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Automatic Differentiation #82

Merged
merged 26 commits into from
Sep 29, 2023
Merged

Automatic Differentiation #82

merged 26 commits into from
Sep 29, 2023

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lkdvos
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@lkdvos lkdvos commented Sep 25, 2023

This PR adds rrules and tests for most linear algebra methods.

Note that the tests for tsvd are disabled when working with Complex, as I have not been able to figure out how to make the lack of uniqueness of U and V work with finite differences and or the ChainRulesTestUtils interface.

return _repartition(p, N₁)
end

TensorKit.block(t::ZeroTangent, c::Sector) = t
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This seems a bit suspicious? Why is this needed?

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This is mostly to avoid having to manually deal with the ZeroTangent type. For example, a QR decomposition where the final result does not depend on R, would generate a ZeroTangent for dR, which is just an abstract representation that behaves as the zero vector in any (co)vectorspace. As some of the rrules are implemented "blockwise", this would either require manually checking if a tangent is a ZeroTangent, or, which is what I chose to do, rely on the hope that the compiler would recognize that the blockwise operation results in ZeroTangents anyways, and thus automatically takes care of this

@lkdvos lkdvos merged commit 6a0fa69 into master Sep 29, 2023
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@lkdvos lkdvos deleted the ad branch September 29, 2023 15:33
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3 participants