Fix flaky layer tests by disabling TF32 against eager reference#515
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jlamypoirier wants to merge 1 commit into
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Fix flaky layer tests by disabling TF32 against eager reference#515jlamypoirier wants to merge 1 commit into
jlamypoirier wants to merge 1 commit into
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`test_post_norms` and `test_hybrid_moe_mlp` compare the block forward (which uses Triton RMSNorm) to an eager reference built from `torch.rms_norm`. The two norm implementations agree to ~1e-7 (FP32 noise floor), but PyTorch's default TF32 matmul has only ~1e-3 mantissa precision and amplifies that tiny input perturbation into ~1e-5 output drift through the block's matmuls — flakily crossing the 1e-5 tolerance. `test_attention` already worked around this with a local `_no_tf32` context manager. Promote it to `tests.utils.utils.no_tf32` and use it in `test_post_norms` / `test_hybrid_moe_mlp` too. Also: - `test_post_norms` now uses `Assert.rms_close_relative` instead of `torch.testing.assert_close`, matching the codebase convention (the RMS-based assertion is robust to single-element outliers from FP rounding). - The `output_scale` parametrization uses 0.8 (a realistic Gemma 4 layer_scalar value) instead of 2.5. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
test_post_norms(intest_decoder_block.py) andtest_hybrid_moe_mlp(intest_mlp.py) were flakily failing on CUDA: the block forward uses Triton RMSNorm while the eager reference usestorch.rms_norm, and the ~1e-7 FP-noise between the two gets amplified into ~1e-5 output drift through TF32 matmuls (~1e-3 mantissa precision), occasionally crossing the 1e-5 tolerance.test_attention.py's local_no_tf32context manager totests/utils/utils.py::no_tf32and use it in both layer tests for the forward-vs-reference comparison.test_decoder_block.py::test_post_norms:torch.testing.assert_close→Assert.rms_close_relativeto match the codebase convention used elsewhere (RMS-based comparison, robust to single-element outliers).output_scaleparametrization from2.5to0.8— a realistic Gemma 4layer_scalarvalue rather than an artificially-large multiplier.Test plan
pytest -v -n 4 tests/layers/test_decoder_block.py tests/layers/test_mlp.py— all 17 tests pass each time.pytest -v -n 8 tests/→ 2603 passed, 99 skipped (vs. 2599 passed / 4 failed before the fix, no other regressions).🤖 Generated with Claude Code