chore: matmul cleanup

Cargo.toml

@@ -153,7 +153,6 @@ k256 = "=0.13.4"  # secp256k1 elliptic curve - LOW RISK: RustCrypto org, 33M+ do
 minijinja = { version = "=2.11.0", features = ["loader"] }  # Template engine - HIGH RISK: Individual maintainer (mitsuhiko), despite exceptional track record
 ml-kem = { version = "=0.2.2", features = ["zeroize"] }  # ML-KEM (Kyber) post-quantum KEM - MEDIUM RISK: New standard implementation, needs security audit
 mockall = "=0.13.1"  # Mocking for tests - HIGH RISK: Individual maintainer (asomers), test-only dependency
-ndarray = { version = "=0.16.1", features = ["serde"] }  # N-dimensional arrays - LOW RISK: rust-ndarray team
 nom = "=8.0.0"  # Parser combinator library - HIGH RISK: Individual maintainer (Geal), despite 319M+ downloads
 num-integer = "=0.1.46"  # Integer utilities - LOW RISK: rust-num team
 num-traits = "=0.2.19"  # Numeric traits - LOW RISK: rust-num team

core/threshold-algebra/Cargo.toml

@@ -11,7 +11,6 @@ threshold-types.workspace = true
 g2p.workspace = true
 error-utils.workspace   = true
 itertools.workspace   = true
-ndarray.workspace   = true
 rand.workspace   = true
 serde.workspace   = true
 sha3.workspace   = true
@@ -33,3 +32,7 @@ rstest.workspace = true
 [[bench]]
 name = "bivariate"
 harness = false
+
+[[bench]]
+name = "matrix"
+harness = false

core/threshold-algebra/benches/matrix.rs

@@ -0,0 +1,73 @@
+use aes_prng::AesRng;
+use criterion::{Criterion, criterion_group, criterion_main};
+use rand::SeedableRng;
+use std::hint::black_box;
+use threshold_algebra::{
+    galois_rings::degree_4::ResiduePolyF4Z128, matrix::VdmMatrix, structure_traits::Sample,
+};
+
+const PRODUCTION_PARTIES: usize = 13;
+const PRODUCTION_THRESHOLD: usize = 4;
+const EXTRACTED_WIDTH: usize = PRODUCTION_PARTIES - PRODUCTION_THRESHOLD;
+
+fn sample_vec(rng: &mut AesRng, len: usize) -> Vec<ResiduePolyF4Z128> {
+    (0..len).map(|_| ResiduePolyF4Z128::sample(rng)).collect()
+}
+
+fn bench_single_sharing_vdm(c: &mut Criterion) {
+    let mut rng = AesRng::seed_from_u64(0);
+    let shares = sample_vec(&mut rng, PRODUCTION_PARTIES);
+    let vdm = VdmMatrix::<ResiduePolyF4Z128>::from_exceptional_sequence(
+        PRODUCTION_PARTIES,
+        EXTRACTED_WIDTH,
+    )
+    .unwrap();
+
+    c.bench_function("matrix/production/single_sharing_vdm/n13_t4", |b| {
+        b.iter(|| black_box(black_box(&vdm).mul_vector(black_box(&shares)).unwrap()))
+    });
+}
+
+fn bench_double_sharing_vdm(c: &mut Criterion) {
+    let mut rng = AesRng::seed_from_u64(1);
+    let shares_t = sample_vec(&mut rng, PRODUCTION_PARTIES);
+    let shares_2t = sample_vec(&mut rng, PRODUCTION_PARTIES);
+    let vdm = VdmMatrix::<ResiduePolyF4Z128>::from_exceptional_sequence(
+        PRODUCTION_PARTIES,
+        EXTRACTED_WIDTH,
+    )
+    .unwrap();
+
+    c.bench_function("matrix/production/double_sharing_vdm/n13_t4", |b| {
+        b.iter(|| {
+            black_box((
+                black_box(&vdm).mul_vector(black_box(&shares_t)).unwrap(),
+                black_box(&vdm).mul_vector(black_box(&shares_2t)).unwrap(),
+            ))
+        })
+    });
+}
+
+fn bench_robust_prss_vdm(c: &mut Criterion) {
+    let mut rng = AesRng::seed_from_u64(2);
+    let shares = sample_vec(&mut rng, PRODUCTION_PARTIES);
+    let vdm = VdmMatrix::<ResiduePolyF4Z128>::from_exceptional_sequence(
+        PRODUCTION_PARTIES,
+        EXTRACTED_WIDTH,
+    )
+    .unwrap();
+
+    // Keep the Criterion ID stable so this branch can compare against the
+    // original transposed ndarray baseline.
+    c.bench_function("matrix/production/robust_prss_transposed_vdm/n13_t4", |b| {
+        b.iter(|| black_box(black_box(&vdm).mul_vector(black_box(&shares)).unwrap()))
+    });
+}
+
+criterion_group!(
+    matrix,
+    bench_single_sharing_vdm,
+    bench_double_sharing_vdm,
+    bench_robust_prss_vdm,
+);
+criterion_main!(matrix);