FlowCache/FlowCache4MAGI-1-dev6-adaptive/inference/infra/parallelism/context_parallel.py

# Copyright (c) 2025 SandAI. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import math
from typing import Callable, List, Tuple, Union

import torch
import torch.distributed
from einops import rearrange

from inference.common import ModelMetaArgs, PackedCoreAttnParams, PackedCrossAttnParams, divide
from inference.infra.distributed import parallel_state as mpu


#####################################################
# Common Primitives
#####################################################
def scatter_to_context_parallel_region(input_, cp_split_sizes, cp_shuffle_num=1, cp_pad_size=0):
    """Split the tensor along its first dimension and keep the
    corresponding slice."""

    world_size = mpu.get_cp_world_size()
    # Bypass the function if we are using only 1 GPU.
    if world_size == 1:
        return input_

    # Split along first dimension with padding.
    rank = mpu.get_cp_rank()
    if cp_shuffle_num > 1:
        cp_pad_size = divide(cp_pad_size, cp_shuffle_num)
        cp_split_sizes = [divide(s, cp_shuffle_num) for s in cp_split_sizes]
        dim_offset = sum(cp_split_sizes[:rank])
        xs = []
        for x in torch.chunk(input_, cp_shuffle_num, dim=0):
            x = torch.nn.functional.pad(x, [0, 0] * (x.dim() - 1) + [0, cp_pad_size], mode="constant", value=0)
            xs.append(x[dim_offset : dim_offset + cp_split_sizes[rank]])
        output = torch.concat(xs, dim=0)
    else:
        dim_offset = sum(cp_split_sizes[:rank])
        x = torch.nn.functional.pad(input_, [0, 0] * (input_.dim() - 1) + [0, cp_pad_size], mode="constant", value=0)
        output = x[dim_offset : dim_offset + cp_split_sizes[rank]].contiguous()
    return output


def gather_from_context_parallel_region(input_, cp_split_sizes, cp_shuffle_num=1, cp_pad_size=0):
    """Gather tensors and concatinate along the first dimension."""

    world_size = mpu.get_cp_world_size()
    # Bypass the function if we are using only 1 GPU.
    if world_size == 1:
        return input_

    input_ = input_.contiguous()
    total_seq_len = sum(cp_split_sizes)
    dim_size = list(input_.size())
    dim_size[0] = total_seq_len

    output = torch.empty(dim_size, dtype=input_.dtype, device=input_.device)
    outputs = list(torch.split(output, cp_split_sizes, dim=0))
    torch.distributed.all_gather(outputs, input_, group=mpu.get_cp_group())
    if cp_shuffle_num > 1:
        total_seq_len = divide(total_seq_len, cp_shuffle_num)
        cp_pad_size = divide(cp_pad_size, cp_shuffle_num)
        chunks = [torch.chunk(o, cp_shuffle_num, dim=0) for o in outputs]
        output = torch.concat(
            [
                torch.concat([chunk[i] for chunk in chunks], dim=0)[: total_seq_len - cp_pad_size]
                for i in range(cp_shuffle_num)
            ],
            dim=0,
        )
    else:
        output = torch.concat(outputs, dim=0)[: total_seq_len - cp_pad_size]

    return output


class FakeHandle:
    def __init__(self):
        pass

    def wait(self):
        pass


#####################################################
# Context Parallel Process
#####################################################
def update_packed_seq_params_for_cuda_graph(cross_attn_params: PackedCrossAttnParams, xattn_mask: torch.Tensor):
    assert xattn_mask is not None
    # xattn_mask: (N * denoising_range_num, L, 1, 1)
    xattn_mask = xattn_mask.reshape(xattn_mask.shape[0], -1)
    batch_size, static_caption_length = xattn_mask.shape

