correct mistakes, simplify, assert

arkworks-rs · Feb 8, 2021 · 691d9a1 · 691d9a1
1 parent 113e7c0
commit 691d9a1
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Showing 2 changed files with 19 additions and 24 deletions.
diff --git a/ff/src/fields/mod.rs b/ff/src/fields/mod.rs
@@ -192,24 +192,11 @@ pub trait Field:
     /// Exponentiates this element by a number represented with `u64` limbs,
     /// least significant limb first.
     #[inline]
-    fn pow_with_table<S: AsRef<[u64]>>(&self, exp: S, pows_2: &[Self]) -> Self {
-        let exp = exp.as_ref();
-        let len = exp.len();
-        let mut max = len * 64;
-        for i in 0..len {
-            let lz = exp[len - 1 - i].leading_zeros() as usize;
-            max -= lz;
-            if lz == 64 {
-                break;
-            }
-        }
-
-        let mut res = Self::zero();
-        for i in 0..max {
-            let part = i / 64;
-            let bit = i - (64 * part);
-            if exp[part] & (1 << bit) > 0 {
-                res *= pows_2[i]
+    fn pow_with_table<S: AsRef<[u64]>>(pows_2: &[Self], exp: S) -> Self {
+        let mut res = Self::one();
+        for (pow, bit) in BitIteratorLE::without_trailing_zeros(exp).enumerate() {
+            if bit {
+                res *= &pows_2[pow];
             }
         }
         res

diff --git a/poly/src/polynomial/univariate/sparse.rs b/poly/src/polynomial/univariate/sparse.rs
@@ -66,19 +66,27 @@ impl<F: Field> Polynomial<F> for SparsePolynomial<F> {
         let total_bits = core::mem::size_of::<usize>() * 8;
         let max_pow_2 = total_bits - self.degree().leading_zeros() as usize;
 
-        let mut pows_2 = Vec::with_capacity(max_pow_2);
+        let mut pows_2 = Vec::<F>::with_capacity(max_pow_2);
 
-        let mut point = *point;
-        pows_2.push(point);
+        let mut p = *point;
+        pows_2.push(p);
         for _ in 1..max_pow_2 {
-            point.square_in_place();
-            pows_2.push(point);
+            p.square_in_place();
+            pows_2.push(p);
         }
+        // assert_eq!(pows_2.len(), max_pow_2);
         // compute all coeff * point^{i} and then sum the results
         let total = self
             .coeffs
             .iter()
-            .map(|(i, c)| (*c * point.pow_with_table(&[*i as u64], &pows_2[..])))
+            .map(|(i, c)| {
+                debug_assert_eq!(
+                    F::pow_with_table(&pows_2[..], &[*i as u64]),
+                    point.pow(&[*i as u64]),
+                    "pows not equal"
+                );
+                F::pow_with_table(&pows_2[..], &[*i as u64])
+            })
             .sum();
         total
     }