p3_matrix/
util.rs

1use p3_maybe_rayon::prelude::*;
2use p3_util::{log2_strict_usize, reverse_bits_len};
3
4use crate::dense::RowMajorMatrix;
5use crate::Matrix;
6
7pub fn reverse_matrix_index_bits<F: Clone + Send + Sync>(mat: &mut RowMajorMatrix<F>) {
8    let w = mat.width();
9    let h = mat.height();
10    let log_h = log2_strict_usize(h);
11    let values = mat.values.as_mut_ptr() as usize;
12
13    (0..h).into_par_iter().for_each(|i| {
14        let values = values as *mut F;
15        let j = reverse_bits_len(i, log_h);
16        if i < j {
17            unsafe { swap_rows_raw(values, w, i, j) };
18        }
19    });
20}
21
22/// Assumes `i < j`.
23pub fn swap_rows<F: Clone + Send + Sync>(mat: &mut RowMajorMatrix<F>, i: usize, j: usize) {
24    let w = mat.width();
25    let (upper, lower) = mat.values.split_at_mut(j * w);
26    let row_i = &mut upper[i * w..(i + 1) * w];
27    let row_j = &mut lower[..w];
28    row_i.swap_with_slice(row_j);
29}
30
31/// Assumes `i < j`.
32///
33/// SAFETY: The caller must ensure `i < j < h`, where `h` is the height of the matrix.
34pub(crate) unsafe fn swap_rows_raw<F>(mat: *mut F, w: usize, i: usize, j: usize) {
35    let row_i = core::slice::from_raw_parts_mut(mat.add(i * w), w);
36    let row_j = core::slice::from_raw_parts_mut(mat.add(j * w), w);
37    row_i.swap_with_slice(row_j);
38}