diff --git "a/llmeval-env/lib/python3.10/site-packages/torch/nn/parallel/distributed.py" "b/llmeval-env/lib/python3.10/site-packages/torch/nn/parallel/distributed.py" new file mode 100644--- /dev/null +++ "b/llmeval-env/lib/python3.10/site-packages/torch/nn/parallel/distributed.py" @@ -0,0 +1,2350 @@ +import copy +import functools +import inspect +import itertools +import logging +import os +import sys +import warnings +import weakref +from collections import defaultdict, deque +from contextlib import contextmanager +from dataclasses import dataclass, fields, is_dataclass +from enum import auto, Enum +from typing import Any, Callable, List, Optional, Tuple, Type + +import torch +import torch.distributed as dist +from torch.autograd import Function, Variable +from torch.distributed.algorithms.join import Join, Joinable, JoinHook +from torch.utils._pytree import tree_flatten, tree_unflatten +from torch.utils.hooks import RemovableHandle + +RPC_AVAILABLE = False +if dist.is_available(): + from torch.distributed.distributed_c10d import ( + _get_default_group, + _rank_not_in_group, + ReduceOp, + ) + from torch.distributed.utils import ( + _alloc_storage, + _cast_forward_inputs, + _free_storage, + _sync_module_states, + _to_kwargs, + _verify_param_shape_across_processes, + ) +if torch.distributed.rpc.is_available(): + RPC_AVAILABLE = True + from torch.distributed.rpc import RRef + +from torch._utils import _get_device_index + +from ..modules import Module +from .scatter_gather import gather, scatter_kwargs # noqa: F401 + +__all__ = ["DistributedDataParallel"] + +logger = logging.getLogger(__name__) + + +@dataclass +class _MixedPrecision: + """ + This configures DDP-native mixed precision training. + + Attributes: + param_dtype (torch.dtype): This specifies the dtype for model + parameters, inputs (when ``cast_forward_inputs`` is set to + ``True``), and therefore the dtype for computation. + However, outside the forward and backward passes, parameters are in + full precision. Model checkpointing always happens in full + precision. + reduce_dtype (torch.dtype): This specifies the dtype for gradient + reduction, which is permitted to differ from ``param_dtype``. + buffer_dtype (torch.dtype): This specifies the dtype for buffers. + + .. note:: This API is experimental and subject to change. + + .. note:: Only floating point tensors are cast to their specified dtypes. + + .. note:: ``state_dict`` checkpoints parameters and buffers in full + precision. + + .. note:: Each low precision dtype must be specified explicitly. For + example, ``_MixedPrecision(reduce_dtype=torch.float16)`` only specifies + the reduction dtype to be low precision, and DDP will not cast + parameters or buffers. + + .. note:: If a ``reduce_dtype`` is not specified, then gradient reduction + happens in ``param_dtype`` if specified or the original parameter dtype + otherwise. For example, ``_MixedPrecision(param_dtype=torch.float16)`` + would result in communication occurring in fp16. + """ + + param_dtype: Optional[torch.dtype] = None + reduce_dtype: Optional[torch.dtype] = None + buffer_dtype: Optional[torch.dtype] = None + # TODO (rohan-varma): keep_low_precision_grads: bool = False + # TODO (rohan-varma): APIs to allow users to run batchnorm and layernorm + # in full precision. For DDP, this can be implemented by not performing the + # parameter cast for BN and LN units. + + +def _cast_buffers(mixed_precision_config, root_module): + """Casts buffers to the given ``buffer_dtype``.""" + for buf in root_module.buffers(): + if hasattr(buf, "_ddp_ignored") and buf._ddp_ignored: + continue + + buf.data = buf.to(dtype=mixed_precision_config.buffer_dtype) + + +def _setup_mixed_precision_params(mixed_precision_config, root_module): + """Create and free storage for the mixed precision parameters.""" + for param in root_module.parameters(): + # Do not setup mixed precision for DDP ignored parameters. + if hasattr(param, "_ddp_ignored") and param._ddp_ignored: + continue + + if not hasattr(param, "_mp_param"): + param._mp_param = torch.zeros_like( + param, + device=param.device, + dtype=mixed_precision_config.param_dtype, + requires_grad=param.requires_grad, + ) + _free_storage(param._mp_param) + # _fp_param will point to the full precision param so it can be switched + # back to at the end of forward / backward. + param._fp_param = param.data + + +def _tree_flatten_with_rref(output): + output_is_rref = RPC_AVAILABLE and isinstance(output, RRef) + if output_is_rref: + output_tensor_list, treespec = tree_flatten(output.local_value()) + else: + output_tensor_list, treespec = tree_flatten(output) + # Need to return flattened tensors, spec to re-pack them, as well + # as if the return type was actually an RRef to reconstruct. + return output_tensor_list, treespec, output_is_rref + + +def _tree_unflatten_with_rref(output, treespec, output_is_rref): + output = tree_unflatten(output, treespec) + if output_is_rref: + output = RRef(output) + return output + + +def _find_tensors(obj): + r"""Recursively find all tensors contained in the specified object.""" + if RPC_AVAILABLE and isinstance(obj, RRef): + # If the current node is the owner of the RRef, unwrap it and try to + # find Tensors. + # TODO: Expand to remote RRefs. + if obj.is_owner(): + return _find_tensors(obj.local_value()) + if isinstance(obj, torch.Tensor): + return [obj] + if isinstance(obj, (list, tuple)): + return itertools.chain.from_iterable(map(_find_tensors, obj)) + if isinstance(obj, dict): + return itertools.chain.from_iterable(map(_find_tensors, obj.values())) + if is_dataclass(obj): + return itertools.chain.from_iterable( + map(_find_tensors, (getattr(obj, f.name) for f in fields(obj))) + ) + + return [] + + +def _dump_DDP_relevant_env_vars(): + relevant_env_vars = [ + "RANK", + "LOCAL_RANK", + "WORLD_SIZE", + "MASTER_PORT", + "MASTER_ADDR", + "CUDA_VISIBLE_DEVICES", + "GLOO_SOCKET_IFNAME", + "GLOO_DEVICE_TRANSPORT", + "NCCL_SOCKET_IFNAME", + "TORCH_NCCL_BLOCKING_WAIT", + "NCCL_DEBUG", + "NCCL_DEBUG_SUBSYS", + "NCCL_IB_DISABLE", + # More NCCL env vars: + "NCCL_P2P_DISABLE", + "NCCL_P2P_LEVEL", + "NCCL_SHM_DISABLE", + "NCCL_SOCKET_NTHREADS", + "NCCL_NSOCKS_PERTHREAD", + "NCCL_BUFFSIZE", + "NCCL_NTHREADS", + "NCCL_RINGS", + "NCCL_MAX_NCHANNELS", + "NCCL_MIN_NCHANNELS", + "NCCL_CHECKS_DISABLE", + "NCCL_CHECK_POINTERS", + "NCCL_LAUNCH_MODE", + "NCCL_IB_HCA", + "NCCL_IB_TIMEOUT", + "NCCL_IB_RETRY_CNT", + "NCCL_IB_GID_INDEX", + "NCCL_IB_SL", + "NCCL_IB_TC", + "NCCL_IB_AR_THRESHOLD", + "NCCL_IB_CUDA_SUPPORT", + "NCCL_NET_GDR_LEVEL", + "NCCL_NET_GDR_READ", + "NCCL_SINGLE_RING_THRESHOLD", + "NCCL_LL_THRESHOLD", + "NCCL_TREE_THRESHOLD", + "NCCL_ALGO", + "NCCL_PROTO", + "NCCL_IGNORE_CPU_AFFINITY", + "NCCL_DEBUG_FILE", + "NCCL_COLLNET_ENABLE", + "NCCL_TOPO_FILE", + "NCCL_TOPO_DUMP_FILE", + "TORCH_NCCL_ASYNC_ERROR_HANDLING", + ] + formatted_output = "" + for var in relevant_env_vars: + value = os.environ[var] if var in os.environ else "N/A" + formatted_output += f"env:{var}={value}\n" + print(formatted_output) + + +class _BufferCommHookLocation(Enum): + PRE_FORWARD = auto() + POST_FORWARD = auto() + + +@dataclass +class _BufferCommHook: + buffer_comm_hook: Callable + buffer_comm_hook_state: Any + buffer_comm_hook_location: _BufferCommHookLocation + + +# Add a DDPSink to run various functions when backwards starts, such as +# queueing call back of out-most backward/graph task, +# this helps call back is fired after all gradients' calculation +# is completed. +class _DDPSink(Function): + @staticmethod + def forward(ctx, ddp_weakref, *inputs): + # set_materialize_grads(False) will ensure that None gradients stay as + # None and are not filled with zeros. + ctx.set_materialize_grads(False) + ctx.ddp_weakref = ddp_weakref + ret = tuple( + inp.clone() if isinstance(inp, torch.Tensor) else inp for inp in inputs + ) + return ret + + @staticmethod + def backward(ctx, *grad_outputs): + # Enqueue delay allreduce for static graph training on the first + # iteration. + ddp_weakref = ctx.ddp_weakref() + reducer = ddp_weakref.reducer + static_graph = ddp_weakref.static_graph + delay_ar_enqueued = ( + static_graph and ddp_weakref._static_graph_delay_allreduce_enqueued + ) + if static_graph and not delay_ar_enqueued: + Variable._execution_engine.queue_callback( # type: ignore[call-arg,misc] + reducer._delay_all_reduce + ) + ddp_weakref._static_graph_delay_allreduce_enqueued = True + + return (None, *grad_outputs) + + +class _DDPJoinHook(JoinHook): + def __init__(self, ddp, divide_by_initial_world_size): + """Set config variables for internal usage.""" + assert isinstance(ddp, DistributedDataParallel), ( + "DDP join hook requires passing in a DistributedDataParallel " + "instance as the state" + ) + assert ddp.logger is not None + ddp.logger._set_uneven_input_join() + self.ddp = ddp + self.ddp._divide_by_initial_world_size = divide_by_initial_world_size + super().__init__() + + def main_hook(self): + """Shadow the DDP collective communication operations in the forward and backward passes.""" + ddp = self.ddp + # Buckets are rebuilt only once during a training period + ddp.reducer._rebuild_buckets() + + # Schedule a broadcast if we are syncing module buffers in the + # forward pass + # TODO: make DDP uneven inputs context manager support buffer + # comm hook (https://github.com/pytorch/pytorch/issues/65436) + ddp._check_and_sync_module_buffers() + + # Check if need to sync in the backward pass + should_sync_backwards = ddp._check_global_requires_backward_grad_sync( + is_joined_rank=True + ) + # Forward parameter sync is disabled in the next iteration if we + # are skipping gradient sync this iteration, so set + # `require_forward_param_sync` accordingly + ddp.require_forward_param_sync = should_sync_backwards + if not should_sync_backwards: + return + + # Schedule one allreduce per gradient bucket to match the backward + # pass allreduce + ddp._match_all_reduce_for_bwd_pass() + + # Check if we need to allreduce locally unused parameters + if ddp.find_unused_parameters: + ddp._match_unused_params_allreduce() + + # Rebuilt parameters are pushed only once during a training period + ddp.reducer._push_all_rebuilt_params() + + def post_hook(self, is_last_joiner: bool): + """Sync the final model to ensure that the model is the same across all processes.""" + self.ddp._sync_final_model(is_last_joiner) + + +class DistributedDataParallel(Module, Joinable): + r"""Implement distributed data parallelism based on ``torch.distributed`` at module level. + + This container provides data parallelism by synchronizing gradients + across each model replica. The devices to synchronize across are + specified by the input ``process_group``, which is the entire world + by default. Note that ``DistributedDataParallel`` does not chunk or + otherwise shard the input across participating GPUs; the user is + responsible for defining how to do so, for example through the use + of a :class:`DistributedSampler`. + + See also: :ref:`distributed-basics` and :ref:`cuda-nn-ddp-instead`. + The