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Add test for lagrange interpolation.

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Sean Bowe 2020-10-15 14:15:03 -06:00
parent 63d7de3bc2
commit 588de0e024
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GPG key ID: 95684257D8F8B031
1 changed files with 22 additions and 9 deletions
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31
src/arithmetic.rs
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@ -440,7 +440,6 @@ pub fn lagrange_interpolate<F: Field>(points: &[F], evals: &[F]) -> Vec<F> {
// Constant polynomial // Constant polynomial
return vec![evals[0]]; return vec![evals[0]];
} else { } else {
let mut interpolation_polys = vec![];
let mut denoms = Vec::with_capacity(points.len()); let mut denoms = Vec::with_capacity(points.len());
for (j, x_j) in points.iter().enumerate() { for (j, x_j) in points.iter().enumerate() {
let mut denom = Vec::with_capacity(points.len() - 1); let mut denom = Vec::with_capacity(points.len() - 1);
@ -457,7 +456,8 @@ pub fn lagrange_interpolate<F: Field>(points: &[F], evals: &[F]) -> Vec<F> {
// Compute (x_j - x_k)^(-1) for each j != i // Compute (x_j - x_k)^(-1) for each j != i
denoms.iter_mut().flat_map(|v| v.iter_mut()).batch_invert(); denoms.iter_mut().flat_map(|v| v.iter_mut()).batch_invert();
for (j, denoms) in denoms.into_iter().enumerate() { let mut final_poly = vec![F::zero(); points.len()];
for (j, (denoms, eval)) in denoms.into_iter().zip(evals.iter()).enumerate() {
let mut tmp: Vec<F> = Vec::with_capacity(points.len()); let mut tmp: Vec<F> = Vec::with_capacity(points.len());
let mut product = Vec::with_capacity(points.len() - 1); let mut product = Vec::with_capacity(points.len() - 1);
tmp.push(F::one()); tmp.push(F::one());
@ -481,15 +481,28 @@ pub fn lagrange_interpolate<F: Field>(points: &[F], evals: &[F]) -> Vec<F> {
} }
assert_eq!(tmp.len(), points.len()); assert_eq!(tmp.len(), points.len());
assert_eq!(product.len(), points.len() - 1); assert_eq!(product.len(), points.len() - 1);
interpolation_polys.push(tmp); for (final_coeff, interpolation_coeff) in final_poly.iter_mut().zip(tmp.into_iter()) {
} *final_coeff += interpolation_coeff * eval;
let mut final_poly = vec![F::zero(); points.len()];
for (interpolation_poly, evaluation) in interpolation_polys.into_iter().zip(evals.iter()) {
for (final_coeff, interpolation_coeff) in final_poly.iter_mut().zip(interpolation_poly)
{
*final_coeff += interpolation_coeff * evaluation;
} }
} }
final_poly final_poly
} }
} }
#[test]
fn test_lagrange_interpolate() {
let points = (0..5).map(|_| Fp::random()).collect::<Vec<_>>();
let evals = (0..5).map(|_| Fp::random()).collect::<Vec<_>>();
for coeffs in 0..5 {
let points = &points[0..coeffs];
let evals = &evals[0..coeffs];
let poly = lagrange_interpolate(points, evals);
assert_eq!(poly.len(), points.len());
for (point, eval) in points.iter().zip(evals) {
assert_eq!(eval_polynomial(&poly, *point), *eval);
}
}
}