[Bug fix][Core] assert num_new_tokens == 1 fails when SamplingParams.n is not 1 and max_tokens is large & Add tests for preemption (#4451)

tests/basic_correctness/test_preemption.py

@@ -0,0 +1,138 @@
+"""Compare the short outputs of HF and vLLM when using greedy sampling.
+
+VLLM_TEST_ENABLE_ARTIFICIAL_PREEMPT=1 has to be set before running this test.
+
+Run `VLLM_TEST_ENABLE_ARTIFICIAL_PREEMPT=1
+pytest tests/basic_correctness/test_preemption.py`.
+"""
+import pytest
+
+from vllm.core.scheduler import (ARTIFICIAL_PREEMPTION_MAX_CNT,
+                                 ENABLE_ARTIFICIAL_PREEMPT)
+
+MODELS = [
+    "facebook/opt-125m",
+]
+
+assert ENABLE_ARTIFICIAL_PREEMPT is True, (
+    "Use an env var VLLM_TEST_ENABLE_ARTIFICIAL_PREEMPT=1. "
+    "`VLLM_TEST_ENABLE_ARTIFICIAL_PREEMPT=1 pytest "
+    "tests/basic_correctness/test_preemption.py`")
+
+
+@pytest.mark.parametrize("model", MODELS)
+@pytest.mark.parametrize("dtype", ["half"])
+@pytest.mark.parametrize("max_tokens", [96])
+@pytest.mark.parametrize("chunked_prefill_token_size", [16])
+def test_chunked_prefill_recompute(
+    hf_runner,
+    vllm_runner,
+    example_prompts,
+    model: str,
+    dtype: str,
+    max_tokens: int,
+    chunked_prefill_token_size: int,
+) -> None:
+    """Ensure that chunked prefill works with preemption."""
+    max_num_seqs = min(chunked_prefill_token_size, 256)
+    enable_chunked_prefill = False
+    max_num_batched_tokens = None
+    if chunked_prefill_token_size != -1:
+        enable_chunked_prefill = True
+        max_num_batched_tokens = chunked_prefill_token_size
+
+    hf_model = hf_runner(model, dtype=dtype)
+    hf_outputs = hf_model.generate_greedy(example_prompts, max_tokens)
+    del hf_model
+
+    vllm_model = vllm_runner(
+        model,
+        dtype=dtype,
+        max_num_batched_tokens=max_num_batched_tokens,
+        enable_chunked_prefill=enable_chunked_prefill,
+        max_num_seqs=max_num_seqs,
+    )
+    vllm_outputs = vllm_model.generate_greedy(example_prompts, max_tokens)
+    assert (vllm_model.model.llm_engine.scheduler.artificial_preempt_cnt <
+            ARTIFICIAL_PREEMPTION_MAX_CNT)
+    del vllm_model
+
+    for i in range(len(example_prompts)):
+        hf_output_ids, hf_output_str = hf_outputs[i]
+        vllm_output_ids, vllm_output_str = vllm_outputs[i]
+        assert hf_output_str == vllm_output_str, (
+            f"Test{i}:\nHF: {hf_output_str!r}\nvLLM: {vllm_output_str!r}")
+        assert hf_output_ids == vllm_output_ids, (
+            f"Test{i}:\nHF: {hf_output_ids}\nvLLM: {vllm_output_ids}")
+
+
+@pytest.mark.parametrize("model", MODELS)
+@pytest.mark.parametrize("dtype", ["float"])
+@pytest.mark.parametrize("max_tokens", [96])
+def test_preemption(
+    hf_runner,
+    vllm_runner,
+    example_prompts,
+    model: str,
+    dtype: str,
+    max_tokens: int,
+) -> None:
+    """By default, recompute preemption is enabled"""
+
+    hf_model = hf_runner(model, dtype=dtype)
+    hf_outputs = hf_model.generate_greedy(example_prompts, max_tokens)
+    del hf_model
+
+    vllm_model = vllm_runner(
+        model,
+        dtype=dtype,
+    )
+    vllm_outputs = vllm_model.generate_greedy(example_prompts, max_tokens)
+    assert (vllm_model.model.llm_engine.scheduler.artificial_preempt_cnt <
+            ARTIFICIAL_PREEMPTION_MAX_CNT)
+    del vllm_model
+
+    for i in range(len(example_prompts)):
+        hf_output_ids, hf_output_str = hf_outputs[i]
+        vllm_output_ids, vllm_output_str = vllm_outputs[i]
+        assert hf_output_str == vllm_output_str, (
+            f"Test{i}:\nHF: {hf_output_str!r}\nvLLM: {vllm_output_str!r}")
+        assert hf_output_ids == vllm_output_ids, (
+            f"Test{i}:\nHF: {hf_output_ids}\nvLLM: {vllm_output_ids}")
+
+
+@pytest.mark.parametrize("model", MODELS)
+@pytest.mark.parametrize("dtype", ["float"])
+@pytest.mark.parametrize("max_tokens", [96])
+@pytest.mark.parametrize("beam_width", [4])
+def test_swap(
+    hf_runner,
+    vllm_runner,
+    example_prompts,
+    model: str,
+    dtype: str,
+    max_tokens: int,
+    beam_width: int,
+) -> None:
+    """Use beam search enables swapping."""
+    example_prompts = example_prompts[:1]
+    hf_model = hf_runner(model, dtype=dtype)
+    hf_outputs = hf_model.generate_beam_search(example_prompts, beam_width,
+                                               max_tokens)
+    del hf_model
+
+    vllm_model = vllm_runner(model, dtype=dtype, swap_space=10)
+    vllm_outputs = vllm_model.generate_beam_search(example_prompts, beam_width,
+                                                   max_tokens)
+    assert (vllm_model.model.llm_engine.scheduler.artificial_preempt_cnt <
+            ARTIFICIAL_PREEMPTION_MAX_CNT)
+    del vllm_model
+
+    for i in range(len(example_prompts)):
+        hf_output_ids, _ = hf_outputs[i]
+        vllm_output_ids, _ = vllm_outputs[i]
+        assert len(hf_output_ids) == len(vllm_output_ids)
+        for j in range(len(hf_output_ids)):
+            assert hf_output_ids[j] == vllm_output_ids[j], (
+                f"Test{i} output{j}:\nHF: {hf_output_ids}\n"
+                f"vLLM: {vllm_output_ids}")