diff options
Diffstat (limited to 'vendor/libm-0.1.4/src/math/k_expo2f.rs')
-rw-r--r-- | vendor/libm-0.1.4/src/math/k_expo2f.rs | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/vendor/libm-0.1.4/src/math/k_expo2f.rs b/vendor/libm-0.1.4/src/math/k_expo2f.rs new file mode 100644 index 000000000..de8507772 --- /dev/null +++ b/vendor/libm-0.1.4/src/math/k_expo2f.rs @@ -0,0 +1,15 @@ +use super::expf; + +/* k is such that k*ln2 has minimal relative error and x - kln2 > log(FLT_MIN) */ +const K: i32 = 235; + +/* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */ +#[inline] +#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] +pub(crate) fn k_expo2f(x: f32) -> f32 { + let k_ln2 = f32::from_bits(0x4322e3bc); + /* note that k is odd and scale*scale overflows */ + let scale = f32::from_bits(((0x7f + K / 2) as u32) << 23); + /* exp(x - k ln2) * 2**(k-1) */ + expf(x - k_ln2) * scale * scale +} |