    # Get index_map for kv_range injection, map y_index to static_caption_length
    y_index = torch.sum(xattn_mask, dim=-1)
    cu_seqlens_k = torch.cat([y_index.new_tensor([0]), y_index]).to(torch.int32).to(xattn_mask.device)
    cu_seqlens_k = cu_seqlens_k.cumsum(-1).to(torch.int32)
    static_cu_seqlens_k = torch.arange(0, (batch_size + 1) * static_caption_length, static_caption_length)
    assert cu_seqlens_k.shape[0] == batch_size + 1 == static_cu_seqlens_k.shape[0]
    start_index_map = dict(zip(cu_seqlens_k.flatten().tolist(), static_cu_seqlens_k.flatten().tolist()))

    # Move kv_range to the right position
    kv_range_start_list = cross_attn_params.kv_ranges[:, 0].flatten().tolist()
    static_kv_range_start = [start_index_map[kv_range_start_list[i]] for i in range(len(kv_range_start_list))]
    static_kv_range_start = torch.tensor(static_kv_range_start, dtype=torch.int32, device=xattn_mask.device)
    assert static_kv_range_start.shape[0] == cross_attn_params.kv_ranges.shape[0]
    static_kv_range_diff = cross_attn_params.kv_ranges[:, 1] - cross_attn_params.kv_ranges[:, 0]
    static_kv_range_end = static_kv_range_start + static_kv_range_diff
    static_kv_range = torch.stack((static_kv_range_start, static_kv_range_end), dim=1)

    assert static_kv_range.shape == cross_attn_params.kv_ranges.shape
    return PackedCrossAttnParams(
        q_ranges=cross_attn_params.q_ranges,
        kv_ranges=static_kv_range,
        cu_seqlens_q=cross_attn_params.cu_seqlens_q,
        cu_seqlens_kv=cross_attn_params.cu_seqlens_kv,
        max_seqlen_q=cross_attn_params.max_seqlen_q,
        max_seqlen_kv=cross_attn_params.max_seqlen_kv,
    )


def cp_update_cross_attn_qkv_range(
    cross_attn_params: PackedCrossAttnParams,
    batch_size: int,
    cp_split_sizes: List[int],
    device: torch.device,
    cp_shuffle_num: int = 1,
    cp_pad_size: int = 0,
):
    """
    Update cross_attn_params for cross_attn in context parallel.

    Input:
        cross_attn_params: PackedCrossAttnParams. Packed sequence parameters for cross_atten
        batch_size: int. Batch size
        cp_split_sizes: List[int]. Split sizes for each rank
        device: torch.device. Device

    Output:
        cross_attn_params: PackedCrossAttnParams. Updated packed parameters for cross_atten
    """
    # Update cu_seqlens_q and max_seqlen_q because split x maybe unbalanced
    cp_rank = mpu.get_cp_rank()
    seq_len_cur_rank = cp_split_sizes[cp_rank]
    cp_split_sizes = [divide(x, cp_shuffle_num) for x in cp_split_sizes]
    cp_split_sizes = torch.tensor(cp_split_sizes, dtype=torch.int32, device=device)
    base_cp_boundaries = torch.cat((torch.zeros(1, dtype=torch.int32, device=device), cp_split_sizes.cumsum(0)))
    total_seq_len = base_cp_boundaries[-1]

    cu_seqlens_q = cross_attn_params.cu_seqlens_q
    cu_seqlens_k = cross_attn_params.cu_seqlens_kv
    cu_seqlens_pad = torch.arange(cu_seqlens_q.shape[0], dtype=torch.int32, device=device) * divide(
        cp_pad_size, cp_shuffle_num
    )
    cu_seqlens_q = cu_seqlens_q + cu_seqlens_pad

    q_seg_starts, q_seg_ends = cu_seqlens_q[:-1], cu_seqlens_q[1:]

    xattn_q_ranges, xattn_k_ranges = [], []
    for i in range(batch_size):
        inner_xattn_q_ranges, inner_xattn_k_ranges = [], []
        for j in range(cp_shuffle_num):
            global_offset = i * total_seq_len * cp_shuffle_num + j * total_seq_len
            cp_boundaries = base_cp_boundaries + global_offset
            this_cp_start, this_cp_end = (cp_boundaries[cp_rank], cp_boundaries[cp_rank + 1])

