small changes

Author: quangvdao

ff/src/fields/models/fp/montgomery_backend.rs

@@ -408,7 +408,8 @@ pub trait MontConfig<const N: usize>: 'static + Sync + Send + Sized {
         } else if BigInt::from(r) >= <MontBackend<Self, N>>::MODULUS {
             None
         } else {
-            Some(Fp::new_unchecked(Self::R2).mul_u64(r))
+            // Multiply R (one in Montgomery form) with the u64
+            Some(Fp::new_unchecked(Self::R).mul_u64(r))
         }
     }
 
@@ -939,9 +940,10 @@ impl<T: MontConfig<N>, const N: usize> Fp<MontBackend<T, N>, N> {
     /// Multiply by a u128.
     /// Uses optimized mul_u64 if the input fits within u64,
     /// otherwise falls back to standard multiplication.
+    /// DO NOT USE right now, highly inefficient (2x slower than regular mul)
     #[inline(always)]
     pub fn mul_u128(self, other: u128) -> Self {
-        if other <= u64::MAX as u128 {
+        if other >> 64 == 0 {
             self.mul_u64(other as u64)
         } else {
             // Fallback: Convert u128 to Fp and multiply.
@@ -953,6 +955,7 @@ impl<T: MontConfig<N>, const N: usize> Fp<MontBackend<T, N>, N> {
     /// Multiply by an i128.
     /// Uses optimized mul_i64 if the input fits within i64,
     /// otherwise falls back to standard multiplication.
+    /// DO NOT USE right now, highly inefficient (2x slower than regular mul)
     #[inline(always)]
     pub fn mul_i128(self, other: i128) -> Self {
         if other >= i64::MIN as i128 && other <= i64::MAX as i128 {

test-curves/Cargo.toml

@@ -79,10 +79,10 @@ path = "benches/mnt6_753.rs"
 harness = false
 
 [[bench]]
-name = "field_mul_u64"
-path = "benches/field_mul_u64.rs"
+name = "small_mul"
+path = "benches/small_mul.rs"
 harness = false
-required-features = ["secp256k1"]
+required-features = ["bn254"]
 
 [[bench]]
 name = "bn254"

test-curves/benches/field_mul_u64.rs renamed to test-curves/benches/small_mul.rs

@@ -1,21 +1,34 @@
 use ark_ff::{Field, UniformRand};
 use ark_std::rand::{rngs::StdRng, Rng, SeedableRng};
-use ark_test_curves::secp256k1::Fr;
+use ark_test_curves::bn254::Fr;
 use criterion::{criterion_group, criterion_main, Criterion};
 
-fn mul_u64_bench(c: &mut Criterion) {
+fn mul_small_bench(c: &mut Criterion) {
     const SAMPLES: usize = 1000;
     // Use a fixed seed for reproducibility
     let mut rng = StdRng::seed_from_u64(0u64);
 
     let a_s = (0..SAMPLES)
         .map(|_| Fr::rand(&mut rng))
         .collect::<Vec<_>>();
-    let b_s = (0..SAMPLES)
+
+    let b_u64_s = (0..SAMPLES)
         .map(|_| rng.gen::<u64>())
         .collect::<Vec<_>>();
     // Convert u64 to Fr for standard multiplication benchmark
-    let b_fr_s = b_s.iter().map(|&b| Fr::from(b)).collect::<Vec<_>>();
+    let b_fr_s = b_u64_s.iter().map(|&b| Fr::from(b)).collect::<Vec<_>>();
+
+    let b_i64_s = (0..SAMPLES)
+        .map(|_| rng.gen::<i64>())
+        .collect::<Vec<_>>();
+
+    let b_u128_s = (0..SAMPLES)
+        .map(|_| rng.gen::<u128>())
+        .collect::<Vec<_>>();
+
+    let b_i128_s = (0..SAMPLES)
+        .map(|_| rng.gen::<i128>())
+        .collect::<Vec<_>>();
 
     // Generate another set of random Fr elements for addition
     let c_s = (0..SAMPLES)
@@ -29,7 +42,31 @@ fn mul_u64_bench(c: &mut Criterion) {
         bench.iter(|| {
             i = (i + 1) % SAMPLES;
             // Make sure the computation is not optimized away
-            criterion::black_box(a_s[i].mul_u64(b_s[i]))
+            criterion::black_box(a_s[i].mul_u64(b_u64_s[i]))
+        })
+    });
+
+    group.bench_function("mul_i64", |bench| {
+        let mut i = 0;
+        bench.iter(|| {
+            i = (i + 1) % SAMPLES;
+            criterion::black_box(a_s[i].mul_i64(b_i64_s[i]))
+        })
+    });
+
+    group.bench_function("mul_u128", |bench| {
+        let mut i = 0;
+        bench.iter(|| {
+            i = (i + 1) % SAMPLES;
+            criterion::black_box(a_s[i].mul_u128(b_u128_s[i]))
+        })
+    });
+
+    group.bench_function("mul_i128", |bench| {
+        let mut i = 0;
+        bench.iter(|| {
+            i = (i + 1) % SAMPLES;
+            criterion::black_box(a_s[i].mul_i128(b_i128_s[i]))
         })
     });
 
@@ -63,5 +100,5 @@ fn mul_u64_bench(c: &mut Criterion) {
     group.finish();
 }
 
-criterion_group!(benches, mul_u64_bench);
+criterion_group!(benches, mul_small_bench);
 criterion_main!(benches);