test_async_scheduling.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from itertools import repeat
from typing import Any

import pytest
import torch._dynamo.config as dynamo_config

from vllm import SamplingParams
from vllm.logprobs import Logprob
from vllm.sampling_params import StructuredOutputsParams
from vllm.v1.metrics.reader import Metric

from ...conftest import VllmRunner
from ...models.utils import check_outputs_equal

MODEL = "Qwen/Qwen3-0.6B"
MTP_MODEL = "XiaomiMiMo/MiMo-7B-Base"


first_prompt = (
    "The following numbers of the sequence "
    + ", ".join(str(i) for i in range(10))
    + " are:"
)
example_prompts = [first_prompt, "In one word, the capital of France is "] + [
    f"Tell me about the number {i}: " for i in range(32)
]

default_params = dict(
    temperature=0.0,  # greedy
    max_tokens=20,
)


def test_without_spec_decoding(
    sample_json_schema,
    monkeypatch: pytest.MonkeyPatch,
):
    """Test consistency of combos of async scheduling, preemption,
    uni/multiproc executor, prefill chunking."""
    struct_outputs = StructuredOutputsParams(json=sample_json_schema)
    test_sampling_params: list[dict[str, Any]] = [
        dict(),
        # dict(min_tokens=20),
        dict(presence_penalty=-1.0),
        dict(bad_words=["the", " the"]),
        dict(logprobs=2),
        dict(logprobs=2, presence_penalty=-1.0),
        dict(structured_outputs=struct_outputs),
        dict(
            structured_outputs=struct_outputs,
            logprobs=2,
            presence_penalty=-1.0,
        ),
    ]

    # test_preemption, executor, async_scheduling,
    # spec_config, test_prefill_chunking
    test_configs = [
        (False, "mp", False, None, False),
        (True, "mp", False, None, True),
        (False, "mp", True, None, False),
        (False, "uni", True, None, False),
        (True, "mp", True, None, False),
        (True, "uni", True, None, False),
        (False, "mp", True, None, True),
        (True, "mp", True, None, True),
        (True, "uni", True, None, True),
    ]

    run_tests(
        monkeypatch,
        MODEL,
        test_configs,
        test_sampling_params,
    )


@pytest.mark.skip("MTP model too big to run in fp32 in CI")
def test_with_spec_decoding(monkeypatch: pytest.MonkeyPatch):
    """Test consistency and acceptance rates with some different combos of
    preemption, executor, async scheduling, prefill chunking,
    spec decoding model length.
    """

    spec_config = {
        "method": "mtp",
        "num_speculative_tokens": 2,
    }
    spec_config_short = spec_config | {"max_model_len": 50}

    # test_preemption, executor, async_scheduling,
    # spec_config, test_prefill_chunking
    test_configs = [
        (False, "mp", False, None, False),
        (False, "mp", False, spec_config, False),
        (True, "mp", False, spec_config, True),
        (True, "uni", False, spec_config_short, True),
        (False, "mp", True, spec_config, False),
        (True, "mp", True, spec_config, False),
        (False, "mp", True, spec_config_short, True),
        (True, "uni", True, spec_config, False),
        (True, "uni", True, spec_config_short, False),
        (True, "mp", True, spec_config, True),
        (True, "uni", True, spec_config_short, True),
    ]

    run_tests(
        monkeypatch,
        MTP_MODEL,
        test_configs,
        [{}],
    )


@dynamo_config.patch(cache_size_limit=16)
def run_tests(
    monkeypatch: pytest.MonkeyPatch,
    model: str,
    test_configs: list[tuple],
    test_sampling_params: list[dict[str, Any]],
):
    """Test consistency of combos of async scheduling, preemption,
    uni/multiproc executor with spec decoding."""

    with monkeypatch.context() as m:
        # avoid precision errors
        m.setenv("VLLM_ATTENTION_BACKEND", "FLEX_ATTENTION")
        # m.setenv("VLLM_BATCH_INVARIANT", "1")
        outputs: list[tuple[str, list, list]] = []
        for n, (
            test_preemption,
            executor,
            async_scheduling,
            spec_config,
            test_prefill_chunking,
        ) in enumerate(test_configs, 1):
            test_str = f"{n}/{len(test_configs)}"
            test_results = run_test(
                model,
                test_str,
                test_sampling_params,
                test_preemption,
                executor,
                async_scheduling,
                spec_config,
                test_prefill_chunking=test_prefill_chunking,
            )
            outputs.append(test_results)

    baseline_config, baseline_tests, _ = outputs[0]
    _, _, baseline_acceptances = next(
        (o for o in outputs if o[2] is not None), (None, None, None)
    )

    print(f"BASELINE: config=[{baseline_config}], accept_rates={baseline_acceptances}")

    failure = None
    for test_config, test_outputs, test_acceptance_rates in outputs[1:]:
        for (base_outs, base_logprobs), base_acceptance_rate, (
            test_outs,
            test_logprobs,
        ), test_acceptance_rate, params in zip(
            baseline_tests,
            baseline_acceptances or repeat(None),
            test_outputs,
            test_acceptance_rates or repeat(None),
            test_sampling_params,
        ):
            try:
                check_outputs_equal(
                    outputs_0_lst=base_outs,
                    outputs_1_lst=test_outs,
                    name_0=f"baseline=[{baseline_config}], params={params}",
                    name_1=f"config=[{test_config}], params={params}",
                )
                assert _all_logprobs_match(base_logprobs, test_logprobs)

