You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
441 lines
15 KiB
441 lines
15 KiB
import torch
|
|
import torch.distributed as dist
|
|
from torch.autograd import Function
|
|
# The two imports below are not always available depending on the
|
|
# USE_DISTRIBUTED compile flag. Make sure they raise import error
|
|
# if we're trying to use them.
|
|
from torch.distributed import group, ReduceOp
|
|
|
|
def broadcast(tensor, src, group=group.WORLD):
|
|
"""
|
|
Broadcasts the tensor to the whole group.
|
|
|
|
``tensor`` must have the same number of elements in all processes
|
|
participating in the collective.
|
|
|
|
Arguments:
|
|
tensor (Tensor): Data to be sent if ``src`` is the rank of current
|
|
process.
|
|
src (int): Source rank.
|
|
group (ProcessGroup, optional): The process group to work on.
|
|
|
|
Returns:
|
|
Tensor: Received tensor from the broadcast op.
|
|
|
|
"""
|
|
return _Broadcast.apply(src, group, tensor)
|
|
|
|
|
|
def gather(tensor, dst=0, group=group.WORLD):
|
|
"""
|
|
Gathers a list of tensors in a single process.
|
|
|
|
Arguments:
|
|
tensor (Tensor): Input tensor.
|
|
dst (int, optional): Destination rank (default is 0).
|
|
group (ProcessGroup, optional): The process group to work on.
|
|
|
|
Returns:
|
|
tuple[Tensor]: List of appropriately-sized tensors with the gathered data.
|
|
"""
|
|
return _Gather.apply(dst, group, tensor)
|
|
|
|
|
|
def scatter(tensors, src=0, group=group.WORLD):
|
|
"""
|
|
Scatters a list of tensors to all processes in a group.
|
|
|
|
Each process will receive exactly one tensor and store its data in the
|
|
``tensor`` argument.
|
|
|
|
Arguments:
|
|
tensors (list[Tensor]): List of tensors to scatter on the source rank.
|
|
Receivers must pass ``None`.
|
|
src (int, optional): Source rank (default is 0).
|
|
group (ProcessGroup, optional): The process group to work on.
|
|
|
|
Returns:
|
|
Tensor: Output tensor from the scatter operation.
|
|
|
|
"""
|
|
return _Scatter.apply(src, group, *tensors)
|
|
|
|
|
|
def reduce(tensor, dst, op=ReduceOp.SUM, group=group.WORLD):
|
|
"""
|
|
Reduces the tensor data across all machines.
|
|
|
|
Only the process with rank ``dst`` is going to receive the final result.
|
|
|
|
Arguments:
|
|
tensor (Tensor): Input of the collective.
|
|
dst (int): Destination rank.
|
|
op (optional): One of the values from
|
|
``torch.distributed.ReduceOp``
|
|
enum. Specifies an operation used for element-wise reductions.
|
|
group (ProcessGroup, optional): The process group to work on.
|
|
|
|
Returns:
|
|
Tensor: Output of the collective.
|
|
|
|
"""
|
|
return _Reduce.apply(dst, op, group, tensor)
|
|
|
|
|
|
def reduce_scatter(output, input_list, op=ReduceOp.SUM, group=group.WORLD):
|
|
"""
|
|
Reduces, then scatters a list of tensors to all processes in a group.
|
|
|
|
Arguments:
|
|
output (Tensor): Output tensor.
|
|
input_list (list[Tensor]): List of tensors to reduce and scatter.
|
|
op (optional): One of the values from
|
|
``torch.distributed.ReduceOp``
|
|
enum. Specifies an operation used for element-wise reductions.
|
|
group (ProcessGroup, optional): The process group to work on.
|
|
|
|
Returns:
|
|
Tensor: Output of the collective.
|
|
|
|
"""
|
|
return _Reduce_Scatter.apply(op, group, output, *input_list)
|
|
|
|
|
|
def all_gather(tensor, group=group.WORLD):
|
|
"""
|
|
Gathers tensors from the whole group in a list.
|
|
|
|
Arguments:
|
|
tensor (Tensor): Tensor to be broadcast from current process.
|
|
group (ProcessGroup, optional): The process group to work on.
|
|
|
|
Returns:
|
|
tuple([Tensor]): Output of the collective.
|
|
|
|
"""
|
|
return _AllGather.apply(group, tensor)
|
|
|
|
def _all_gather_base(output_tensor, input_tensor, group=group.WORLD):
|
|
"""
|
|
Single tensor all gather. Gathers a single tensor from all ranks, and puts them in a single output tensor.
