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words insertion on k_expo2

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This commit is contained in:
Cássio Kirch 2018-07-15 21:36:22 -03:00
parent 1e61787694
commit e8e1197629
1 changed files with 2 additions and 2 deletions
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4
library/compiler-builtins/libm/src/math/k_expo2.rs
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@ -1,14 +1,14 @@
use super::exp;
/* k is such that k*ln2 has minimal relative error and x - kln2 > log(FLT_MIN) */
const K: i64 = 2043;
const K: i32 = 2043;
/* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */
#[inline]
pub(crate) fn k_expo2(x: f64) -> f64 {
let k_ln2 = f64::from_bits(0x40962066151add8b);
/* note that k is odd and scale*scale overflows */
let scale = f64::from_bits(((0x3ff + K / 2) as u64) << 20);
let scale = f64::from_bits(((((0x3ff + K / 2) as u32) << 20) as u64) << 32);
/* exp(x - k ln2) * 2**(k-1) */
exp(x - k_ln2) * scale * scale
}