                if (
                    base_acceptance_rate is not None
                    and test_acceptance_rate is not None
                ):
                    if "spec_mml=None" in test_config:
                        # because the acceptance rate can vary, we use a looser
                        # tolerance here.
                        assert (
                            pytest.approx(test_acceptance_rate, rel=5e-2)
                            == base_acceptance_rate
                        )
                    else:
                        # Currently the reported acceptance rate is expected to be
                        # lower when we skip drafting altogether.
                        assert test_acceptance_rate > 0.05
                print(
                    f"PASSED: config=[{test_config}], params={params}"
                    f" accept_rate={test_acceptance_rate}"
                )
            except AssertionError as e:
                print(
                    f"FAILED: config=[{test_config}], params={params}"
                    f" accept_rate={test_acceptance_rate}"
                )
                if failure is None:
                    failure = e

    if failure is not None:
        raise failure


def run_test(
    model: str,
    test_str: str,
    sampling_param_tests: list[dict[str, Any]],
    test_preemption: bool,
    executor: str,
    async_scheduling: bool,
    spec_config: dict[str, Any] | None,
    test_prefill_chunking: bool,
):
    spec_decoding = spec_config is not None
    cache_arg: dict[str, Any] = (
        dict(num_gpu_blocks_override=32)
        if test_preemption
        else dict(gpu_memory_utilization=0.9)
    )
    spec_mml = (spec_config or {}).get("max_model_len")
    test_config = (
        f"executor={executor}, preemption={test_preemption}, "
        f"async_sched={async_scheduling}, "
        f"chunk_prefill={test_prefill_chunking}, "
        f"spec_decoding={spec_decoding}, spec_mml={spec_mml}"
    )
    print("-" * 80)
    print(f"---- TESTING {test_str}: {test_config}")
    print("-" * 80)
    with VllmRunner(
        model,
        max_model_len=512,
        enable_chunked_prefill=test_prefill_chunking,
        max_num_batched_tokens=48 if test_prefill_chunking else None,
        # enforce_eager=True,
        async_scheduling=async_scheduling,
        distributed_executor_backend=executor,
        dtype="float32",  # avoid precision errors
        speculative_config=spec_config,
        disable_log_stats=False,
        **cache_arg,
    ) as vllm_model:
        results = []
        acceptance_rates: list[float] | None = [] if spec_decoding else None
        for override_params in sampling_param_tests:
            metrics_before = vllm_model.llm.get_metrics()
            print(f"----------- RUNNING PARAMS: {override_params}")
            results.append(
                vllm_model.generate(
                    example_prompts,
                    sampling_params=SamplingParams(
                        **default_params,
                        **override_params,
                    ),
                    return_logprobs=True,
                )
            )
            metrics_after = vllm_model.llm.get_metrics()
            if acceptance_rates is not None:
                acceptance_rate = _get_acceptance_rate(metrics_before, metrics_after)
                acceptance_rates.append(acceptance_rate)
                print(f"ACCEPTANCE RATE {acceptance_rate}")

            if test_preemption:
                preemptions = _get_count(
                    metrics_before,
                    metrics_after,
                    "vllm:num_preemptions",
                )
                assert preemptions > 0, "preemption test had no preemptions"

    if len(results) > 1:
        # First check that the different parameter configs
        # actually result in different output.
        for (other_test_outs, other_test_logprobs), params in zip(
            results[1:], sampling_param_tests[1:]
        ):
            with pytest.raises(AssertionError):
                check_outputs_equal(
                    outputs_0_lst=results[0][0],
                    outputs_1_lst=other_test_outs,
                    name_0=f"baseline params={params}",
                    name_1=f"other params={params}",
                )
                assert _all_logprobs_match(results[0][1], other_test_logprobs)

    return test_config, results, acceptance_rates


def _all_logprobs_match(req_a, req_b) -> bool:
    return (
        req_a == req_b
        or len(req_a) == len(req_b)
        and all(
            len(seq_a) == len(seq_b)
            and all(_logprobs_match(a, b) for a, b in zip(seq_a, seq_b))
            for seq_a, seq_b in zip(req_a, req_b)
        )
    )


def _logprobs_match(lps_a: dict[int, Logprob], lps_b: dict[int, Logprob]) -> bool:
    return len(lps_a) == len(lps_b) and all(
        a.decoded_token == b.decoded_token
        and a.rank == b.rank
        and a.logprob == pytest.approx(b.logprob, rel=1e-3, abs=1e-6)
        for a, b in ((lps_a[x], lps_b[x]) for x in lps_a)
    )


def _get_acceptance_rate(before: list[Metric], after: list[Metric]) -> float:
    draft = _get_count(before, after, "vllm:spec_decode_num_draft_tokens")
    accept = _get_count(before, after, "vllm:spec_decode_num_accepted_tokens")
    return accept / draft if draft > 0 else 0.0


def _get_count(before: list[Metric], after: list[Metric], name: str) -> int:
    before_val = next(m.value for m in before if m.name == name)
    after_val = next(m.value for m in after if m.name == name)
    return after_val - before_val