 1))
+
+    if rearrange_input:
+        # Need to re-arrange reshard_dim of local_tensor before all2all.
+        indices: List[int] = []
+        for metadata in shards_metadata:
+            offset_start_idx = metadata.shard_offsets[reshard_dim]
+            split_size = metadata.shard_sizes[reshard_dim]
+            indices += range(offset_start_idx, offset_start_idx + split_size)
+        local_tensor = local_tensor.index_select(
+            reshard_dim, torch.tensor(indices, device=local_tensor.device)
+        )
+
+    # Because reshard_dim != original shard_dim. We need to compute the
+    # size of tensor from each rank.
+    output_tensor_list = [torch.tensor(1)] * world_size
+    split_size = get_split_size(st_size[current_sharding_dim], world_size)
+    rearrange_output_list = False
+    indices = []
+    for idx, placement in enumerate(sharding_spec.placements):  # type: ignore[attr-defined]
+        sharded_dim_size = get_chunked_dim_size(
+            st_size[current_sharding_dim], split_size, idx
+        )
+        output_tensor_size = list(st_size)
+        output_tensor_size[current_sharding_dim] = sharded_dim_size
+        output_tensor_size[reshard_dim] = input_split_sizes[current_rank]
+        output_tensor_list[
+            placement.rank()
+        ] = torch.empty(  # type: ignore[union-attr, index]
+            output_tensor_size, device=local_tensor.device, dtype=local_tensor.dtype
+        )
+        indices.append(placement.rank())  # type: ignore[union-attr, index, arg-type]
+        if idx != placement.rank():  # type: ignore[union-attr]
+            rearrange_output_list = True
+
+    # Perform autograd enabled all2all.
+    input_tensor_tuple = torch.split(local_tensor, input_split_sizes, dim=reshard_dim)
+    input_tensor_list = [tensor.contiguous() for tensor in input_tensor_tuple]
+    output_tensor_list = all_to_all(
+        output_tensor_list,
+        input_tensor_list,
+        group=pg,
+    )
+
+    if rearrange_output_list:
+        # Need to re-arrange original shard_dim of output_tensor_list.
+        output_tensor_list = [output_tensor_list[idx] for idx in indices]  # type: ignore[call-overload]
+    local_tensor = torch.cat(output_tensor_list, dim=current_sharding_dim)
+    local_shards = [Shard(local_tensor, shards_metadata[current_rank])]
+    return local_shards, shards_metadata

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/shard.py

@@ -0,0 +1,58 @@
+from dataclasses import dataclass
+from typing import List
+
+import torch
+from torch.distributed._shard.metadata import ShardMetadata
+from torch.distributed.remote_device import _remote_device
+
+
+@dataclass
+class Shard:
+    """
+    Container which holds the data for a shard as a Tensor and also
+    the associated metadata for that shard.
+
+    Args:
+        tensor(torch.Tensor): Local tensor for the shard.
+        metadata(:class `torch.distributed._shard.sharded_tensor.ShardMetadata`):
+            The metadata for the shard, including offsets, lengths and device placement.
+    """
+    __slots__ = ['tensor', 'metadata']
+    tensor: torch.Tensor
+    metadata: ShardMetadata
+
+    def __post_init__(self):
+        # verification between local tensor and metadata
+        if list(self.tensor.size()) != self.metadata.shard_sizes:
+            raise ValueError(
+                "Shard tensor size does not match with metadata.shard_lengths! "
+                f"Found shard tensor size: {list(self.tensor.size())}, "
+                f"metadata.shard_lengths: {self.metadata.shard_sizes}, "
+            )
+        placement_device = self.metadata.placement
+        if placement_device is not None and placement_device.device() != self.tensor.device:
+            raise ValueError(
+                f"Local shard tensor device does not match with local Shard's placement! "
+                f"Found local shard tensor device: {self.tensor.device}, "
+                f"local shard metadata placement device: {placement_device.device()}"
+            )
+
+    @classmethod
+    def from_tensor_and_offsets(cls, tensor: torch.Tensor, shard_offsets: List[int], rank: int):
+        """
+        Creates a Shard of a ShardedTensor from a local torch.Tensor, shard_offsets and rank.
+
+        Args:
+            tensor(torch.Tensor): Local tensor for the shard.
+            shard_offsets(List[int]): List of integers specify the offset
+                of the shard on each dimension.
+            rank(int): Specify the rank for the shard.
+        """
+        shard_sizes = list(tensor.size())
+        placement = _remote_device(f"rank:{rank}/{str(tensor.device)}")
+        shard_meta = ShardMetadata(
+            shard_offsets=shard_offsets,
+            shard_sizes=shard_sizes,
+            placement=placement
+        )
+        return Shard(tensor, shard_meta)

