## Abstract

A non-comparison-based sort that sorts an array in *O(k n)* work
and *O(k log(n))* span, where *k* is the number of bits in each element.

Generally, this is the sorting function we recommend for Futhark
programs, but be careful about negative integers (use
`radix_sort_int`

) and floating-point numbers (use
`radix_sort_float`

). If you need a comparison-based sort,
consider `merge_sort`

.

## Synopsis

val radix_sort | [n] t : | (num_bits: i32) -> (get_bit: i32 -> t -> i32) -> (xs: [n]t) -> [n]t |

val with_indices | [n] a : | (xs: [n]a) -> [n](a, i32) |

val radix_sort_by_key | [n] t k : | (key: t -> k) -> (num_bits: i32) -> (get_bit: i32 -> k -> i32) -> (xs: [n]t) -> [n]t |

val radix_sort_int | [n] t : | (num_bits: i32) -> (get_bit: i32 -> t -> i32) -> (xs: [n]t) -> [n]t |

val radix_sort_int_by_key | [n] t k : | (key: t -> k) -> (num_bits: i32) -> (get_bit: i32 -> k -> i32) -> (xs: [n]t) -> [n]t |

val radix_sort_float | [n] t : | (num_bits: i32) -> (get_bit: i32 -> t -> i32) -> (xs: [n]t) -> [n]t |

val radix_sort_float_by_key | [n] t k : | (key: t -> k) -> (num_bits: i32) -> (get_bit: i32 -> k -> i32) -> (xs: [n]t) -> [n]t |

## Description

- ↑val radix_sort [n] t: (num_bits: i32) -> (get_bit: i32 -> t -> i32) -> (xs: [n]t) -> [n]t
The

`num_bits`

and`get_bit`

arguments can be taken from one of the numeric modules of module type`integral`

or`float`

, such as`i32`

or`f64`

. However, if you know that the input array only uses lower-order bits (say, if all integers are less than 100), then you can profitably pass a smaller`num_bits`

value to reduce the number of sequential iterations.**Warning:**while radix sort can be used with numbers, the bitwise representation of of both integers and floats means that negative numbers are sorted as*greater*than non-negative. Negative floats are further sorted according to their absolute value. For example, radix-sorting`[-2.0, -1.0, 0.0, 1.0, 2.0]`

will produce`[0.0, 1.0, 2.0, -1.0, -2.0]`

. Use`radix_sort_int`

and`radix_sort_float`

in the (likely) cases that this is not what you want.- ↑val with_indices [n] a: (xs: [n]a) -> [n](a, i32)
- ↑val radix_sort_by_key [n] t k: (key: t -> k) -> (num_bits: i32) -> (get_bit: i32 -> k -> i32) -> (xs: [n]t) -> [n]t
Like

`radix_sort`

, but sort based on key function.- ↑val radix_sort_int [n] t: (num_bits: i32) -> (get_bit: i32 -> t -> i32) -> (xs: [n]t) -> [n]t
A thin wrapper around

`radix_sort`

that ensures negative integers are sorted as expected. Simply pass the usual`num_bits`

and`get_bit`

definitions from e.g.`i32`

.- ↑val radix_sort_int_by_key [n] t k: (key: t -> k) -> (num_bits: i32) -> (get_bit: i32 -> k -> i32) -> (xs: [n]t) -> [n]t
Like

`radix_sort_int`

, but sort based on key function.- ↑val radix_sort_float [n] t: (num_bits: i32) -> (get_bit: i32 -> t -> i32) -> (xs: [n]t) -> [n]t
A thin wrapper around

`radix_sort`

that ensures floats are sorted as expected. Simply pass the usual`num_bits`

and`get_bit`

definitions from`f32`

and`f64`

.- ↑val radix_sort_float_by_key [n] t k: (key: t -> k) -> (num_bits: i32) -> (get_bit: i32 -> k -> i32) -> (xs: [n]t) -> [n]t
Like

`radix_sort_float`

, but sort based on key function.

## See Also

`merge_sort`