same constraints on input as in :class:`torch.nn.DataParallel` apply. + + Creation of this class requires that ``torch.distributed`` to be already + initialized, by calling :func:`torch.distributed.init_process_group`. + + ``DistributedDataParallel`` is proven to be significantly faster than + :class:`torch.nn.DataParallel` for single-node multi-GPU data + parallel training. + + To use ``DistributedDataParallel`` on a host with N GPUs, you should spawn + up ``N`` processes, ensuring that each process exclusively works on a single + GPU from 0 to N-1. This can be done by either setting + ``CUDA_VISIBLE_DEVICES`` for every process or by calling: + + >>> # xdoctest: +SKIP("undefined variables") + >>> torch.cuda.set_device(i) + + where i is from 0 to N-1. In each process, you should refer the following + to construct this module: + + >>> # xdoctest: +SKIP("undefined variables") + >>> torch.distributed.init_process_group( + >>> backend='nccl', world_size=N, init_method='...' + >>> ) + >>> model = DistributedDataParallel(model, device_ids=[i], output_device=i) + + In order to spawn up multiple processes per node, you can use either + ``torch.distributed.launch`` or ``torch.multiprocessing.spawn``. + + .. note:: + Please refer to `PyTorch Distributed Overview `__ + for a brief introduction to all features related to distributed training. + + .. note:: + ``DistributedDataParallel`` can be used in conjunction with + :class:`torch.distributed.optim.ZeroRedundancyOptimizer` to reduce + per-rank optimizer states memory footprint. Please refer to + `ZeroRedundancyOptimizer recipe `__ + for more details. + + .. note:: ``nccl`` backend is currently the fastest and highly recommended + backend when using GPUs. This applies to both single-node and + multi-node distributed training. + + .. note:: This module also supports mixed-precision distributed training. + This means that your model can have different types of parameters such + as mixed types of ``fp16`` and ``fp32``, the gradient reduction on these + mixed types of parameters will just work fine. + + .. note:: If you use ``torch.save`` on one process to checkpoint the module, + and ``torch.load`` on some other processes to recover it, make sure that + ``map_location`` is configured properly for every process. Without + ``map_location``, ``torch.load`` would recover the module to devices + where the module was saved from. + + .. note:: When a model is trained on ``M`` nodes with ``batch=N``, the + gradient will be ``M`` times smaller when compared to the same model + trained on a single node with ``batch=M*N`` if the loss is summed (NOT + averaged as usual) across instances in a batch (because the gradients + between different nodes are averaged). You should take this into + consideration when you want to obtain a mathematically equivalent + training process compared to the local training counterpart. But in most + cases, you can just treat a DistributedDataParallel wrapped model, a + DataParallel wrapped model and an ordinary model on a single GPU as the + same (E.g. using the same learning rate for equivalent batch size). + + .. note:: + Parameters are never broadcast between processes. The module performs + an all-reduce step on gradients and assumes that they will be modified + by the optimizer in all processes in the same way. Buffers + (e.g. BatchNorm stats) are broadcast from the module in process of rank + 0, to all other replicas in the system in every iteration. + + .. note:: + If you are using DistributedDataParallel in conjunction with the + :ref:`distributed-rpc-framework`, you should always use + :meth:`torch.distributed.autograd.backward` to compute gradients and + :class:`torch.distributed.optim.DistributedOptimizer` for optimizing + parameters. + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> import torch.distributed.autograd as dist_autograd + >>> from torch.nn.parallel import DistributedDataParallel as DDP + >>> import torch + >>> from torch import optim + >>> from torch.distributed.optim import DistributedOptimizer + >>> import torch.distributed.rpc as rpc + >>> from torch.distributed.rpc import RRef + >>> + >>> t1 = torch.rand((3, 3), requires_grad=True) + >>> t2 = torch.rand((3, 3), requires_grad=True) + >>> rref = rpc.remote("worker1", torch.add, args=(t1, t2)) + >>> ddp_model = DDP(my_model) + >>> + >>> # Setup optimizer + >>> optimizer_params = [rref] + >>> for param in ddp_model.parameters(): + >>> optimizer_params.append(RRef(param)) + >>> + >>> dist_optim = DistributedOptimizer( + >>> optim.SGD, + >>> optimizer_params, + >>> lr=0.05, + >>> ) + >>> + >>> with dist_autograd.context() as context_id: + >>> pred = ddp_model(rref.to_here()) + >>> loss = loss_func(pred, target) + >>> dist_autograd.backward(context_id, [loss]) + >>> dist_optim.step(context_id) + + .. note:: + DistributedDataParallel currently offers limited support for gradient + checkpointing with :meth:`torch.utils.checkpoint`. + If the checkpoint is done with use_reentrant=False (recommended), DDP + will work as expected without any limitations. + If, however, the checkpoint is done with use_reentrant=True (the default), + DDP will work as expected when there are no unused parameters in the model + and each layer is checkpointed at most once (make sure you are not passing + `find_unused_parameters=True` to DDP). We currently do not support the + case where a layer is checkpointed multiple times, or when there unused + parameters in the checkpointed model. + + .. note:: + To let a non-DDP model load a state dict from a DDP model, + :meth:`~torch.nn.modules.utils.consume_prefix_in_state_dict_if_present` + needs to be applied to strip the prefix "module." in the DDP state dict before loading. + + .. warning:: + Constructor, forward method, and differentiation of the output (or a + function of the output of this module) are distributed synchronization + points. Take that into account in case different processes might be + executing different code. + + .. warning:: + This module assumes all parameters are registered in the model by the + time it is created. No parameters should be added nor removed later. + Same applies to buffers. + + .. warning:: + This module assumes all parameters are registered in the model of each + distributed processes are in the same order. The module itself will + conduct gradient ``allreduce`` following the reverse order of the + registered parameters of the model. In other words, it is users' + responsibility to ensure that each distributed process has the exact + same model and thus the exact same parameter registration order. + + .. warning:: + This module allows parameters with non-rowmajor-contiguous strides. + For example, your model may contain some parameters whose + :class:`torch.memory_format` is ``torch.contiguous_format`` + and others whose format is ``torch.channels_last``. However, + corresponding parameters in different processes must have the + same strides. + + .. warning:: + This module doesn't work with :func:`torch.autograd.grad` (i.e. it will + only work if gradients are to be accumulated in ``.grad`` attributes of + parameters). + + .. warning:: + If you plan on using this module with a ``nccl`` backend or a ``gloo`` + backend (that uses Infiniband), together with a DataLoader that uses + multiple workers, please change the multiprocessing start method to + ``forkserver`` (Python 3 only) or ``spawn``. Unfortunately + Gloo (that uses Infiniband) and NCCL2 are not fork safe, and you will + likely experience deadlocks if you don't change this setting. + + .. warning:: + You should never try to change your model's parameters after wrapping + up your model with ``DistributedDataParallel``. Because, when + wrapping up your model with ``DistributedDataParallel``, the constructor + of ``DistributedDataParallel`` will register the additional gradient + reduction functions on all the parameters of the model itself at the + time of construction. If you change the model's parameters afterwards, + gradient reduction functions no longer match the correct set of + parameters. + + .. warning:: + Using ``DistributedDataParallel`` in conjunction with the + :ref:`distributed-rpc-framework` is experimental and subject to change. + + Args: + module (Module): module to be parallelized + device_ids (list of int or torch.device): CUDA devices. + 1) For single-device modules, ``device_ids`` can + contain exactly one device id, which represents the only + CUDA device where the input module corresponding to this process resides. + Alternatively, ``device_ids`` can also be ``None``. + 2) For multi-device modules and CPU modules, + ``device_ids`` must be ``None``. + + When ``device_ids`` is ``None`` for both cases, + both the input data for the forward pass and the actual module + must be placed on the correct device. + (default: ``None``) + output_device (int or torch.device): Device location of output for + single-device CUDA modules. For multi-device modules and + CPU modules, it must be ``None``, and the module itself + dictates the output location. (default: ``device_ids[0]`` + for single-device modules) + broadcast_buffers (bool): Flag that enables syncing (broadcasting) + buffers of the module at beginning of the ``forward`` + function. (default: ``True``) + process_group: The process group to be used for distributed data + all-reduction. If ``None``, the default process group, which + is created by :func:`torch.distributed.init_process_group`, + will be used. (default: ``None``) + bucket_cap_mb: ``DistributedDataParallel`` will bucket parameters into + multiple buckets so that gradient reduction of each + bucket can potentially overlap with backward computation. + :attr:`bucket_cap_mb` controls the bucket size in + MegaBytes (MB). (default: 25) + find_unused_parameters (bool): Traverse the autograd graph from all + tensors contained in the return value of the + wrapped module's ``forward`` function. Parameters + that don't receive gradients as part of this + graph are preemptively marked as being ready to + be reduced. In addition, parameters that may have + been used in the wrapped module's ``forward`` + function but were not part of loss computation and + thus would also not receive gradients are + preemptively marked as ready to be reduced. + (default: ``False``) + check_reduction: This argument is deprecated. + gradient_as_bucket_view (bool): When set to ``True``, gradients will be views + pointing to different offsets of ``allreduce`` communication + buckets. This can reduce peak memory usage, where the + saved memory size will be equal to the total gradients + size. Moreover, it avoids the overhead of copying between + gradients and ``allreduce`` communication buckets. When + gradients are views, ``detach_()`` cannot be called on the + gradients. If hitting such errors, please fix it by + referring to the :meth:`~torch.optim.Optimizer.zero_grad` + function in ``torch/optim/optimizer.py`` as a solution. + Note that gradients will be views after first iteration, so + the