222 lines
9.0 KiB
Python
222 lines
9.0 KiB
Python
# Copyright (c) Microsoft Corporation and Jiarui Fang
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# SPDX-License-Identifier: Apache-2.0
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# DeepSpeed Team & Jiarui Fang
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# from https://github.com/feifeibear/long-context-attention/blob/main/yunchang/comm/all_to_all.py
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from typing import Any
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import torch
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import torch.distributed as dist
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from torch import Tensor
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def all_to_all_4D(
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input: torch.tensor, scatter_idx: int = 2, gather_idx: int = 1, group=None, use_sync: bool = False
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) -> torch.tensor:
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"""
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all-to-all for QKV
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Args:
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input (torch.tensor): a tensor sharded along dim scatter dim
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scatter_idx (int): default 1
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gather_idx (int): default 2
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group (torch.distributed.ProcessGroup): torch process group
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use_sync (bool): whether to synchronize after all-to-all
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Returns:
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torch.tensor: resharded tensor (bs, seqlen/P, hc, hs)
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"""
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assert input.dim() == 4, f"input must be 4D tensor, got {input.dim()} and shape {input.shape}"
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seq_world_size = dist.get_world_size(group)
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if scatter_idx == 2 and gather_idx == 1:
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# input (torch.tensor): a tensor sharded along dim 1 (bs, seqlen/P, hc, hs) output: (bs, seqlen, hc/P, hs)
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bs, shard_seqlen, hc, hs = input.shape
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seqlen = shard_seqlen * seq_world_size
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shard_hc = hc // seq_world_size
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# transpose groups of heads with the seq-len parallel dimension, so that we can scatter them!
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# (bs, seqlen/P, hc, hs) -reshape-> (bs, seq_len/P, P, hc/P, hs) -transpose(0,2)-> (P, seq_len/P, bs, hc/P, hs)
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input_t = input.reshape(bs, shard_seqlen, seq_world_size, shard_hc, hs).transpose(0, 2).contiguous()
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output = torch.empty_like(input_t)
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# https://pytorch.org/docs/stable/distributed.html#torch.distributed.all_to_all_single
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# (P, seq_len/P, bs, hc/P, hs) scatter seqlen -all2all-> (P, seq_len/P, bs, hc/P, hs) scatter head
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if seq_world_size > 1:
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dist.all_to_all_single(output, input_t, group=group)
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if use_sync:
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torch.cuda.synchronize()
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else:
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output = input_t
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# if scattering the seq-dim, transpose the heads back to the original dimension
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output = output.reshape(seqlen, bs, shard_hc, hs)
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# (seq_len, bs, hc/P, hs) -reshape-> (bs, seq_len, hc/P, hs)
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output = output.transpose(0, 1).contiguous().reshape(bs, seqlen, shard_hc, hs)
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return output
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elif scatter_idx == 1 and gather_idx == 2:
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# input (torch.tensor): a tensor sharded along dim 1 (bs, seqlen, hc/P, hs) output: (bs, seqlen/P, hc, hs)
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bs, seqlen, shard_hc, hs = input.shape
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hc = shard_hc * seq_world_size
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shard_seqlen = seqlen // seq_world_size
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seq_world_size = dist.get_world_size(group)
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# transpose groups of heads with the seq-len parallel dimension, so that we can scatter them!
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# (bs, seqlen, hc/P, hs) -reshape-> (bs, P, seq_len/P, hc/P, hs) -transpose(0, 3)->
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# (hc/P, P, seqlen/P, bs, hs) -transpose(0, 1) -> (P, hc/P, seqlen/P, bs, hs)
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input_t = (
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input.reshape(bs, seq_world_size, shard_seqlen, shard_hc, hs)
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.transpose(0, 3)
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.transpose(0, 1)
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.contiguous()
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.reshape(seq_world_size, shard_hc, shard_seqlen, bs, hs)
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)
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output = torch.empty_like(input_t)
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# https://pytorch.org/docs/stable/distributed.html#torch.distributed.all_to_all_single
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# (P, bs x hc/P, seqlen/P, hs) scatter seqlen -all2all-> (P, bs x seq_len/P, hc/P, hs) scatter head
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if seq_world_size > 1:
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dist.all_to_all_single(output, input_t, group=group)
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if use_sync:
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torch.cuda.synchronize()
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else:
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output = input_t
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# if scattering the seq-dim, transpose the heads back to the original dimension
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output = output.reshape(hc, shard_seqlen, bs, hs)
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# (hc, seqlen/N, bs, hs) -transpose(0,2)-> (bs, seqlen/N, hc, hs)
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output = output.transpose(0, 2).contiguous().reshape(bs, shard_seqlen, hc, hs)
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return output
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else:
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raise RuntimeError("scatter_idx must be 1 or 2 and gather_idx must be 1 or 2")
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class SeqAllToAll4D(torch.autograd.Function):
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@staticmethod
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def forward(
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ctx: Any,
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group: dist.ProcessGroup,
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input: Tensor,
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scatter_idx: int,
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gather_idx: int,
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use_sync: bool = False,
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) -> Tensor:
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ctx.group = group
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ctx.scatter_idx = scatter_idx
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ctx.gather_idx = gather_idx
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ctx.use_sync = use_sync
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return all_to_all_4D(input, scatter_idx, gather_idx, group=group, use_sync=use_sync)
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def all_to_all_5D(
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input: torch.tensor, scatter_idx: int = 3, gather_idx: int = 1, group=None, use_sync: bool = False
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) -> torch.tensor:
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"""
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all-to-all for QKV
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forward (bs, seqlen/N, 3, hc, hs) -> (bs, seqlen, 3, hc/N, hs)
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Args:
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input (torch.tensor): a tensor sharded along dim scatter dim
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scatter_idx (int): default 1
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gather_idx (int): default 2
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group (torch.distributed.ProcessGroup): torch process group
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use_sync (bool): whether to synchronize after all-to-all
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Returns:
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torch.tensor: resharded tensor (bs, seqlen/P, 3, hc, hs)
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"""
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assert input.dim() == 5, f"input must be 5D tensor, got {input.dim()} and shape {input.shape}"
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seq_world_size = dist.get_world_size(group)
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if scatter_idx == 3 and gather_idx == 1:
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# input (torch.tensor): a tensor sharded along dim 1 (bs, seqlen/P, 3, hc, hs) output: (bs, seqlen, 3, hc/P, hs)
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bs, shard_seqlen, t_cnt, hc, hs = input.shape
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assert t_cnt == 3
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seqlen = shard_seqlen * seq_world_size
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shard_hc = hc // seq_world_size
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# transpose groups of heads with the seq-len parallel dimension, so that we can scatter them!
