254 lines
10 KiB
Python
254 lines
10 KiB
Python
import math
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import torch
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from .block_sparse_attn import block_sparse_attn, block_sparse_attn_from_indices
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from .block_sparse_attn_256 import (
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block_sparse_attn_256,
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block_sparse_attn_256_bshd,
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)
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from .triton_kernels.st_attn_triton import sliding_tile_attention_triton
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# Try to load the C++ extension
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try:
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from fastvideo_kernel._C import fastvideo_kernel_ops
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sta_fwd = getattr(fastvideo_kernel_ops, "sta_fwd", None)
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except ImportError:
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sta_fwd = None
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def sliding_tile_attention(
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q: torch.Tensor,
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k: torch.Tensor,
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v: torch.Tensor,
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window_size: list,
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text_length: int,
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has_text: bool = True,
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seq_shape: str = "30x48x80",
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) -> torch.Tensor:
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# Check if the specific op is available
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if sta_fwd is None:
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return sliding_tile_attention_triton(
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q, k, v, window_size, text_length, has_text, seq_shape
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)
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seq_length = q.shape[2]
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shape_map = {"30x48x80": 1, "36x48x48": 2, "18x48x80": 3}
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if has_text:
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target_size = math.ceil(seq_length / 384) * 384
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pad_size = target_size - seq_length
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if pad_size > 0:
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q = torch.cat([q, q[:, :, -pad_size:]], dim=2)
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k = torch.cat([k, k[:, :, -pad_size:]], dim=2)
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v = torch.cat([v, v[:, :, -pad_size:]], dim=2)
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output = torch.empty_like(q)
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flag = shape_map[seq_shape]
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for head_idx, (t, h, w) in enumerate(window_size):
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# Per-head slices are not contiguous in the batch dimension when batch>1
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# (they keep the original head-stride). The TK kernel assumes contiguous
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# [B, H, S, D] layout, so we materialize a contiguous [B,1,S,D] view.
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q_h = q[:, head_idx:head_idx + 1].contiguous()
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k_h = k[:, head_idx:head_idx + 1].contiguous()
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v_h = v[:, head_idx:head_idx + 1].contiguous()
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o_h = torch.empty_like(q_h)
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sta_fwd(
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q_h, k_h,
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v_h, o_h,
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t, h, w, text_length, False, has_text, flag
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)
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output[:, head_idx:head_idx + 1] = o_h
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if has_text:
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sta_fwd(q.contiguous(), k.contiguous(), v.contiguous(), output, 3, 3, 3, text_length, True, True, flag)
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return output[:, :, :seq_length]
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def video_sparse_attn(
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q: torch.Tensor,
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k: torch.Tensor,
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v: torch.Tensor,
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variable_block_sizes: torch.Tensor,
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q_variable_block_sizes: torch.Tensor,
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topk: int,
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block_size: int | tuple = 64,
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compress_attn_weight: torch.Tensor = None,
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) -> torch.Tensor:
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"""VSA entrypoint for [B, H, S, D] tensors.
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Dispatches the sparse branch by ``block_elements = prod(block_size)``:
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- 64 -> existing TK/Triton path (see ``block_sparse_attn_from_indices``).
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- 256 -> CuTe FA4 block-sparse attention (see ``block_sparse_attn_256``).
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Backend overrides:
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- ``FASTVIDEO_VSA_TRITON=1`` forces Triton in either path.
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- ``FASTVIDEO_VSA_TK=1`` prefers the sm_90 TK kernel in the 64-block path.
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- ``FASTVIDEO_VSA_CUTEDSL=1`` prefers CuTe in the 256-block path.
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"""
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if isinstance(block_size, int):
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block_size = (block_size, block_size, block_size)
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block_elements = block_size[0] * block_size[1] * block_size[2]
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batch, heads, q_seq_len, dim = q.shape
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kv_seq_len = k.shape[2]
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if k.shape[0] != batch or v.shape[0] != batch or k.shape[1] != heads or v.shape[1] != heads:
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raise ValueError("Expected q/k/v to have the same batch and head dimensions.")