|
|
|
|
Args:
|
|
output_tensor (Tensor): Output tensor. It should contain
|
|
correctly-sized tensors to be used for output of the collective.
|
|
input_tensor (Tensor): Tensor to be broadcast from current process.
|
|
group (ProcessGroup, optional): The process group to work on. If None,
|
|
the default process group will be used.
|
|
|
|
Examples:
|
|
>>> # All tensors below are of torch.int64 dtype.
|
|
>>> # We have 2 process groups, 2 ranks.
|
|
>>> # xdoctest: +SKIP("incorrect want text")
|
|
>>> output_tensor = torch.zeros(2, dtype=torch.int64)
|
|
>>> output_tensor
|
|
[tensor([0, 0])] # Rank 0 and 1
|
|
>>> tensor = torch.arange(1, dtype=torch.int64) + 1 + rank
|
|
>>> tensor
|
|
tensor([1]) # Rank 0
|
|
tensor([2]) # Rank 1
|
|
>>> dist.all_gather_base(output_tensor, tensor)
|
|
>>> output_tensor
|
|
tensor([1,2]) # Rank 0
|
|
tensor([1,2]) # Rank 1
|
|
|
|
.. warning::
|
|
`_all_gather_base` is experimental and subject to change.
|
|
It is the caller's responsibility to ensure the output_tensor
|
|
is correctly sized.
|
|
|
|
"""
|
|
return _AllGatherBase.apply(output_tensor, input_tensor, group)
|
|
|
|
|
|
def all_to_all(output_tensor_list, input_tensor_list, group=group.WORLD):
|
|
"""
|
|
Each process scatters list of input tensors to all processes in a group and return gathered list of tensors in output list.
|
|
|
|
Arguments:
|
|
output_tensor_list (list[Tensor]): list of tensors to gather one per rank.
|
|
input_tensor_list (list[Tensor]): List of tensors to scatter one per rank.
|
|
group (ProcessGroup, optional): The process group to work on.
|
|
|
|
Returns:
|
|
tuple([Tensor]): Output of the collective.
|
|
|
|
"""
|
|
return _AlltoAll.apply(group, output_tensor_list, *input_tensor_list)
|
|
|
|
|
|
def all_to_all_single(
|
|
output,
|
|
input,
|
|
output_split_sizes=None,
|
|
input_split_sizes=None,
|
|
group=group.WORLD,
|
|
):
|
|
"""
|
|
Each process splits input tensor and then scatters the split list to all processes in a group.
|
|
|
|
Then concatenate the received tensors from all the processes in the group and return single output tensor.
|
|
|
|
Arguments:
|
|
output (Tensor): Gathered concatenated output tensor.
|
|
input (Tensor): Input tensor to scatter.
|
|
output_split_sizes: (list[Int], optional): Output split sizes for dim 0
|
|
if specified None or empty, dim 0 of ``output`` tensor must divide
|
|
equally by ``world_size``.
|
|
input_split_sizes: (list[Int], optional): Input split sizes for dim 0
|
|
if specified None or empty, dim 0 of ``input`` tensor must divide
|
|
equally by ``world_size``.
|
|
|
|
Returns:
|
|
Tensor: Output of the collective.
|
|
|
|
"""
|
|
return _AlltoAllSingle.apply(
|
|
group, output, output_split_sizes, input_split_sizes, input
|
|
)
|
|
|
|
|
|
def all_reduce(tensor, op=ReduceOp.SUM, group=group.WORLD):
|
|
"""
|
|
Reduces the tensor data across all machines in such a way that all get the final result.
|
|
|
|
After the call the returned tensor is going to be bitwise
|
|
identical in all processes.
|
|
|
|
Arguments:
|
|
tensor (Tensor): Input of the collective.
|
|
op (optional): One of the values from
|
|
``torch.distributed.ReduceOp``
|
|
enum. Specifies an operation used for element-wise reductions.
|
|
group (ProcessGroup, optional): The process group to work on.
