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factor::numeric: Simplify Montgomery (remove superfluous Wrapping)

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This commit is contained in:
nicoo 2020-05-31 13:15:53 +02:00
parent 19a0645a0a
commit 2238065c9d
1 changed files with 4 additions and 5 deletions
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9
src/uu/factor/src/numeric.rs
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@ -8,7 +8,6 @@
// * that was distributed with this source code.
use std::mem::swap;
use std::num::Wrapping;
pub fn gcd(mut a: u64, mut b: u64) -> u64 {
while b > 0 {
@ -89,7 +88,7 @@ impl Montgomery {
impl Arithmetic for Montgomery {
// Montgomery transform, R=2⁶⁴
// Provides fast arithmetic mod n (n odd, u64)
type I = Wrapping<u64>;
type I = u64;
fn new(n: u64) -> Self {
let a = inv_mod_u64(n).wrapping_neg();
@ -104,13 +103,13 @@ impl Arithmetic for Montgomery {
fn from_u64(&self, x: u64) -> Self::I {
// TODO: optimise!
assert!(x < self.n);
let r = Wrapping((((x as u128) << 64) % self.n as u128) as u64);
let r = (((x as u128) << 64) % self.n as u128) as u64;
debug_assert_eq!(x, self.to_u64(r));
r
}
fn to_u64(&self, n: Self::I) -> u64 {
self.reduce(n.0)
self.reduce(n)
}
fn add(&self, a: Self::I, b: Self::I) -> Self::I {
@ -134,7 +133,7 @@ impl Arithmetic for Montgomery {
}
fn mul(&self, a: Self::I, b: Self::I) -> Self::I {
let r = Wrapping(self.reduce((a * b).0));
let r = self.reduce(a.wrapping_mul(b));
// Check that r (reduced back to the usual representation) equals
// a*b % n