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import torch.distributed as dist | ||
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def print_rank(var_name, var_value, rank=0): | ||
if dist.get_rank() == 0: | ||
print(f'[Rank {rank}] {var_name}: {var_value}') |
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import torch | ||
import torch.distributed as dist | ||
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def _all_to_all_single(input_, seq_world_size, group, scatter_dim, gather_dim): | ||
inp_shape = list(input_.shape) | ||
inp_shape[scatter_dim] = inp_shape[scatter_dim] // seq_world_size | ||
if scatter_dim < 2: | ||
input_t = input_.reshape([seq_world_size, inp_shape[scatter_dim]] + inp_shape[scatter_dim + 1 :]).contiguous() | ||
else: | ||
input_t = ( | ||
input_.reshape([-1, seq_world_size, inp_shape[scatter_dim]] + inp_shape[scatter_dim + 1 :]) | ||
.transpose(0, 1) | ||
.contiguous() | ||
) | ||
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output = torch.empty_like(input_t) | ||
dist.all_to_all_single(output, input_t, group=group) | ||
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if scatter_dim < 2: | ||
output = output.transpose(0, 1).contiguous() | ||
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return output.reshape( | ||
inp_shape[:gather_dim] | ||
+ [ | ||
inp_shape[gather_dim] * seq_world_size, | ||
] | ||
+ inp_shape[gather_dim + 1 :] | ||
).contiguous() | ||
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def _all_to_all(input_, world_size, group, scatter_dim, gather_dim): | ||
input_list = [t.contiguous() for t in torch.tensor_split(input_, world_size, scatter_dim)] | ||
output_list = [torch.empty_like(input_list[0]) for _ in range(world_size)] | ||
dist.all_to_all(output_list, input_list, group=group) | ||
return torch.cat(output_list, dim=gather_dim).contiguous() | ||
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class _AllToAll(torch.autograd.Function): | ||
"""All-to-all communication. | ||
Args: | ||
input_: input matrix | ||
process_group: communication group | ||
scatter_dim: scatter dimension | ||
gather_dim: gather dimension | ||
""" | ||
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@staticmethod | ||
def forward(ctx, input_, process_group, scatter_dim, gather_dim): | ||
ctx.process_group = process_group | ||
ctx.scatter_dim = scatter_dim | ||
ctx.gather_dim = gather_dim | ||
world_size = dist.get_world_size(process_group) | ||
bsz, _, _ = input_.shape | ||
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#Todo: Try to make all_to_all_single compatible with a large batch size | ||
if bsz == 1: | ||
return _all_to_all_single(input_, world_size, process_group, scatter_dim, gather_dim) | ||
else: | ||
return _all_to_all(input_, world_size, process_group, scatter_dim, gather_dim) | ||
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@staticmethod | ||
def backward(ctx, *grad_output): | ||
process_group = ctx.process_group | ||
scatter_dim = ctx.gather_dim | ||
gather_dim = ctx.scatter_dim | ||
return_grad = _AllToAll.apply(*grad_output, process_group, scatter_dim, gather_dim) | ||
return (return_grad, None, None, None) |