peak memory saving should be checked after first iteration. + static_graph (bool): When set to ``True``, DDP knows the trained graph is + static. Static graph means 1) The set of used and unused + parameters will not change during the whole training loop; in + this case, it does not matter whether users set + ``find_unused_parameters = True`` or not. 2) How the graph is trained + will not change during the whole training loop (meaning there is + no control flow depending on iterations). + When static_graph is set to be ``True``, DDP will support cases that + can not be supported in the past: + 1) Reentrant backwards. + 2) Activation checkpointing multiple times. + 3) Activation checkpointing when model has unused parameters. + 4) There are model parameters that are outside of forward function. + 5) Potentially improve performance when there are unused parameters, + as DDP will not search graph in each iteration to detect unused + parameters when static_graph is set to be ``True``. + To check whether you can set static_graph to be ``True``, one way is to + check ddp logging data at the end of your previous model training, + if ``ddp_logging_data.get("can_set_static_graph") == True``, mostly you + can set ``static_graph = True`` as well. + + Example:: + >>> # xdoctest: +SKIP("undefined variables") + >>> model_DDP = torch.nn.parallel.DistributedDataParallel(model) + >>> # Training loop + >>> ... + >>> ddp_logging_data = model_DDP._get_ddp_logging_data() + >>> static_graph = ddp_logging_data.get("can_set_static_graph") + delay_all_reduce_named_params (list of tuple of str and torch.nn.Parameter): a list + of named parameters whose all reduce will be delayed when the gradient of + the parameter specified in ``param_to_hook_all_reduce`` is ready. Other + arguments of DDP do not apply to named params specified in this argument + as these named params will be ignored by DDP reducer. + param_to_hook_all_reduce (torch.nn.Parameter): a parameter to hook delayed all reduce + of parameters specified in ``delay_all_reduce_named_params``. + + + Attributes: + module (Module): the module to be parallelized. + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> torch.distributed.init_process_group(backend='nccl', world_size=4, init_method='...') + >>> net = torch.nn.parallel.DistributedDataParallel(model) + """ + + # used to track whether the given thread is inside ddp forward for torchdynamo purposes + _active_ddp_module: Optional["DistributedDataParallel"] = None + + def __init__( + self, + module, + device_ids=None, + output_device=None, + dim=0, + broadcast_buffers=True, + process_group=None, + bucket_cap_mb=25, + find_unused_parameters=False, + check_reduction=False, + gradient_as_bucket_view=False, + static_graph=False, + delay_all_reduce_named_params=None, + param_to_hook_all_reduce=None, + mixed_precision: Optional[_MixedPrecision] = None, + device_mesh=None, + ): + super().__init__() + Joinable.__init__(self) + self.logger = None + if bool(delay_all_reduce_named_params is not None) != bool( + param_to_hook_all_reduce is not None + ): + self._log_and_throw( + ValueError, + "delay_all_reduce_named_params and param_to_hook_all_reduce " + "need to be set at the same time.", + ) + + self._delay_all_reduce_params = [] + if hasattr(module, "_ddp_params_and_buffers_to_ignore"): + self.parameters_to_ignore = set(module._ddp_params_and_buffers_to_ignore) + else: + self.parameters_to_ignore = set() + if delay_all_reduce_named_params is not None: + for name, param in delay_all_reduce_named_params: + self.parameters_to_ignore.add(name) + self._delay_all_reduce_params.append(param) + + self._module_parameters = [ + p + for n, p in module.named_parameters() + if n not in self.parameters_to_ignore + ] + if not any(p.requires_grad for p in self._module_parameters): + if len(self._delay_all_reduce_params): + logger.info("Delay the AllReduce of all parameters.") + else: + self._log_and_throw( + RuntimeError, + "DistributedDataParallel is not needed when a module " + "doesn't have any parameter that requires a gradient.", + ) + + if device_ids is not None and len(device_ids) > 1: + self._log_and_throw( + ValueError, + "device_ids can only be None or contain a single element.", + ) + + self.is_multi_device_module = ( + len({p.device for p in self._module_parameters}) > 1 + ) + distinct_device_types = { + p.device.type for p in self._module_parameters if p.device is not None + } + if len(distinct_device_types) != 1: + self._log_and_throw( + ValueError, + "DistributedDataParallel's input module must be on " + f"the same type of devices, but input module parameters locate in {distinct_device_types}.", + ) + + self.device_type = next(iter(distinct_device_types)) + + if ( + device_ids is None + or len(device_ids) == 0 # For backward compatibility. + or self.device_type == "cpu" + or self.is_multi_device_module + ): + if device_ids or output_device: + self._log_and_throw( + ValueError, + "DistributedDataParallel device_ids and output_device arguments " + "only work with single-device/multiple-device GPU modules or CPU modules, " + "but got device_ids {}, output_device {}, and module parameters {}.".format( + device_ids, + output_device, + {p.device for p in self._module_parameters}, + ), + ) + + self.device_ids = None + self.output_device = None + else: + self.device_ids = [_get_device_index(x, True) for x in device_ids] + + if output_device is None: + output_device = device_ids[0] + + self.output_device = _get_device_index(output_device, True) + + if process_group and device_mesh is not None: + raise RuntimeError( + "Cannot specify both process_group and device_mesh arguments." + ) + elif process_group is None and device_mesh is None: + self.process_group = _get_default_group() + elif device_mesh is None: + self.process_group = process_group + else: + if device_mesh.ndim != 1: + raise RuntimeError( + f"Only 1D device mesh is supported, but got {device_mesh}." + ) + self.device_mesh = device_mesh + self.process_group = device_mesh.get_group(mesh_dim=0) + + self.static_graph = False + self.dim = dim + self.module = module + self.device = next(iter(self._module_parameters)).device + self.broadcast_buffers = broadcast_buffers + self.find_unused_parameters = find_unused_parameters + self.require_backward_grad_sync = True + self.require_forward_param_sync = True + self.gradient_as_bucket_view = gradient_as_bucket_view + self.mixed_precision = mixed_precision + if self.mixed_precision is not None: + logger.warning("Received mixed precision config %s", self.mixed_precision) + + if check_reduction: + # This argument is no longer used since the reducer + # will ensure reduction completes even if some parameters + # do not receive gradients. + warnings.warn( + "The `check_reduction` argument in `DistributedDataParallel` " + "module is deprecated. Please avoid using it." + ) + + # Check that a module does not have Uninitialized parameters + for param in self._module_parameters: + if isinstance(param, torch.nn.parameter.UninitializedParameter): + self._log_and_throw( + RuntimeError, + "Modules with uninitialized parameters can't be used with `DistributedDataParallel`. " + "Run a dummy forward pass to correctly initialize the modules", + ) + # used for intra-node param sync and inter-node sync as well + self.broadcast_bucket_size = int(250 * 1024 * 1024) + + # reduction bucket size + self.bucket_bytes_cap = int(bucket_cap_mb * 1024 * 1024) + # Whether to perform input tensor CPU to GPU copies on a side-stream + self.use_side_stream_for_tensor_copies = ( + os.environ.get("PYTORCH_DDP_USE_SIDE_STREAM", "1") == "1" + ) + + # Initialize gradient buffers and register all reduce hook + self._delay_grad_buffer = None + self._delay_grad_views: List[torch.Tensor] = [] + self._delay_all_reduce_all_params = False + if len(self._delay_all_reduce_params) != 0: + self._register_delay_all_reduce_hook( + bucket_cap_mb=bucket_cap_mb, + param_to_hook_all_reduce=param_to_hook_all_reduce, + device_ids=device_ids, + ) + if self._delay_all_reduce_all_params: + return + + # Build parameters for reducer. + parameters, expect_sparse_gradient = self._build_params_for_reducer() + # Verify model equivalence. + _verify_param_shape_across_processes(self.process_group, parameters) + # Sync params and buffers. Ensures all DDP models start off at the same value. + _sync_module_states( + module=self.module, + process_group=self.process_group, + broadcast_bucket_size=self.broadcast_bucket_size, + src=0, + params_and_buffers_to_ignore=self.parameters_to_ignore, + broadcast_buffers=self.broadcast_buffers, + ) + # In debug mode, build a mapping of parameter index -> parameter. + param_to_name_mapping = self._build_debug_param_to_name_mapping(parameters) + + # Builds reducer. + self._ddp_init_helper( + parameters, + expect_sparse_gradient, + param_to_name_mapping, + static_graph, + ) + self._comm_hooks: List[Tuple[Callable, object]] = [] + + if self.mixed_precision is not None: + _setup_mixed_precision_params(self.mixed_precision, self.module) + _cast_buffers(self.mixed_precision, self.module) + # Stream used for async low precision copies. + self._mp_stream = torch.cuda.Stream() + self._submodule_to_event = defaultdict(deque) # type: ignore[var-annotated] + # Add forward pre-hook to root module to kick off copies to lower + # precision. + self.module.register_forward_pre_hook( + self._root_copy_hook, prepend=False, with_kwargs=True + ) + # Add forward pre hook to all submodules to wait for copy events + # before running computation. + for module in self.module.modules(): + module.register_forward_pre_hook( + self._module_wait_for_copy_hook, + prepend=False, + with_kwargs=True, + ) + # Set up callbacks in backward to upcast and use full precision + # params. TODO (rohan-varma): Make this compose with general + # comm hooks and apply_optimizer_in_backward. Importing inline to + # avoid circular import issue. + from torch.distributed.algorithms.ddp_comm_hooks.mixed_precision_hooks import ( + _AllreduceUpcastHookState, + _reducer_allreduce_and_upcast_hook, + ) + + upcast_hook_state = _AllreduceUpcastHookState( + ddp_weakref=weakref.ref(self), + upcast_stream=torch.cuda.Stream(), + ) + self.register_comm_hook( + upcast_hook_state, + _reducer_allreduce_and_upcast_hook, + ) + # Inform reducer of reduced precision param dtype for correctness + # of type checks between gradient and bucket. + self.reducer._set_mixed_precision_param_dtype( # type: ignore[attr-defined] + self.mixed_precision.param_dtype + ) + + self._has_rebuilt_buckets = False + + if static_graph: + self._set_static_graph() + + self._lazy_init_ran = False + + # Register the AccumulateGrad post hooks if optimize_ddp is + # True. The hooks will be deregistered if compiled_autograd is not + # enabled. + self._accum_grad_hooks: List[RemovableHandle] = [] + optimize_ddp = torch._dynamo.config._get_optimize_ddp_mode() + self._use_python_reducer = optimize_ddp in ( + "python_reducer", + "python_reducer_without_compiled_forward", + ) + self._force_to_disable_cpp_reducer = ( + optimize_ddp == "python_reducer_without_compiled_forward" + ) + if self._use_python_reducer: + self._register_accum_grad_hook() + + def _register_accum_grad_hook(self): + import torch.distributed._functional_collectives as fcol + + def compiled_accum_grad_hook( + param, + *, + param_index: int, + ): + if not self.require_backward_grad_sync: + return + + if param.grad is None: + return + + if self._comm_hooks: + for hook, state in self._comm_hooks: + hook(state, (param.grad, param)) + else: + gradient = param.grad / self.process_group.size() + gradient = fcol.all_reduce(gradient, "sum", self.process_group) + param.grad.copy_(gradient) + + for index, param in enumerate(self._module_parameters): + self._accum_grad_hooks.append( + param.register_post_accumulate_grad_hook( + functools.partial( + compiled_accum_grad_hook, + param_index=index, + ) + ) + ) + + def _delayed_all_reduce_hook(self, grad): + world_size = dist.get_world_size(self.process_group) + + self._delay_grad_buffer.div_(world_size) # type: ignore[union-attr] + _ = dist.all_reduce( + self._delay_grad_buffer, group=self.process_group, async_op=True + ) + return grad + + def _register_delay_all_reduce_hook( + self, + bucket_cap_mb, + param_to_hook_all_reduce, + device_ids, + ): + # 1. Create gradient buffer + device = torch.device("cpu") if device_ids is None else device_ids[0] + self._delay_grad_buffer = torch.zeros( + sum([p.numel() for p in self._delay_all_reduce_params]), + device=device, + ) + + # 2. Broadcast the parameters + detached_params = [p.detach() for p in self._delay_all_reduce_params] + dist._broadcast_coalesced(self.process_group, detached_params, bucket_cap_mb, 0) + + # 3. Hook all reduce to the specified parameter + param_to_hook_all_reduce.register_hook(self._delayed_all_reduce_hook) + + # 4. Build tensor views for gradients + offset = 0 + for param in self._delay_all_reduce_params: + grad_view = self._delay_grad_buffer[offset : (offset + param.numel())].view( + param.shape + ) + self._delay_grad_views.append(grad_view) + offset = offset + param.numel() + + # 5. Check whether the all reduce of all params requiring grad is delayed. + for module_name, module in self.module.named_modules(): + for param_name, param in module.named_parameters(recurse=False): + if param.requires_grad: + full_name = f"{module_name}.{param_name}" + if full_name not in self.parameters_to_ignore: + # There is at least a param whose all reduce will not be delayed. + # In this case, we should not set self._delay_all_reduce_all_params + # to True. + return + self._delay_all_reduce_all_params = True + + def _setup_in_backward_optimizers(self): + # Check if user has used apply_optim_in_backward to overlap optimizer + # step + DDP backward. Current constraints: + # 1. Only allreduce is supported at the moment, no custom communication. + # 2. For DDP-managed parameters that have their optimizer run in + # backward, their gradients are set to ``None``. If your use case + # requires DDP parameters grad not to be set to ``None`` after their + # in-backward optimizer runs, please ping + # https://github.com/pytorch/pytorch/issues/90052. + # NOTE: we use self._module_parameters instead of .parameters() since + # the former excludes ignored (non-DDP managed) parameters. + if any(hasattr(p, "_in_backward_optimizers") for p in self._module_parameters): + torch._C._log_api_usage_once("ddp.optimizer_in_backward") + # Remove hooks that apply_optim_in_backward had registered because + # DDP customizes how optimizer is overlapped with backward due to + # the allreduce. + param_to_handle_map = ( + dist.optim.apply_optimizer_in_backward.param_to_optim_hook_handle_map + ) + for p in self._module_parameters: + for handle in param_to_handle_map.get(p, []): + handle.remove() + + # Need a weakref to DDP instance to run all_reduce (from reducer) + # and get managed DDP parameters. + ddp_weakref = weakref.ref(self) + # Note: importing in function, otherwise this will cause a circular + # import. + from torch.distributed.algorithms.ddp_comm_hooks.optimizer_overlap_hooks import ( + _apply_optim_in_backward_hook, + ) + + self.register_comm_hook( + ddp_weakref, + _apply_optim_in_backward_hook( + gradient_is_bucket_view=self.gradient_as_bucket_view + ), + ) + + self.reducer._set_optimizer_in_backward() # type: ignore[attr-defined] + + def _fire_reducer_autograd_hook(self, idx, *unused): + """ + Fire the reducer's autograd hook to allreduce params in a Reducer bucket. + + Note that this is only used during mixed precision training as the + Reducer's hooks installed during construction time would not be called + as we're working in the low precision parameter setting. + """ + self.reducer._autograd_hook(idx) # type: ignore[attr-defined] + + def _root_copy_hook(self, *args: Any, **kwargs: Any) -> None: + """ + For DDP mixed precision, put low precision copies on separate stream and create events to wait for them. + + When training with DDP mixed precision, this root pre-forward hook kicks + off low precision copies on a separate stream and creates respective + events to wait for them. + """ + # Clear out previous iteration submodule to event. This is because we + # may have populated some events for modules that didn't end up being + # used. + self._submodule_to_event = defaultdict(deque) # type: ignore[var-annotated] + with torch.cuda.stream(self._mp_stream): + for submodule in self.module.modules(): + for param in submodule.parameters(recurse=False): + # Do not cast DDP ignored parameters. + if hasattr(param, "_ddp_ignored") and param._ddp_ignored: + continue + _alloc_storage(param._mp_param, param.size()) + # copy() implicitly casts to low precision + with torch.no_grad(): + param._mp_param.copy_(param.data) + # TODO: when zero_grad(set_to_none=False) or in grad + # accumulation case, accumulated grads can be in fp32 + # which can cause errors when running DDP backwards due + # to mismatched incoming and accumulated gradient types. + # So we manually cast the accumulated grad down for now, + # in the future we may shift to FSDP style gradient + # accumulation management where the accumulated gradient + # is saved and .grad field is set to None, bypassing + # this issue. + if param.grad is not None: + param.grad.data = param.grad.to( + self.mixed_precision.param_dtype # type: ignore[union-attr] + ) + param.data = param._mp_param + copy_event = torch.cuda.Event() + copy_event.record() + self._submodule_to_event[submodule].append(copy_event) + + def _module_wait_for_copy_hook( + self, + module, + *args: Any, + **kwargs: Any, + ) -> None: + """Before carrying out computation, wait on the appropriate event to ensure low precision copies have finished.""" + try: + event = self._submodule_to_event[module].popleft() + except IndexError: + # copy event has already been waited on + return + + event.wait(stream=torch.cuda.current_stream()) + for p in module.parameters(recurse=False): + # Don't register hooks if param does not require grad + if not p.requires_grad or (hasattr(p, "_ddp_ignored") and p._ddp_ignored): + continue + # We need to register autograd hook here instead of DDP's ctor + # since we're working with the low precision param. Register them + # via obtaining the gradient accumulator. + tmp = p.expand_as(p) + grad_acc = tmp.grad_fn.next_functions[0][0] + + hook = grad_acc.register_hook( + functools.partial(self._fire_reducer_autograd_hook, p._idx) + ) + p._ddp_mp_hook_state = (grad_acc, hook) + + def _log_and_throw(self, err_type, err_msg): + if self.logger is not None: + self.logger.set_error_and_log(f"{str(err_type)}: {err_msg}") + raise err_type(err_msg) + + def _ddp_init_helper( + self, + parameters, + expect_sparse_gradient, + param_to_name_mapping, + static_graph, + ): + """ + DDP init helper function to manage parameters, grad hooks, logging, and SyncBatchNorm. + + Initialization helper function that does the following: + (1) bucketing the parameters for reductions + (2) resetting the bucketing states + (3) registering the grad hooks + (4) Logging construction-time DDP logging data + (5) passing a handle of DDP to SyncBatchNorm Layer + """ + # Notice, the parameters order is not in the order in which they are used, + # especially in models with control flow. + # + # Alongside parameters are not presented in the real execution order, + # if a certain model happens to also + # 1) have other collectives comm ops in its backward graph. + # 2) have unused parameter in subset ranks of the whole world. + # bucketing could insert ALL-REDUCE comm op too early on the rank with unused parameter, + # matching up with other collectives comm ops on other ranks unexpectedly. + # + # In order to handle this corner case, when the parameters are not in the real execution order, + # we don't do bucketing, thus only one ALL-REDUCE is inserted after all the gradients + # of the whole graph are computed. + # + # Notice, here we only disable bucketing for the first iteration. + # After the first iteration, it's OK to rebuild buckets, + # because "bucket rebuild" bucketizes parameters based on its real execution order in backward graph. + + # Can remove this branching once #73732 is landed. + if static_graph is True or self.find_unused_parameters is False: + bucket_size_limits = [sys.maxsize] + else: + bucket_size_limits = [ + dist._DEFAULT_FIRST_BUCKET_BYTES, + self.bucket_bytes_cap, + ] + ( + bucket_indices, + per_bucket_size_limits, + ) = dist._compute_bucket_assignment_by_size( + parameters, + bucket_size_limits, + expect_sparse_gradient, + ) + + # Remember index for parameters if we are in mixed precision, as we + # need to pass in index to Reducer's autograd hook via python. + if self.mixed_precision is not None: + for i, p in enumerate(parameters): + p._idx = i + + # Note: reverse list of buckets because we want to approximate the + # order in which their gradients are produced, and assume they + # are used in the forward pass in the order they are defined. + self.reducer = dist.Reducer( + parameters, + list(reversed(bucket_indices)), + list(reversed(per_bucket_size_limits)), + self.process_group, + expect_sparse_gradient, + # The bucket size limit is specified in the constructor. + # Additionally, we allow for a single small bucket for parameters + # that are defined first, such that their gradients don't spill into + # a much larger bucket, adding unnecessary latency after gradient + # computation finishes. Experiments showed 1MB is a reasonable value. + self.bucket_bytes_cap, + self.find_unused_parameters, + self.gradient_as_bucket_view, + param_to_name_mapping, + # User can set dist._DEFAULT_FIRST_BUCKET_BYTES to tune DDP first + # bucket. + dist._DEFAULT_FIRST_BUCKET_BYTES, + ) + + self.logger = dist.Logger(self.reducer) + # Set as a weak reference to avoid reference cycle between + # logger and reducer. + self.reducer.set_logger(self.logger) + + has_sync_bn = False + for submodule in self.module.modules(): + if isinstance(submodule, torch.nn.SyncBatchNorm): + has_sync_bn = True + break + + # Set logging data that can be got during construction time. + self.logger.set_construction_data_and_log( + self.module.