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added a_mul_by_x_pow_b_into_a

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This commit is contained in:
Jean-Philippe Bossuat
2025-01-22 11:18:06 +01:00
parent a50fbc1c74
commit 9c021d3c76
2 changed files with 35 additions and 1 deletions
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20
math/src/ring/impl_u64/ring.rs
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@@ -2,7 +2,7 @@ use crate::dft::ntt::Table;
use crate::modulus::barrett::Barrett;
use crate::modulus::montgomery::Montgomery;
use crate::modulus::prime::Prime;
use crate::modulus::VectorOperations;
use crate::modulus::{VectorOperations, ONCE};
use crate::modulus::{BARRETT, REDUCEMOD};
use crate::poly::Poly;
use crate::ring::Ring;
@@ -430,4 +430,22 @@ impl Ring<u64> {
&mut c.0,
);
}
pub fn a_mul_by_x_pow_b_into_a(&self, b: i32, a: &mut Poly<u64>) {
let n: usize = self.n();
let cyclotomic_order: usize = self.cyclotomic_order();
let b_0: usize = (b as usize).wrapping_add(cyclotomic_order) & (cyclotomic_order - 1);
let b_1: usize = b as usize & (n - 1);
a.0.rotate_right(b_1);
if b_0 > b_1 {
self.modulus
.va_neg_into_va::<CHUNK, 1, ONCE>(&mut a.0[b_1..])
} else {
self.modulus
.va_neg_into_va::<CHUNK, 1, ONCE>(&mut a.0[..b_1])
}
}
}