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Use Simd::wrapping_neg (#1414)

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Diggory Hardy 2024-03-22 07:23:16 +00:00 committed by GitHub
parent 1015e709da
commit a457907255
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1 changed files with 4 additions and 10 deletions
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14
src/distributions/uniform.rs
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@ -701,21 +701,15 @@ macro_rules! uniform_simd_int_impl {
if !(low.simd_le(high).all()) {
return Err(Error::EmptyRange);
}
let unsigned_max = Simd::splat(::core::$unsigned::MAX);
// NOTE: all `Simd` operations are inherently wrapping,
// see https://doc.rust-lang.org/std/simd/struct.Simd.html
let range: Simd<$unsigned, LANES> = ((high - low) + Simd::splat(1)).cast();
// `% 0` will panic at runtime.
// We must avoid divide-by-zero by using 0 % 1 == 0.
let not_full_range = range.simd_gt(Simd::splat(0));
// replacing 0 with `unsigned_max` allows a faster `select`
// with bitwise OR
let modulo = not_full_range.select(range, unsigned_max);
// wrapping addition
// TODO: replace with `range.wrapping_neg() % module` when Simd supports this.
let ints_to_reject = (Simd::splat(0) - range) % modulo;
// When `range` is 0, `lo` of `v.wmul(range)` will always be
// zero which means only one sample is needed.
let modulo = not_full_range.select(range, Simd::splat(1));
let ints_to_reject = range.wrapping_neg() % modulo;
Ok(UniformInt {
low,