Add secure powers generation for simd

crates/prover/src/core/backend/simd/utils.rs

@@ -1,5 +1,12 @@
 use std::simd::Swizzle;
 
+use itertools::Itertools;
+
+use crate::core::backend::simd::m31::N_LANES;
+use crate::core::backend::simd::qm31::PackedSecureField;
+use crate::core::fields::qm31::SecureField;
+use crate::core::utils::generate_secure_powers;
+
 /// Used with [`Swizzle::concat_swizzle`] to interleave the even values of two vectors.
 pub struct InterleaveEvens;
 
@@ -51,11 +58,35 @@ impl<T> UnsafeConst<T> {
 unsafe impl<T> Send for UnsafeConst<T> {}
 unsafe impl<T> Sync for UnsafeConst<T> {}
 
+// TODO(Gali): Remove #[allow(dead_code)].
+#[allow(dead_code)]
+pub fn generate_secure_powers_simd(felt: SecureField, n_powers: usize) -> Vec<SecureField> {
+    let base_arr = generate_secure_powers(felt, N_LANES).try_into().unwrap();
+    let base_packed_felt = PackedSecureField::from_array(base_arr);
+
+    let step = base_arr[N_LANES - 1] * felt;
+    let step = PackedSecureField::broadcast(step);
+
+    let packed_size = (n_powers + N_LANES - 1) / N_LANES;
+
+    (0..packed_size)
+        .scan(base_packed_felt, |acc, _| {
+            let res = *acc;
+            *acc *= step;
+            Some(res)
+        })
+        .flat_map(|x| x.to_array())
+        .take(n_powers)
+        .collect_vec()
+}
+
 #[cfg(test)]
 mod tests {
     use std::simd::{u32x4, Swizzle};
 
-    use super::{InterleaveEvens, InterleaveOdds};
+    use super::{generate_secure_powers_simd, InterleaveEvens, InterleaveOdds};
+    use crate::core::utils::generate_secure_powers;
+    use crate::qm31;
 
     #[test]
     fn interleave_evens() {
@@ -76,4 +107,14 @@ mod tests {
 
         assert_eq!(res, u32x4::from_array([1, 5, 3, 7]));
     }
+
+    #[test]
+    fn test_generate_secure_powers_simd() {
+        let felt = qm31!(1, 2, 3, 4);
+        let n_powers = 10;
+
+        let cpu_powers = generate_secure_powers(felt, n_powers);
+        let powers = generate_secure_powers_simd(felt, n_powers);
+        assert_eq!(powers, cpu_powers);
+    }
 }