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharded_tensor/utils.py

@@ -0,0 +1,211 @@
+import collections.abc
+import copy
+from typing import Optional, List, Sequence
+
+import torch
+from torch.distributed import distributed_c10d
+from torch.distributed import rpc
+from torch.distributed._shard.sharding_spec._internals import (
+    check_tensor,
+    validate_non_overlapping_shards_metadata,
+)
+
+from torch.distributed._shard.metadata import ShardMetadata
+from .metadata import TensorProperties, ShardedTensorMetadata
+from .shard import Shard
+
+def _parse_and_validate_remote_device(pg, remote_device):
+    if remote_device is None:
+        raise ValueError("remote device is None")
+
+    worker_name = remote_device.worker_name()
+    rank = remote_device.rank()
+    device = remote_device.device()
+
+    # Validate rank, skip validation if rank is not part of process group.
+    if not distributed_c10d._rank_not_in_group(pg):
+        if rank is not None and (rank < 0 or rank >= distributed_c10d.get_world_size(pg)):
+            raise ValueError(f'Invalid rank: {rank}')
+
+    if worker_name is not None:
+        if not rpc._is_current_rpc_agent_set():
+            raise RuntimeError(f'RPC framework needs to be initialized for using worker names: {worker_name}')
+
+        workers = rpc._get_current_rpc_agent().get_worker_infos()
+        for worker in workers:
+            if worker.name == worker_name:
+                return worker.id, device
+
+        raise ValueError(f'Invalid worker name: {worker_name}')
+
+    return rank, device
+
+def _validate_output_tensor_for_gather(
+    my_rank: int,
+    dst_rank: int,
+    size: torch.Size,
+    dst_tensor: Optional[torch.Tensor],
+) -> None:
+    if dst_rank == my_rank:
+        if dst_tensor is None:
+            raise ValueError(
+                f"Argument ``dst_tensor`` must be specified on destination rank {dst_rank}"
+            )
+        if tuple(size) != (dst_tensor.size()):
+            raise ValueError(
+                f"Argument ``dst_tensor`` have size {tuple(dst_tensor.size())},"
+                f"but should be {tuple(size)}"
+            )
+    elif dst_tensor:
+        raise ValueError(
+            "Argument ``dst_tensor`` must NOT be specified "
+            "on non-destination ranks."
+        )
+
+def _flatten_tensor_size(size) -> torch.Size:
+    """
+    Checks if tensor size is valid, then flatten/return a torch.Size object.
+    """
+    if len(size) == 1 and isinstance(size[0], collections.abc.Sequence):
+        dims = list(*size)
+    else:
+        dims = list(size)
+
+    for dim in dims:
+        if not isinstance(dim, int):
+            raise TypeError(f'size has to be a sequence of ints, found: {dims}')
+
+    return torch.Size(dims)
+
+def _raise_if_mismatch(expected, actual, prop_name, ranks, is_local=True):
+    if is_local:
+        assert isinstance(ranks, int)
+        if expected != actual:
+            raise ValueError(f"Local shards' tensor {prop_name} property need to be the same on rank:{ranks}! "
+                             f"Found one local shard tensor {prop_name}={expected}, "
+                             f"the other local shard tensor {prop_name}={actual}.")
+    else:
+        # compare failure check across ranks, ranks list should have two rank
+        assert len(ranks) == 2
+        if expected != actual:
+            raise ValueError(f"ShardedTensor {prop_name} property does not match from different ranks! "
+                             f"Found {prop_name}={expected} on rank:{ranks[0]}, "
+                             f"and {prop_name}={actual} on rank:{ranks[1]}.")
+
+
+def build_metadata_from_local_shards(
+    local_shards: List[Shard],
+    global_size: torch.Size,
+    current_rank: int,
+    pg: distributed_c10d.ProcessGroup
+) -> ShardedTensorMetadata:
+
+    assert len(local_shards) > 0, "must have local shards!"
+    local_shard_metadatas: List[ShardMetadata] = []
+
+    first_shard_dtype = local_shards[0].tensor.dtype
+    first_shard_layout = local_shards[0].tensor.layout
+    first_shard_requires_grad = local_shards[0].tensor.requires_grad
+    first_shard_is_pinned = local_shards[0].tensor.is_pinned()
+
+    # 1). Validate local tensors and associated metadatas
+    for local_shard in local_shards:
+        local_shard_tensor = local_shard.tensor
+        local_shard_meta = local_shard.metadata
+        local_shard_metadatas.append(local_shard_meta)
+        rank, local_device = _parse_and_validate_remote_device(pg, local_shard_meta.placement)
+
+        if local_shard_tensor.layout != torch.strided or local_shard_tensor.layout != first_shard_layout:
