transpose/lib.rs
1//! Utility for transposing multi-dimensional data stored as a flat slice
2//!
3//! This library treats Rust slices as flattened row-major 2D arrays, and provides functions to transpose these 2D arrays, so that the row data becomes the column data, and vice versa.
4//! ```
5//! // Create a 2D array in row-major order: the rows of our 2D array are contiguous,
6//! // and the columns are strided
7//! let input_array = vec![ 1, 2, 3,
8//! 4, 5, 6];
9//!
10//! // Treat our 6-element array as a 2D 3x2 array, and transpose it to a 2x3 array
11//! let mut output_array = vec![0; 6];
12//! transpose::transpose(&input_array, &mut output_array, 3, 2);
13//!
14//! // The rows have become the columns, and the columns have become the rows
15//! let expected_array = vec![ 1, 4,
16//! 2, 5,
17//! 3, 6];
18//! assert_eq!(output_array, expected_array);
19//!
20//! // If we transpose our data again, we should get our original data back.
21//! let mut final_array = vec![0; 6];
22//! transpose::transpose(&output_array, &mut final_array, 2, 3);
23//! assert_eq!(final_array, input_array);
24//! ```
25//!
26//! This library supports both in-place and out-of-place transposes. The out-of-place
27//! transpose is much, much faster than the in-place transpose -- the in-place transpose should
28//! only be used in situations where the system doesn't have enough memory to do an out-of-place transpose.
29//!
30//! The out-of-place transpose uses one out of three different algorithms depending on the length of the input array.
31//!
32//! - Small: simple iteration over the array.
33//! - Medium: divide the array into tiles of fixed size, and process each tile separately.
34//! - Large: recursively split the array into smaller parts until each part is of a good size for the tiling algorithm, and then transpose each part.
35
36#![no_std]
37
38extern crate num_integer;
39extern crate strength_reduce;
40
41mod in_place;
42mod out_of_place;
43pub use in_place::transpose_inplace;
44pub use out_of_place::transpose;