            q_inter_starts = torch.maximum(this_cp_start, q_seg_starts)
            q_inter_ends = torch.minimum(this_cp_end, q_seg_ends)

            q_mask = q_inter_starts < q_inter_ends
            valid_q_starts = q_inter_starts[q_mask]
            valid_q_ends = q_inter_ends[q_mask]

            k_seg_starts, k_seg_ends = cu_seqlens_k[:-1], cu_seqlens_k[1:]
            valid_indices = torch.nonzero(q_mask, as_tuple=True)[0]

            valid_k_starts = k_seg_starts[valid_indices]
            valid_k_ends = k_seg_ends[valid_indices]

            part_xattn_q_rangs = torch.stack((valid_q_starts, valid_q_ends), dim=1)
            offset = part_xattn_q_rangs[:, 0].min()
            part_xattn_q_rangs = part_xattn_q_rangs - offset

            inner_xattn_q_ranges.append(part_xattn_q_rangs)
            inner_xattn_k_ranges.append(torch.stack((valid_k_starts, valid_k_ends), dim=1))
        inner_end_values = torch.tensor([ranges[-1, -1] for ranges in inner_xattn_q_ranges], dtype=torch.int32)
        inner_offsets = torch.cat((torch.zeros(1, dtype=inner_end_values.dtype), torch.cumsum(inner_end_values[:-1], dim=0)))
        inner_xattn_q_ranges = [tensor + int(offset) for tensor, offset in zip(inner_xattn_q_ranges, inner_offsets)]
        xattn_q_ranges.append(torch.cat(inner_xattn_q_ranges, dim=0))
        xattn_k_ranges.append(torch.cat(inner_xattn_k_ranges, dim=0))

    end_values = torch.tensor([ranges[-1, -1].item() for ranges in xattn_q_ranges], dtype=torch.int32)
    offsets = torch.cat((torch.zeros(1, dtype=end_values.dtype), torch.cumsum(end_values[:-1], dim=0)))

    shifted_tensors = [tensor + int(offset) for tensor, offset in zip(xattn_q_ranges, offsets)]
    xattn_q_ranges_ts = torch.cat(shifted_tensors, dim=0)
    xattn_k_ranges_ts = torch.cat(xattn_k_ranges, dim=0)

    cu_seqlens_q = torch.unique(xattn_q_ranges_ts)
    cu_seqlens_k = torch.unique(xattn_k_ranges_ts)
    assert (
        cu_seqlens_q.shape == cu_seqlens_k.shape
    ), f"cu_seqlens_q.shape: {cu_seqlens_q.shape}, cu_seqlens_k.shape: {cu_seqlens_k.shape}, "

    return PackedCrossAttnParams(
        q_ranges=xattn_q_ranges_ts,
        kv_ranges=xattn_k_ranges_ts,
        cu_seqlens_q=cu_seqlens_q,
        cu_seqlens_kv=cu_seqlens_k,
        max_seqlen_q=seq_len_cur_rank,
        max_seqlen_kv=cross_attn_params.max_seqlen_kv,
    )


def cp_ulysses_process(
    cp_size: int,
    x: torch.Tensor,
    condition_map: torch.Tensor,
    rope: torch.Tensor,
    xattn_mask_for_cuda_graph: Union[torch.Tensor, None],
    cross_attn_params: PackedCrossAttnParams,
):
    seq_len, N, D = x.shape
    assert seq_len == rope.size(0), f"seq_len: {seq_len} != rope.size(0): {rope.size(0)}"
    assert condition_map.size(0) == seq_len, f"condition_map.size(0): {condition_map.size(0)} != seq_len: {seq_len}"

    # Part1: split for CP
    cp_split_sizes = [seq_len // cp_size] * cp_size
    for i in range(seq_len % cp_size):
        cp_split_sizes[i] += 1

    # Part2: scatter to CP
    x = scatter_to_context_parallel_region(x, cp_split_sizes)
    condition_map = scatter_to_context_parallel_region(condition_map, cp_split_sizes)
    rope = scatter_to_context_parallel_region(rope, cp_split_sizes)

