init

tests/samplers/test_seeded_generate.py

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+"""Verify that seeded random sampling is deterministic.
+
+Run `pytest tests/samplers/test_seeded_generate.py`.
+"""
+import copy
+import random
+from itertools import combinations
+
+import pytest
+
+from vllm import SamplingParams
+from vllm.model_executor.utils import set_random_seed
+
+MODEL = "facebook/opt-125m"
+RANDOM_SEEDS = list(range(5))
+
+
+@pytest.fixture
+def vllm_model(vllm_runner):
+    vllm_model = vllm_runner(MODEL, dtype="half")
+    yield vllm_model
+    del vllm_model
+
+
+@pytest.mark.parametrize("seed", RANDOM_SEEDS)
+def test_random_sample_with_seed(
+    vllm_model,
+    example_prompts,
+    seed: int,
+) -> None:
+    set_random_seed(seed)
+
+    sampling_params = SamplingParams(
+        # Parameters to ensure sufficient randomness
+        temperature=2.0,
+        top_p=min(random.random() + 0.3, 1),
+        top_k=random.randint(5, 20),
+        n=random.randint(1, 10),
+        presence_penalty=random.randint(0, 1),
+        max_tokens=8,
+        ignore_eos=True,
+    )
+
+    sampling_params_seed_1 = copy.deepcopy(sampling_params)
+    sampling_params_seed_1.seed = 100
+    sampling_params_seed_2 = copy.deepcopy(sampling_params)
+    sampling_params_seed_2.seed = 200
+
+    llm = vllm_model.model
+
+    for prompt in example_prompts:
+        for params in (
+                sampling_params,
+                sampling_params_seed_1,
+                sampling_params_seed_2,
+                sampling_params,
+                sampling_params_seed_1,
+                sampling_params_seed_2,
+        ):
+            llm._add_request(
+                prompt=prompt,
+                prompt_token_ids=None,
+                sampling_params=params,
+            )
+
+    results = llm._run_engine(use_tqdm=False)
+    all_outputs = [[out.token_ids for out in output.outputs]
+                   for output in results]
+
+    for i in range(0, len(example_prompts), 6):
+        outputs = all_outputs[i:i + 6]
+
+        # verify all non-seeded requests differ
+        for output_a, output_b in combinations(
+            (outputs[0], outputs[1], outputs[2], outputs[3]),
+                2,
+        ):
+            assert output_a != output_b
+
+        # verify requests with the same seed match
+        assert outputs[1] == outputs[4]
+        assert outputs[2] == outputs[5]