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if v.shape[2] != kv_seq_len:
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raise ValueError(
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f"Expected k and v to have the same sequence length, got "
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f"k.shape[2]={kv_seq_len}, v.shape[2]={v.shape[2]}"
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)
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if q_seq_len % block_elements != 0 or kv_seq_len % block_elements != 0:
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raise ValueError(
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f"q_seq_len and kv_seq_len must be divisible by block_elements={block_elements}, "
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f"got q_seq_len={q_seq_len}, kv_seq_len={kv_seq_len}"
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)
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q_num_blocks = q_seq_len // block_elements
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kv_num_blocks = kv_seq_len // block_elements
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if variable_block_sizes.numel() != kv_num_blocks:
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raise ValueError(
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f"variable_block_sizes must have length kv_num_blocks={kv_num_blocks}, "
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f"got {variable_block_sizes.numel()}"
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)
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if q_variable_block_sizes.numel() != q_num_blocks:
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raise ValueError(
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f"q_variable_block_sizes must have length q_num_blocks={q_num_blocks}, "
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f"got {q_variable_block_sizes.numel()}"
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)
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# Compression branch (token-level average per block + dense block-level attn).
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q_c = q.view(batch, heads, q_num_blocks, block_elements, dim)
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k_c = k.view(batch, heads, kv_num_blocks, block_elements, dim)
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v_c = v.view(batch, heads, kv_num_blocks, block_elements, dim)
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q_c = (q_c.float().sum(dim=3) / q_variable_block_sizes.view(1, 1, -1, 1)).to(q.dtype)
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k_c = (k_c.float().sum(dim=3) / variable_block_sizes.view(1, 1, -1, 1)).to(k.dtype)
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v_c = (v_c.float().sum(dim=3) / variable_block_sizes.view(1, 1, -1, 1)).to(v.dtype)
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scores = torch.matmul(q_c, k_c.transpose(-2, -1)) / (dim ** 0.5)
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attn = torch.softmax(scores, dim=-1)
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out_c = torch.matmul(attn, v_c)
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out_c = out_c.view(batch, heads, q_num_blocks, 1, dim)
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out_c = out_c.repeat(1, 1, 1, block_elements, 1).view(batch, heads, q_seq_len, dim)
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# Sparse branch.
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topk_idx = torch.topk(scores, topk, dim=-1).indices
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if block_elements == 256:
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# CuTe path consumes a bool mask (full/partial split inside the wrapper).
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mask = torch.zeros_like(scores, dtype=torch.bool).scatter_(-1, topk_idx, True)
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out_s = block_sparse_attn_256(q, k, v, mask, variable_block_sizes)[0]
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else:
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# Index-native path for 64-block (TK/Triton).
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q2k_idx = topk_idx.to(torch.int32).contiguous()
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q2k_num = torch.full(
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(batch, heads, q_num_blocks),
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topk,
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dtype=torch.int32,
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device=q.device,
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)
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out_s = block_sparse_attn_from_indices(
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q, k, v, q2k_idx, q2k_num, variable_block_sizes
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)[0]
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if compress_attn_weight is not None:
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return out_c * compress_attn_weight + out_s
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return out_c + out_s
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def video_sparse_attn_bshd(
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q: torch.Tensor,
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k: torch.Tensor,
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v: torch.Tensor,
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variable_block_sizes: torch.Tensor,
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q_variable_block_sizes: torch.Tensor,
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topk: int,
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block_size: int | tuple = 64,
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compress_attn_weight: torch.Tensor = None,
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) -> torch.Tensor:
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"""VSA entrypoint for [B, S, H, D] tensors.
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Avoids the BHSD<->BSHD round-trip that ``video_sparse_attn`` performs on
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the CuTe 256-block path; the 64-block path still expects BHSD and is not
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supported here.
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"""
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if isinstance(block_size, int):
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block_size = (block_size, block_size, block_size)
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block_elements = block_size[0] * block_size[1] * block_size[2]
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if block_elements != 256:
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raise ValueError(
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"video_sparse_attn_bshd is only defined for block_elements=256 "
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f"(got {block_elements}); use video_sparse_attn for the 64-block path."
