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Fix sincosf for interval (7*pi/4, 9*pi/4) (#233)

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A mistake was made in porting musl's implementation which caused the sin
and cos components to be reversed.

closes rust-lang/libm#232
This commit is contained in:
AJ Frantz 2019-11-22 14:16:00 -05:00 • committed by Alex Crichton
parent 3b3f3e977c
commit a8d9eb7521
1 changed files with 22 additions and 4 deletions
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26
library/compiler-builtins/libm/src/math/sincosf.rs
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@ -89,11 +89,11 @@ pub fn sincosf(x: f32) -> (f32, f32) {
}
} else {
if sign {
s = k_cosf((x + S4PIO2) as f64);
c = k_sinf((x + S4PIO2) as f64);
s = k_sinf((x + S4PIO2) as f64);
c = k_cosf((x + S4PIO2) as f64);
} else {
s = k_cosf((x - S4PIO2) as f64);
c = k_sinf((x - S4PIO2) as f64);
s = k_sinf((x - S4PIO2) as f64);
c = k_cosf((x - S4PIO2) as f64);
}
}
@ -133,4 +133,22 @@ mod tests {
_eqf(s.abs(), 0.0).unwrap();
_eqf(c, -1.0).unwrap();
}
#[test]
fn rotational_symmetry() {
use core::f32::consts::PI;
const N: usize = 24;
for n in 0..N {
let theta = 2. * PI * (n as f32) / (N as f32);
let (s, c) = sincosf(theta);
let (s_plus, c_plus) = sincosf(theta + 2. * PI);
let (s_minus, c_minus) = sincosf(theta - 2. * PI);
const TOLERANCE: f32 = 1e-6;
assert!((s - s_plus).abs() < TOLERANCE);
assert!((s - s_minus).abs() < TOLERANCE);
assert!((c - c_plus).abs() < TOLERANCE);
assert!((c - c_minus).abs() < TOLERANCE);
}
}
}