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Switch to using a simpler scheme for complex remainders

This commit is contained in:
Isaac Carruthers 2017-08-22 16:14:36 -04:00
parent 42a6ae5353
commit 263bd0ec44
1 changed files with 6 additions and 27 deletions
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33
complex/src/lib.rs
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@ -531,30 +531,7 @@ impl<T: Clone + Num + PartialOrd> Rem<Complex<T>> for Complex<T> {
// This is the gaussian integer corresponding to the true ratio // This is the gaussian integer corresponding to the true ratio
// rounded towards zero. // rounded towards zero.
let (re0, im0) = (re.clone() - re % T::one(), im.clone() - im % T::one()); let (re0, im0) = (re.clone() - re % T::one(), im.clone() - im % T::one());
self - modulus * Complex::new(re0, im0)
let zero = T::zero();
let one = T::one();
let neg = zero.clone() - one.clone();
// Traverse the 3x3 square of gaussian integers surrounding our
// current approximation, and select the one whose product with
// `modulus` is closest to `self`.
let mut bestrem = self.clone() - modulus.clone() *
Complex::new(re0.clone(), im0.clone());
let mut bestnorm = bestrem.norm_sqr();
for &(dr, di) in
vec![(&one, &zero), (&one, &one), (&zero, &one), (&neg, &one),
(&neg, &zero), (&neg, &neg), (&zero, &neg), (&one, &neg)]
.iter() {
let newrem = self.clone() - modulus.clone() *
Complex::new(re0.clone() + dr.clone(),
im0.clone() + di.clone());
let newnorm = newrem.norm_sqr();
if newnorm < bestnorm {
bestrem = newrem;
bestnorm = newnorm;
}
}
bestrem
} }
} }
@ -1702,7 +1679,7 @@ mod test {
mod real_arithmetic { mod real_arithmetic {
use super::super::Complex; use super::super::Complex;
use super::_4_2i; use super::{_4_2i, _neg1_1i};
#[test] #[test]
fn test_add() { fn test_add() {
@ -1731,8 +1708,10 @@ mod test {
#[test] #[test]
fn test_rem() { fn test_rem() {
assert_eq!(_4_2i % 2.0, Complex::new(0.0, 0.0)); assert_eq!(_4_2i % 2.0, Complex::new(0.0, 0.0));
assert_eq!(_4_2i % 3.0, Complex::new(1.0, -1.0)); assert_eq!(_4_2i % 3.0, Complex::new(1.0, 2.0));
assert_eq!(3.0 % _4_2i, Complex::new(-1.0, -2.0)); assert_eq!(3.0 % _4_2i, Complex::new(3.0, 0.0));
assert_eq!(_neg1_1i % 2.0, _neg1_1i);
assert_eq!(-_4_2i % 3.0, Complex::new(-1.0, -2.0));
} }
} }