| 1 | use super::expf; |
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| 3 | /* k is such that k*ln2 has minimal relative error and x - kln2 > log(FLT_MIN) */ |
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| 4 | const K: i32 = 235; |
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| 5 | |
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| 6 | /* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */ |
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| 7 | #[cfg_attr (all(test, assert_no_panic), no_panic::no_panic)] |
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| 8 | pub(crate) fn k_expo2f(x: f32) -> f32 { |
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| 9 | let k_ln2: f32 = f32::from_bits(0x4322e3bc); |
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| 10 | /* note that k is odd and scale*scale overflows */ |
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| 11 | let scale: f32 = f32::from_bits(((0x7f + K / 2) as u32) << 23); |
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| 12 | /* exp(x - k ln2) * 2**(k-1) */ |
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| 13 | expf(x - k_ln2) * scale * scale |
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| 14 | } |
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| 15 | |
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