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Implement variable-sized windows into multiexp

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Closes https://github.com/serai-dex/serai/issues/17 by using the 
PrimeFieldBits API to do so.

Should greatly speed up small batches, along with batches in the 
hundreds. Saves almost a full second on the cross-group DLEq proof.
This commit is contained in:
Luke Parker
2022-06-30 09:30:24 -04:00
parent 5d115f1e1c
commit 7890827a48
15 changed files with 342 additions and 148 deletions
Download Patch File Download Diff File Expand all files Collapse all files

66
crypto/multiexp/src/pippenger.rs
View File

@@ -1,42 +1,23 @@
use group::{ff::PrimeField, Group};
use ff::PrimeFieldBits;
use group::Group;
fn prep<G: Group>(pairs: &[(G::Scalar, G)], little: bool) -> (Vec<Vec<u8>>, Vec<G>) {
let mut res = vec![];
let mut points = vec![];
for pair in pairs {
let p = res.len();
res.push(vec![]);
{
let mut repr = pair.0.to_repr();
let bytes = repr.as_mut();
if !little {
bytes.reverse();
}
use crate::prep_bits;
res[p].resize(bytes.len(), 0);
for i in 0 .. bytes.len() {
res[p][i] = bytes[i];
}
}
points.push(pair.1);
}
(res, points)
}
pub(crate) fn pippenger<G: Group>(pairs: &[(G::Scalar, G)], little: bool) -> G {
let (bytes, points) = prep(pairs, little);
pub(crate) fn pippenger<G: Group>(
pairs: &[(G::Scalar, G)],
window: u8
) -> G where G::Scalar: PrimeFieldBits {
let bits = prep_bits(pairs, window);
let mut res = G::identity();
for n in (0 .. bytes[0].len()).rev() {
for _ in 0 .. 8 {
for n in (0 .. bits[0].len()).rev() {
for _ in 0 .. window {
res = res.double();
}
let mut buckets = [G::identity(); 256];
for p in 0 .. bytes.len() {
buckets[usize::from(bytes[p][n])] += points[p];
let mut buckets = vec![G::identity(); 2_usize.pow(window.into())];
for p in 0 .. bits.len() {
buckets[usize::from(bits[p][n])] += pairs[p].1;
}
let mut intermediate_sum = G::identity();
@@ -49,22 +30,25 @@ pub(crate) fn pippenger<G: Group>(pairs: &[(G::Scalar, G)], little: bool) -> G {
res
}
pub(crate) fn pippenger_vartime<G: Group>(pairs: &[(G::Scalar, G)], little: bool) -> G {
let (bytes, points) = prep(pairs, little);
pub(crate) fn pippenger_vartime<G: Group>(
pairs: &[(G::Scalar, G)],
window: u8
) -> G where G::Scalar: PrimeFieldBits {
let bits = prep_bits(pairs, window);
let mut res = G::identity();
for n in (0 .. bytes[0].len()).rev() {
if n != (bytes[0].len() - 1) {
for _ in 0 .. 8 {
for n in (0 .. bits[0].len()).rev() {
if n != (bits[0].len() - 1) {
for _ in 0 .. window {
res = res.double();
}
}
let mut buckets = [G::identity(); 256];
for p in 0 .. bytes.len() {
let nibble = usize::from(bytes[p][n]);
let mut buckets = vec![G::identity(); 2_usize.pow(window.into())];
for p in 0 .. bits.len() {
let nibble = usize::from(bits[p][n]);
if nibble != 0 {
buckets[nibble] += points[p];
buckets[nibble] += pairs[p].1;
}
}