Add lookups for x_rev and q_rev

Author: Kunming Jiang

spartan_parallel/src/r1csinstance.rs

@@ -19,10 +19,8 @@ use super::sparse_mlpoly::{
 use super::timer::Timer;
 use flate2::{write::ZlibEncoder, Compression};
 use merlin::Transcript;
-use rayon::prelude::*;
 use serde::{Deserialize, Serialize};
 use std::iter::zip;
-use std::sync::{Arc, Mutex};
 
 #[derive(Debug, Serialize, Deserialize, Clone)]
 pub struct R1CSInstance<S: SpartanExtensionField> {
@@ -249,39 +247,52 @@ impl<S: SpartanExtensionField + Send + Sync> R1CSInstance<S> {
       Bz.push(Vec::new());
       Cz.push(Vec::new());
 
+      // Map x and y to x_rev and y_rev so we don't have to do it everytime
+      let x_step = max_num_cons / num_cons[p];
+      let x_rev_map = (0..num_cons[p]).map(|x|
+        rev_bits(x, max_num_cons) / x_step
+      ).collect();
+      let y_step = max_num_inputs / num_inputs[p];
+      let y_rev_map = (0..num_inputs[p]).map(|y|
+        rev_bits(y, max_num_inputs) / y_step
+      ).collect();
+
       Az[p] = (0..num_proofs[p])
         .into_par_iter()
         .map(|q| {
           vec![self.A_list[p_inst].multiply_vec_disjoint_rounds(
-            max_num_cons,
             num_cons[p_inst].clone(),
             max_num_inputs,
             num_inputs[p],
             &z_list[q],
+            &x_rev_map,
+            &y_rev_map,
           )]
         })
         .collect();
       Bz[p] = (0..num_proofs[p])
         .into_par_iter()
         .map(|q| {
           vec![self.B_list[p_inst].multiply_vec_disjoint_rounds(
-            max_num_cons,
             num_cons[p_inst].clone(),
             max_num_inputs,
             num_inputs[p],
             &z_list[q],
+            &x_rev_map,
+            &y_rev_map,
           )]
         })
         .collect();
       Cz[p] = (0..num_proofs[p])
         .into_par_iter()
         .map(|q| {
           vec![self.C_list[p_inst].multiply_vec_disjoint_rounds(
-            max_num_cons,
             num_cons[p_inst].clone(),
             max_num_inputs,
             num_inputs[p],
             &z_list[q],
+            &x_rev_map,
+            &y_rev_map,
           )]
         })
         .collect();

spartan_parallel/src/r1csproof.rs

@@ -184,17 +184,20 @@ impl<S: SpartanExtensionField + Send + Sync> R1CSProof<S> {
       for p in 0..num_instances {
         z_mat.push(vec![vec![vec![S::field_zero(); num_inputs[p]]; num_witness_secs]; num_proofs[p]]);
         let q_step = max_num_proofs / num_proofs[p];
+
+        let y_step = max_num_inputs / num_inputs[p];
+        let y_rev_map: Vec<usize> = (0..num_inputs[p]).map(|y|
+          rev_bits(y, max_num_inputs) / y_step
+        ).collect();
         for q in 0..num_proofs[p] {
           let q_rev = rev_bits(q, max_num_proofs) / q_step;
           for w in 0..witness_secs.len() {
             let ws = witness_secs[w];
             let p_w = if ws.w_mat.len() == 1 { 0 } else { p };
             let q_w = if ws.w_mat[p_w].len() == 1 { 0 } else { q };
-            let y_step = max_num_inputs / num_inputs[p];
             // Only append the first num_inputs_entries of w_mat[p][q]
             for i in 0..min(ws.num_inputs[p_w], num_inputs[p]) {
-              let y_rev = rev_bits(i, max_num_inputs) / y_step;
-              z_mat[p][q_rev][w][y_rev] = ws.w_mat[p_w][q_w][i];
+              z_mat[p][q_rev][w][y_rev_map[i]] = ws.w_mat[p_w][q_w][i];
             }
           }
         }

spartan_parallel/src/sparse_mlpoly.rs

@@ -405,31 +405,24 @@ impl<S: SpartanExtensionField> SparseMatPolynomial<S> {
   // Z[i] contains entries i * max_num_cols ~ i * max_num_cols + num_cols
   pub fn multiply_vec_disjoint_rounds(
     &self, 
-    max_num_rows: usize,
     num_rows: usize, 
     max_num_cols: usize, 
-    num_cols: usize, 
-    z: &Vec<Vec<S>>
+    _num_cols: usize, 
+    z: &Vec<Vec<S>>,
+    x_rev_map: &Vec<usize>,
+    y_rev_map: &Vec<usize>,
   ) -> Vec<S> {
-    let step_r = max_num_rows / num_rows;
     (0..self.M.len())
       .map(|i| {
         let row = self.M[i].row;
         let col = self.M[i].col;
         let val = self.M[i].val.clone();
         let w = col / max_num_cols;
         let y = col % max_num_cols;
-        // Z expresses y in reverse bits order, so have to find the correct y
-        let y_step = max_num_cols / num_cols;
-        let y_rev = rev_bits(y, max_num_cols) / y_step;
-        (row, val * z[w][y_rev])
+        (row, val * z[w][y_rev_map[y]])
       })
       .fold(vec![S::field_zero(); num_rows], |mut Mz, (r, v)| {
-        // Reverse the bits of r. r_rev is a multiple of step_r
-        let r_rev = rev_bits(r, max_num_rows);
-        // Now r_rev is between 0 to num_inputs[p]
-        let r_rev = r_rev / step_r;
-        Mz[r_rev] += v;
+        Mz[x_rev_map[r]] += v;
         Mz
       })
   }