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)
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batch, q_seq_len, heads, dim = q.shape
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kv_seq_len = k.shape[1]
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if k.shape[0] != batch or v.shape[0] != batch or k.shape[2] != heads or v.shape[2] != heads:
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raise ValueError("Expected q/k/v to have the same batch and head dimensions.")
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if v.shape[1] != kv_seq_len:
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raise ValueError(
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f"Expected k and v to have the same sequence length, got "
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f"k.shape[1]={kv_seq_len}, v.shape[1]={v.shape[1]}"
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)
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if q_seq_len % block_elements != 0 or kv_seq_len % block_elements != 0:
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raise ValueError(
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f"q_seq_len and kv_seq_len must be divisible by block_elements={block_elements}, "
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f"got q_seq_len={q_seq_len}, kv_seq_len={kv_seq_len}"
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)
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q_num_blocks = q_seq_len // block_elements
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kv_num_blocks = kv_seq_len // block_elements
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if variable_block_sizes.numel() != kv_num_blocks:
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raise ValueError(
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f"variable_block_sizes must have length kv_num_blocks={kv_num_blocks}, "
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f"got {variable_block_sizes.numel()}"
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)
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if q_variable_block_sizes.numel() != q_num_blocks:
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raise ValueError(
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f"q_variable_block_sizes must have length q_num_blocks={q_num_blocks}, "
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f"got {q_variable_block_sizes.numel()}"
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)
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# Compression branch (BSHD-native: mean over the 256-token axis).
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token_idx = torch.arange(block_elements, device=q.device, dtype=torch.int32)
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q_token_valid = (token_idx.view(1, -1) < q_variable_block_sizes.view(-1, 1)).view(
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1, q_num_blocks, block_elements, 1, 1
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)
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kv_token_valid = (token_idx.view(1, -1) < variable_block_sizes.view(-1, 1)).view(
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1, kv_num_blocks, block_elements, 1, 1
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)
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q_c = q.view(batch, q_num_blocks, block_elements, heads, dim)
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k_c = k.view(batch, kv_num_blocks, block_elements, heads, dim)
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v_c = v.view(batch, kv_num_blocks, block_elements, heads, dim)
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q_c = ((q_c.float() * q_token_valid).sum(dim=2)
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/ q_variable_block_sizes.view(1, -1, 1, 1)).to(q.dtype)
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k_c = ((k_c.float() * kv_token_valid).sum(dim=2)
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/ variable_block_sizes.view(1, -1, 1, 1)).to(k.dtype)
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v_c = ((v_c.float() * kv_token_valid).sum(dim=2)
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/ variable_block_sizes.view(1, -1, 1, 1)).to(v.dtype)
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q_ch = q_c.permute(0, 2, 1, 3).contiguous()
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k_ch = k_c.permute(0, 2, 1, 3).contiguous()
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v_ch = v_c.permute(0, 2, 1, 3).contiguous()
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scores = torch.matmul(q_ch, k_ch.transpose(-2, -1)) / (dim ** 0.5)
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attn = torch.softmax(scores, dim=-1)
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out_c_ch = torch.matmul(attn, v_ch)
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out_c_blk = out_c_ch.permute(0, 2, 1, 3).contiguous()
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# Sparse branch (CuTe BSHD).
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topk_idx = torch.topk(scores, topk, dim=-1).indices
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mask = torch.zeros_like(scores, dtype=torch.bool).scatter_(-1, topk_idx, True)
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out_s, _ = block_sparse_attn_256_bshd(q, k, v, mask, variable_block_sizes)
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out = out_s
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out_view = out.view(batch, q_num_blocks, block_elements, heads, dim)
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if compress_attn_weight is not None:
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gate_view = compress_attn_weight.view(
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batch, q_num_blocks, block_elements, heads, dim
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)
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out_view.add_(out_c_blk.unsqueeze(2) * gate_view)
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else:
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out_view.add_(out_c_blk.unsqueeze(2))
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return out
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