Re-enable dim=4 in strided matmul test with proper cross-BLAS tolerances#2949
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Re-enable dim=4 in strided matmul test with proper cross-BLAS tolerances#2949antonwolfy wants to merge 4 commits into
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Array API standard conformance tests for dpnp=0.21.0dev3=py313h509198e_8 ran successfully. |
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coverage: 78.118% (-0.009%) from 78.127% — revert-gh-2912 into master |
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View rendered docs @ https://intelpython.github.io/dpnp/pull/2949/index.html |
…test The revert of gh-2912 removed the widened tolerance on TestMatvec::test_axes, which reintroduced a CI failure on ubuntu-latest: dpnp computes matvec via oneMKL gemm_batch while NumPy uses OpenBLAS gemv, so the summation order differs and the float64 result deviates at the noise floor (~1.4e-14), exceeding the default 8e-15 tolerance. Restore factor=40 on test_axes (with an explanatory comment) while keeping the rest of the revert, i.e. re-enabling dim=4 in TestMatmul::test_strided1, whose factor=16 tolerance already absorbs any cross-BLAS discrepancy. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Re-enabling dim=4 in TestMatmul::test_strided1 reintroduced the CI failure gh-2912 had worked around by skipping it: for float32 the strided matmul deviates by ~1.87e-5, just above the factor=16 bound (~1.81e-5). The cause is benign cross-BLAS non-associativity -- dpnp copies the strided input to c-contiguous and runs oneMKL gemm_batch, while NumPy uses OpenBLAS, so the length-20 float32 contraction accumulates in a different order. Bump the tolerance to factor=24 (pass-bound ~2.27e-5) for float32 only; integer input is compared exactly, so the factor does not affect it. This keeps dim=4 covered without masking real regressions in the exact path. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary
gh-2912 introduced two temporary test workarounds after a CI failure on
ubuntu-latest:TestMatvec::test_axestofactor=40;dim=4iteration inTestMatmul::test_strided1.Both failures share the same benign root cause, so this PR re-enables the disabled coverage and replaces the ad-hoc mitigations with documented, dtype-aware tolerances:
test_axes(matvec, float64) — keepsfactor=40. dpnp computesmatvecvia oneMKLgemm_batchwhile NumPy uses OpenBLASgemv; the summation order differs and the float64 result deviates at the noise floor (~1.4e-14), which exceeds the default8e-15tolerance.test_strided1(matmul) — re-enablesdim=4. dpnp copies the strided input to c-contiguous and runs it through oneMKLgemm_batch, again against NumPy's OpenBLAS. For float32, the length-20 contraction deviates by ~1.87e-5, just above the oldfactor=16bound (~1.81e-5), so the tolerance is bumped tofactor=24for float32 only (pass-bound ~2.27e-5). Integer input is compared exactly and is unaffected.Root cause
Neither discrepancy is a dpnp correctness bug. Both are expected floating-point non-associativity between two different BLAS backends (oneMKL vs OpenBLAS), surfaced when the conda-forge NumPy in CI advanced its bundled OpenBLAS. There is nothing to fix upstream, so documented tolerances are the correct handling and let us keep full test coverage (including
dim=4).