fadd_fast benchmark

fadd_fast_bench.rs

#![feature(core_intrinsics)]

use std::intrinsics::fadd_fast;

use criterion::{criterion_group, criterion_main, Criterion};

const XS: &'static [f32] = &[3.14; 1000];

fn slow_sum(xs: &[f32]) -> f32 {
    xs.iter().sum()
}

fn fast_sum(xs: &[f32]) -> f32 {
    xs.iter().fold(0.0, |x, y| unsafe { fadd_fast(x, *y) })
}

fn bench_sums(c: &mut Criterion) {
    let mut group = c.benchmark_group("f32 sum");
    group.bench_function("slow sum", |b| b.iter(|| slow_sum(XS)));
    group.bench_function("fast sum", |b| b.iter(|| fast_sum(XS)));
    group.finish();
}

criterion_group!(benches, bench_sums);
criterion_main!(benches);