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Commit | Line | Data |
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8faf50e0 XL |
1 | use super::expf; |
2 | ||
3 | /* k is such that k*ln2 has minimal relative error and x - kln2 > log(FLT_MIN) */ | |
4 | const K: i32 = 235; | |
5 | ||
6 | /* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */ | |
48663c56 | 7 | #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
dc9dc135 | 8 | pub(crate) fn k_expo2f(x: f32) -> f32 { |
8faf50e0 XL |
9 | let k_ln2 = f32::from_bits(0x4322e3bc); |
10 | /* note that k is odd and scale*scale overflows */ | |
11 | let scale = f32::from_bits(((0x7f + K / 2) as u32) << 23); | |
12 | /* exp(x - k ln2) * 2**(k-1) */ | |
13 | expf(x - k_ln2) * scale * scale | |
14 | } |