integer_sort.hpp
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//Templated Spreadsort-based implementation of integer_sort
// Copyright Steven J. Ross 2001 - 2014.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// See http://www.boost.org/libs/sort/ for library home page.
/*
Some improvements suggested by:
Phil Endecott and Frank Gennari
Doxygen comments by Paul A. Bristow Jan 2015
*/
#ifndef BOOST_INTEGER_SORT_HPP
#define BOOST_INTEGER_SORT_HPP
#include <algorithm>
#include <vector>
#include <cstring>
#include <limits>
#include <boost/static_assert.hpp>
#include <boost/sort/spreadsort/detail/constants.hpp>
#include <boost/sort/spreadsort/detail/integer_sort.hpp>
namespace boost {
namespace sort {
//Top-level sorting call for integers.
/*! \brief Integer sort algorithm using random access iterators.
(All variants fall back to @c std::sort if the data size is too small, < @c detail::min_sort_size).
\details @c integer_sort is a fast templated in-place hybrid radix/comparison algorithm,
which in testing tends to be roughly 50% to 2X faster than @c std::sort for large tests (>=100kB).\n
Worst-case performance is <em> O(N * (lg(range)/s + s)) </em>,
so @c integer_sort is asymptotically faster
than pure comparison-based algorithms. @c s is @c max_splits, which defaults to 11,
so its worst-case with default settings for 32-bit integers is
<em> O(N * ((32/11) </em> slow radix-based iterations fast comparison-based iterations).\n\n
Some performance plots of runtime vs. n and log(range) are provided:\n
<a href="../../doc/graph/windows_integer_sort.htm"> windows_integer_sort</a>
\n
<a href="../../doc/graph/osx_integer_sort.htm"> osx_integer_sort</a>
\tparam RandomAccessIter <a href="http://www.cplusplus.com/reference/iterator/RandomAccessIterator/">Random access iterator</a>
\param[in] first Iterator pointer to first element.
\param[in] last Iterator pointing to one beyond the end of data.
\pre [@c first, @c last) is a valid range.
\pre @c RandomAccessIter @c value_type is mutable.
\pre @c RandomAccessIter @c value_type is <a href="http://en.cppreference.com/w/cpp/concept/LessThanComparable">LessThanComparable</a>
\pre @c RandomAccessIter @c value_type supports the @c operator>>,
which returns an integer-type right-shifted a specified number of bits.
\post The elements in the range [@c first, @c last) are sorted in ascending order.
\throws 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.
\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 Invalid arguments cause undefined behaviour.
\note @c spreadsort function provides a wrapper that calls the fastest sorting algorithm available for a data type,
enabling faster generic-programming.
\remark The lesser of <em> O(N*log(N)) </em> comparisons and <em> O(N*log(K/S + S)) </em>operations worst-case, where:
\remark * N is @c last - @c first,
\remark * K is the log of the range in bits (32 for 32-bit integers using their full range),
\remark * S is a constant called max_splits, defaulting to 11 (except for strings where it is the log of the character size).
*/
template <class RandomAccessIter>
inline void integer_sort(RandomAccessIter first, RandomAccessIter last)
{
// Don't sort if it's too small to optimize.
if (last - first < detail::min_sort_size)
std::sort(first, last);
else
detail::integer_sort(first, last, *first >> 0);
}
/*! \brief Integer sort algorithm using random access iterators with both right-shift and user-defined comparison operator.
(All variants fall back to @c std::sort if the data size is too small, < @c detail::min_sort_size).
\details @c integer_sort is a fast templated in-place hybrid radix/comparison algorithm,
which in testing tends to be roughly 50% to 2X faster than @c std::sort for large tests (>=100kB).\n
Worst-case performance is <em> O(N * (lg(range)/s + s)) </em>,
so @c integer_sort is asymptotically faster
than pure comparison-based algorithms. @c s is @c max_splits, which defaults to 11,
so its worst-case with default settings for 32-bit integers is
<em> O(N * ((32/11) </em> slow radix-based iterations fast comparison-based iterations).\n\n
Some performance plots of runtime vs. n and log(range) are provided:\n
<a href="../../doc/graph/windows_integer_sort.htm"> windows_integer_sort</a>
\n
<a href="../../doc/graph/osx_integer_sort.htm"> osx_integer_sort</a>
\tparam RandomAccessIter <a href="http://www.cplusplus.com/reference/iterator/RandomAccessIterator/">Random access iterator</a>
\tparam Right_shift functor for right-shift by parameter @c shift bits.
\tparam Comp To provide @c operator< for user-defined comparison.
\param[in] first Iterator pointer to first element.
\param[in] last Iterator pointing to one beyond the end of data.
\param[in] shift Number of bits to right-shift (using functor).