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# (bs, seqlen/P, 3, hc, hs) -reshape-> (bs, seq_len/P, 3, P, hc/P, hs) -transpose(0,3)->
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# (P, seq_len/P, 3, bs, hc/P, hs)
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input_t = input.reshape(bs, shard_seqlen, 3, seq_world_size, shard_hc, hs).transpose(0, 3).contiguous()
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output = torch.empty_like(input_t)
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# https://pytorch.org/docs/stable/distributed.html#torch.distributed.all_to_all_single
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# (P, seq_len/P, 3, bs, hc/P, hs) scatter seqlen -all2all-> (P, seq_len/P, 3, bs, hc/P, hs) scatter head
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if seq_world_size > 1:
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dist.all_to_all_single(output, input_t, group=group)
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if use_sync:
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torch.cuda.synchronize()
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else:
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output = input_t
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# if scattering the seq-dim, transpose the heads back to the original dimension
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output = output.reshape(seqlen, 3, bs, shard_hc, hs)
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# (seq_len, 3, bs, hc/P, hs) -trans-> (bs, seq_len, 3, hc/P, hs)
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output = output.transpose(0, 2).transpose(1, 2).contiguous()
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return output.reshape(bs, seqlen, 3, shard_hc, hs).contiguous()
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elif scatter_idx == 1 and gather_idx == 3:
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# input (torch.tensor): a tensor sharded along dim 1 (bs, seqlen, hc/P, hs) output: (bs, seqlen/P, hc, hs)
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bs, seqlen, _, shard_hc, hs = input.shape
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hc = shard_hc * seq_world_size
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shard_seqlen = seqlen // seq_world_size
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seq_world_size = dist.get_world_size(group)
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# transpose groups of heads with the seq-len parallel dimension, so that we can scatter them!
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# (bs, seqlen, 3, hc/P, hs) -reshape-> (bs, P, seq_len/P, 3, hc/P, hs) -transpose(0, 4)->
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# (hc/P, P, seqlen/P, 3, bs, hs) -transpose(0, 1) -> (P, hc/P, seqlen/P, 3, bs, hs)
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input_t = (
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input.reshape(bs, seq_world_size, shard_seqlen, 3, shard_hc, hs)
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.transpose(0, 4)
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.transpose(0, 1)
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.contiguous()
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.reshape(seq_world_size, shard_hc, shard_seqlen, 3, bs, hs)
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)
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output = torch.empty_like(input_t)
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# https://pytorch.org/docs/stable/distributed.html#torch.distributed.all_to_all_single
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# (P, bs x hc/P, seqlen/P, hs) scatter seqlen -all2all-> (P, bs x seq_len/P, hc/P, hs) scatter head
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if seq_world_size > 1:
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dist.all_to_all_single(output, input_t, group=group)
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if use_sync:
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torch.cuda.synchronize()
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else:
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output = input_t
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# if scattering the seq-dim, transpose the heads back to the original dimension
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output = output.reshape(hc, shard_seqlen, 3, bs, hs)
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# (hc, seqlen/N, bs, hs) -transpose(0,2)-> (bs, seqlen/N, hc, hs)
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output = output.transpose(0, 3).contiguous()
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return output.reshape(bs, shard_seqlen, 3, hc, hs).contiguous()
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else:
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raise RuntimeError("scatter_idx must be 1 or 3 and gather_idx must be 1 or 3")
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class SeqAllToAll5D(torch.autograd.Function):
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@staticmethod
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def forward(
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ctx: Any,
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group: dist.ProcessGroup,
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input: Tensor,
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scatter_idx: int = 3,
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gather_idx: int = 1,
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use_sync: bool = False,
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) -> Tensor:
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ctx.group = group
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ctx.scatter_idx = scatter_idx
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ctx.gather_idx = gather_idx
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ctx.use_sync = use_sync
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return all_to_all_5D(input, scatter_idx, gather_idx, group=group, use_sync=use_sync)
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