    # Part3: update cross_attn cross_attn_params
    cross_attn_params = cp_update_cross_attn_qkv_range(cross_attn_params, N, cp_split_sizes, x.device)
    if xattn_mask_for_cuda_graph is not None:
        cross_attn_params = update_packed_seq_params_for_cuda_graph(cross_attn_params, xattn_mask_for_cuda_graph)

    return x, condition_map, rope, cp_split_sizes, cross_attn_params


def cp_shuffle_overlap_process(
    cp_size: int,
    x: torch.Tensor,
    condition_map: torch.Tensor,
    rope: torch.Tensor,
    xattn_mask_for_cuda_graph: Union[torch.Tensor, None],
    ardf_meta: dict,
    core_attn_params: PackedCoreAttnParams,
    cross_attn_params: PackedCrossAttnParams,
):
    seq_len, N, D = x.shape
    assert seq_len == rope.size(0), f"seq_len: {seq_len} != rope.size(0): {rope.size(0)}"
    assert condition_map.size(0) == seq_len, f"condition_map.size(0): {condition_map.size(0)} != seq_len: {seq_len}"
    cp_shuffle_num = ardf_meta["denoising_range_num"]

    # Part1: calculate cp_pad_size and cp_split_sizes
    cp_pad_size = 0
    if divide(seq_len, cp_shuffle_num) % cp_size != 0:
        cp_pad_size = (cp_size - divide(seq_len, cp_shuffle_num) % cp_size) * cp_shuffle_num
    cp_split_sizes = [(seq_len + cp_pad_size) // cp_size] * cp_size

    # Part2: scatter to CP
    x = scatter_to_context_parallel_region(x, cp_split_sizes, cp_shuffle_num, cp_pad_size)
    condition_map = scatter_to_context_parallel_region(condition_map, cp_split_sizes, cp_shuffle_num, cp_pad_size)
    rope = scatter_to_context_parallel_region(rope, cp_split_sizes, cp_shuffle_num, cp_pad_size)

    # Part3: update core_attn_params
    gcd = math.gcd(seq_len, seq_len + cp_pad_size)
    _sq = seq_len // gcd
    _psq = (seq_len + cp_pad_size) // gcd
    q_range = ardf_meta["q_range"] * _psq // _sq
    max_seqlen_q = ardf_meta["max_seqlen_q"] * _psq // _sq
    core_attn_params = PackedCoreAttnParams(
        q_range=q_range,
        k_range=ardf_meta["k_range"],
        np_q_range=q_range.cpu().numpy(),
        np_k_range=ardf_meta["k_range"].cpu().numpy(),
        max_seqlen_q=max_seqlen_q,
        max_seqlen_k=ardf_meta["max_seqlen_k"],
    )

    # Part4: update cross_attn cross_attn_params
    cross_attn_params = cp_update_cross_attn_qkv_range(
        cross_attn_params, N, cp_split_sizes, x.device, cp_shuffle_num, cp_pad_size
    )
    if xattn_mask_for_cuda_graph is not None:
        cross_attn_params = update_packed_seq_params_for_cuda_graph(cross_attn_params, xattn_mask_for_cuda_graph)

    return x, condition_map, rope, cp_pad_size, cp_split_sizes, core_attn_params, cross_attn_params


def cp_pre_process(
    cp_size: int,
    cp_strategy: str,
    x: torch.Tensor,
    condition_map: torch.Tensor,
    rope: torch.Tensor,
    xattn_mask_for_cuda_graph: Union[torch.Tensor, None],
    ardf_meta: dict,
    core_attn_params: PackedCoreAttnParams,
    cross_attn_params: PackedCrossAttnParams,
):
    """
    This function is used to handle context parallel behavior,
    split input tensors into multiple parts and scatter them to different GPUs.

