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Fix TensorExtensions.StdDev#110392

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michaelgsharp merged 6 commits intodotnet:mainfrom
lilinus:fix-tensor-stddev
Dec 11, 2024
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Fix TensorExtensions.StdDev#110392
michaelgsharp merged 6 commits intodotnet:mainfrom
lilinus:fix-tensor-stddev

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@lilinus lilinus commented Dec 4, 2024 •
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Fixes #110381

I use IPowerFunctions<T>.Pow(x, 0.5) to replicate sqrt, but special case double and float to use Math.Sqrt and MathF.Sqrt respectively.

Would prefer to add IRootFunctions to method constraints to use T.Sqrt but I don't know if it is possible to add new constraints.

N.b. TensorExtensions is still marked as experimental

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@michaelgsharp michaelgsharp merged commit 9bededd into dotnet:main Dec 11, 2024
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tannergooding reviewed Dec 11, 2024
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src/libraries/System.Numerics.Tensors/src/System/Numerics/Tensors/netcore/TensorExtensions.cs
{
return T.CreateChecked(Math.Sqrt(double.CreateChecked(variance)));
}
return T.Pow(variance, T.CreateChecked(0.5));
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This should indeed be updated to use IRootFunctions instead; not Pow which isn't guaranteed to behave the same in many important edge cases

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hez2010 commented Dec 11, 2024 •
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For floating point numbers Pow(0.5) is not the equivalent to Sqrt, so this could result in unexpected behavior for some custom types.
Considering TensorExtensions is still an experimental API, we can take the minor breaking change here to add an additional generic constraint IRootFunctions<T> and use T.Sqrt instead.
@lilinus Would you like to make a follow-up PR for this?

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hez2010 pushed a commit to hez2010/runtime that referenced this pull request Dec 14, 2024
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Fix TensorExtensions.StdDev (dotnet#110392)
fe9a96a 
* Fix TensorExtensions.StdDev

* Add constraint to ref

* Revert "Add constraint to ref"

This reverts commit f740f50.

* Revert "Fix TensorExtensions.StdDev"

This reverts commit c212984.

* Use pow method

* Use existing variable
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TensorTests.cs and Tensor.cs StdDev calculates Variance rather than Standard deviations

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