+            raise ValueError(
+                f'Only torch.strided layout is currently supported, but found '
+                f'{local_shard_tensor.layout} on rank:{current_rank}!'
+            )
+
+        if not local_shard_tensor.is_contiguous():
+            raise ValueError('Only torch.contiguous_format memory_format is currently supported!')
+
+        if rank != current_rank:
+            raise ValueError(
+                f"Local shard metadata's rank does not match with the rank in its process group! "
+                f'Found current rank in the process group: {current_rank}, '
+                f"local ShardMetadata placement's rank: {rank}"
+            )
+        if local_shard_tensor.device != local_device:
+            raise ValueError(
+                f"Local shard tensor device does not match with local Shard's placement! "
+                f"Found local shard tensor device: {local_shard_tensor.device}, "
+                f"local shard metadata placement device: {local_device}"
+            )
+
+        _raise_if_mismatch(local_shard_meta.shard_sizes, list(local_shard_tensor.size()), "size", current_rank)
+        _raise_if_mismatch(local_shard_tensor.is_pinned(), first_shard_is_pinned, "pin_memory", current_rank)
+        _raise_if_mismatch(local_shard_tensor.dtype, first_shard_dtype, "dtype", current_rank)
+        _raise_if_mismatch(local_shard_tensor.requires_grad, first_shard_requires_grad, "requires_grad", current_rank)
+
+    # 2). Build a "local" ShardedTensorMetadata with all local shards on this rank, then
+    #    do all_gather to collect local_sharded_tensor_metadata from all ranks
+    local_tensor_properties = TensorProperties(
+        dtype=first_shard_dtype,
+        layout=first_shard_layout,
+        requires_grad=first_shard_requires_grad,
+        memory_format=torch.contiguous_format,
+        pin_memory=first_shard_is_pinned
+    )
+
+    local_sharded_tensor_metadata = ShardedTensorMetadata(
+        shards_metadata=local_shard_metadatas,
+        size=global_size,
+        tensor_properties=local_tensor_properties)
+
+    return local_sharded_tensor_metadata
+
+
+def build_global_metadata(gathered_metadatas: Sequence[Optional[ShardedTensorMetadata]]):
+    global_sharded_tensor_metadata = None
+    global_metadata_rank = 0
+
+    for rank, rank_metadata in enumerate(gathered_metadatas):
+        if rank_metadata is None:
+            continue
+
+        if global_sharded_tensor_metadata is None:
+            global_sharded_tensor_metadata = copy.deepcopy(rank_metadata)
+            global_metadata_rank = rank
+        else:
+            _raise_if_mismatch(global_sharded_tensor_metadata.size,
+                               rank_metadata.size,
+                               "global_size",
+                               [global_metadata_rank, rank],
+                               is_local=False)
+
+            # don't need to check layout and memory format as we already checked in local shards validation stage
+            _raise_if_mismatch(global_sharded_tensor_metadata.tensor_properties.dtype,
+                               rank_metadata.tensor_properties.dtype,
+                               "dtype",
+                               [global_metadata_rank, rank],
+                               is_local=False)
+
+            _raise_if_mismatch(global_sharded_tensor_metadata.tensor_properties.requires_grad,
+                               rank_metadata.tensor_properties.requires_grad,
+                               "requires_grad",
+                               [global_metadata_rank, rank],
+                               is_local=False)
+
+            _raise_if_mismatch(global_sharded_tensor_metadata.tensor_properties.pin_memory,
+                               rank_metadata.tensor_properties.pin_memory,
+                               "pin_memory",
+                               [global_metadata_rank, rank],
+                               is_local=False)
+            # pass all validations, extend shards metadata
+            global_sharded_tensor_metadata.shards_metadata.extend(rank_metadata.shards_metadata)
+
+    if global_sharded_tensor_metadata is not None:
+        # check if shards_metadata have overlap shards
+        validate_non_overlapping_shards_metadata(global_sharded_tensor_metadata.shards_metadata)
+
+        # check if the shards_metadata is compatible with global size of the sharded tensor.
+        check_tensor(global_sharded_tensor_metadata.shards_metadata, global_sharded_tensor_metadata.size)
+    else:
+        raise ValueError("ShardedTensor have no local shards on all ranks!")
+
+    return global_sharded_tensor_metadata