    Input:
        cp_strategy: str. cp_ulysses for hopper or newer, cp_shuffle_overlap for 4090 or older
        x: (S, N, D). torch.Tensor of inputs embedding (images or latent representations of images)
        condition_map: (N * S). torch.Tensor determine which condition to use for each token
        rope: (S, 96). torch.Tensor of rope
        xattn_mask_for_cuda_graph: (N * denoising_range_num, L, 1, 1). torch.Tensor of xattn mask for cuda graph, None means no cuda graph
        core_attn_params: PackedCoreAttnParams. Packed sequence parameters for core_atten
        cross_attn_params: PackedCrossAttnParams. Packed sequence parameters for cross_atten

    Output:
        x: (S', N, D). torch.Tensor of inputs embedding (images or latent representations of images)
        condition_map: (N * S'). torch.Tensor determine which condition to use for each token
        rope: (S', 96). torch.Tensor of rope
        cp_split_sizes: List[int]. Split sizes for each rank
        core_attn_params: PackedCoreAttnParams
        cross_attn_params: PackedCrossAttnParams
    """
    if cp_size == 1:
        return x, condition_map, rope, None, None, core_attn_params, cross_attn_params
    if cp_strategy == "cp_ulysses":
        (x, condition_map, rope, cp_split_sizes, cross_attn_params) = cp_ulysses_process(
            cp_size, x, condition_map, rope, xattn_mask_for_cuda_graph, cross_attn_params
        )
        return (x, condition_map, rope, 0, cp_split_sizes, core_attn_params, cross_attn_params)
    elif cp_strategy == "cp_shuffle_overlap":
        (
            x,
            condition_map,
            rope,
            cp_pad_size,
            cp_split_sizes,
            core_attn_params,
            cross_attn_params,
        ) = cp_shuffle_overlap_process(
            cp_size, x, condition_map, rope, xattn_mask_for_cuda_graph, ardf_meta, core_attn_params, cross_attn_params
        )
        return (x, condition_map, rope, cp_pad_size, cp_split_sizes, core_attn_params, cross_attn_params)
    else:
        raise ValueError(f"Invalid CP strategy: {cp_strategy}, expected cp_ulysses or cp_shuffle_overlap")


def cp_post_process(cp_size: int, cp_strategy: str, x: torch.Tensor, meta_args: ModelMetaArgs) -> torch.Tensor:
    if cp_size == 1:
        return x
    if cp_strategy == "cp_shuffle_overlap":
        x = gather_from_context_parallel_region(
            x, meta_args.cp_split_sizes, meta_args.denoising_range_num, meta_args.cp_pad_size
        )
    elif cp_strategy == "cp_ulysses":
        x = gather_from_context_parallel_region(x, meta_args.cp_split_sizes)
    else:
        raise ValueError(f"Invalid CP strategy: {cp_strategy}, expected cp_ulysses or cp_shuffle_overlap")
    return x


#####################################################
# Ulysses Attention Pipeline
#####################################################
def all_to_all_input_split(tensor: torch.Tensor, cp_split_sizes: List[int]) -> Tuple[torch.Tensor, torch.distributed.Work]:
    """
    Scatter head_number and gather seq_len, for example:
    input: (seq_len, cp * hn, hd)
    output: (seq_len * cp, hn, hd)
    NOTE: seq_len of input maybe not equal, which depends on cp_split_sizes[mpu.get_cp_rank()]
    """
    cp_world_size = mpu.get_cp_world_size()
    if cp_world_size == 1:
        return tensor, FakeHandle()
    assert cp_split_sizes is not None
    _, hn, _ = tensor.shape
    if cp_world_size % hn == 0 and cp_world_size != hn:
        tensor = torch.repeat_interleave(tensor, repeats=divide(cp_world_size, hn), dim=1).contiguous()
    assert tensor.is_contiguous()
    input = rearrange(tensor, "seq (cp hn) hd -> (cp seq) hn hd", cp=cp_world_size).contiguous()
    output = torch.empty([sum(cp_split_sizes), *input.shape[1:]], device=input.device, dtype=input.dtype)
    handle = torch.distributed.all_to_all_single(
        output, input, output_split_sizes=cp_split_sizes, group=mpu.get_cp_group(), async_op=True
    )
    return output, handle


