[release/10.0] Fix Tensor.StdDev vs TensorPrimitives.StdDev differences for Complex input #119798
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…nces for Complex input Co-authored-by: jeffhandley <[email protected]>
…input Co-authored-by: jeffhandley <[email protected]>
…tion - Fix typo: "TensorPrimitivers" -> "TensorPrimitives" in test comment - Replace custom SumOfSquaredMagnitudeDifferences operation with direct use of TensorPrimitives.StdDev - Leverage TensorPrimitives vectorization optimizations where T.Abs is only called when necessary - Remove unnecessary custom operation that always called T.Abs for all types - Use TryGetSpan for contiguous tensors and fallback to FlattenTo for non-contiguous tensors Co-authored-by: jeffhandley <[email protected]>
…lines Co-authored-by: jeffhandley <[email protected]>
…or non-essential methods and convert StdDev tests to Theory tests Co-authored-by: jeffhandley <[email protected]>
Added comment to clarify absolute value usage for complex numbers.
Co-authored-by: Copilot <[email protected]>
jeffhandley
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Sep 17, 2025
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@artl93 Seeking your approval of this backport to 10.0 RC2, with it meeting the bug bar as a broken scenario in a new API. |
artl93
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Sep 17, 2025
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RC2 - we should do math correctly.
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Backport of #119229 to release/10.0
/cc @jeffhandley @copilot
Customer Impact
As reported by a customer in Tensor.StdDev vs TensorPrimitives.StdDev differences for Complex input (dotnet/runtime#116133), the
Tensor.StdDevAPI being stablized in .NET 10 reports incorrect results for complex numbers, whileTensorPrimitives.StdDevproduces the correct results.Regression
This is a broken scenario on new APIs being marked as stable in .NET 10. The customer reported the issue against a preview, providing a repro that exhibited the incorrect results.
Testing
The customer's repro was used as the foundation for additional unit testing, with the tests verifying that
TensorandTensorPrimitivesproduce the same, expected results.Risk
Low. Only the new
Tensor.StdDevAPI is affected, and it now hasAbs(x - mean)logic matchingTensorPrimitivesbehavior. This algorithm also matches the behavior of other platforms' math libraries, including NumPy. The introduction of theAbscall will have a very minor perf hit, and approaches for avoiding that hit when unnecessary were discussed and ruled out as they would incur more substantial perf hits to conduct the check.