Integer sort algorithm using random access iterators. All variants fall back to std::sort if the data is too small.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:
windows_integer_sort
osx_integer_sort

Template Parameters

RandomAccessIter Random access iterator

Parameters

[in]	first	Iterator pointer to first element.
[in]	last	Iterator pointing to one beyond the end of data.

Precondition: [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.

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

Returns: void.

Exceptions

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.

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.; Invalid arguments cause undefined behaviour.

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

Remarks: 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).