Working commitments and verifier

src/fri/verifier.rs

@@ -168,17 +168,22 @@ fn fri_combine_initial<F: Field + Extendable<D>, const D: usize>(
     ]
     .iter()
     .flat_map(|&p| proof.unsalted_evals(p))
-    .map(|&e| F::Extension::from_basefield(e));
+    .map(|&e| F::Extension::from_basefield(e))
+    .collect::<Vec<_>>();
     let single_openings = os
         .constants
         .iter()
         .chain(&os.plonk_s_sigmas)
-        .chain(&os.quotient_polys);
+        .chain(&os.quotient_polys)
-    let single_diffs = single_evals.zip(single_openings).map(|(e, &o)| e - o);
+        .collect::<Vec<_>>();
-    let single_numerator = reduce_with_iter(single_diffs, &mut alpha_powers);
+    let single_diffs = single_evals
+        .into_iter()
+        .zip(single_openings)
+        .map(|(e, &o)| e - o);
+    let single_numerator = alpha.scale(single_diffs);
     let single_denominator = subgroup_x - zeta;
     sum += single_numerator / single_denominator;
-    alpha.shift(sum);
+    alpha.reset();
 
     // Polynomials opened at `x` and `g x`, i.e., the Zs polynomials.
     let zs_evals = proof
@@ -188,13 +193,13 @@ fn fri_combine_initial<F: Field + Extendable<D>, const D: usize>(
     let zs_composition_eval = alpha.clone().scale(zs_evals);
     let zeta_right = F::Extension::primitive_root_of_unity(degree_log) * zeta;
     let zs_interpol = interpolant(&[
-        (zeta, alpha.clone().scale(&os.plonk_zs)),
+        (zeta, alpha.clone().scale(os.plonk_zs.iter())),
-        (zeta_right, alpha.scale(&os.plonk_zs_right)),
+        (zeta_right, alpha.scale(os.plonk_zs_right.iter())),
     ]);
     let zs_numerator = zs_composition_eval - zs_interpol.eval(subgroup_x);
     let zs_denominator = (subgroup_x - zeta) * (subgroup_x - zeta_right);
+    sum = alpha.shift(sum);
     sum += zs_numerator / zs_denominator;
-    alpha.shift(sum);
 
     // Polynomials opened at `x` and `x.frobenius()`, i.e., the wires polynomials.
     let wire_evals = proof
@@ -203,17 +208,18 @@ fn fri_combine_initial<F: Field + Extendable<D>, const D: usize>(
         .map(|&e| F::Extension::from_basefield(e));
     let wire_composition_eval = alpha.clone().scale(wire_evals);
     let zeta_frob = zeta.frobenius();
-    let wire_eval = alpha.clone().scale(&os.wires);
+    let wire_eval = alpha.clone().scale(os.wires.iter());
     // We want to compute `sum a^i*phi(w_i)`, where `phi` denotes the Frobenius automorphism.
     // Since `phi^D=id` and `phi` is a field automorphism, we have the following equalities:
     // `sum a^i*phi(w_i) = sum phi(phi^(D-1)(a^i)*w_i) = phi(sum phi^(D-1)(a)^i*w_i)`
     // So we can compute the original sum using only one call to the `D-1`-repeated Frobenius of alpha,
     // and one call at the end of the sum.
     let mut alpha_frob = alpha.repeated_frobenius(D - 1);
-    let wire_eval_frob = alpha_frob.scale(&os.wires).frobenius();
+    let wire_eval_frob = alpha_frob.scale(os.wires.iter()).frobenius();
     let wire_interpol = interpolant(&[(zeta, wire_eval), (zeta_frob, wire_eval_frob)]);
     let wire_numerator = wire_composition_eval - wire_interpol.eval(subgroup_x);
     let wire_denominator = (subgroup_x - zeta) * (subgroup_x - zeta_frob);
+    sum = alpha_frob.shift(sum);
     sum += wire_numerator / wire_denominator;
 