|
|
|
|
Returns:
|
|
Tensor: Output of the collective
|
|
|
|
"""
|
|
return _AllReduce.apply(op, group, tensor)
|
|
|
|
|
|
class _Broadcast(Function):
|
|
@staticmethod
|
|
def forward(ctx, src, group, tensor):
|
|
ctx.src = src
|
|
ctx.group = group
|
|
ctx.rank = dist.get_rank(group=group)
|
|
# torch.distributed makes all the calls in place
|
|
# we allocate new tensors to avoid this
|
|
tensor = tensor.clone()
|
|
dist.broadcast(tensor, src, group=group)
|
|
return tensor
|
|
|
|
@staticmethod
|
|
def backward(ctx, grad_output):
|
|
gx = _Reduce.apply(ctx.src, ReduceOp.SUM, ctx.group, grad_output)
|
|
if ctx.src != ctx.rank:
|
|
gx.zero_()
|
|
return (None, None, gx)
|
|
|
|
|
|
class _Gather(Function):
|
|
@staticmethod
|
|
def forward(ctx, dst, group, tensor):
|
|
ctx.dst = dst
|
|
ctx.group = group
|
|
# Need to create a list of tensors here to do the
|
|
# aggregation, get it from the group size
|
|
# tensor should be correctly sized for the method
|
|
# gathering
|
|
tensor_list = [
|
|
torch.zeros_like(tensor) for i in range(dist.get_world_size(group=group))
|
|
]
|
|
|
|
tensor = tensor.contiguous()
|
|
if dist.get_rank(group=group) == dst:
|
|
dist.gather(tensor, tensor_list, dst, group=group)
|
|
else:
|
|
dist.gather(tensor, None, dst, group=group)
|
|
return tuple(tensor_list)
|
|
|
|
@staticmethod
|
|
def backward(ctx, *grad_outputs):
|
|
return (None, None) + (_Scatter.apply(ctx.dst, ctx.group, *grad_outputs),)
|
|
|
|
|
|
class _Scatter(Function):
|
|
@staticmethod
|
|
def forward(ctx, src, group, *tensors):
|
|
ctx.src = src
|
|
ctx.group = group
|
|
assert all(t.size() == tensors[0].size() for t in tensors)
|
|
output = torch.zeros_like(tensors[0])
|
|
if dist.get_rank(group=group) == src:
|
|
dist.scatter(output, list(tensors), src, group=group)
|
|
else:
|
|
dist.scatter(output, None, src, group=group)
|
|
return output
|
|
|
|
@staticmethod
|
|
def backward(ctx, grad_output):
|
|
return (None, None) + _Gather.apply(ctx.src, ctx.group, grad_output)
|
|
|
|
|
|
class _Reduce(Function):
|
|
@staticmethod
|
|
def forward(ctx, src, op, group, tensor):
|
|
ctx.src = src
|
|
ctx.group = group
|
|
tensor = tensor.clone()
|
|
dist.reduce(tensor, src, op=op, group=group)
|
|
return tensor
|
|
|
|
@staticmethod
|
|
def backward(ctx, grad_output):
|
|
return (None, None, None) + (_Broadcast.apply(ctx.src, ctx.group, grad_output),)
|
|
|
|
|
|
class _Reduce_Scatter(Function):
|
|
@staticmethod
|
|
def forward(ctx, op, group, tensor, *input_tensor_list):
|
|
ctx.group = group
|
|
# Need contiguous tensors for collectives.
|
|
tensor = tensor.contiguous()
|
|
input_tensor_list = tuple(t.contiguous() for t in input_tensor_list)
|
|
dist.reduce_scatter(tensor, list(input_tensor_list), op=op, group=group)
|
|
return tensor
|
|
|
|
@staticmethod
|
|
def backward(ctx, grad_output):
|
|
return (None, None, None) + _AllGather.apply(ctx.group, grad_output)
|
|
|
|
|
|
class _AllGather(Function):
|
|
@staticmethod
|
|
def forward(ctx, group, tensor):
