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vllm-omni/tests/diffusion/attention/test_sage_attn3.py

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Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import importlib
import sys
import types
import pytest
import torch
from vllm.platforms import current_platform
pytestmark = [pytest.mark.core_model, pytest.mark.diffusion, pytest.mark.cpu]
SAGE_ATTN3_MODULE = "vllm_omni.diffusion.attention.backends.sage_attn3"
def load_sage_attn3_module(monkeypatch: pytest.MonkeyPatch, kernel_impl):
fake_module = types.ModuleType("sageattn3")
fake_module.sageattn3_blackwell = kernel_impl
monkeypatch.setitem(sys.modules, "sageattn3", fake_module)
sys.modules.pop(SAGE_ATTN3_MODULE, None)
return importlib.import_module(SAGE_ATTN3_MODULE)
def test_sage_attn3_forward_uses_blackwell_layout(monkeypatch: pytest.MonkeyPatch):
calls = {}
def fake_kernel(query, key, value, is_causal=False):
calls["query_shape"] = query.shape
calls["is_causal"] = is_causal
return query + key + value
backend_module = load_sage_attn3_module(monkeypatch, fake_kernel)
impl = backend_module.SageAttention3Impl(
num_heads=4,
head_size=64,
softmax_scale=1.0 / 8.0,
causal=False,
)
query = torch.randn(2, 8, 4, 64)
key = torch.randn(2, 8, 4, 64)
value = torch.randn(2, 8, 4, 64)
output = impl.forward_cuda(query, key, value)
assert calls["query_shape"] == (2, 4, 8, 64)
assert calls["is_causal"] is False
expected = (query.transpose(1, 2) + key.transpose(1, 2) + value.transpose(1, 2)).transpose(1, 2)
assert torch.allclose(output, expected)
def test_sage_attn3_falls_back_to_sdpa_for_gqa(monkeypatch: pytest.MonkeyPatch):
def fake_kernel(*args, **kwargs):
raise AssertionError("sageattn3_blackwell should not be used for GQA")
backend_module = load_sage_attn3_module(monkeypatch, fake_kernel)
sdpa_calls = {}
def fake_sdpa(query, key, value, **kwargs):
sdpa_calls["query_shape"] = query.shape
sdpa_calls["key_shape"] = key.shape
sdpa_calls["enable_gqa"] = kwargs["enable_gqa"]
return query + 1
monkeypatch.setattr(backend_module.F, "scaled_dot_product_attention", fake_sdpa)
impl = backend_module.SageAttention3Impl(
num_heads=4,
head_size=64,
softmax_scale=1.0 / 8.0,
causal=False,
)
query = torch.randn(2, 8, 4, 64)
key = torch.randn(2, 8, 2, 64)
value = torch.randn(2, 8, 2, 64)
output = impl.forward_cuda(query, key, value)
assert sdpa_calls["query_shape"] == (2, 4, 8, 64)
assert sdpa_calls["key_shape"] == (2, 2, 8, 64)
assert sdpa_calls["enable_gqa"] is True
expected = (query.permute(0, 2, 1, 3) + 1).permute(0, 2, 1, 3)
assert torch.allclose(output, expected)
@pytest.mark.skipif(not current_platform.is_cuda(), reason="sage_attn3 tests require CUDA platform")
def test_cuda_platform_selects_sage_attn3_alias(monkeypatch: pytest.MonkeyPatch):
from vllm.platforms.interface import DeviceCapability
from vllm_omni.diffusion.attention.backends.registry import DiffusionAttentionBackendEnum
from vllm_omni.diffusion.envs import PACKAGES_CHECKER
from vllm_omni.platforms.cuda import platform as cuda_platform_module
from vllm_omni.platforms.cuda.platform import CudaOmniPlatform
original_import_module = importlib.import_module
monkeypatch.setattr(
CudaOmniPlatform,
"get_device_capability",
classmethod(lambda cls, device_id=0: DeviceCapability(10, 0)),
)
monkeypatch.setattr(PACKAGES_CHECKER, "get_packages_info", lambda: {"has_flash_attn": False})
monkeypatch.setattr(
cuda_platform_module.importlib,
"import_module",
lambda module_name: object() if module_name == "sageattn3" else original_import_module(module_name),
)
backend_path = CudaOmniPlatform.get_diffusion_attn_backend_cls("SAGE_ATTN_3", head_size=64)
assert backend_path == DiffusionAttentionBackendEnum.SAGE_ATTN_3.get_path()
@pytest.mark.skipif(not current_platform.is_cuda(), reason="sage_attn3 tests require CUDA platform")
def test_cuda_platform_falls_back_when_sage_attn3_gpu_is_unsupported(monkeypatch: pytest.MonkeyPatch):
from vllm.platforms.interface import DeviceCapability
from vllm_omni.diffusion.attention.backends.registry import DiffusionAttentionBackendEnum
from vllm_omni.diffusion.envs import PACKAGES_CHECKER
from vllm_omni.platforms.cuda.platform import CudaOmniPlatform
monkeypatch.setattr(
CudaOmniPlatform,
"get_device_capability",
classmethod(lambda cls, device_id=0: DeviceCapability(9, 0)),
)
monkeypatch.setattr(PACKAGES_CHECKER, "get_packages_info", lambda: {"has_flash_attn": False})
backend_path = CudaOmniPlatform.get_diffusion_attn_backend_cls("SAGE_ATTN_3", head_size=64)
assert backend_path == DiffusionAttentionBackendEnum.TORCH_SDPA.get_path()