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Multilinear extension evaluation speedup #603

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merged 5 commits into from
Feb 15, 2023
Merged

Multilinear extension evaluation speedup #603

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255d032
Reduce # multiplications in dense ml extension eval
protoben Jan 10, 2023
e198f83
Reduce # multiplications in sparse ml extension eval
protoben Jan 10, 2023
c3b4f9d
Eliminate extra vector allocation in precompute_eq
protoben Jan 10, 2023
85ac4d8
Merge remote-tracking branch 'origin/master' into ml-extension-eval-s…
protoben Feb 15, 2023
8c3cf45
Add entry to changelog on mul reduction in eval functions
protoben Feb 15, 2023
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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -2,6 +2,8 @@

## Pending

- (`ark-poly`) Reduce the number of field multiplications performed by `SparseMultilinearExtension::evaluate` and `DenseMultilinearExtension::evaluate`

### Breaking changes

### Features
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4 changes: 3 additions & 1 deletion poly/src/evaluations/multivariate/multilinear/dense.rs
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Expand Up @@ -119,7 +119,9 @@ impl<F: Field> MultilinearExtension<F> for DenseMultilinearExtension<F> {
for i in 1..dim + 1 {
let r = partial_point[i - 1];
for b in 0..(1 << (nv - i)) {
poly[b] = poly[b << 1] * (F::one() - r) + poly[(b << 1) + 1] * r;
let left = poly[b << 1];
let right = poly[(b << 1) + 1];
poly[b] = left + r * (right - left);
}
}
Self::from_evaluations_slice(nv - dim, &poly[..(1 << (nv - dim))])
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9 changes: 4 additions & 5 deletions poly/src/evaluations/multivariate/multilinear/sparse.rs
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Expand Up @@ -102,15 +102,14 @@ impl<F: Field> SparseMultilinearExtension<F> {
/// utility: precompute f(x) = eq(g,x)
fn precompute_eq<F: Field>(g: &[F]) -> Vec<F> {
let dim = g.len();
let mut dp = Vec::with_capacity(1 << dim);
dp.resize(1 << dim, F::zero());
let mut dp = vec![F::zero(); 1 << dim];
dp[0] = F::one() - g[0];
dp[1] = g[0];
for i in 1..dim {
let dp_prev = dp[0..(1 << i)].to_vec();
for b in 0..(1 << i) {
dp[b] = dp_prev[b] * (F::one() - g[i]);
dp[b + (1 << i)] = dp_prev[b] * g[i];
let prev = dp[b];
dp[b + (1 << i)] = prev * g[i];
dp[b] = prev - dp[b + (1 << i)];
}
}
dp
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