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vllm-omni/vllm_omni/diffusion/attention/backends/sdpa.py
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Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import torch
from vllm.logger import init_logger
from vllm_omni.diffusion.attention.backends.abstract import (
AttentionBackend,
AttentionImpl,
AttentionMetadata,
)
logger = init_logger(__name__)
def _maybe_reshape_attn_mask(query: torch.Tensor, key: torch.Tensor, attn_mask: torch.Tensor | None = None):
"""
Reshape Attention Mask
[batch_size, seq_len_k] -> [batch_size, 1, seq_len_q, seq_len_k]
"""
# Skip Attention Mask if all values are 1, `None` mask can speedup the computation
if attn_mask is not None and torch.all(attn_mask != 0):
attn_mask = None
# Reshape Attention Mask
# [batch_size, seq_len_k] -> [batch_size, 1, seq_len_q, seq_len_k]
if (
attn_mask is not None
and attn_mask.ndim == 2
and attn_mask.shape[0] == query.shape[0]
and attn_mask.shape[1] == key.shape[1]
):
B, Sq, Skv = attn_mask.shape[0], query.shape[1], key.shape[1]
attn_mask = attn_mask.to(torch.bool)
attn_mask = attn_mask.unsqueeze(1).expand(B, Sq, Skv).unsqueeze(1).contiguous()
return attn_mask
class SDPABackend(AttentionBackend):
accept_output_buffer: bool = True
@classmethod
def supports_attention_mask(cls) -> bool:
return True
@staticmethod
def get_supported_head_sizes() -> list[int]:
return [x for x in range(1024)] # todo
@staticmethod
def get_name() -> str:
return "SDPA"
@staticmethod
def get_impl_cls() -> type["SDPAImpl"]:
return SDPAImpl
class SDPAImpl(AttentionImpl):
def __init__(
self,
num_heads: int,
head_size: int,
softmax_scale: float,
causal: bool = False,
num_kv_heads: int | None = None,
prefix: str = "",
**extra_impl_args,
) -> None:
self.causal = causal
self.softmax_scale = softmax_scale
def forward_cuda(
self,
query: torch.Tensor,
key: torch.Tensor,
value: torch.Tensor,
attn_metadata: AttentionMetadata | None = None,
) -> torch.Tensor:
query, key, value = (x.permute(0, 2, 1, 3) for x in (query, key, value))
attention_mask = attn_metadata.attn_mask if attn_metadata else None
output = torch.nn.functional.scaled_dot_product_attention(
query,
key,
value,
attn_mask=attention_mask,
dropout_p=0.0,
is_causal=self.causal,
scale=self.softmax_scale,
)
out = output.permute(0, 2, 1, 3)
return out
def forward_xpu(
self,
query: torch.Tensor,
key: torch.Tensor,
value: torch.Tensor,
attn_metadata: AttentionMetadata | None = None,
) -> torch.Tensor:
return self.forward_cuda(query, key, value, attn_metadata)
def forward_hip(
self,
query: torch.Tensor,
key: torch.Tensor,
value: torch.Tensor,
attn_metadata: AttentionMetadata | None = None,
) -> torch.Tensor:
return self.forward_cuda(query, key, value, attn_metadata)
def forward_npu(
self,
query: torch.Tensor,
key: torch.Tensor,
value: torch.Tensor,
attn_metadata: AttentionMetadata | None = None,
) -> torch.Tensor:
if attn_metadata:
attention_mask = _maybe_reshape_attn_mask(query, key, attn_metadata.attn_mask)
setattr(attn_metadata, "attn_mask", attention_mask)
return self.forward_cuda(query, key, value, attn_metadata)