Crate quickersort [−] [src]
This crate implements the introsort sorting algorithm.
Interface
The interface is similar to the standard library sort
and sort_by
functions.
An example:
extern crate quickersort; fn main() { let mut ss = vec!["Introsort", "or", "introspective", "sort", "is", "a", "hybrid", "sorting", "algorithm", "that", "provides", "both", "fast", "average", "performance", "and", "(asymptotically)", "optimal", "worst-case", "performance"]; quickersort::sort(&mut ss[..]); println!("alphabetically"); for s in ss.iter() { println!("\t{}", s); } quickersort::sort_by(&mut ss[..], &|a, b| a.len().cmp(&b.len())); println!("\nby length"); for s in ss.iter() { println!("\t{}", s); } }
Unlike the standard library sort function, introsort is not a stable sort.
Details
At its heart, it is a dual-pivot quicksort. For partition with many equal elements, it will instead use a single-pivot quicksort optimized for this case. It detects excessive recursion during quicksort and switches to heapsort if need be, guaranteeing O(n log(n)) runtime on all inputs. For small partitions it uses insertion sort instead of quicksort.
Unlike the std
sort, it does not allocate.
Performance
It is quite fast, outperforming the standard sort on all data sets I have tried. The performance difference varies depending on the characteristics of the data. On large, completely random arrays, introsort is only 5-10% faster than the standard sort. However, introsort's performance is greatly improved if the data has few unique values or is (partially) sorted (including reversed data). For sorted data, introsort is ~4-5 times faster, and for data with few unique values it can be more than 20 times faster.
Floating point
The crate, if built with the "float" feature (which is the default), also
includes a sort_floats
function. Floating point numbers are not Ord
,
only PartialOrd
, so sort
can not be used on them. The ordering used by
sort_floats
is
| -inf | < 0 | -0 | +0 | > 0 | +inf | NaN |
sort_floats
is much more efficient than passing a comparator function
implementing this ordering to sort_by
.
Functions
heapsort |
Perform a heapsort using a comparison function. |
insertion_sort |
Perform an insertion sort using a comparison function. |
sort |
Sort using the default comparison function. |
sort_by |
Sort using a comparison function. |
sort_by_key |
Sort using a conversion function. |
sort_floats |
Sorts floating point number. The ordering used is | -inf | < 0 | -0 | +0 | > 0 | +inf | NaN | |