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stl_algo.h (__heap_select, [...]): New. 

2006-08-28  Roger Sayle  <roger@eyesopen.com>
	    Paolo Carlini  <pcarlini@suse.de>

	* include/bits/stl_algo.h (__heap_select, __introselect): New.
	(nth_element): New implementation.
	(partial_copy): Use __heap_select.
	* testsuite/performance/25_algorithms/nth_element_worst_case.cc: New.

Co-Authored-By: Paolo Carlini <pcarlini@suse.de>

From-SVN: r116520
This commit is contained in:
Roger Sayle 2006-08-28 18:32:35 +00:00 committed by Paolo Carlini
parent 03a569a38c
commit 8c093661a3
3 changed files with 207 additions and 56 deletions
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8
libstdc++-v3/ChangeLog
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@ -1,3 +1,11 @@
2006-08-28 Roger Sayle <roger@eyesopen.com>
Paolo Carlini <pcarlini@suse.de>
* include/bits/stl_algo.h (__heap_select, __introselect): New.
(nth_element): New implementation.
(partial_copy): Use __heap_select.
* testsuite/performance/25_algorithms/nth_element_worst_case.cc: New.
2006-08-28 Paolo Carlini <pcarlini@suse.de>
Roger Sayle <roger@eyesopen.com>