def all_to_all_output_split(tensor: torch.Tensor, cp_split_sizes: List[int]) -> Tuple[torch.Tensor, torch.distributed.Work]:
    """
    Scatter seq_len and gather head_number, for example:
    input: (seq_len * cp, hn, hd)
    output: (seq_len, cp * hn, hd)
    NOTE: seq_len of output maybe not equal, which depends on cp_split_sizes[mpu.get_cp_rank()]
    """
    cp_world_size = mpu.get_cp_world_size()
    if cp_world_size == 1:
        return tensor, FakeHandle()
    assert cp_split_sizes is not None
    assert tensor.is_contiguous()
    _, hn, _ = tensor.shape
    output = torch.empty(
        [cp_split_sizes[mpu.get_cp_rank()] * cp_world_size, *tensor.shape[1:]], device=tensor.device, dtype=tensor.dtype
    )
    handle = torch.distributed.all_to_all_single(
        output, tensor, input_split_sizes=cp_split_sizes, group=mpu.get_cp_group(), async_op=True
    )
    return output, handle


def fused_qkv_communication(
    q: torch.Tensor, k: torch.Tensor, v: torch.Tensor, cp_split_sizes: List[int]
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
    cp_world_size = mpu.get_cp_world_size()
    if cp_world_size == 1:
        return q, k, v
    assert cp_split_sizes is not None
    _, k_head, _ = k.shape
    if cp_world_size % k_head == 0 and cp_world_size != k_head:
        k = torch.repeat_interleave(k, repeats=divide(cp_world_size, k_head), dim=1)
        v = torch.repeat_interleave(v, repeats=divide(cp_world_size, k_head), dim=1)

    q = rearrange(q, "seq (cp hn) hd -> (cp seq) hn hd", cp=cp_world_size).contiguous()
    k = rearrange(k, "seq (cp hn) hd -> (cp seq) hn hd", cp=cp_world_size).contiguous()
    v = rearrange(v, "seq (cp hn) hd -> (cp seq) hn hd", cp=cp_world_size).contiguous()
    head_split_number = [q.shape[1], k.shape[1], v.shape[1]]
    qkv = torch.cat([q, k, v], dim=1).contiguous()

    qkv_output = torch.empty([sum(cp_split_sizes), *qkv.shape[1:]], device=qkv.device, dtype=qkv.dtype)
    torch.distributed.all_to_all_single(
        qkv_output, qkv, output_split_sizes=cp_split_sizes, group=mpu.get_cp_group(), async_op=False
    )
    q, k, v = torch.split(qkv_output, head_split_number, dim=1)
    return q, k, v


class UlyssesScheduler:
    def __init__(self):
        pass

    @staticmethod
    def get_attn_and_xattn_with_comm_overlap(
        get_q_func: Callable,  # [seq hn hd]
        get_k_func: Callable,  # [seq hn hd]
        get_v_func: Callable,  # [seq hn hd]
        kv_cache_func: Callable,
        core_attn_func: Callable,
        cross_attn_func: Callable,
        overlap_degree: int,
        batch_size: int,
        cp_size: int,
        cp_split_sizes: List[int] = None,
    ):
        """
        Get Q, K, V with communication overlap.
        Input:
            get_q: Callable, function to get q, shape [b, sq, hn, hd]
            get_k: Callable, function to get k, shape [sq, b, hn, hd]
            get_v: Callable, function to get v, shape [sq, b, hn, hd]
        NOTE: Why follow such compute and comm order?
        1. v_compute
        2. k_compute(overlap with v_comm)
        3. q_compute(overlap with k_comm)
        4. kv_cache_func(overlap with q_comm)
        Follow the principle: We need to begin comm as soon as possible to hide the comm latency.
        The computation flops and commnunication order is:
        flops order: q_compute (larger hidden_size + layernorm) > k_compute (layernorm) > v_compute
        comm order: q_compute (larger hidden_size) > k_compute = v_compute
        """
        value = get_v_func()
        value, handle_v = all_to_all_input_split(value, cp_split_sizes)
        key = get_k_func()
        key, handle_k = all_to_all_input_split(key, cp_split_sizes)
        query = get_q_func()
        query, handle_q = all_to_all_input_split(query, cp_split_sizes)

