ndarray-rand 0.16.0

Constructors for randomized arrays. `rand` integration for `ndarray`.
Documentation 
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use ndarray::{Array, Array2, ArrayView1, Axis};
#[cfg(feature = "quickcheck")]
use ndarray_rand::rand::{distr::Distribution, rng};

use ndarray::ShapeBuilder;
use ndarray_rand::rand_distr::Uniform;
use ndarray_rand::{RandomExt, SamplingStrategy};
use quickcheck::{quickcheck, TestResult};

#[test]
fn test_dim()
{
    let (mm, nn) = (5, 5);
    for m in 0..mm {
        for n in 0..nn {
            let a = Array::random((m, n), Uniform::new(0., 2.).unwrap());
            assert_eq!(a.shape(), &[m, n]);
            assert!(a.iter().all(|x| *x < 2.));
            assert!(a.iter().all(|x| *x >= 0.));
            assert!(a.is_standard_layout());
        }
    }
}

#[test]
fn test_dim_f()
{
    let (mm, nn) = (5, 5);
    for m in 0..mm {
        for n in 0..nn {
            let a = Array::random((m, n).f(), Uniform::new(0., 2.).unwrap());
            assert_eq!(a.shape(), &[m, n]);
            assert!(a.iter().all(|x| *x < 2.));
            assert!(a.iter().all(|x| *x >= 0.));
            assert!(a.t().is_standard_layout());
        }
    }
}

#[test]
fn sample_axis_on_view()
{
    let m = 5;
    let a = Array::random((m, 4), Uniform::new(0., 2.).unwrap());
    let _samples = a
        .view()
        .sample_axis(Axis(0), m, SamplingStrategy::WithoutReplacement);
}

#[test]
#[should_panic]
fn oversampling_without_replacement_should_panic()
{
    let m = 5;
    let a = Array::random((m, 4), Uniform::new(0., 2.).unwrap());
    let _samples = a.sample_axis(Axis(0), m + 1, SamplingStrategy::WithoutReplacement);
}

quickcheck! {
    #[cfg_attr(miri, ignore)] // Takes an insufferably long time
    fn oversampling_with_replacement_is_fine(m: u8, n: u8) -> TestResult {
        let (m, n) = (m as usize, n as usize);
        let a = Array::random((m, n), Uniform::new(0., 2.).unwrap());
        // Higher than the length of both axes
        let n_samples = m + n + 1;

        // We don't want to deal with sampling from 0-length axes in this test
        if m != 0 {
            if !sampling_works(&a, SamplingStrategy::WithReplacement, Axis(0), n_samples) {
                return TestResult::failed();
            }
        } else {
            return TestResult::discard();
        }

        // We don't want to deal with sampling from 0-length axes in this test
        if n != 0 {
            if !sampling_works(&a, SamplingStrategy::WithReplacement, Axis(1), n_samples) {
                return TestResult::failed();
            }
        } else {
            return TestResult::discard();
        }
        TestResult::passed()
    }
}

#[cfg(feature = "quickcheck")]
quickcheck! {
    #[cfg_attr(miri, ignore)] // This takes *forever* with Miri
    fn sampling_behaves_as_expected(m: u8, n: u8, strategy: SamplingStrategy) -> TestResult {
        let (m, n) = (m as usize, n as usize);
        let a = Array::random((m, n), Uniform::new(0., 2.).unwrap());
        let mut rng = &mut rng();

        // We don't want to deal with sampling from 0-length axes in this test
        if m != 0 {
            let n_row_samples = Uniform::new(1, m+1).unwrap().sample(&mut rng);
            if !sampling_works(&a, strategy.clone(), Axis(0), n_row_samples) {
                return TestResult::failed();
            }
        } else {
            return TestResult::discard();
        }

        // We don't want to deal with sampling from 0-length axes in this test
        if n != 0 {
            let n_col_samples = Uniform::new(1, n+1).unwrap().sample(&mut rng);
            if !sampling_works(&a, strategy, Axis(1), n_col_samples) {
                return TestResult::failed();
            }
        } else {
            return TestResult::discard();
        }

        TestResult::passed()
    }
}

fn sampling_works(a: &Array2<f64>, strategy: SamplingStrategy, axis: Axis, n_samples: usize) -> bool
{
    let samples = a.sample_axis(axis, n_samples, strategy);
    samples
        .axis_iter(axis)
        .all(|lane| is_subset(a, &lane, axis))
}

// Check if, when sliced along `axis`, there is at least one lane in `a` equal to `b`
fn is_subset(a: &Array2<f64>, b: &ArrayView1<f64>, axis: Axis) -> bool
{
    a.axis_iter(axis).any(|lane| &lane == b)
}

#[test]
#[should_panic]
fn sampling_without_replacement_from_a_zero_length_axis_should_panic()
{
    let n = 5;
    let a = Array::random((0, n), Uniform::new(0., 2.).unwrap());
    let _samples = a.sample_axis(Axis(0), 1, SamplingStrategy::WithoutReplacement);
}

#[test]
#[should_panic]
fn sampling_with_replacement_from_a_zero_length_axis_should_panic()
{
    let n = 5;
    let a = Array::random((0, n), Uniform::new(0., 2.).unwrap());
    let _samples = a.sample_axis(Axis(0), 1, SamplingStrategy::WithReplacement);
}