[Test] Test multiple attn backend for chunked prefill. (vllm-project#4023)

Author: rkooo567

.buildkite/test-pipeline.yaml

@@ -12,7 +12,13 @@ steps:
   command: pytest -v -s async_engine
 
 - label: Basic Correctness Test
-  command: pytest -v -s basic_correctness
+  commands:
+  - VLLM_ATTENTION_BACKEND=XFORMERS pytest -v -s basic_correctness/test_basic_correctness.py
+  - VLLM_ATTENTION_BACKEND=FLASH_ATTN pytest -v -s basic_correctness/test_basic_correctness.py
+  - VLLM_ATTENTION_BACKEND=ROCM_FLASH pytest -v -s basic_correctness/test_basic_correctness.py
+  - VLLM_ATTENTION_BACKEND=XFORMERS pytest -v -s basic_correctness/test_chunked_prefill.py
+  - VLLM_ATTENTION_BACKEND=FLASH_ATTN pytest -v -s basic_correctness/test_chunked_prefill.py
+  - VLLM_ATTENTION_BACKEND=ROCM_FLASH pytest -v -s basic_correctness/test_chunked_prefill.py
 
 - label: Core Test
   command: pytest -v -s core

tests/basic_correctness/test_basic_correctness.py

@@ -4,8 +4,6 @@
 """
 import pytest
 
-from vllm.attention.selector import VLLM_ATTENTION_BACKEND
-
 MODELS = [
     "facebook/opt-125m",
     "meta-llama/Llama-2-7b-hf",
@@ -16,7 +14,6 @@
 @pytest.mark.parametrize("dtype", ["half"])
 @pytest.mark.parametrize("max_tokens", [5])
 @pytest.mark.parametrize("enforce_eager", [False, True])
-@pytest.mark.parametrize("attn_backend", ["XFORMERS", "FLASH_ATTN"])
 def test_models(
     hf_runner,
     vllm_runner,
@@ -25,10 +22,7 @@ def test_models(
     dtype: str,
     max_tokens: int,
     enforce_eager: bool,
-    attn_backend: str,
-    monkeypatch,
 ) -> None:
-    monkeypatch.setenv(VLLM_ATTENTION_BACKEND, attn_backend)
     hf_model = hf_runner(model, dtype=dtype)
     hf_outputs = hf_model.generate_greedy(example_prompts, max_tokens)
     del hf_model

tests/basic_correctness/test_chunked_prefill.py

@@ -34,10 +34,6 @@ def test_models(
     enforce_eager: bool,
     tensor_parallel_size: int,
 ) -> None:
-    if (tensor_parallel_size == 2 and chunked_prefill_token_size != 16
-            and not enforce_eager):
-        pytest.skip(f"Skip {chunked_prefill_token_size=} and {enforce_eager=} "
-                    "for high TP to save testing time.")
     max_num_seqs = min(chunked_prefill_token_size, 256)
     enable_chunked_prefill = False
     max_num_batched_tokens = None

vllm/attention/backends/rocm_flash_attn.py

@@ -162,7 +162,7 @@ def __init__(
             # AMD Radeon 7900 series (gfx1100) currently does not support
             # xFormers nor FlashAttention. As a temporary workaround, we use
             # naive PyTorch implementation of attention.
-            self.attn_fuc = _naive_attention()
+            self.attn_fuc = _naive_attention
             logger.debug("Using naive attention in ROCmBackend")
         elif self.use_triton_flash_attn:
             from vllm.attention.ops.triton_flash_attention import (  # noqa: F401
@@ -334,26 +334,21 @@ def _naive_attention(
     prompt_lens: List[int],
     scale: float,
 ) -> torch.Tensor:
-    num_tokens = query.shape[0]
     output = torch.empty_like(query)
     start = 0
     for _, prompt_len in enumerate(prompt_lens):
         end = start + prompt_len
         out = _naive_masked_attention(
-            query[None, start:end],
-            key[None, start:end],
-            value[None, start:end],
+            query[start:end],
+            key[start:end],
+            value[start:end],
             scale,
         )
         # TODO(woosuk): Unnecessary copy. Optimize.
         output[start:end].copy_(out)
         start += prompt_len
 
-    # Using view got RuntimeError: view size is not compatible
-    # with input tensor's size and stride (at least one
-    # dimension spans across two contiguous subspaces).
-    # Use reshape instead.
-    return output.reshape(num_tokens, -1)
+    return output
 
 
 def _naive_masked_attention(
@@ -362,14 +357,13 @@ def _naive_masked_attention(
     value: torch.Tensor,
     scale: float,
 ) -> torch.Tensor:
-    seq_len, _, _ = query.shape
+    seq_len, head_size, head_dim = query.shape
     attn_mask = torch.triu(torch.ones(seq_len,
                                       seq_len,
                                       dtype=query.dtype,
                                       device=query.device),
                            diagonal=1)
     attn_mask = attn_mask * torch.finfo(query.dtype).min
-
     attn_weights = scale * torch.einsum("qhd,khd->hqk", query, key).float()
     attn_weights = attn_weights + attn_mask.float()
     attn_weights = torch.softmax(attn_weights, dim=-1).to(value.dtype)