Update QuadExtField::sqrt for better performance
#352
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Better rebase on top of #354 before merging so the performance difference will be clear and documented |
Currently, the QuadExtField uses an expensive runtime inverse of two calculation defined as `P::BaseField::one().double().inverse()`. With the proposed change, we compute the BigInt `(p+1)/2` that is ~15% cheaper than the previous method, by avoiding `inverse`. Alternatively, we could require a compile-time constant provided by the user that represents `1/2`. However, having a constant requirement to satisfy a single use-case isn't ideal. `PrimeField::modulus` was introduced to facilitate the available constants usage. Closes #210
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Description
Currently, the QuadExtField uses an expensive runtime inverse of two
calculation defined as
P::BaseField::one().double().inverse().With the proposed change, we compute the BigInt
(p+1)/2that is ~15%cheaper than the previous method.
Alternatively, we could require a compile-time constant provided by the
user that represents
1/2. However, having a constant requirement tosatisfy a single use-case isn't ideal.
closes: #210
Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.
Targeted PR against correct branch (master)
Linked to GitHub issue with discussion and accepted design OR have an explanation in the PR that describes this work.
Updated relevant documentation in the code
Added a relevant changelog entry to the
Pendingsection inCHANGELOG.mdRe-reviewed
Files changedin the GitHub PR explorerWrote unit tests (tests are already covering this section:
bls12_381::tests::test_fq2)