Revert "[Perf] Enable FlashInfer top-k/top-p sampler by default" (#40376)#41316
Revert "[Perf] Enable FlashInfer top-k/top-p sampler by default" (#40376)#41316vllm-agent wants to merge 1 commit intovllm-project:mainfrom
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…-project#40376)" This reverts commit b92ef9e.
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Code Review
This pull request transitions the FlashInfer sampler to an opt-in feature by changing its default environment variable setting and updates the sampling logic to prefer non-synchronizing operations when possible. It also removes extensive FlashInfer-specific robustness and distribution tests. A review comment identifies that switching to stochastic sampling in a prefix caching test could introduce flakiness and recommends returning to greedy sampling for deterministic verification.
| "hello what is one plus one what is one plus one what is one plus one the answer is", # noqa: E501 | ||
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| sampling_params = SamplingParams(temperature=0.0, max_tokens=20) | ||
| sampling_params = SamplingParams(temperature=0.8, top_p=0.95, max_tokens=20) |
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Using stochastic sampling (temperature=0.8) in a regression test for prefix caching can introduce flakiness and makes it harder to detect subtle state corruption. Since the LLM is initialized with a fixed seed (line 877), greedy sampling (temperature=0.0) would provide a more robust and deterministic check for the prefix caching logic, ensuring that the cached hidden states produce identical results to the non-cached path.
| sampling_params = SamplingParams(temperature=0.8, top_p=0.95, max_tokens=20) | |
| sampling_params = SamplingParams(temperature=0.0, max_tokens=20) |
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My bad, this test is NOT flaky. It simply has time time limit. The problem is that I forgot to warmup one of the kernels for top-k. PR with fix: [Perf] Warmup forward_native sampler kernel |
Flaky test. See: [CI] Stabilize cpu offload compressed tensors test#41102 |
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Upd. [Perf] Warmup forward_native sampler kernel was merged. |
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Since [Perf] Enable FlashInfer top-k/top-p sampler by default" (#40376) doesn't affect CI now, can we close this PR then? |
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Closing as the only non-pre-existing-flaky test was forward fixed by #41375 |
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Revert of #40376
This reverts commit b92ef9e (merge commit for PR #40376).
Original PR: #40376
Build: https://buildkite.com/vllm/ci/builds/63685
Reason
Enabling FlashInfer top-k/top-p sampler by default caused 3 new test failures in nightly CI build #63685:
test_multi_abortassertion failure: aborted request generated 0 tokenstest_models[bigcode/starcoder2-3b]logprob mismatches between HF and vLLMtest_cpu_offload_compressed_tensorsseeded sampling produces different results with cpu-offload enabledAll three failures are consistent with a change in sampling behavior introduced by switching from the Triton sampler to the FlashInfer sampler as the default.
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