__class__.__name__, + [] if self.device_ids is None else self.device_ids, + -1 if self.output_device is None else self.output_device, + self.broadcast_buffers, + has_sync_bn, + static_graph, + ) + + # passing a handle to torch.nn.SyncBatchNorm layer + self._passing_sync_batchnorm_handle(self.module) + + def __getstate__(self): + self._check_default_group() + attrs = copy.copy(self.__dict__) + del attrs["process_group"] + del attrs["reducer"] + del attrs["logger"] + return attrs + + def __setstate__(self, state): + # If serializable, then the process group should be the default one + self.process_group = _get_default_group() + super().__setstate__(state) + self.__dict__.setdefault("require_forward_param_sync", True) + self.__dict__.setdefault("require_backward_grad_sync", True) + parameters, expect_sparse_gradient = self._build_params_for_reducer() + # In debug mode, build a mapping of parameter index -> parameter. + param_to_name_mapping = self._build_debug_param_to_name_mapping(parameters) + # Builds reducer. + self._ddp_init_helper( + parameters, + expect_sparse_gradient, + param_to_name_mapping, + self.static_graph, + ) + if self.static_graph: + self.reducer._set_static_graph() + assert self.logger is not None + self.logger._set_static_graph() + + def _build_params_for_reducer(self): + # Build tuple of (module, parameter) for all parameters that require grads. + modules_and_parameters = [ + (module, parameter) + for module_name, module in self.module.named_modules() + for parameter in [ + param + # Note that we access module.named_parameters instead of + # parameters(module). parameters(module) is only needed in the + # single-process multi device case, where it accesses replicated + # parameters through _former_parameters. + for param_name, param in module.named_parameters(recurse=False) + if param.requires_grad + and f"{module_name}.{param_name}" not in self.parameters_to_ignore + ] + ] + + # Deduplicate any parameters that might be shared across child modules. + memo = set() + modules_and_parameters = [ + # "p not in memo" is the deduplication check. + # "not memo.add(p)" is always True, and it's only there to cause "add(p)" if needed. + (m, p) + for m, p in modules_and_parameters + if p not in memo and not memo.add(p) # type: ignore[func-returns-value] + ] + + # Build list of parameters. + parameters = [parameter for _, parameter in modules_and_parameters] + + # Checks if a module will produce a sparse gradient. + def produces_sparse_gradient(module): + if isinstance(module, (torch.nn.Embedding, torch.nn.EmbeddingBag)): + return module.sparse + return False + + # Build list of booleans indicating whether or not to expect sparse + # gradients for the corresponding parameters. + expect_sparse_gradient = [ + produces_sparse_gradient(module) for module, _ in modules_and_parameters + ] + + self._assign_modules_buffers() + + return parameters, expect_sparse_gradient + + def _assign_modules_buffers(self): + """ + Assign self.module.named_buffers to self.modules_buffers. + + Assigns module buffers to self.modules_buffers which are then used to + broadcast across ranks when broadcast_buffers=True. Note that this + must be called every time buffers need to be synced because buffers can + be reassigned by user module, + see https://github.com/pytorch/pytorch/issues/63916. + """ + # Collect buffers for modules, filtering out buffers that should be ignored. + named_module_buffers = [ + (buffer, buffer_name) + for buffer_name, buffer in self.module.named_buffers() + if buffer_name not in self.parameters_to_ignore + ] + self.modules_buffers = [ + buffer for (buffer, buffer_name) in named_module_buffers + ] + # Dict[str, tensor] representing module buffers not ignored by DDP. + self.named_module_buffers = { + buffer_name: buffer for (buffer, buffer_name) in named_module_buffers + } + + def _build_debug_param_to_name_mapping(self, parameters): + param_to_param_index = {parameters[i]: i for i in range(len(parameters))} + param_set = set(parameters) + param_index_to_param_fqn = {} + for module_name, module in self.module.named_modules(): + for param_name, param in module.named_parameters(recurse=False): + fqn = f"{module_name}.{param_name}" + # Bypass ignored parameters since those are not reduced by DDP + # to begin with. + if fqn not in self.parameters_to_ignore and param.requires_grad: + if param not in param_set: + self._log_and_throw( + ValueError, + f"Param with name {fqn} found in module parameters, but not DDP parameters." + " This indicates a bug in DDP, please report an issue to PyTorch.", + ) + param_index = param_to_param_index[param] + param_index_to_param_fqn[param_index] = fqn + + # Ensure we covered all parameters + if len(param_set) != len(param_index_to_param_fqn): + self._log_and_throw( + ValueError, + ( + "Expected param to name mapping to cover all parameters, but" + f" got conflicting lengths: {len(param_set)} vs " + f"{len(param_index_to_param_fqn)}. This indicates a bug in DDP" + ", please report an issue to PyTorch." + ), + ) + + return param_index_to_param_fqn + + def _get_parameters(self, m, recurse=True): + """Return a generator of module parameters.""" + + def model_parameters(m): + ps = ( + m._former_parameters.values() + if hasattr(m, "_former_parameters") + else m.parameters(recurse=False) + ) + yield from ps + + for mod in m.modules() if recurse else [m]: + yield from model_parameters(mod) + + def _check_default_group(self): + pickle_not_supported = False + try: + if self.process_group != _get_default_group(): + pickle_not_supported = True + except RuntimeError: + pickle_not_supported = True + + if pickle_not_supported: + self._log_and_throw( + RuntimeError, + "DDP Pickling/Unpickling are only supported " + "when using DDP with the default process " + "group. That is, when you have called " + "init_process_group and have not passed " + "process_group argument to DDP constructor", + ) + + @contextmanager + def no_sync(self): + r""" + Context manager to disable gradient synchronizations across DDP processes. + + Within this context, gradients will be accumulated on module + variables, which will later be synchronized in the first + forward-backward pass exiting the context. + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> ddp = torch.nn.parallel.DistributedDataParallel(model, pg) + >>> with ddp.no_sync(): + >>> for input in inputs: + >>> ddp(input).backward() # no synchronization, accumulate grads + >>> ddp(another_input).backward() # synchronize grads + + .. warning:: + The forward pass should be included inside the context manager, or + else gradients will still be synchronized. + """ + old_require_backward_grad_sync = self.require_backward_grad_sync + self.require_backward_grad_sync = False + try: + yield + finally: + self.require_backward_grad_sync = old_require_backward_grad_sync + + @classmethod + def _get_active_ddp_module(cls): + """`TorchDynamo` requires DDP's status and module for cooperative optimization.""" + return cls._active_ddp_module + + # note, this ctxmgr function is marked 'skip' in torchdynamo, so dynamo only kicks in + # for the 'module_to_run' underneath + # see torch._dynamo/eval_frame.py TorchPatcher.patch for more details + @contextmanager + @torch._disable_dynamo(recursive=False) + def _inside_ddp_forward(self): + DistributedDataParallel._active_ddp_module = self + try: + yield + finally: + DistributedDataParallel._active_ddp_module = None + + def _run_ddp_forward(self, *inputs, **kwargs): + if self._use_python_reducer: + return self.module(*inputs, **kwargs) # type: ignore[index] + else: + with self._inside_ddp_forward(): + return self.module(*inputs, **kwargs) # type: ignore[index] + + def _clear_grad_buffer(self): + # Making param.grad points to the grad buffers before backward is based on the + # assumption that the grad accumulation is done in place in autograd engine, + # for some edge cases, if the grad accumulation in autograd engine is not in + # place, then the param.grad and grad buffers are detached. + if self._delay_grad_buffer is not None: + # We batch zero_grad for all params by resetting the whole grad + # buffer when the grad of all params is set to None. + all_param_grad_none = all( + param.grad is None for param in self._delay_all_reduce_params + ) + + for index, param in enumerate(self._delay_all_reduce_params): + if param.grad is None: + param.grad = self._delay_grad_views[index] + if not all_param_grad_none: + param.grad.zero_() + + if all_param_grad_none: + self._delay_grad_buffer.zero_() + + def _lazy_init(self): + # Initialization for DDP that occurs after construction, but lazily + # before the first forward pass. + self._setup_in_backward_optimizers() + self._lazy_init_ran = True + + def _should_disable_cpp_reducer(self) -> bool: + return self._use_python_reducer and ( + torch._utils.is_compiling() or self._force_to_disable_cpp_reducer + ) + + def _pre_forward(self, *inputs, **kwargs): + if self._should_disable_cpp_reducer(): + return inputs, kwargs + + # Disable the python reducer if compiled_autograd is not enabled. + if self._accum_grad_hooks: + for index, h in enumerate(self._accum_grad_hooks): + h.remove() + self._accum_grad_hooks.clear() + + if not self._lazy_init_ran and not torch._utils.is_compiling(): + self._lazy_init() + + if self._delay_all_reduce_all_params: + return inputs, kwargs + + if torch.is_grad_enabled() and self.require_backward_grad_sync: + assert self.logger is not None + self.logger.set_runtime_stats_and_log() + self.reducer.prepare_for_forward() + + # Notify the join context that this process has not joined, if + # needed + work = Join.notify_join_context(self) + if work: + self.reducer._set_forward_pass_work_handle( + work, self._divide_by_initial_world_size # type: ignore[arg-type] + ) + + # Calling _rebuild_buckets before forward computation, + # It may allocate new buckets before deallocating old buckets + # inside _rebuild_buckets. To save peak memory usage, + # call _rebuild_buckets before the peak memory usage increases + # during forward computation. + # This should be called only once during whole training period. + if torch.is_grad_enabled() and self.reducer._rebuild_buckets(): + logger.info("Reducer buckets have been rebuilt in this iteration.") + self._has_rebuilt_buckets = True + + # sync params according to location (before/after forward) user + # specified as part of hook, if hook was specified. + if self._check_sync_bufs_pre_fwd(): + self._sync_buffers() + + if self._join_config.enable: + # Notify joined ranks whether they should sync in backwards pass or not. + self._check_global_requires_backward_grad_sync(is_joined_rank=False) + + if self.device_ids: + moved_inputs, moved_kwargs = _to_kwargs( + inputs, + kwargs, + torch.device(self.device_type, self.device_ids[0]), + self.use_side_stream_for_tensor_copies, + ) + args, kwargs = moved_inputs[0], moved_kwargs[0] + # Cast inputs to reduced precision if needed. + if self.mixed_precision