Store and reuse small powers

0xPolygonZero · Jul 31, 2023 · 53d8fd2 · 53d8fd2
1 parent a02dfc2
commit 53d8fd2
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Showing 2 changed files with 30 additions and 24 deletions.
diff --git a/evm/src/prover.rs b/evm/src/prover.rs
@@ -499,25 +499,28 @@ where
     // When opening the `Z`s polys at the "next" point, need to look at the point `next_step` steps away.
     let next_step = 1 << quotient_degree_bits;
 
+    let powers_vec = SmallPowers::<F>::new(F::coset_shift().to_noncanonical_u64() as u32)
+        .take(degree << quotient_degree_bits)
+        .collect_vec();
     // Evaluation of the first Lagrange polynomial on the LDE domain, with custom lde_onto_coset.
     let lagrange_first = PolynomialValues::<F>::selector(degree, 0);
     let coeffs = ifft(lagrange_first).lde(quotient_degree_bits);
-    let modified_poly: PolynomialCoeffs<F> =
-        SmallPowers::<F>::new(F::coset_shift().to_noncanonical_u64() as u32)
-            .zip(&coeffs.coeffs)
-            .map(|(r, &c)| r * c)
-            .collect::<Vec<_>>()
-            .into();
+    let modified_poly: PolynomialCoeffs<F> = powers_vec
+        .iter()
+        .zip(&coeffs.coeffs)
+        .map(|(&r, &c)| r * c)
+        .collect::<Vec<_>>()
+        .into();
     let lagrange_first = modified_poly.fft_with_options(None, None);
     // Evaluation of the last Lagrange polynomial on the LDE domain, with custom lde_onto_coset.
     let lagrange_last = PolynomialValues::<F>::selector(degree, degree - 1);
     let coeffs = ifft(lagrange_last).lde(quotient_degree_bits);
-    let modified_poly: PolynomialCoeffs<F> =
-        SmallPowers::<F>::new(F::coset_shift().to_noncanonical_u64() as u32)
-            .zip(&coeffs.coeffs)
-            .map(|(r, &c)| r * c)
-            .collect::<Vec<_>>()
-            .into();
+    let modified_poly: PolynomialCoeffs<F> = powers_vec
+        .into_iter()
+        .zip(&coeffs.coeffs)
+        .map(|(r, &c)| r * c)
+        .collect::<Vec<_>>()
+        .into();
     let lagrange_last = modified_poly.fft_with_options(None, None);
 
     let z_h_on_coset = ZeroPolyOnCoset::<F>::new(degree_bits, quotient_degree_bits);

diff --git a/starky/src/prover.rs b/starky/src/prover.rs
@@ -228,25 +228,28 @@ where
     // When opening the `Z`s polys at the "next" point, need to look at the point `next_step` steps away.
     let next_step = 1 << quotient_degree_bits;
 
+    let powers_vec = SmallPowers::<F>::new(F::coset_shift().to_noncanonical_u64() as u32)
+        .take(degree << quotient_degree_bits)
+        .collect_vec();
     // Evaluation of the first Lagrange polynomial on the LDE domain, with custom lde_onto_coset.
     let lagrange_first = PolynomialValues::<F>::selector(degree, 0);
     let coeffs = ifft(lagrange_first).lde(quotient_degree_bits);
-    let modified_poly: PolynomialCoeffs<F> =
-        SmallPowers::<F>::new(F::coset_shift().to_noncanonical_u64() as u32)
-            .zip(&coeffs.coeffs)
-            .map(|(r, &c)| r * c)
-            .collect::<Vec<_>>()
-            .into();
+    let modified_poly: PolynomialCoeffs<F> = powers_vec
+        .iter()
+        .zip(&coeffs.coeffs)
+        .map(|(&r, &c)| r * c)
+        .collect::<Vec<_>>()
+        .into();
     let lagrange_first = modified_poly.fft_with_options(None, None);
     // Evaluation of the last Lagrange polynomial on the LDE domain, with custom lde_onto_coset.
     let lagrange_last = PolynomialValues::<F>::selector(degree, degree - 1);
     let coeffs = ifft(lagrange_last).lde(quotient_degree_bits);
-    let modified_poly: PolynomialCoeffs<F> =
-        SmallPowers::<F>::new(F::coset_shift().to_noncanonical_u64() as u32)
-            .zip(&coeffs.coeffs)
-            .map(|(r, &c)| r * c)
-            .collect::<Vec<_>>()
-            .into();
+    let modified_poly: PolynomialCoeffs<F> = powers_vec
+        .into_iter()
+        .zip(&coeffs.coeffs)
+        .map(|(r, &c)| r * c)
+        .collect::<Vec<_>>()
+        .into();
     let lagrange_last = modified_poly.fft_with_options(None, None);
     let z_h_on_coset = ZeroPolyOnCoset::<F>::new(degree_bits, quotient_degree_bits);