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factor: Ensure we only need to find every single factor once [WiP]

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~17% faster, many optimisation opportunities still missed  >:)
This commit is contained in:
nicoo 2020-07-31 14:59:52 +02:00 • committed by Roy Ivy III
parent 3743a3e1e7
commit ce218e01b6
1 changed files with 37 additions and 3 deletions
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40
src/uu/factor/src/factor.rs
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@ -10,7 +10,7 @@ extern crate rand;
use std::cell::RefCell;
use std::fmt;
use crate::numeric::{Arithmetic, Montgomery};
use crate::numeric::{gcd, Arithmetic, Montgomery};
use crate::{miller_rabin, rho, table};
type Exponent = u8;
@ -164,8 +164,42 @@ pub fn factor(num: u64) -> Factors {
let (f, e) = dec.pop().unwrap();
if let Some(d) = find_factor(f) {
dec.add(f / d, e);
dec.add(d, e);
let mut gcd_queue = Decomposition::one();
gcd_queue.add(d, e);
gcd_queue.add(f / d, e);
let mut non_trivial_gcd = true;
while non_trivial_gcd {
debug_assert_eq!(f, gcd_queue.product());
let mut tmp = Decomposition::one();
non_trivial_gcd = false;
for i in 0..gcd_queue.0.len() - 1 {
let (a, e_a) = gcd_queue.0[i];
let (b, e_b) = gcd_queue.0[i + 1];
let g = gcd(a, b);
if g != 1 {
non_trivial_gcd = true;
tmp.add(a / g, e_a);
tmp.add(g, e_a + e_b);
if i + 1 == gcd_queue.0.len() {
tmp.add(b / g, e_b)
} else {
gcd_queue.0[i + 1] = (b / g, e_b);
}
} else {
tmp.add(a, e_a);
if i + 1 == gcd_queue.0.len() - 1 {
tmp.add(b, e_b)
}
}
}
gcd_queue = tmp;
}
debug_assert_eq!(f, gcd_queue.product());
dec.0.extend(gcd_queue.0);
} else {
// f is prime
factors.add(f, e);