is not None: + args, kwargs = _cast_forward_inputs( + self.mixed_precision.param_dtype, + *args, + **kwargs, + ) + return args, kwargs + else: + # Cast inputs to reduced precision if needed. + # TODO (rohan-varma) test this codepath. + if self.mixed_precision is not None: + inputs, kwargs = _cast_forward_inputs( + self.mixed_precision.param_dtype, + *inputs, + **kwargs, + ) + return inputs, kwargs + + def _post_forward(self, output): + if self._should_disable_cpp_reducer(): + return output + + if self._delay_all_reduce_all_params: + self._clear_grad_buffer() + return output + + # sync params according to location (before/after forward) user + # specified as part of hook, if hook was specified. + if self._check_sync_bufs_post_fwd(): + self._sync_buffers() + + if torch.is_grad_enabled() and self.require_backward_grad_sync: + self.require_forward_param_sync = True + # We'll return the output object verbatim since it is a freeform + # object. We need to find any tensors in this object, though, + # because we need to figure out which parameters were used during + # this forward pass, to ensure we short circuit reduction for any + # unused parameters. Only if `find_unused_parameters` is set. + if self.find_unused_parameters and not self.static_graph: + # Do not need to populate this for static graph. + self.reducer.prepare_for_backward(list(_find_tensors(output))) + else: + self.reducer.prepare_for_backward([]) + else: + self.require_forward_param_sync = False + + # TODO: DDPSink is currently enabled for unused parameter detection and + # static graph training for first iteration. + if (self.find_unused_parameters and not self.static_graph) or ( + self.static_graph and not self._static_graph_delay_allreduce_enqueued + ): + ( + output_tensor_list, + treespec, + output_is_rref, + ) = _tree_flatten_with_rref(output) + output_placeholders = [None for _ in range(len(output_tensor_list))] + # Do not touch tensors that have no grad_fn, which can cause issues + # such as https://github.com/pytorch/pytorch/issues/60733 + for i, output in enumerate(output_tensor_list): + if torch.is_tensor(output) and output.grad_fn is None: + output_placeholders[i] = output + + # When find_unused_parameters=True, makes tensors which require grad + # run through the DDPSink backward pass. When not all outputs are + # used in loss, this makes those corresponding tensors receive + # undefined gradient which the reducer then handles to ensure + # param.grad field is not touched and we don't error out. + passthrough_tensor_list = _DDPSink.apply( + weakref.ref(self), + *output_tensor_list, + ) + for i in range(len(output_placeholders)): + if output_placeholders[i] is None: + output_placeholders[i] = passthrough_tensor_list[i] + + # Reconstruct output data structure. + output = _tree_unflatten_with_rref( + output_placeholders, treespec, output_is_rref + ) + + # At the end of the forward pass, reset the grad buffer and grad views + self._clear_grad_buffer() + return output + + def forward(self, *inputs, **kwargs): + with torch.autograd.profiler.record_function("DistributedDataParallel.forward"): + inputs, kwargs = self._pre_forward(*inputs, **kwargs) + output = ( + self.module.forward(*inputs, **kwargs) + if self._delay_all_reduce_all_params + else self._run_ddp_forward(*inputs, **kwargs) + ) + return self._post_forward(output) + + def scatter(self, inputs, kwargs, device_ids): + return scatter_kwargs(inputs, kwargs, device_ids, dim=self.dim) + + def to_kwargs(self, inputs, kwargs, device_id): + # Kept for BC + return _to_kwargs( + inputs, + kwargs, + torch.device(self.device_type, device_id), + self.use_side_stream_for_tensor_copies, + ) + + def gather(self, outputs, output_device): + return gather(outputs, output_device, dim=self.dim) + + def train(self, mode=True): + super().train(mode) + return self + + # When running in join mode, schedules an allreduce to notify joined ranks + # of whether backwards pass synchronization will run this iteration or not. + def _check_global_requires_backward_grad_sync(self, is_joined_rank): + if not is_joined_rank and self.require_backward_grad_sync: + requires_sync_tensor = torch.ones(1, device=self.device) + else: + requires_sync_tensor = torch.zeros(1, device=self.device) + + work = dist.all_reduce( + requires_sync_tensor, group=self.process_group, async_op=True + ) + + # (kwen2501) This if condition is a plain translation of previous + # behavior, i.e. in the `is_joined_rank=False` case, `work.wait()` + # is not called and it doesn't care about the result. I am guessing + # that it just wants to fire a matching all-reduce and does not want + # the main stream to wait. + if is_joined_rank: + work.wait() + should_sync_backwards = requires_sync_tensor.item() != 0 + return should_sync_backwards + else: + return None # Return value is not/should not be used. + + # When running in join mode, checks and performs sync of module buffers if + # the models have buffers that should be synchronized in the forward pass. + def _check_and_sync_module_buffers(self): + if self._check_sync_bufs_pre_fwd(): + authoritative_rank = self._find_common_rank(self._distributed_rank, False) + self._sync_module_buffers(authoritative_rank) + + # When running in join model, agrees upon a common rank and broadcast model + # parameters to all other ranks. + def _sync_final_model(self, is_last_joiner): + # Agree upon the process that will be the authoritative model copy. + # The current rank is a candidate for being the authoritative copy if + # is_last_joiner=True. We break ties via picking the larger rank. + self._authoritative_rank = self._find_common_rank( + self._distributed_rank, is_last_joiner + ) + _sync_module_states( + module=self.module, + process_group=self.process_group, + broadcast_bucket_size=self.broadcast_bucket_size, + src=self._authoritative_rank, + params_and_buffers_to_ignore=self.parameters_to_ignore, + broadcast_buffers=self.broadcast_buffers, + ) + + # Schedule comm ops to match those scheduled in the reducer's backward + # pass. + def _match_all_reduce_for_bwd_pass(self): + comm_work = [] + # Schedule comm in the same order as Reducer schedules them, i.e. + # the order of the buckets. Retrieving the bucket order from the reducer + # ensures that we keep the same order in join mode, such as when bucket + # order is rebuilt dynamically. + + # Returns grad_buckets in order, but real tensors are substituted with + # zero tensors of the same shape. + grad_buckets = self.reducer._get_zeros_like_grad_buckets() + for grad_bucket in grad_buckets: + # Joined processes contribute zero gradient. In the case that + # divide_by_initial_world_size=True, we divide grads by the static + # world size, if not, the dividing factor is reduced by the number + # of joined processes. + work = self.reducer._run_comm_hook(grad_bucket) + comm_work.append(work) + for work in comm_work: + work.wait() + + # Allreduces the used parameter mapping across ranks. + def _match_unused_params_allreduce(self): + locally_used_param_map = self.reducer._get_local_used_map() + self.process_group.allreduce(locally_used_param_map) + + def join( + self, + divide_by_initial_world_size: bool = True, + enable: bool = True, + throw_on_early_termination: bool = False, + ): + r""" + Context manager for training with uneven inputs across processes in DDP. + + This context manager will keep track of already-joined DDP processes, + and "shadow" the forward and backward passes by inserting collective + communication operations to match with the ones created by non-joined + DDP processes. This will ensure each collective call has a corresponding + call by already-joined DDP processes, preventing hangs or errors that + would otherwise happen when training with uneven inputs across + processes. Alternatively, if the flag ``throw_on_early_termination`` is + specified to be ``True``, all trainers will throw an error once one rank + runs out of inputs, allowing these errors to be caught and handled + according to application logic. + + Once all DDP processes have joined, the context manager will broadcast + the model corresponding to the last joined process to all processes to + ensure the model is the same across all processes + (which is guaranteed by DDP). + + To use this to enable training with uneven inputs across processes, + simply wrap this context manager around your training loop. No further + modifications to the model or data loading is required. + + .. warning:: + If the model or training loop this context manager is wrapped around + has additional distributed collective operations, such as + ``SyncBatchNorm`` in the model's forward pass, then the flag + ``throw_on_early_termination`` must be enabled. This is because this + context manager is not aware of non-DDP collective communication. + This flag will cause all ranks to throw when any one rank + exhausts inputs, allowing these errors to be caught and recovered + from across all ranks. + + Args: + divide_by_initial_world_size (bool): If ``True``, will divide + gradients by the initial ``world_size`` DDP training was launched + with. If ``False``, will compute the effective world size + (number of ranks that have not depleted their inputs yet) and + divide gradients by that during allreduce. Set + ``divide_by_initial_world_size=True`` to ensure every input + sample including the uneven inputs have equal weight in terms of + how much they contribute to the global gradient. This is + achieved by always dividing the gradient by the initial + ``world_size`` even when we encounter uneven inputs. If you set + this to ``False``, we divide the gradient by the remaining + number of nodes. This ensures parity with training on a smaller + ``world_size`` although it also means the uneven inputs would + contribute more towards the global gradient. Typically, you + would want to set this to ``True`` for cases where the last few + inputs of your training job are uneven. In extreme cases, where + there is a large discrepancy in the number of inputs, setting + this to ``False`` might provide better results. + enable (bool): Whether to enable uneven input detection or not. Pass + in ``enable=False`` to disable in cases where you know that + inputs are even across participating processes. Default is + ``True``. + throw_on_early_termination (bool): Whether to throw an error + or continue training when at least one rank has exhausted + inputs. If ``True``, will throw upon the first rank reaching end + of data. If ``False``, will continue training with a smaller + effective world size until all ranks are joined. Note that if + this flag is specified, then the flag + ``divide_by_initial_world_size`` would be ignored. Default + is ``False``. + + + Example:: + + >>> # xdoctest: +SKIP("Distributed") + >>> import torch + >>> import torch.distributed as dist + >>> import os + >>> import torch.multiprocessing as mp + >>> import torch.nn as nn + >>> # On each spawned worker + >>> def worker(rank): + >>> dist.init_process_group("nccl", rank=rank, world_size=2) + >>> torch.cuda.set_device(rank) + >>> model = nn.Linear(1, 1, bias=False).to(rank) + >>> model = torch.nn.parallel.DistributedDataParallel( + >>> model, device_ids=[rank], output_device=rank + >>> ) + >>> # Rank 1 gets one more input than rank 0. + >>> inputs = [torch.tensor([1]).float() for _ in range(10 + rank)] + >>> with model.join(): + >>> for _ in range(5): + >>> for inp in inputs: + >>> loss = model(inp).sum() + >>> loss.backward() + >>> # Without the join() API, the below synchronization will hang + >>> # blocking for rank 1's allreduce to complete. + >>> torch.cuda.synchronize(device=rank) + """ + return Join( + [self], + enable, + throw_on_early_termination, + divide_by_initial_world_size=divide_by_initial_world_size, + ) + + def join_hook( + self, + **kwargs, + ): + r""" + DDP join hook enables training on uneven inputs by mirroring communications in forward and backward passes. + + Arguments: + kwargs (dict): a :class:`dict` containing any keyword arguments + to modify the behavior of the join hook at run time; all + :class:`Joinable` instances sharing the same join context + manager are forwarded the same value for ``kwargs``. + + The hook supports the following keyword arguments: + divide_by_initial_world_size (bool, optional): + If ``True``, then gradients are divided by the initial world + size that DDP was launched with. + If ``False``, then gradients are divided by the effective world + size (i.e. the number of non-joined processes), meaning that + the uneven inputs contribute more toward the global gradient. + Typically, this should be set to ``True`` if the degree of + unevenness is small but can be set to ``False`` in extreme + cases for possibly better results. + Default is ``True``. + """ + divide_by_initial_world_size = kwargs.get("divide_by_initial_world_size", True) + return _DDPJoinHook( + self, divide_by_initial_world_size=divide_by_initial_world_size + ) + + @property + def join_device(self): + return self.device + + @property + def join_process_group(self): + return self.process_group + + def _register_buffer_comm_hook( + self, + state, + hook: Callable, + comm_hook_location=_BufferCommHookLocation.POST_FORWARD, + ): + r""" + Allow custom registration of hooks that define how buffer are synchronized across ranks. + + The hook takes in an optional state and is passed in a Dict[str, Tensor] + corresponding to buffer names and the buffers, and can run arbitrary reductions + on buffers as opposed to DDP's default broadcast from rank 0. This is useful for + example if a counter needs to be summed or averaged across ranks every iteration. + + Args: + state (Any): Optional state that is passed to the hook. + hook (Callable): Callable with the following signature: + ``hook(state: object, bucket: dist.GradBucket) -> torch.futures.Future[torch.Tensor]`` + comm_hook_location (_BufferCommHookLocation): Enum value indicating + where to run the hook. + _BufferCommHookLocation.PRE_FORWARD means that the + hook will run _before_ the forward pass, and + _BufferCommHookLocation.POST_FORWARD means that the + hook will run _after_ the forward pass. + + NOTE: To maximize performance, users can return a + List[torch.futures.Future] from their hook, and DDP will + install and await these hooks appropriately at the end of + the backward pass. This will ensure all buffers are + synchronized by the end of the backward pass. If this + setting is used, it is recommended to pass + comm_hook_location=_BufferCommHookLocation.POST_FORWARD, + which will trigger the hook after the forward pass. + If _BufferCommHookLocation.PRE_FORWARD is used, users must + ensure appropriate synchronization when manipulating GPU + buffers in the forward pass. + """ + assert callable(hook) + self.buffer_hook = _BufferCommHook( + buffer_comm_hook=hook, + buffer_comm_hook_state=state, + buffer_comm_hook_location=comm_hook_location, + ) + + def register_comm_hook(self, state: object, hook: Callable): + r""" + Register communication hook for user-defined DDP aggregation of gradients across multiple workers. + + This hook would be very useful for researchers to try out new ideas. For + example, this hook can be used to implement several algorithms like GossipGrad + and gradient compression which involve different communication strategies for + parameter syncs while running Distributed DataParallel training. + + Args: + state (object): Passed to the hook to maintain any state information during the training process. + Examples include error feedback in gradient compression, + peers to communicate with next in GossipGrad, etc. + + It is locally stored by each worker + and shared by all the gradient tensors on the worker. + hook (Callable): Callable with the following signature: + ``hook(state: object, bucket: dist.GradBucket) -> torch.futures.Future[torch.Tensor]``: + + This function is called once the bucket is ready. The + hook can perform whatever processing is needed and return + a Future indicating completion of any async work (ex: allreduce). + If the hook doesn't perform any communication, it still + must return a completed Future. The Future should hold the + new value of grad bucket's tensors. Once a bucket is ready, + c10d reducer would call this hook and use the tensors returned + by the Future and copy grads to individual parameters. + Note that the future's return type must be a single tensor. + + We also provide an API called ``get_future`` to retrieve a + Future associated with the completion of ``c10d.ProcessGroup.Work``. + ``get_future`` is currently supported for NCCL and also supported for most + operations on GLOO and MPI, except for peer to peer operations (send/recv). + + .. warning :: + Grad bucket's tensors will not be predivided by world_size. User is responsible + to divide by the world_size in case of operations like allreduce. + + .. warning :: + DDP communication hook can only be registered once and should be registered + before calling backward. + + .. warning :: + The Future object that hook returns should contain a single tensor + that has the same shape with the tensors inside grad bucket. + + .. warning :: + ``get_future`` API supports NCCL, and partially GLOO and MPI backends (no support + for peer-to-peer operations like send/recv) and will return a ``torch.futures.Future``. + + Example:: + Below is an example of a noop hook that returns the same tensor. + + >>> # xdoctest: +SKIP('undefined name') + >>> def noop(state: object, bucket: dist.GradBucket) -> torch.futures.Future[torch.Tensor]: + >>> fut = torch.futures.Future() + >>> fut.set_result(bucket.buffer()) + >>> return fut + >>> ddp.register_comm_hook(state=None, hook=noop) + + Example:: + Below is an example of a Parallel SGD algorithm where gradients are encoded before + allreduce, and then decoded after allreduce. + + >>> # xdoctest: +SKIP('undefined name') + >>> def encode_and_decode(state: object, bucket: dist.GradBucket) -> torch.futures.Future[torch.Tensor]: + >>> encoded_tensor = encode(bucket.buffer()) # encode gradients + >>> fut = torch.distributed.all_reduce(encoded_tensor).get_future() + >>> # Define the then callback to decode. + >>> def decode(fut): + >>> decoded_tensor = decode(fut.value()[0]) # decode gradients + >>> return decoded_tensor + >>> return fut.then(decode) + >>> ddp.register_comm_hook(state=None, hook=encode_and_decode) + """ + self._check_comm_hook(hook) + if hook.__name__ in ["bf16_compress_hook", "fp16_compress_hook"]: + # If we pass None, then the hook will try to get the world size + # by calling `dist.group.WORLD.size()`, which causes compilation + # errors. So we pre-decode the process group and pass it to the + # hook. + if state is None: + state = dist.group.WORLD + assert self.logger is not None + self.logger._set_comm_hook_name(hook.__qualname__) + self._comm_hooks.append((hook, state)) + dist._register_comm_hook(self.reducer, state, hook) + + def _register_builtin_comm_hook(self, comm_hook_type): + r""" + Register a built-in communication hook that specifies how DDP aggregates gradients across multiple workers. + + The built-in hooks aim to provide efficient C++ implementations for certain hooks, + which might not be as efficient if implemented in Python using a Python communication hook. + + Args: + comm_hook_type (dist.BuiltinCommHookType): type of communication hook, such as ALLREDUCE, FP16_COMPRESS, etc. + + .. warning :: + DDP communication hook can only be registered once and should be registered + before calling backward. + + Example:: + Below is an example of a FP16 compression where gradients are + compressed into 16-bit floating-point numbers before allreduce, and + then decompressed after allreduce. + + >>> # xdoctest: +SKIP('undefined name') + >>> ddp._register_builtin_comm_hook(dist.BuiltinCommHookType.FP16_COMPRESS) + + """ + assert self.logger is not None + self.logger._set_comm_hook_name(str(comm_hook_type)) + dist._register_builtin_comm_hook(self.reducer, comm_hook_type) + + def _register_fused_optim(self, optim: Type, *args, optim_params=None, **kwargs): + r""" + Register an optimizer in DDP to optimize parameter immediately after its gradient reduction. + + Registers an optimizer with DDP such that the optimization for a + parameter will run immediately when that parameter's gradient is + finished with reduction, instead of waiting for all parameters' + gradients to finish reduction. This can result in a training speedup + depending on your workload since the optimizer can run while gradient + reduction for other parameters are still ongoing. In addition, this has + the potential to reduce peak memory consumption during training, as it + only needs to load the per-parameter optimizer states of a single + parameter at a time, instead of loading all per-parameter optimizer + states at once. + + Args: + optim (Type): a ``torch.optim.Optimizer`` class to be registered + as a fused optimizer. + *args (Sequence[Any]): Arguments to forward to `optim`. + optim_params (Optional[Iterable[torch.Tensor]]): Set of parameters + to optimize, similar to `params` argument of traditional `torch.optim` + Optimizers. If this is omitted, all DDP model parameters will be + optimized. + **kwargs: (Dict[str, Any]): Keyword arguments to forward to `optim`. + + .. warning :: + _register_fused_optim should only be called once on a DDP instance, + and registering multiple fused optimizers for the same DDP model + is not currently supported. Please ping + https://github.com/pytorch/pytorch/issues/71595 if this is necessary + for your use case. + + .. warning :: + _register_fused_optim and register_comm_hook currently do not + compose together, meaning that custom DDP communication hooks are + not supported with overlapped optimizers. Please ping + https://github.com/pytorch/pytorch/issues/71595 if this is necessary + for your use case. + + .. warning :: + Gradient accumulation and DDP `no_sync` are currently not supported + with overlapped optimizer. Please ping + https://github.com/pytorch/pytorch/issues/71595 if this is necessary + for your