\param[in] comp comparison functor.
\pre [@c first, @c last) is a valid range.
\pre @c RandomAccessIter @c value_type is mutable.
\pre @c RandomAccessIter @c value_type is <a href="http://en.cppreference.com/w/cpp/concept/LessThanComparable">LessThanComparable</a>
\pre @c RandomAccessIter @c value_type supports the @c operator>>,
which returns an integer-type right-shifted a specified number of bits.
\post The elements in the range [@c first, @c last) are sorted in ascending order.
\return @c void.
\throws 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.
\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 Invalid arguments cause undefined behaviour.
\note @c spreadsort function provides a wrapper that calls the fastest sorting algorithm available for a data type,
enabling faster generic-programming.
\remark The lesser of <em> O(N*log(N)) </em> comparisons and <em> O(N*log(K/S + S)) </em>operations worst-case, where:
\remark * N is @c last - @c first,
\remark * K is the log of the range in bits (32 for 32-bit integers using their full range),
\remark * S is a constant called max_splits, defaulting to 11 (except for strings where it is the log of the character size).
*/
template <class RandomAccessIter, class Right_shift, class Compare>
inline void integer_sort(RandomAccessIter first, RandomAccessIter last,
Right_shift shift, Compare comp) {
if (last - first < detail::min_sort_size)
std::sort(first, last, comp);
else
detail::integer_sort(first, last, shift(*first, 0), shift, comp);
}
/*! \brief Integer sort algorithm using random access iterators with just right-shift functor.
(All variants fall back to @c std::sort if the data size is too small, < @c detail::min_sort_size).
\details @c integer_sort is a fast templated in-place hybrid radix/comparison algorithm,
which in testing tends to be roughly 50% to 2X faster than @c std::sort for large tests (>=100kB).\n
\par Performance:
Worst-case performance is <em> O(N * (lg(range)/s + s)) </em>,
so @c integer_sort is asymptotically faster
than pure comparison-based algorithms. @c s is @c max_splits, which defaults to 11,
so its worst-case with default settings for 32-bit integers is
<em> O(N * ((32/11) </em> slow radix-based iterations fast comparison-based iterations).\n\n
Some performance plots of runtime vs. n and log(range) are provided:\n
* <a href="../../doc/graph/windows_integer_sort.htm"> windows_integer_sort</a>\n
* <a href="../../doc/graph/osx_integer_sort.htm"> osx_integer_sort</a>
\tparam RandomAccessIter <a href="http://www.cplusplus.com/reference/iterator/RandomAccessIterator/">Random access iterator</a>
\tparam Right_shift functor for right-shift by parameter @c shift bits.
\param[in] first Iterator pointer to first element.
\param[in] last Iterator pointing to one beyond the end of data.
\param[in] shift Number of bits to right-shift (using functor).
\pre [@c first, @c last) is a valid range.
\pre @c RandomAccessIter @c value_type is mutable.
\pre @c RandomAccessIter @c value_type is <a href="http://en.cppreference.com/w/cpp/concept/LessThanComparable">LessThanComparable</a>
\pre @c RandomAccessIter @c value_type supports the @c operator>>,
which returns an integer-type right-shifted a specified number of bits.
\post The elements in the range [@c first, @c last) are sorted in ascending order.
\throws 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.
\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 Invalid arguments cause undefined behaviour.
\note @c spreadsort function provides a wrapper that calls the fastest sorting algorithm available for a data type,
enabling faster generic-programming.
\remark The lesser of <em> O(N*log(N)) </em> comparisons and <em> O(N*log(K/S + S)) </em>operations worst-case, where:
\remark * N is @c last - @c first,
\remark * K is the log of the range in bits (32 for 32-bit integers using their full range),
\remark * S is a constant called max_splits, defaulting to 11 (except for strings where it is the log of the character size).
*/
template <class RandomAccessIter, class Right_shift>
inline void integer_sort(RandomAccessIter first, RandomAccessIter last,
Right_shift shift) {
if (last - first < detail::min_sort_size)
std::sort(first, last);
else
detail::integer_sort(first, last, shift(*first, 0), shift);
}
}
}
#endif
boost::sort::integer_sort
void integer_sort(RandomAccessIter first, RandomAccessIter last)
Integer sort algorithm using random access iterators. (All variants fall back to std::sort if the dat...
Definition: integer_sort.hpp:75
boost
Definition: float_sort.hpp:27
boost::sort::integer_sort
void integer_sort(RandomAccessIter first, RandomAccessIter last, Right_shift shift)
Integer sort algorithm using random access iterators with just right-shift functor. (All variants fall back to std::sort if the data size is too small, < detail::min_sort_size).
Definition: integer_sort.hpp:186