use criterion::{black_box, BenchmarkId};
use criterion::{criterion_group, criterion_main, BatchSize, Criterion};

use lace_stats::seq::SobolSeq;

fn u2s_alloc(mut uvec: Vec<f64>) -> Vec<f64> {
    let n = uvec.len();
    uvec[0] = 0.0;
    uvec[n - 1] = 1.0;
    uvec.sort_by(|a, b| a.partial_cmp(b).unwrap());

    // turn off mutability
    let uvec = uvec;

    let mut z = Vec::with_capacity(n);
    for i in 1..n {
        z.push(uvec[i] - uvec[i - 1]);
    }

    z
}

fn u2s_update(mut uvec: Vec<f64>) -> Vec<f64> {
    let n = uvec.len();
    uvec[n - 1] = 1.0;
    uvec.sort_by(|a, b| a.partial_cmp(b).unwrap());

    let mut um = uvec[0];

    #[allow(clippy::needless_range_loop)]
    for i in 1..n {
        let diff = uvec[i] - um;
        um = uvec[i];
        uvec[i] = diff;
    }

    uvec
}

fn bench_compare(c: &mut Criterion) {
    let mut group = c.benchmark_group("Sobol to 3-simplex over NDims");

    let parameters = vec![3_usize, 5_usize, 10_usize, 20_usize, 30_usize];

    for dims_param in parameters {
        let new_alloc_id = BenchmarkId::new("new alloc", dims_param);
        group.bench_with_input(new_alloc_id, &dims_param, |b, &dims| {
            let mut sobol = SobolSeq::new(dims + 1);
            b.iter_batched(
                || sobol.next().unwrap(),
                |x| black_box(u2s_alloc(x)),
                BatchSize::SmallInput,
            )
        });

        let update_inplace_id = BenchmarkId::new("update inplace", dims_param);
        group.bench_with_input(update_inplace_id, &dims_param, |b, &dims| {
            let mut sobol = SobolSeq::new(dims);
            b.iter_batched(
                || sobol.next().unwrap(),
                |x| black_box(u2s_update(x)),
                BatchSize::SmallInput,
            )
        });
    }
}

criterion_group!(simplex_benches, bench_compare,);
criterion_main!(simplex_benches);