        handle_v.wait()
        handle_k.wait()
        kv = torch.concat([key, value], dim=-1)

        key, value = kv_cache_func(kv)
        handle_q.wait()
        return UlyssesScheduler.get_attn_and_xattn_base(
            query, key, value, core_attn_func, cross_attn_func, overlap_degree, batch_size, cp_size, cp_split_sizes
        )

    @staticmethod
    def get_attn_and_xattn_with_fused_kv_comm(
        get_q_func: Callable,
        get_kv_func: Callable,
        kv_cache_func: Callable,
        core_attn_func: Callable,
        cross_attn_func: Callable,
        overlap_degree: int,
        batch_size: int,
        cp_size: int,
        cp_split_sizes: List[int] = None,
    ):
        """
        When seq_len is very small, CPU-bound issues are severe. By fusing kv communication,
        CPU operations and the number of kernel launches are reduced.
        """
        kv = get_kv_func()
        kv, handle_kv = all_to_all_input_split(kv, cp_split_sizes)
        query = get_q_func()
        query, handle_q = all_to_all_input_split(query, cp_split_sizes)
        handle_kv.wait()
        key, value = kv_cache_func(kv)
        handle_q.wait()
        return UlyssesScheduler.get_attn_and_xattn_base(
            query, key, value, core_attn_func, cross_attn_func, overlap_degree, batch_size, cp_size, cp_split_sizes
        )

    def get_attn_and_xattn_with_fused_qkv_comm(
        get_qkv_func: Callable,
        kv_cache_func: Callable,
        core_attn_func: Callable,
        cross_attn_func: Callable,
        overlap_degree: int,
        batch_size: int,
        cp_size: int,
        cp_split_sizes: List[int] = None,
    ):
        """
        By fusing the communication of q, k, and v together, further optimize CPU-bound issues.
        """
        q, k, v = get_qkv_func()
        q, k, v = fused_qkv_communication(q, k, v, cp_split_sizes)
        k, v = kv_cache_func(torch.cat([k, v], dim=-1))
        return UlyssesScheduler.get_attn_and_xattn_base(
            q, k, v, core_attn_func, cross_attn_func, overlap_degree, batch_size, cp_size, cp_split_sizes
        )

    @staticmethod
    def get_attn_and_xattn_base(
        query: torch.Tensor,
        key: torch.Tensor,
        value: torch.Tensor,
        core_attn_func: Callable,
        cross_attn_func: Callable,
        overlap_degree: int,
        batch_size: int,
        cp_size: int,
        cp_split_sizes: List[int] = None,
    ):
        # Split Query, Key, Value into multiple parts
        # k/v may have different sequence length with q due to kv cache
        q_seq, q_head, q_hidden = query.shape
        kv_seq, kv_head, kv_hidden = key.shape
        if overlap_degree == -1:
            overlap_degree = q_head // kv_head
        else:
            assert overlap_degree <= q_head

        if overlap_degree == 1:
            query = [query]
        elif kv_head == 1:  # MQA
            query = query.chunk(overlap_degree, dim=1)
        else:  # GQA
            assert q_head % (overlap_degree * kv_head) == 0
            query = query.reshape(q_seq, kv_head, -1, q_hidden)
            query = query.chunk(overlap_degree, dim=2)
            query = [q.reshape(q_seq, -1, q_hidden) for q in query]