use case. + + Example:: + + >>> # xdoctest: +SKIP("No rendezvous handler") + >>> torch.distributed.init_process_group(backend='nccl', world_size=4, init_method='...') + >>> net = torch.nn.parallel.DistributedDataParallel(model, pg) + >>> lr = 1e-2 + >>> betas = (0.9, 0.99) + >>> eps = 1e-6 + >>> net._register_fused_optim(torch.optim.Adam, lr, betas=betas, eps=eps) + >>> # Example with subset of parameters + >>> params_to_opt = [list(net.parameters())[0]] + >>> net._register_fused_optim( + ... torch.optim.Adam, lr, optim_params=params_to_opt, betas=betas, eps=eps + ... ) + """ + # Note: importing in function, otherwise this will cause a circular + # import as optimizer_overlap module needs to import DistributedDataParallel. + from torch.distributed.algorithms._optimizer_overlap import _as_overlapped_optim + + overlapped_optim = _as_overlapped_optim(optim, optim_params, *args, **kwargs) + try: + overlapped_optim.register_ddp(self) + except NotImplementedError as e: + raise RuntimeError( + f"{optim} does not support overlapped DDP. Please file an issue to PyTorch or the respective owner of {optim}." + ) from e + + def _distributed_broadcast_coalesced( + self, tensors, buffer_size, authoritative_rank=0 + ): + dist._broadcast_coalesced( + self.process_group, tensors, buffer_size, authoritative_rank + ) + + def _check_sync_bufs_post_fwd(self): + return ( + self.will_sync_module_buffers() + and hasattr(self, "buffer_hook") + and self.buffer_hook.buffer_comm_hook_location + == _BufferCommHookLocation.POST_FORWARD + ) + + def _check_sync_bufs_pre_fwd(self): + return self.will_sync_module_buffers() and ( + not hasattr(self, "buffer_hook") + or self.buffer_hook.buffer_comm_hook_location + == _BufferCommHookLocation.PRE_FORWARD + ) + + def will_sync_module_buffers(self): + return ( + self.require_forward_param_sync + and self.broadcast_buffers + and len(self.modules_buffers) > 0 + ) + + def _find_common_rank(self, input_rank, rank_cond): + # -1 indicates that this rank is not under consideration to be the + # common_rank + rank_to_use = torch.tensor( + [input_rank if rank_cond else -1], + device=self.device, + ) + dist.all_reduce(rank_to_use, op=ReduceOp.MAX, group=self.process_group) + if rank_to_use.item() == -1: + self._log_and_throw( + ValueError, + "BUG! Expected rank_cond to be true for at least one process." + " This indicates a bug in PyTorch, please report an issue.", + ) + return rank_to_use.item() + + def _sync_buffers(self): + with torch.no_grad(): + # module buffer sync + # Synchronize buffers across processes. + # If we are running DDP with the join manager, we have to agree + # upon a rank to sync module buffers from, since rank 0 may + # already have been joined and have stale module buffers. + if self._join_config.enable: + authoritative_rank = self._find_common_rank( + self._distributed_rank, True + ) + else: + # The process with rank 0 is considered the authoritative copy. + authoritative_rank = 0 + # Update self.modules_buffers incase any buffers were + # reassigned. + self._assign_modules_buffers() + self._sync_module_buffers(authoritative_rank) + + def _sync_module_buffers(self, authoritative_rank): + if not hasattr(self, "buffer_hook"): + self._default_broadcast_coalesced(authoritative_rank=authoritative_rank) + else: + hook = self.buffer_hook.buffer_comm_hook + state = self.buffer_hook.buffer_comm_hook_state + futs = hook(state, self.named_module_buffers) + if futs is not None: + self.reducer._install_post_backward_futures(futs) + + def _default_broadcast_coalesced( + self, bufs=None, bucket_size=None, authoritative_rank=0 + ): + """ + Broadcasts buffers from rank 0 to rest of workers. + + If bufs, bucket_size are None, default values self.modules_buffers + and self.broadcast_bucket_size are used instead. + """ + if bufs is None: + bufs = self.modules_buffers + if bucket_size is None: + bucket_size = self.broadcast_bucket_size + + self._distributed_broadcast_coalesced(bufs, bucket_size, authoritative_rank) + + def _passing_sync_batchnorm_handle(self, module): + for layer in module.modules(): + if isinstance(layer, torch.nn.modules.SyncBatchNorm): + if self.device_type == "cpu": + self._log_and_throw( + ValueError, + "SyncBatchNorm layers only work with GPU modules", + ) + + def _check_comm_hook(self, hook): + if not callable(hook): + self._log_and_throw(TypeError, "Communication hook must be callable.") + + sig = inspect.signature(hook) + if ( + sig.parameters["bucket"].annotation != inspect._empty + and sig.parameters["bucket"].annotation != dist.GradBucket + ): + self._log_and_throw( + ValueError, + "Communication hook: bucket annotation should be dist.GradBucket.", + ) + + if ( + sig.return_annotation != inspect._empty + and sig.return_annotation != torch.futures.Future[torch.Tensor] + ): + self._log_and_throw( + ValueError, + "Communication hook: return annotation should be torch.futures.Future[torch.Tensor].", + ) + + if hook.__name__ in [ + "bf16_compress_hook", + "bf16_compress_wrapper_hook", + ] and ( + (torch.version.cuda is None and torch.version.hip is None) + or ( + torch.version.cuda is not None + and int(torch.version.cuda.split(".")[0]) < 11 + ) + or not dist.is_available() + or not dist.is_nccl_available() + or torch.cuda.nccl.version() < (2, 10) + ): + self._log_and_throw( + TypeError, + "BF16 all reduce communication hook required CUDA 11+ and NCCL 2.10+.", + ) + + @property + def _distributed_rank(self): + return dist.get_rank(self.process_group) + + @staticmethod + def _get_data_parallel_params(module, named_params=False): + """Return a generator of parameters managed by a given DDP unit.""" + for param in ( + module.parameters() if not named_params else module.named_parameters() + ): + if not hasattr(param, "_ddp_ignored"): + yield param + + @staticmethod + def _set_params_and_buffers_to_ignore_for_model( + module, params_and_buffers_to_ignore + ): + """ + Set parameters and buffers to be ignored by DDP. + + Expected format for parameters is the fully qualified name: {module_name}.{param_name}, and + similarly, {module_name}.{buffer_name} for buffers. For example: + params_to_ignore = [] + # NB: model here is vanilla PyTorch module, not yet wrapped with DDP. + for module_name, module in model.named_modules(): + for param_name, param in module.named_parameters(recurse=False): + if should_ignore(param): + # Create expected format + fqn = f"{module_name}.{param_name}" + params_to_ignore.append(fqn) + torch.nn.parallel.DistributedDataParallel._set_params_and_buffers_to_ignore_for_model( + model, + params_to_ignore + ) + """ + # This is a workaround to set parameters and buffers DDP should ignore + # during synchronization. It will be removed when the API is finalized + # as part of addressing https://github.com/pytorch/pytorch/issues/43690. + module._ddp_params_and_buffers_to_ignore = params_and_buffers_to_ignore + for name, param in module.named_parameters(): + if name in params_and_buffers_to_ignore: + param._ddp_ignored = True + for name, buffer in module.named_buffers(): + if name in params_and_buffers_to_ignore: + buffer._ddp_ignored = True + + def _get_ddp_logging_data(self): + r""" + Return a dictionary of logging data for debugging and analysis. + + This interface can be called after DistributedDataParallel() is + constructed. It returns a dictionary of logging data. It could help + for debugging and analysis. The logging data includes DistributedDataParallel + constructor input parameters, some internal states of DistributedDataParallel + and performance metrics. Simply print the dictionary and see what + these metrics are. + This is a prototype interface and subject to change in the future. + """ + assert self.logger is not None + ddp_logging_data = self.logger._get_ddp_logging_data() + return {**ddp_logging_data.strs_map, **ddp_logging_data.ints_map} + + def _set_ddp_runtime_logging_sample_rate(self, sample_rate): + r""" + Set sample_rate of collecting runtime stats. + + This interface allows users to set sample_rate of collecting + runtime stats. The runtime stats will be recorded for the + first 10 iterations, after 10 iterations runtime stats will be + recorded once every "sample_rate" training iterations. In + default, runtime stats are recorded for the first 10 iterations, + after 10 iterations runtime stats are recorded once every + "kDDPRuntimeLoggingSampleRate=100" training iterations. + This is a prototype interface and subject to change in the future. + """ + if sample_rate < 1: + self._log_and_throw( + ValueError, + "DDP runtime logging sample rate should be equal or greater than 1", + ) + self.reducer._set_ddp_runtime_logging_sample_rate(sample_rate) + + def _set_static_graph(self): + """ + Set static graph for DDP. + + It is recommended to set static graph in the DDP constructor, which will + call this private API internally. + """ + # If self.static_graph has been set, no need to set it again + if self.static_graph: + warnings.warn( + "You've set static_graph to be True, no need to set it again." + ) + return + self.static_graph = True + self._static_graph_delay_allreduce_enqueued = False + self.reducer._set_static_graph() + assert self.logger is not None + self.logger._set_static_graph() + if self.find_unused_parameters: + warnings.warn( + "You passed find_unused_parameters=true to DistributedDataParallel, " + "`_set_static_graph` will detect unused parameters automatically, so " + "you do not need to set find_unused_parameters=true, just be sure these " + "unused parameters will not change during training loop while calling " + "`_set_static_graph`." + ) + + def _remove_autograd_hooks(self): + """Remove autograd hooks registered by the reducer on the model parameters.""" + self.reducer._remove_autograd_hooks() + + def _check_reducer_finalized(self): + """ + Check if the reducer has processed all buckets and finalized the backward appropriately. + + It is useful to call this method after calling .backward() in your training loop + in order to avoid subsequent hard to debug errors down the road due to the + reducer not finalizing backward. + """ + self.reducer._check_reducer_finalized() + + def _set_sparse_metadata(self, global_unique_ids): + self.reducer._set_sparse_metadata(global_unique_ids) + + def _update_process_group(self, new_process_group): + """ + Dynamically updates the process group for DDP so that we can shrink/expand DDP + world size without having to reinitialize DDP. + + NOTE: If you are using custom communications hooks via, register_comm_hook, + you need to update the process groups for those hooks separately. + """ + # Force a rebuild of buckets for a new process group. This ensures all ranks + # are synchronized in terms of when they will rebuild buckets and also + # re-evaluates previous assumptions of buckets given the world size might have + # changed. + self._has_rebuilt_buckets = False + self.reducer._reset_state() + + if not _rank_not_in_group(new_process_group): + self.process_group = new_process_group + self.reducer._update_process_group(new_process_group)