ndarray 0.13.1

#![feature(test)]

extern crate test;
use test::Bencher;

use ndarray::prelude::*;
use ndarray::NdProducer;

#[bench]
fn chunk2x2_iter_sum(bench: &mut Bencher) {
    let a = Array::<f32, _>::zeros((256, 256));
    let chunksz = (2, 2);
    let mut sum = Array::zeros(a.exact_chunks(chunksz).raw_dim());
    bench.iter(|| {
        azip!((a in a.exact_chunks(chunksz), sum in &mut sum) {
            *sum = a.iter().sum::<f32>();
        });
    });
}

#[bench]
fn chunk2x2_sum(bench: &mut Bencher) {
    let a = Array::<f32, _>::zeros((256, 256));
    let chunksz = (2, 2);
    let mut sum = Array::zeros(a.exact_chunks(chunksz).raw_dim());
    bench.iter(|| {
        azip!((a in a.exact_chunks(chunksz), sum in &mut sum) {
            *sum = a.sum();
        });
    });
}

#[bench]
fn chunk2x2_sum_get1(bench: &mut Bencher) {
    let a = Array::<f32, _>::zeros((256, 256));
    let chunksz = (2, 2);
    let mut sum = Array::<f32, _>::zeros(a.exact_chunks(chunksz).raw_dim());
    bench.iter(|| {
        let (m, n) = a.dim();
        for i in 0..m {
            for j in 0..n {
                sum[[i / 2, j / 2]] += a[[i, j]];
            }
        }
    });
}

#[bench]
fn chunk2x2_sum_uget1(bench: &mut Bencher) {
    let a = Array::<f32, _>::zeros((256, 256));
    let chunksz = (2, 2);
    let mut sum = Array::<f32, _>::zeros(a.exact_chunks(chunksz).raw_dim());
    bench.iter(|| {
        let (m, n) = a.dim();
        for i in 0..m {
            for j in 0..n {
                unsafe {
                    *sum.uget_mut([i / 2, j / 2]) += *a.uget([i, j]);
                }
            }
        }
    });
}

#[bench]
#[allow(clippy::identity_op)]
fn chunk2x2_sum_get2(bench: &mut Bencher) {
    let a = Array::<f32, _>::zeros((256, 256));
    let chunksz = (2, 2);
    let mut sum = Array::<f32, _>::zeros(a.exact_chunks(chunksz).raw_dim());
    bench.iter(|| {
        let (m, n) = sum.dim();
        for i in 0..m {
            for j in 0..n {
                sum[[i, j]] += a[[i * 2 + 0, j * 2 + 0]];
                sum[[i, j]] += a[[i * 2 + 0, j * 2 + 1]];
                sum[[i, j]] += a[[i * 2 + 1, j * 2 + 1]];
                sum[[i, j]] += a[[i * 2 + 1, j * 2 + 0]];
            }
        }
    });
}