        # Compute Core Attention
        handle_attn = None
        core_attn_out = None
        core_attn_outs = []
        for i in range(overlap_degree):
            core_attn_out_new = core_attn_func(query[i], key, value)
            if not torch.isfinite(core_attn_out_new).all():
                import pdb; pdb.set_trace()
            if handle_attn is not None:
                handle_attn.wait()
                core_attn_outs.append(core_attn_out)
            core_attn_out, handle_attn = all_to_all_output_split(core_attn_out_new, cp_split_sizes)
            if not torch.isfinite(core_attn_out).all():
                import pdb; pdb.set_trace()

        xattn_out = cross_attn_func()
        handle_attn.wait()
        if not torch.isfinite(core_attn_out).all():
            import pdb; pdb.set_trace()
        core_attn_outs.append(core_attn_out)
        core_attn_out = torch.cat(core_attn_outs, dim=1)

        if not torch.isfinite(core_attn_out).all():
            import pdb; pdb.set_trace()

        core_attn_out = rearrange(core_attn_out, "(cp sq b) hn hd -> (sq) b (cp hn hd)", cp=cp_size, b=batch_size)
        return core_attn_out, xattn_out


#####################################################
# CSO(context shuffle overlap) Attention Pipeline
#####################################################
def cso_communication(
    input: torch.Tensor, cp_world_size: int, cp_split_sizes: List[int], comm_type: str = None
) -> Tuple[torch.Tensor, torch.distributed.Work]:
    if cp_world_size == 1:
        return input, FakeHandle()
    assert cp_split_sizes is not None
    _, hn, _ = input.shape
    if comm_type == "kv":
        if cp_world_size % hn == 0 and cp_world_size != hn:
            input = torch.repeat_interleave(input, repeats=divide(cp_world_size, hn), dim=1)
        input = rearrange(input, "spb (cp hn) hd -> (cp spb) hn hd", cp=cp_world_size).contiguous()
    output = torch.empty(input.shape, device=input.device, dtype=input.dtype)

    handle = torch.distributed.all_to_all_single(
        output, input, input_split_sizes=cp_split_sizes, group=mpu.get_cp_group(), async_op=True
    )

    return output, handle


class CSOHelper:
    def __init__(self, cp_shuffle_num, cp_world_size, cp_split_sizes):
        self.cp_shuffle_num = cp_shuffle_num
        self.cp_world_size = cp_world_size
        self.cp_split_sizes = [divide(x, self.cp_shuffle_num) for x in cp_split_sizes]

    def split_query_for_overlap(self, query):
        query = rearrange(
            query, "(dn spb) (cp hn) hd -> (dn cp spb) hn hd", cp=self.cp_world_size, dn=self.cp_shuffle_num
        ).contiguous()
        querys = list(torch.chunk(query, self.cp_shuffle_num, dim=0))
        querys[0], handle_q = cso_communication(querys[0], self.cp_world_size, self.cp_split_sizes)
        return querys, handle_q

    def overlap(self, fattn, qs, k, v):
        core_attn_outs = []
        for i in range(self.cp_shuffle_num):
            if self.cp_shuffle_num == 1:
                q = qs[0]
            elif i == 0:
                q = qs[0]
                loop_var, loop_handle = cso_communication(qs[i + 1], self.cp_world_size, self.cp_split_sizes)
            else:
                loop_handle.wait()
                if loop_var.numel() == qs[0].numel():
                    q = loop_var
                else:
                    assert loop_var.numel() == qs[0].numel() * 2
                    q, ready_o = torch.chunk(loop_var, 2, dim=-1)
                    core_attn_outs.append(ready_o)
                loop_var = torch.concat([qs[i + 1], o], dim=-1) if i < self.cp_shuffle_num - 1 else o
                loop_var, loop_handle = cso_communication(loop_var, self.cp_world_size, self.cp_split_sizes)

            o = fattn(q, k, v, i)
            if i == self.cp_shuffle_num - 1:
                if i != 0:
                    loop_handle.wait()
                    assert loop_var.numel() == qs[0].numel()
                    core_attn_outs.append(loop_var)
                last_o, handle_attn = cso_communication(o, self.cp_world_size, self.cp_split_sizes)
                core_attn_outs.append(last_o)
        return core_attn_outs, handle_attn