Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for a snapshot of the develop branch, built from commit 09d2b4ed73.

Function template integer_sort

boost::sort::spreadsort::integer_sort — Integer sort algorithm using random access iterators. (All variants fall back to boost::sort::pdqsort if the data size is too small, < detail::min_sort_size).


// In header: <boost/sort/spreadsort/integer_sort.hpp>

template<typename RandomAccessIter> 
  void integer_sort(RandomAccessIter first, RandomAccessIter last);


integer_sort is a fast templated in-place hybrid radix/comparison algorithm, which in testing tends to be roughly 50% to 2X faster than std::sort for large tests (>=100kB).
Worst-case performance is O(N * (lg(range)/s + s)) , so integer_sort is asymptotically faster than pure comparison-based algorithms. s is max_splits, which defaults to 11, so its worst-case with default settings for 32-bit integers is O(N * ((32/11) slow radix-based iterations fast comparison-based iterations).

Some performance plots of runtime vs. n and log(range) are provided:

[Warning] Warning

Throwing an exception may cause data loss. This will also throw if a small vector resize throws, in which case there will be no data loss.

[Warning] Warning

Invalid arguments cause undefined behaviour.

[Note] Note

spreadsort function provides a wrapper that calls the fastest sorting algorithm available for a data type, enabling faster generic-programming.

The lesser of O(N*log(N)) comparisons and O(N*log(K/S + S)) operations worst-case, where:

* N is last - first,

* K is the log of the range in bits (32 for 32-bit integers using their full range),

* S is a constant called max_splits, defaulting to 11 (except for strings where it is the log of the character size).



Iterator pointer to first element.


Iterator pointing to one beyond the end of data.


[first, last) is a valid range.


RandomAccessIter value_type is mutable.


RandomAccessIter value_type is LessThanComparable


RandomAccessIter value_type supports the operator>>, which returns an integer-type right-shifted a specified number of bits.


The elements in the range [first, last) are sorted in ascending order.


std::exception Propagates exceptions if any of the element comparisons, the element swaps (or moves), the right shift, subtraction of right-shifted elements, functors, or any operations on iterators throw.