[Bugfix] Honor request-level seed in VoxCPM2 CFM noise (#7866)

Signed-off-by: tly <2200895168@qq.com>

tests/model_executor/models/voxcpm2/test_request_seed_cfm_noise.py

@@ -0,0 +1,116 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Request-level seeds must control the VoxCPM2 CFM noise stream (#7658).
+
+``/v1/audio/speech`` folds ``request.seed`` into ``SamplingParams.seed``, which
+reaches vLLM's sampler but never the CFM (flow-matching) noise draws: every
+noise site used the global RNG, so identical text + seed returned different
+audio. A seeded request now carries a dedicated ``torch.Generator`` in its
+``_RequestState``; these tests pin the noise semantics without instantiating
+the full model.
+"""
+
+from __future__ import annotations
+
+import functools
+
+import pytest
+
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+
+torch = pytest.importorskip("torch")
+
+
+@functools.lru_cache(maxsize=1)
+def _talker_cls():
+    """Defer talker import (pulls vLLM model_executor) until first use."""
+    from vllm_omni.model_executor.models.voxcpm2.voxcpm2_talker import (
+        VoxCPM2TalkerForConditionalGeneration,
+    )
+
+    return VoxCPM2TalkerForConditionalGeneration
+
+
+def _make_talker(deterministic_cfm_noise: bool = False):
+    cls = _talker_cls()
+    talker = cls.__new__(cls)
+    talker._deterministic_cfm_noise = deterministic_cfm_noise
+    return talker
+
+
+def _make_state(request_id: str = "req-1", seed: int | None = 42):
+    from vllm_omni.model_executor.models.voxcpm2.voxcpm2_talker import _RequestState
+
+    state = _RequestState(request_id=request_id)
+    if seed is not None:
+        state.cfm_generator = torch.Generator(device="cpu")
+        state.cfm_generator.manual_seed(seed)
+    return state
+
+
+def test_seeded_noise_is_deterministic_across_requests():
+    talker = _make_talker()
+
+    a1 = torch.empty(1, 128, 5)
+    a2 = torch.empty(1, 128, 5)
+    talker._fill_deterministic_cfm_noise_for_state(_make_state(seed=7), a1)
+    talker._fill_deterministic_cfm_noise_for_state(_make_state(seed=7), a2)
+
+    assert torch.equal(a1, a2)
+
+
+def test_seed_value_changes_the_noise_stream():
+    talker = _make_talker()
+
+    a = torch.empty(1, 128, 5)
+    b = torch.empty(1, 128, 5)
+    talker._fill_deterministic_cfm_noise_for_state(_make_state(seed=7), a)
+    talker._fill_deterministic_cfm_noise_for_state(_make_state(seed=8), b)
+
+    assert not torch.equal(a, b)
+
+
+def test_seeded_noise_advances_with_each_draw():
+    talker = _make_talker()
+    state = _make_state(seed=7)
+
+    first = torch.empty(1, 128, 5)
+    second = torch.empty(1, 128, 5)
+    talker._fill_deterministic_cfm_noise_for_state(state, first)
+    talker._fill_deterministic_cfm_noise_for_state(state, second)
+
+    assert not torch.equal(first, second)
+
+
+def test_seeded_noise_is_batch_position_independent():
+    """A seeded row draws the same bytes whether it sits alone or mid-batch."""
+    talker = _make_talker()
+
+    solo = torch.empty(1, 128, 5)
+    talker._fill_deterministic_cfm_noise_for_state(_make_state(seed=7), solo)
+
+    batch = torch.empty(3, 128, 5)
+    talker._fill_deterministic_cfm_noise_for_state(_make_state(seed=7), batch[1:2])
+
+    assert torch.equal(solo, batch[1:2])
+
+
+def test_has_deterministic_noise_prefers_request_seed_over_flag():
+    unflagged = _make_talker(deterministic_cfm_noise=False)
+    assert unflagged._has_deterministic_cfm_noise(_make_state(seed=1))
+    assert not unflagged._has_deterministic_cfm_noise(_make_state(seed=None))
+
+    flagged = _make_talker(deterministic_cfm_noise=True)
+    assert flagged._has_deterministic_cfm_noise(_make_state(seed=None))
+
+
+def test_request_seed_wins_over_replay_hash():
+    """The per-request generator keys noise off the seed, not the request id."""
+    talker = _make_talker(deterministic_cfm_noise=True)
+
+    r1 = torch.empty(1, 128, 5)
+    r2 = torch.empty(1, 128, 5)
+    talker._fill_deterministic_cfm_noise_for_state(_make_state(request_id="111", seed=7), r1)
+    talker._fill_deterministic_cfm_noise_for_state(_make_state(request_id="222", seed=7), r2)
+
+    assert torch.equal(r1, r2)