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# Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
"""Communications utilities."""
import torch
from megatron.core import mpu
# TODO: use functions from megatron/p2p
def recv_from_prev_pipeline_rank_(recv_buffer=None):
"""Receive from previous pipeline stage and update the
input buffer inplace."""
if not mpu.is_pipeline_first_stage():
assert recv_buffer is not None
recv_prev_op = torch.distributed.P2POp(
torch.distributed.irecv, recv_buffer,
mpu.get_pipeline_model_parallel_prev_rank())
reqs = torch.distributed.batch_isend_irecv([recv_prev_op])
for req in reqs:
req.wait()
# To protect against race condition when using batch_isend_irecv().
torch.cuda.synchronize()
# TODO: use functions from megatron/p2p
def send_to_next_pipeline_rank(tensor=None):
"""Send output to the next pipeline stage."""
if not mpu.is_pipeline_last_stage():
assert tensor is not None
send_next_op = torch.distributed.P2POp(
torch.distributed.isend, tensor,
mpu.get_pipeline_model_parallel_next_rank())
reqs = torch.distributed.batch_isend_irecv([send_next_op])
for req in reqs:
req.wait()
# To protect against race condition when using batch_isend_irecv().
torch.cuda.synchronize()
def _is_cuda(tensor):
"""Check if a tensor is not none and is cuda."""
assert tensor is not None
assert tensor.is_cuda
def _is_cuda_contiguous(tensor):
"""Check if a tensor is not none, is cuda, and is contiguous."""
_is_cuda(tensor)
assert tensor.is_contiguous()
def broadcast_from_last_pipeline_stage(size, dtype, tensor=None):
"""Broadcast a tensor from last pipeline stage to all ranks."""
is_last_stage = mpu.is_pipeline_last_stage()
# If first stage and last state are the same, then there is no
# pipeline parallelism and no need to communicate.
if mpu.is_pipeline_first_stage() and is_last_stage:
return tensor
if is_last_stage:
_is_cuda_contiguous(tensor)
else:
tensor = torch.empty(size,
dtype=dtype,
device=torch.cuda.current_device())
# Get the group and corresponding source rank.
src = mpu.get_pipeline_model_parallel_last_rank()
group = mpu.get_pipeline_model_parallel_group()
torch.distributed.broadcast(tensor, src, group)
return tensor
def broadcast_from_last_to_first_pipeline_stage(size, dtype, tensor=None):
"""Broadcast tensor values from last stage into the first stage."""
is_last_stage = mpu.is_pipeline_last_stage()
is_first_stage = mpu.is_pipeline_first_stage()
# If first stage and last state are the same, then there is no
# pipeline parallelism and no need to communicate.
if is_first_stage and is_last_stage:
return tensor
# Only first and last stage pipeline stages need to be involved.
if is_last_stage or is_first_stage:
if is_last_stage:
_is_cuda_contiguous(tensor)
else:
tensor = torch.empty(size,
dtype=dtype,
device=torch.cuda.current_device())
src = mpu.get_pipeline_model_parallel_last_rank()
group = mpu.get_embedding_group()
# Broadcast from last stage into the first stage.
torch.distributed.broadcast(tensor, src, group)
else:
tensor = None
return tensor
def copy_from_last_to_first_pipeline_stage(size, dtype, tensor=None):
"""Copy tensor values from last stage into the first stage.
Note that the input tensor is updated in place."""
is_last_stage = mpu.is_pipeline_last_stage()
is_first_stage = mpu.is_pipeline_first_stage()
# If first stage and last state are the same, then there is no
# pipeline parallelism and no need to communicate.
if is_first_stage and is_last_stage:
return
# Only first and last stage pipeline stages need to be involved.
if is_last_stage or is_first_stage:
_is_cuda(tensor)
is_contiguous = tensor.is_contiguous()
src = mpu.get_pipeline_model_parallel_last_rank()
group = mpu.get_embedding_group()
if is_contiguous:
tensor_ = tensor
else:
if is_last_stage:
tensor_ = tensor.contiguous()
else:
tensor_ = torch.empty(size,
dtype=dtype,
device=torch.cuda.current_device())
# Broadcast from last stage into the first stage.
torch.distributed.broadcast(tensor_, src, group)
# Update the first stage tensor
if is_first_stage and not is_contiguous:
tensor[...] = tensor_
def broadcast_tensor(size, dtype, tensor=None, rank=0):
""" Given size and type of a tensor on all ranks and the tensor value
only on a specific rank, broadcast from that rank to all other ranks.
"""
if torch.distributed.get_rank() == rank:
_is_cuda_contiguous(tensor)
else:
tensor = torch.empty(size,
dtype=dtype,
device=torch.cuda.current_device())
torch.distributed.broadcast(tensor, rank)
return tensor
def broadcast_list(size, dtype, list_values=None, rank=0):
"""Broadcast a list of values with a given type."""
tensor = None
if torch.distributed.get_rank() == rank:
tensor = torch.tensor(list_values, dtype=dtype,
device=torch.cuda.current_device())
return broadcast_tensor(size, dtype, tensor=tensor, rank=rank)
def broadcast_int_list(size, int_list=None, rank=0):
"""Broadcast a list of interger values."""
return broadcast_list(size, torch.int64, list_values=int_list, rank=rank)
def broadcast_float_list(size, float_list=None, rank=0):
"""Broadcast a list of float values."""
return broadcast_list(size, torch.float32, list_values=float_list,
rank=rank)
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