|
|
# Need contiguous tensors for collectives.
|
|
tensor = tensor.contiguous()
|
|
|
|
ctx.group = group
|
|
out_tensor_list = [
|
|
torch.empty_like(tensor) for _ in range(dist.get_world_size(group=group))
|
|
]
|
|
|
|
dist.all_gather(out_tensor_list, tensor, group=group)
|
|
return tuple(out_tensor_list)
|
|
|
|
@staticmethod
|
|
def backward(ctx, *grad_outputs):
|
|
if dist.get_backend(group=ctx.group) is dist.Backend.NCCL:
|
|
rank = dist.get_rank(group=ctx.group)
|
|
gx = torch.empty_like(grad_outputs[rank])
|
|
gx = _Reduce_Scatter.apply(ReduceOp.SUM, ctx.group, gx, *grad_outputs)
|
|
else:
|
|
# As many backends doesn't support ReduceScatter, we use AlltoAll with .sum()
|
|
# to emulate the ReduceScatter behavior
|
|
tensor_list = [torch.empty_like(tensor) for tensor in grad_outputs]
|
|
gxs = _AlltoAll.apply(ctx.group, tensor_list, *grad_outputs)
|
|
gx = torch.sum(torch.stack(gxs), dim=0)
|
|
return (None, gx)
|
|
|
|
class _AllGatherBase(Function):
|
|
@staticmethod
|
|
def forward(ctx, output_tensor, input_tensor, group):
|
|
ctx.group = group
|
|
dist._all_gather_base(output_tensor, input_tensor.contiguous(), group=group)
|
|
return output_tensor
|
|
|
|
@staticmethod
|
|
def backward(ctx, grad_output):
|
|
if dist.get_backend(group=ctx.group) is dist.Backend.NCCL:
|
|
world_size = dist.get_world_size(group=ctx.group)
|
|
out_size = list(grad_output.size())
|
|
if out_size[0] % world_size != 0:
|
|
raise RuntimeError(
|
|
f'Tensor with dimensions: {out_size} does '
|
|
f'not have first dimension divisible by world_size: {world_size}'
|
|
)
|
|
out_size[0] = out_size[0] // dist.get_world_size(group=ctx.group)
|
|
gx = torch.empty(out_size, device=grad_output.device, dtype=grad_output.dtype)
|
|
dist._reduce_scatter_base(gx, grad_output, ReduceOp.SUM, ctx.group)
|
|
else:
|
|
raise RuntimeError("Backend not supported!")
|
|
return (None, gx, None)
|
|
|
|
class _AlltoAll(Function):
|
|
@staticmethod
|
|
def forward(ctx, group, out_tensor_list, *tensors):
|
|
ctx.group = group
|
|
ctx.input_tensor_size_list = [
|
|
tensors[i].size() for i in range(dist.get_world_size(group=group))
|
|
]
|
|
my_rank = dist.get_rank(group=group)
|
|
tensors = tuple(t.contiguous() for t in tensors)
|
|
# Implement it on means of scatter/gather, send/recv async operations have issues
|
|
if dist.get_backend(group=group) is dist.Backend.GLOO:
|
|
for i in range(dist.get_world_size(group=group)):
|
|
to_send = None
|
|
if i == my_rank:
|
|
to_send = list(tensors)
|
|
dist.scatter(out_tensor_list[i], to_send, i, group=group)
|
|
else:
|
|
dist.all_to_all(
|
|
out_tensor_list,
|
|
list(tensors),
|
|
group=group,
|
|
)
|
|
return tuple(out_tensor_list)
|
|
|
|
@staticmethod
|
|
def backward(ctx, *grad_outputs):
|
|
tensor_list = [
|
|
torch.empty(size, device=grad_outputs[0].device, dtype=grad_outputs[0].dtype)
|
|
for size in ctx.input_tensor_size_list
|
|
]
|
|
return (None, None) + _AlltoAll.apply(ctx.group, tensor_list, *grad_outputs)
|
|
|
|
|
|
class _AlltoAllSingle(Function):
|
|
@staticmethod
|
|
def forward(ctx, group, output, output_split_sizes, input_split_sizes, input):
|
|
ctx.group = group
|
|
ctx.input_size = input.size()
|
|
ctx.output_split_sizes = input_split_sizes
|
|
ctx.input_split_sizes = output_split_sizes
|
|
dist.all_to_all_single(
|
|
output,
|
|
input,
|
|
output_split_sizes=output_split_sizes,
|
|
input_split_sizes=input_split_sizes,
|
|
group=group,
|
|
)
|
|
return output
|
|
|
|
@staticmethod
|
|
def backward(ctx, grad_output):
|
|
tensor = torch.empty(ctx.input_size, device=grad_output.device, dtype=grad_output.dtype)
|
|
return (None, None, None, None) + (
|
|
_AlltoAllSingle.apply(
|
|
ctx.group,
|
|
tensor,
|
|
ctx.output_split_sizes,
|
|
ctx.input_split_sizes,
|
|
grad_output.contiguous(),
|
|
),
|
|
)
|
|
|
|
|
|
class _AllReduce(Function):
|
|
@staticmethod
|
|
def forward(ctx, op, group, tensor):
|
|
ctx.group = group
|
|
ctx.op = op
|
|
tensor = tensor.clone()
|
|
dist.all_reduce(tensor, op=op, group=group)
|
|
return tensor
|
|
|
|
@staticmethod
|
|
def backward(ctx, grad_output):
|
|
return (None, None) + (_AllReduce.apply(ctx.op, ctx.group, grad_output),)
|