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Pass exponent bits into multiexp instead of exponents themselves 

This de-duplicates multiple Montgomery reductions.
This commit is contained in:
Jack Grigg 2020-09-02 21:39:32 +01:00
parent f90fa65a32
commit e6a404a29e
2 changed files with 31 additions and 14 deletions
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18
src/groth16/prover.rs
View File

@ -229,14 +229,26 @@ where
let a_len = a.len() - 1;
a.truncate(a_len);
// TODO: parallelize if it's even helpful
let a = Arc::new(a.into_iter().map(|s| s.0).collect::<Vec<_>>());
let a = Arc::new(a.into_iter().map(|s| s.0.to_le_bits()).collect::<Vec<_>>());
multiexp(&worker, params.get_h(a.len())?, FullDensity, a)
};
// TODO: parallelize if it's even helpful
let input_assignment = Arc::new(prover.input_assignment);
let aux_assignment = Arc::new(prover.aux_assignment);
let input_assignment = Arc::new(
prover
.input_assignment
.into_iter()
.map(|s| s.to_le_bits())
.collect::<Vec<_>>(),
);
let aux_assignment = Arc::new(
prover
.aux_assignment
.into_iter()
.map(|s| s.to_le_bits())
.collect::<Vec<_>>(),
);
let l = multiexp(
&worker,

27
src/multiexp.rs
View File

@ -1,6 +1,7 @@
use super::multicore::Worker;
use bit_vec::{self, BitVec};
use ff::{Field, PrimeField};
use bitvec::{array::BitArray, order::Lsb0};
use ff::PrimeField;
use futures::Future;
use group::prime::{PrimeCurve, PrimeCurveAffine};
use std::io;
@ -154,7 +155,7 @@ fn multiexp_inner<Q, D, G, S>(
pool: &Worker,
bases: S,
density_map: D,
exponents: Arc<Vec<G::Scalar>>,
exponents: Arc<Vec<BitArray<Lsb0, <G::Scalar as PrimeField>::ReprBits>>>,
mut skip: u32,
c: u32,
handle_trivial: bool,
@ -181,22 +182,24 @@ where
// Create space for the buckets
let mut buckets = vec![G::identity(); (1 << c) - 1];
let one = G::Scalar::one();
// Sort the bases into buckets
for (&exp, density) in exponents.iter().zip(density_map.as_ref().iter()) {
for (exp, density) in exponents.iter().zip(density_map.as_ref().iter()) {
if density {
if exp.is_zero() {
let (exp_is_zero, exp_is_one) = {
let (first, rest) = exp.split_first().unwrap();
let rest_unset = rest.not_any();
(!*first && rest_unset, *first && rest_unset)
};
if exp_is_zero {
bases.skip(1)?;
} else if exp == one {
} else if exp_is_one {
if handle_trivial {
acc.add_assign_from_source(&mut bases)?;
} else {
bases.skip(1)?;
}
} else {
let exp = exp.to_le_bits();
let exp = exp
.into_iter()
.skip(skip as usize)
@ -266,7 +269,7 @@ pub fn multiexp<Q, D, G, S>(
pool: &Worker,
bases: S,
density_map: D,
exponents: Arc<Vec<G::Scalar>>,
exponents: Arc<Vec<BitArray<Lsb0, <G::Scalar as PrimeField>::ReprBits>>>,
) -> Box<dyn Future<Item = G, Error = SynthesisError>>
where
for<'a> &'a Q: QueryDensity,
@ -309,6 +312,7 @@ fn test_with_bls12() {
}
use bls12_381::{Bls12, Scalar};
use ff::Field;
use group::{Curve, Group};
use pairing::Engine;
use rand;
@ -321,6 +325,7 @@ fn test_with_bls12() {
.map(|_| Scalar::random(&mut rng))
.collect::<Vec<_>>(),
);
let v_bits = Arc::new(v.iter().map(|e| e.to_le_bits()).collect::<Vec<_>>());
let g = Arc::new(
(0..SAMPLES)
.map(|_| <Bls12 as Engine>::G1::random(&mut rng).to_affine())
@ -331,7 +336,7 @@ fn test_with_bls12() {
let pool = Worker::new();
let fast = multiexp(&pool, (g, 0), FullDensity, v).wait().unwrap();
let fast = multiexp(&pool, (g, 0), FullDensity, v_bits).wait().unwrap();
assert_eq!(naive, fast);
}