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factor::miller_rabin: Remove duplicated work

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The duplicate work was introduced in 2015.
This commit is contained in:
nicoo 2020-06-25 05:05:31 +02:00
parent 8cda0f596e
commit e415b17c01
1 changed files with 5 additions and 14 deletions
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19
src/uu/factor/src/miller_rabin.rs
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@ -54,7 +54,7 @@ pub(crate) fn test<A: Arithmetic + Basis>(m: A) -> Result {
let one = m.one(); let one = m.one();
let minus_one = m.minus_one(); let minus_one = m.minus_one();
for _a in A::BASIS.iter() { 'witness: for _a in A::BASIS.iter() {
let _a = _a % n; let _a = _a % n;
if _a == 0 { if _a == 0 {
continue; continue;
@ -65,22 +65,11 @@ pub(crate) fn test<A: Arithmetic + Basis>(m: A) -> Result {
// x = a^r mod n // x = a^r mod n
let mut x = m.pow(a, r); let mut x = m.pow(a, r);
{
// y = ((x²)²...)² i times = x ^ (2ⁱ) = a ^ (r 2ⁱ) = x ^ (n - 1)
let mut y = x;
for _ in 0..i {
y = m.mul(y, y)
}
if y != one {
return Pseudoprime;
};
}
if x == one || x == minus_one { if x == one || x == minus_one {
continue; continue;
} }
loop { for _ in 1..i {
let y = m.mul(x, x); let y = m.mul(x, x);
if y == one { if y == one {
return Composite(gcd(m.to_u64(x) - 1, m.modulus())); return Composite(gcd(m.to_u64(x) - 1, m.modulus()));
@ -88,10 +77,12 @@ pub(crate) fn test<A: Arithmetic + Basis>(m: A) -> Result {
if y == minus_one { if y == minus_one {
// This basis element is not a witness of `n` being composite. // This basis element is not a witness of `n` being composite.
// Keep looking. // Keep looking.
break; continue 'witness;
} }
x = y; x = y;
} }
return Pseudoprime;
} }
Prime Prime