Multiplication-only lambda splitter without bignum #127
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
Did you measure what it did to the Linf norm of the split numbers? |
- In secp256k1_gej_split_exp, there are two divisions used. Since the denominator is a constant known at compile-time, each can be replaced by a multiplication followed by a right-shift (and rounding). - Add the constants g1, g2 for this purpose and rewrite secp256k1_scalar_split_lambda_var accordingly. - Remove secp256k1_num_div since no longer used Rebased-by: Pieter Wuille
This enables the use of the endomorphism optimization without bignum.
|
Rebased. @gmaxwell Going to look at that now. |
|
@gmaxwell: did 1000000 iterations using randomized ECDSA verifications, for each computing max(bits(wnaf(na_1)),bits(wnaf(na_lam))), and computing the quadratic average over those 1000000 max'es (to punish worst cases a bit stronger). Both were done with the same sequence of verifications. |
|
Darn, ... :) I was hoping that was why the improvement was so small. |
|
Normal linear averages: 127.501717 and 126.501716. Probably exactly 1 case in 1000000 where it's one less. |
|
ACK. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This contains a rebased version of @peterdettman's #21 (to account for the move of lambda splitting from group to scalar, and avoiding secp256k1_num_get_bit which got removed), and then simplifies it to a pure scalar-based version.
Gives around a 0.8% speedup on --enable-endomorphism CFLAGS=-O3, and enables the endomorphism optimization without using GMP (with a 28% performance hit).