193
libstdc++-v3/include/bits/stl_algo.h
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@ -2464,7 +2464,47 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
/**
* @if maint
* This is a helper function for the sort routine.
* This is a helper function for the sort routines.
* @endif
*/
template<typename _RandomAccessIterator>
void
__heap_select(_RandomAccessIterator __first,
_RandomAccessIterator __middle,
_RandomAccessIterator __last)
{
typedef typename iterator_traits<_RandomAccessIterator>::value_type
_ValueType;
std::make_heap(__first, __middle);
for (_RandomAccessIterator __i = __middle; __i < __last; ++__i)
if (*__i < *__first)
std::__pop_heap(__first, __middle, __i, _ValueType(*__i));
}
/**
* @if maint
* This is a helper function for the sort routines.
* @endif
*/
template<typename _RandomAccessIterator, typename _Compare>
void
__heap_select(_RandomAccessIterator __first,
_RandomAccessIterator __middle,
_RandomAccessIterator __last, _Compare __comp)
{
typedef typename iterator_traits<_RandomAccessIterator>::value_type
_ValueType;
std::make_heap(__first, __middle, __comp);
for (_RandomAccessIterator __i = __middle; __i < __last; ++__i)
if (__comp(*__i, *__first))
std::__pop_heap(__first, __middle, __i, _ValueType(*__i), __comp);
}
/**
* @if maint
* This is a helper function for the sort routines.
* @endif
*/
template<typename _Size>
@ -2493,7 +2533,7 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
* the range @p [middle,last) then @p *j<*i and @p *k<*i are both false.
*/
template<typename _RandomAccessIterator>
void
inline void
partial_sort(_RandomAccessIterator __first,
_RandomAccessIterator __middle,
_RandomAccessIterator __last)
@ -2508,10 +2548,7 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
__glibcxx_requires_valid_range(__first, __middle);
__glibcxx_requires_valid_range(__middle, __last);
std::make_heap(__first, __middle);
for (_RandomAccessIterator __i = __middle; __i < __last; ++__i)
if (*__i < *__first)
std::__pop_heap(__first, __middle, __i, _ValueType(*__i));
std::__heap_select(__first, __middle, __last);
std::sort_heap(__first, __middle);
}
@ -2534,7 +2571,7 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
* are both false.
*/
template<typename _RandomAccessIterator, typename _Compare>
void
inline void
partial_sort(_RandomAccessIterator __first,
_RandomAccessIterator __middle,
_RandomAccessIterator __last,
@ -2551,10 +2588,7 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
__glibcxx_requires_valid_range(__first, __middle);
__glibcxx_requires_valid_range(__middle, __last);
std::make_heap(__first, __middle, __comp);
for (_RandomAccessIterator __i = __middle; __i < __last; ++__i)
if (__comp(*__i, *__first))
std::__pop_heap(__first, __middle, __i, _ValueType(*__i), __comp);
std::__heap_select(__first, __middle, __last, __comp);
std::sort_heap(__first, __middle, __comp);
}
@ -2792,7 +2826,8 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
if (__first != __last)
{
std::__introsort_loop(__first, __last, __lg(__last - __first) * 2);
std::__introsort_loop(__first, __last,
std::__lg(__last - __first) * 2);
std::__final_insertion_sort(__first, __last);
}
}
@ -2828,8 +2863,8 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
if (__first != __last)
{
std::__introsort_loop(__first, __last, __lg(__last - __first) * 2,
__comp);
std::__introsort_loop(__first, __last,
std::__lg(__last - __first) * 2, __comp);
std::__final_insertion_sort(__first, __last, __comp);
}
}
@ -3904,6 +3939,79 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
_DistanceType(__buf.size()), __comp);
}
template<typename _RandomAccessIterator, typename _Size>
void
__introselect(_RandomAccessIterator __first, _RandomAccessIterator __nth,
_RandomAccessIterator __last, _Size __depth_limit)
{
typedef typename iterator_traits<_RandomAccessIterator>::value_type
_ValueType;
while (__last - __first > 3)
{
if (__depth_limit == 0)
{
std::__heap_select(__first, __nth + 1, __last);
// Place the nth largest element in its final position.
std::iter_swap(__first, __nth);
return;
}
--__depth_limit;
_RandomAccessIterator __cut =
std::__unguarded_partition(__first, __last,
_ValueType(std::__median(*__first,
*(__first
+ (__last
- __first)
/ 2),
*(__last
- 1))));
if (__cut <= __nth)
__first = __cut;
else
__last = __cut;
}
std::__insertion_sort(__first, __last);
}
template<typename _RandomAccessIterator, typename _Size, typename _Compare>
void
__introselect(_RandomAccessIterator __first, _RandomAccessIterator __nth,
_RandomAccessIterator __last, _Size __depth_limit,
_Compare __comp)
{
typedef typename iterator_traits<_RandomAccessIterator>::value_type
_ValueType;
while (__last - __first > 3)
{
if (__depth_limit == 0)
{
std::__heap_select(__first, __nth + 1, __last, __comp);
// Place the nth largest element in its final position.
std::iter_swap(__first, __nth);
return;
}
--__depth_limit;
_RandomAccessIterator __cut =
std::__unguarded_partition(__first, __last,
_ValueType(std::__median(*__first,
*(__first
+ (__last
- __first)
/ 2),
*(__last - 1),
__comp)),
__comp);
if (__cut <= __nth)
__first = __cut;
else
__last = __cut;
}
std::__insertion_sort(__first, __last, __comp);
}
/**
* @brief Sort a sequence just enough to find a particular position.
* @param first An iterator.
@ -3920,9 +4028,8 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
* holds that @p *j<*i is false.
*/
template<typename _RandomAccessIterator>
void
nth_element(_RandomAccessIterator __first,
_RandomAccessIterator __nth,
inline void
nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth,
_RandomAccessIterator __last)
{
typedef typename iterator_traits<_RandomAccessIterator>::value_type
@ -3935,23 +4042,11 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
__glibcxx_requires_valid_range(__first, __nth);
__glibcxx_requires_valid_range(__nth, __last);
while (__last - __first > 3)
{
_RandomAccessIterator __cut =
std::__unguarded_partition(__first, __last,
_ValueType(std::__median(*__first,
*(__first
+ (__last
- __first)
/ 2),
*(__last
- 1))));
if (__cut <= __nth)
__first = __cut;
else
__last = __cut;
}
std::__insertion_sort(__first, __last);
if (__first == __last || __nth == __last)
return;
std::__introselect(__first, __nth, __last,
std::__lg(__last - __first) * 2);
}
/**
@ -3971,11 +4066,9 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
* holds that @p comp(*j,*i) is false.
*/
template<typename _RandomAccessIterator, typename _Compare>
void
nth_element(_RandomAccessIterator __first,
_RandomAccessIterator __nth,
_RandomAccessIterator __last,
_Compare __comp)
inline void
nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth,
_RandomAccessIterator __last, _Compare __comp)
{
typedef typename iterator_traits<_RandomAccessIterator>::value_type
_ValueType;
@ -3988,23 +4081,11 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
__glibcxx_requires_valid_range(__first, __nth);
__glibcxx_requires_valid_range(__nth, __last);
while (__last - __first > 3)
{
_RandomAccessIterator __cut =
std::__unguarded_partition(__first, __last,
_ValueType(std::__median(*__first,
*(__first
+ (__last
- __first)
/ 2),
*(__last - 1),
__comp)), __comp);
if (__cut <= __nth)
__first = __cut;
else
__last = __cut;
}
std::__insertion_sort(__first, __last, __comp);
if (__first == __last || __nth == __last)
return;
std::__introselect(__first, __nth, __last,
std::__lg(__last - __first) * 2, __comp);
}
/**

62
libstdc++-v3/testsuite/performance/25_algorithms/nth_element_worst_case.cc Normal file
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@ -0,0 +1,62 @@
// Copyright (C) 2006 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
#include <vector>
#include <algorithm>
#include <testsuite_performance.h>
int main()
{
using namespace __gnu_test;
time_counter time;
resource_counter resource;
const int max_size = 8192;
std::vector<int> v[max_size];
for (int i = 0; i < max_size; ++i)
{
for (int j = 0; j < i; j += 4)
{
v[i].push_back(j / 2);
v[i].push_back((i - 2) - (j / 2));
}
for (int j = 1; j < i; j += 2)
v[i].push_back(j);
}
start_counters(time, resource);
for (int i = 0; i < max_size; ++i)
std::nth_element(v[i].begin(), v[i].begin() + i, v[i].end());
stop_counters(time, resource);
report_performance(__FILE__, "", time, resource);
return 0;
}