     sum

src/polynomial/commitment.rs

@@ -8,10 +8,11 @@ use crate::field::lagrange::interpolant;
 use crate::fri::{prover::fri_proof, verifier::verify_fri_proof, FriConfig};
 use crate::merkle_tree::MerkleTree;
 use crate::plonk_challenger::Challenger;
-use crate::plonk_common::{reduce_polys_with_iter, reduce_with_iter};
+use crate::plonk_common::{reduce_polys_with_iter, reduce_with_iter, PlonkPolynomials};
 use crate::polynomial::polynomial::PolynomialCoeffs;
 use crate::proof::{FriProof, FriProofTarget, Hash, OpeningSet};
 use crate::timed;
+use crate::util::scaling::ScalingFactor;
 use crate::util::{log2_strict, reverse_index_bits_in_place, transpose};
 
 pub const SALT_SIZE: usize = 2;
@@ -110,20 +111,24 @@ impl<F: Field> ListPolynomialCommitment<F> {
         challenger.observe_opening_set(&os);
 
         let alpha = challenger.get_extension_challenge();
-        let mut alpha_powers = alpha.powers();
+        let mut alpha = ScalingFactor::new(alpha);
 
         // Final low-degree polynomial that goes into FRI.
         let mut final_poly = PolynomialCoeffs::empty();
 
         // Polynomials opened at a single point.
-        let single_polys = [0, 1, 4]
+        let single_polys = [
-            .iter()
+            PlonkPolynomials::CONSTANTS,
-            .flat_map(|&i| &commitments[i].polynomials)
+            PlonkPolynomials::SIGMAS,
-            .map(|p| p.to_extension());
+            PlonkPolynomials::QUOTIENT,
+        ]
+        .iter()
+        .flat_map(|&p| &commitments[p.index].polynomials)
+        .map(|p| p.to_extension());
         let single_os = [&os.constants, &os.plonk_s_sigmas, &os.quotient_polys];
         let single_evals = single_os.iter().flat_map(|v| v.iter());
-        let single_composition_poly = reduce_polys_with_iter(single_polys, alpha_powers.clone());
+        let single_composition_poly = alpha.clone().scale_polys(single_polys);
-        let single_composition_eval = reduce_with_iter(single_evals, &mut alpha_powers);
+        let single_composition_eval = alpha.scale(single_evals);
 
         let single_quotient = Self::compute_quotient(
             &[zeta],
@@ -131,13 +136,17 @@ impl<F: Field> ListPolynomialCommitment<F> {
             &single_composition_poly,
         );
         final_poly = &final_poly + &single_quotient;
+        alpha.reset();
 
         // Zs polynomials are opened at `zeta` and `g*zeta`.
-        let zs_polys = commitments[3].polynomials.iter().map(|p| p.to_extension());
+        let zs_polys = commitments[PlonkPolynomials::ZS.index]
-        let zs_composition_poly = reduce_polys_with_iter(zs_polys, alpha_powers.clone());
+            .polynomials
+            .iter()
+            .map(|p| p.to_extension());
+        let zs_composition_poly = alpha.clone().scale_polys(zs_polys);
         let zs_composition_evals = [
-            reduce_with_iter(&os.plonk_zs, alpha_powers.clone()),
+            alpha.clone().scale(os.plonk_zs.iter()),
-            reduce_with_iter(&os.plonk_zs_right, &mut alpha_powers),
+            alpha.scale(os.plonk_zs_right.iter()),
         ];
 
         let zs_quotient = Self::compute_quotient(
@@ -145,17 +154,21 @@ impl<F: Field> ListPolynomialCommitment<F> {
             &zs_composition_evals,
             &zs_composition_poly,
         );
+        final_poly = alpha.shift_poly(final_poly);
         final_poly = &final_poly + &zs_quotient;
 
