[#1793] Get rid of unnecessary WitnessColumnIndexer

msm/src/ffa/columns.rs

@@ -3,6 +3,9 @@ use crate::columns::ColumnIndexer;
 
 use crate::LIMBS_NUM;
 
+/// Number of columns in the FFA circuits.
+pub const FFA_N_COLUMNS: usize = 4 * LIMBS_NUM;
+
 #[derive(Clone, Copy, Debug, PartialEq)]
 /// Column indexer for MSM columns
 pub enum FFAColumnIndexer {

msm/src/ffa/constraint.rs

@@ -5,11 +5,11 @@ use num_bigint::BigUint;
 use crate::{
     columns::{Column, ColumnIndexer},
     expr::MSMExpr,
-    ffa::columns::FFAColumnIndexer,
+    ffa::columns::{FFAColumnIndexer, FFA_N_COLUMNS},
     lookups::LookupTableIDs,
     proof::ProofInputs,
     witness::Witness,
-    {BN254G1Affine, Ff1, Fp, LIMBS_NUM, MSM_FFADD_N_COLUMNS},
+    {BN254G1Affine, Ff1, Fp, LIMBS_NUM},
 };
 use kimchi::{
     circuits::{
@@ -30,19 +30,12 @@ fn limb_decompose(input: &Ff1) -> [Fp; LIMBS_NUM] {
     ff_el.limbs
 }
 
-pub struct WitnessColumnsIndexer<T> {
-    pub(crate) a: [T; LIMBS_NUM],
-    pub(crate) b: [T; LIMBS_NUM],
-    pub(crate) c: [T; LIMBS_NUM],
-    pub(crate) d: [T; LIMBS_NUM],
-}
-
 #[allow(dead_code)]
 /// Builder environment for a native group `G`.
 pub struct MSMCircuitEnv<G: KimchiCurve> {
     /// Aggregated witness, in raw form. For accessing [`Witness`], see the
     /// `get_witness` method.
-    witness_raw: Vec<WitnessColumnsIndexer<G::ScalarField>>,
+    witness_raw: Vec<Witness<FFA_N_COLUMNS, G::ScalarField>>,
 }
 
 impl MSMCircuitEnv<BN254G1Affine> {
@@ -55,21 +48,13 @@ impl MSMCircuitEnv<BN254G1Affine> {
     /// Each WitnessColumn stands for both one row and multirow. This
     /// function converts from a vector of one-row instantiation to a
     /// single multi-row form (which is a `Witness`).
-    pub fn get_witness(&self) -> ProofInputs<MSM_FFADD_N_COLUMNS, BN254G1Affine, LookupTableIDs> {
-        let mut cols: [Vec<Fp>; MSM_FFADD_N_COLUMNS] = std::array::from_fn(|_| vec![]);
-
-        for wc in &self.witness_raw {
-            let WitnessColumnsIndexer {
-                a: wc_a,
-                b: wc_b,
-                c: wc_c,
-                d: wc_d,
-            } = wc;
-            for i in 0..LIMBS_NUM {
-                cols[i].push(wc_a[i]);
-                cols[LIMBS_NUM + i].push(wc_b[i]);
-                cols[2 * LIMBS_NUM + i].push(wc_c[i]);
-                cols[3 * LIMBS_NUM + i].push(wc_d[i]);
+    pub fn get_witness(&self) -> ProofInputs<FFA_N_COLUMNS, BN254G1Affine, LookupTableIDs> {
+        let mut cols: [Vec<Fp>; FFA_N_COLUMNS] = std::array::from_fn(|_| vec![]);
+
+        for w in &self.witness_raw {
+            let Witness { cols: witness_row } = w;
+            for i in 0..4 * LIMBS_NUM {
+                cols[i].push(witness_row[i]);
             }
         }
 
@@ -158,12 +143,12 @@ impl MSMCircuitEnv<BN254G1Affine> {
             .unwrap_or_else(|_| panic!("Length mismatch"));
         let d_limbs: [Fp; LIMBS_NUM] = [Zero::zero(); LIMBS_NUM];
 
-        self.witness_raw.push(WitnessColumnsIndexer {
-            a: a_limbs,
-            b: b_limbs,
-            c: c_limbs,
-            d: d_limbs,
-        });
+        let witness_row: [Fp; 4 * LIMBS_NUM] = [a_limbs, b_limbs, c_limbs, d_limbs]
+            .concat()
+            .try_into()
+            .unwrap();
+
+        self.witness_raw.push(Witness { cols: witness_row });
     }
 
     pub fn add_test_multiplication(&mut self, a: Ff1, b: Ff1) {
@@ -180,11 +165,11 @@ impl MSMCircuitEnv<BN254G1Affine> {
 
         let c_limbs: [Fp; LIMBS_NUM] = [Zero::zero(); LIMBS_NUM];
 
-        self.witness_raw.push(WitnessColumnsIndexer {
-            a: a_limbs,
-            b: b_limbs,
-            c: c_limbs,
-            d: d_limbs,
-        });
+        let witness_row: [Fp; 4 * LIMBS_NUM] = [a_limbs, b_limbs, c_limbs, d_limbs]
+            .concat()
+            .try_into()
+            .unwrap();
+
+        self.witness_raw.push(Witness { cols: witness_row });
     }
 }

msm/src/lib.rs

@@ -40,11 +40,6 @@ pub type BN254 = ark_ec::bn::Bn<ark_bn254::Parameters>;
 pub type BN254G1Affine = <BN254 as ark_ec::PairingEngine>::G1Affine;
 pub type BN254G2Affine = <BN254 as ark_ec::PairingEngine>::G2Affine;
 
-/// Number of columns
-/// FIXME: we must move it into the subdirectory of the
-/// foreign field addition circuit
-pub const MSM_FFADD_N_COLUMNS: usize = 4 * LIMBS_NUM;
-
 /// The native field we are working with.
 pub type Fp = ark_bn254::Fr;
 

msm/src/main.rs

@@ -4,14 +4,13 @@ use kimchi::circuits::domains::EvaluationDomains;
 use poly_commitment::pairing_proof::PairingSRS;
 
 use kimchi_msm::columns::Column;
-use kimchi_msm::ffa::constraint::MSMCircuitEnv;
+use kimchi_msm::ffa::{columns::FFA_N_COLUMNS, constraint::MSMCircuitEnv};
 use kimchi_msm::lookups::LookupTableIDs;
 use kimchi_msm::precomputed_srs::get_bn254_srs;
 use kimchi_msm::prover::prove;
 use kimchi_msm::verifier::verify;
 use kimchi_msm::{
     BN254G1Affine, BaseSponge, Ff1, Fp, OpeningProof, ScalarSponge, BN254, DOMAIN_SIZE,
-    MSM_FFADD_N_COLUMNS,
 };
 
 pub fn generate_random_msm_witness() -> MSMCircuitEnv<BN254G1Affine> {
@@ -54,12 +53,12 @@ pub fn main() {
         ScalarSponge,
         Column,
         _,
-        MSM_FFADD_N_COLUMNS,
+        FFA_N_COLUMNS,
         LookupTableIDs,
     >(domain, &srs, &constraint_exprs, proof_inputs, &mut rng);
 
     println!("Verifying the proof");
-    let verifies = verify::<_, OpeningProof, BaseSponge, ScalarSponge, MSM_FFADD_N_COLUMNS>(
+    let verifies = verify::<_, OpeningProof, BaseSponge, ScalarSponge, FFA_N_COLUMNS>(
         domain,
         &srs,
         &constraint_exprs,