[ROCm][Test] Fix beam search determinism failures from batch-size-dependent FP divergence and removed wrong marker (#34878)

Signed-off-by: Andreas Karatzas <akaratza@amd.com>

.buildkite/test-amd.yaml

@@ -549,7 +549,7 @@ steps:
   - tests/samplers
   - tests/conftest.py
   commands:
-    - pytest -v -s -m samplers
+    - pytest -v -s samplers
 
 - label: LoRA Test %N # 20min each
   timeout_in_minutes: 30
@@ -2177,7 +2177,7 @@ steps:
   - tests/samplers
   - tests/conftest.py
   commands:
-    - pytest -v -s -m samplers
+    - pytest -v -s samplers
 
 - label: LoRA Test %N # 20min each
   timeout_in_minutes: 30

.buildkite/test_areas/samplers.yaml

@@ -18,4 +18,4 @@ steps:
       depends_on:
       - image-build-amd
       commands:
-      - pytest -v -s -m samplers
+      - pytest -v -s samplers

tests/samplers/test_beam_search.py

@@ -9,6 +9,26 @@ import pytest
 from transformers import AutoModelForSeq2SeqLM
 
 from vllm.assets.audio import AudioAsset
+from vllm.platforms import current_platform
+
+# Extra engine kwargs needed for numerically deterministic beam search.
+# On ROCm, floating-point reductions in attention and GEMM kernels are
+# non-associative and sensitive to batch geometry, so we:
+#   async_scheduling=False      – deterministic batch composition
+#   enforce_eager=True          – no CUDA-graph padding changing effective size
+#   enable_prefix_caching=False – avoid prefix-sharing side effects
+#   max_num_seqs=1              – fixed batch size across runs
+# On other platforms these are not needed and the dict is empty.
+EXTRA_ENGINE_KWARGS: dict = (
+    dict(
+        async_scheduling=False,
+        enforce_eager=True,
+        enable_prefix_caching=False,
+        max_num_seqs=1,
+    )
+    if current_platform.is_rocm()
+    else {}
+)
 
 # FIXME(zhuohan): The test can not pass if we:
 #   1. Increase max_tokens to 256.
@@ -25,6 +45,7 @@ MODELS = ["TinyLlama/TinyLlama-1.1B-Chat-v1.0"]
 @pytest.mark.parametrize("max_tokens", MAX_TOKENS)
 @pytest.mark.parametrize("beam_width", BEAM_WIDTHS)
 def test_beam_search_single_input(
+    monkeypatch,
     hf_runner,
     vllm_runner,
     example_prompts,
@@ -33,13 +54,16 @@ def test_beam_search_single_input(
     max_tokens: int,
     beam_width: int,
 ) -> None:
+    if current_platform.is_rocm():
+        monkeypatch.setenv("VLLM_ROCM_USE_SKINNY_GEMM", "0")
+
     example_prompts = example_prompts[:1]
     with hf_runner(model, dtype=dtype) as hf_model:
         hf_outputs = hf_model.generate_beam_search(
             example_prompts, beam_width, max_tokens
         )
 
-    with vllm_runner(model, dtype=dtype) as vllm_model:
+    with vllm_runner(model, dtype=dtype, **EXTRA_ENGINE_KWARGS) as vllm_model:
         vllm_outputs = vllm_model.generate_beam_search(
             example_prompts, beam_width, max_tokens
         )
@@ -66,6 +90,7 @@ def test_beam_search_single_input(
 @pytest.mark.parametrize("max_tokens", MAX_TOKENS)
 @pytest.mark.parametrize("beam_width", BEAM_WIDTHS)
 def test_beam_search_with_concurrency_limit(
+    monkeypatch,
     hf_runner,
     vllm_runner,
     example_prompts,
@@ -74,21 +99,29 @@ def test_beam_search_with_concurrency_limit(
     max_tokens: int,
     beam_width: int,
 ) -> None:
+    if current_platform.is_rocm():
+        monkeypatch.setenv("VLLM_ROCM_USE_SKINNY_GEMM", "0")
+
     # example_prompts[1]&[3]&[7] fails due to unknown reason even without
     # concurrency limit. skip them for now.
     example_prompts = example_prompts[:8]
     concurrency_limit = 2
     assert len(example_prompts) > concurrency_limit
-    with vllm_runner(model, dtype=dtype) as vllm_model:
+    with vllm_runner(model, dtype=dtype, **EXTRA_ENGINE_KWARGS) as vllm_model:
         outputs_with_limit = vllm_model.generate_beam_search(
-            example_prompts, beam_width, max_tokens, concurrency_limit=concurrency_limit
+            example_prompts,
+            beam_width,
+            max_tokens,
+            concurrency_limit=concurrency_limit,
         )
         outputs_without_limit = []
 
         for i in range(0, len(example_prompts), concurrency_limit):
             outputs_without_limit.extend(
                 vllm_model.generate_beam_search(
-                    example_prompts[i : i + concurrency_limit], beam_width, max_tokens
+                    example_prompts[i : i + concurrency_limit],
+                    beam_width,
+                    max_tokens,
                 )
             )
 
@@ -118,6 +151,7 @@ def test_beam_search_with_concurrency_limit(
 @pytest.mark.parametrize("max_tokens", MAX_TOKENS)
 @pytest.mark.parametrize("beam_width", MM_BEAM_WIDTHS)
 def test_beam_search_passes_multimodal_data(
+    monkeypatch,
     hf_runner,
     vllm_runner,
     dtype: str,
@@ -125,6 +159,9 @@ def test_beam_search_passes_multimodal_data(
     beam_width: int,
 ) -> None:
     """Ensure that beam search passes multimodal data through correctly."""
+    if current_platform.is_rocm():
+        monkeypatch.setenv("VLLM_ROCM_USE_SKINNY_GEMM", "0")
+
     # NOTE - this test is primarily to check that mm data is passed to beams
     # correctly. As such, we just need to check one extra modality to make
     # sure things pass through properly.
@@ -145,7 +182,7 @@ def test_beam_search_passes_multimodal_data(
             audios=audios,
         )
 
-    with vllm_runner(model, dtype=dtype) as vllm_model:
+    with vllm_runner(model, dtype=dtype, **EXTRA_ENGINE_KWARGS) as vllm_model:
         vllm_outputs = vllm_model.generate_beam_search(
             prompts,
             beam_width=beam_width,