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharder.py

@@ -0,0 +1,27 @@
+import abc
+import torch.nn as nn
+
+class Sharder(abc.ABC):
+    """
+    This is an interface which allows user to create more advanced
+    sharding strategies that are not easily be composed by the
+    `ShardingSpec`.
+
+    :class:`torch.distributed._shard.sharding_plan.ShardingPlan` could
+    take an object of the `Sharder` and call `shard` to shard the module,
+    then replace the original module with sharded module returned.
+    """
+    @abc.abstractmethod
+    def shard(self, module: nn.Module) -> nn.Module:
+        """
+        Shard a module base on the implementation of this method, and
+        return the sharded version of the module.
+
+        Args:
+            module (:class:`torch.nn.Module`):
+                The module to apply sharding to.
+        Returns:
+            A :class:`torch.nn.Module` object that represents a module
+            that's already been sharded.
+        """
+        pass

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharding_plan/__init__.py

@@ -0,0 +1,4 @@
+from .api import (
+    ShardingPlan,
+    ShardingPlanner
+)

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharding_plan/api.py

@@ -0,0 +1,86 @@
+import abc
+import torch.nn as nn
+
+from dataclasses import dataclass
+from typing import Dict, List, Optional, Union
+
+from torch.distributed._shard.sharder import Sharder
+from torch.distributed._shard.sharding_spec import ShardingSpec
+
+@dataclass
+class ShardingPlan:
+    """
+    Representation of a sharding plan, describes how to shard a module
+    across hosts. `plan` is used to shard module parameters according to the spec provided,
+    `output_plan` and `return_local_tensor` are optional, they are used to specify the output
+    layout of a module with a spec, and when to convert back to data parallel fashion.
+
+    Args:
+        plan (Dict[str, Union[:class:`torch.distributed._shard.sharding_spec.ShardingSpec`,
+              :class:`torch.distributed._shard.sharder.Sharder`]):
+            a dict describes how to shard a module, there're currently two ways to shard a module:
+                1. directly shard a module parameter by a `ShardingSpec`, keyed by the name of
+                   a parameter to a `ShardingSpec`.
+                2. shard a submodule by applying a `Sharder` on it, keyed by the name of a module
+                   to a `Sharder` object.
+        output_plan (Dict[str, :class:`torch.distributed._shard.sharding_spec.ShardingSpec`), optional):
+            a dict specifies the layout of a module's output which produces a ShardedTensor,
+            keyed by the name of module to ShardingSpec("" in key means the root module).
+            Default: `None`
+        return_local_tensor (List[str], optional): a list of string, each element enables
+            a module's sharded output to be returned as a Tensor from its local shards to
+            ensure further processing in a data parallel fashion. ("" in list means the
+            root module).
+            Default: None
+    Example:
+      Suppose we want to shard a module with two linear layers and then run it with DDP, we also
+      want to convert the output of the second linear layer back to DDP, we can do it as follows:
+
+        >>> # xdoctest: +REQUIRES(module:torch._C._distributed_c10d)
+        >>> class MyModule(nn.Module):
+        >>>     def __init__(self):
+        >>>        super().__init__()
+        >>>        self.fc1 = nn.Linear()
+        >>>        self.gelu = nn.GELU()
+        >>>        self.fc2 = nn.Linear()
+        >>>        self.relu = nn.Linear()
+        >>>
+        >>>     def forward(self, input):
+        >>>         return self.relu(self.fc2(self.gelu(self.fc1(input))))
+
+
+        >>> # xdoctest: +SKIP("Undefined spec1, spec2)
+        >>> sharding_plan = ShardingPlan(
+        >>>    plan={
+        >>>        "fc1.weight": spec1,
+        >>>        "fc2.weight": spec2
+        >>>    },
+        >>>    output_plan={
+        >>>        "fc2": output_spec
+        >>>    },
+        >>>    return_local_tensor=["fc2"]
+        >>> )
+    """
+    plan: Dict[str, Union[ShardingSpec, Sharder]]
+    output_plan: Optional[Dict[str, ShardingSpec]] = None
+    return_local_tensor: Optional[List[str]] = None
+
+
+class ShardingPlanner(abc.ABC):
+    """
+    Default ShardingPlanner interface, can be extended and
+    implement advanced sharding strategies.
+    """
+    @abc.abstractmethod
+    def build_plan(self, module: nn.Module) -> ShardingPlan:
+        """
+        Given a nn.Module, define how to shard the module across
+        ranks, return a ShardingPlan
+        Args:
+            module (:class:`torch.nn.Module`):
+                The module to apply sharding to.
+        Returns:
+            A :class:`torch.distributed._shard.sharding_plan.ShardingPlan` object that
+            represents how to shard the module.
+        """
+        pass

venv/lib/python3.10/site-packages/torch/distributed/_shard/sharding_spec/__init__.py

@@ -0,0 +1,12 @@
+from .api import (
+    DevicePlacementSpec,
+    EnumerableShardingSpec,
+    PlacementSpec,
+    ShardingSpec,
+    _infer_sharding_spec_from_shards_metadata,
+)
+from .chunk_sharding_spec import (
+    ChunkShardingSpec as ChunkShardingSpec,
+)
+
+from torch.distributed._shard.metadata import ShardMetadata