         // When working in an extension field, need to check that wires are in the base field.
         // Check this by opening the wires polynomials at `zeta` and `zeta.frobenius()` and using the fact that
         // a polynomial `f` is over the base field iff `f(z).frobenius()=f(z.frobenius())` with high probability.
-        let wire_polys = commitments[2].polynomials.iter().map(|p| p.to_extension());
+        let wire_polys = commitments[PlonkPolynomials::WIRES.index]
-        let wire_composition_poly = reduce_polys_with_iter(wire_polys, alpha_powers.clone());
+            .polynomials
-        let wire_evals_frob = os.wires.iter().map(|e| e.frobenius()).collect::<Vec<_>>();
+            .iter()
+            .map(|p| p.to_extension());
+        let wire_composition_poly = alpha.clone().scale_polys(wire_polys);
+        let mut alpha_frob = alpha.repeated_frobenius(D - 1);
         let wire_composition_evals = [
-            reduce_with_iter(&os.wires, alpha_powers.clone()),
+            alpha.clone().scale(os.wires.iter()),
-            reduce_with_iter(&wire_evals_frob, alpha_powers),
+            alpha_frob.scale(os.wires.iter()).frobenius(),
         ];
 
         let wires_quotient = Self::compute_quotient(
@@ -163,6 +176,7 @@ impl<F: Field> ListPolynomialCommitment<F> {
             &wire_composition_evals,
             &wire_composition_poly,
         );
+        final_poly = alpha_frob.shift_poly(final_poly);
         final_poly = &final_poly + &wires_quotient;
 
         let lde_final_poly = final_poly.lde(config.rate_bits);

src/util/scaling.rs

@@ -2,8 +2,9 @@ use std::borrow::Borrow;
 
 use crate::field::extension_field::Frobenius;
 use crate::field::field::Field;
+use crate::polynomial::polynomial::PolynomialCoeffs;
 
-#[derive(Copy, Clone)]
+#[derive(Debug, Copy, Clone)]
 pub struct ScalingFactor<F: Field> {
     base: F,
     count: u64,
@@ -14,13 +15,28 @@ impl<F: Field> ScalingFactor<F> {
         Self { base, count: 0 }
     }
 
-    pub fn mul(&mut self, x: F) -> F {
+    fn mul(&mut self, x: F) -> F {
         self.count += 1;
         self.base * x
     }
 
+    fn mul_poly(&mut self, p: PolynomialCoeffs<F>) -> PolynomialCoeffs<F> {
+        self.count += 1;
+        &p * self.base
+    }
+
     pub fn scale(&mut self, iter: impl DoubleEndedIterator<Item = impl Borrow<F>>) -> F {
-        iter.rev().fold(F::ZERO, |acc, x| self.mul(acc) + x)
+        iter.rev()
+            .fold(F::ZERO, |acc, x| self.mul(acc) + *x.borrow())
+    }
+
+    pub fn scale_polys(
+        &mut self,
+        polys: impl DoubleEndedIterator<Item = impl Borrow<PolynomialCoeffs<F>>>,
+    ) -> PolynomialCoeffs<F> {
+        polys.rev().fold(PolynomialCoeffs::empty(), |acc, x| {
+            &self.mul_poly(acc) + x.borrow()
+        })
     }
 
     pub fn shift(&mut self, x: F) -> F {
@@ -29,6 +45,16 @@ impl<F: Field> ScalingFactor<F> {
         tmp
     }
 
+    pub fn shift_poly(&mut self, p: PolynomialCoeffs<F>) -> PolynomialCoeffs<F> {
+        let tmp = &p * self.base.exp(self.count);
+        self.count = 0;
+        tmp
+    }
+
+    pub fn reset(&mut self) {
+        self.count = 0;
+    }
+
     pub fn repeated_frobenius<const D: usize>(&self, count: usize) -> Self
     where
         F: Frobenius<D>,