This is the mail archive of the
libstdc++@gcc.gnu.org
mailing list for the libstdc++ project.
Re: Updating nth_element for C++0x
- From: Paolo Carlini <paolo dot carlini at oracle dot com>
- To: Christopher Jefferson <caj at cs dot st-andrews dot ac dot uk>
- Cc: libstdc++ at gcc dot gnu dot org
- Date: Mon, 24 Aug 2009 17:45:58 +0200
- Subject: Re: Updating nth_element for C++0x
- References: <submission.1MfGRK-0001I9-Ci@mail.cs.st-andrews.ac.uk>
... as applied. Tested x86_64-linux.
Paolo.
////////////////////
2009-08-24 Chris Jefferson <chris@bubblescope.net>
* include/stl_algo.h (__unguarded_partition_pivot,
__move_median_first): New.
(__insertion_sort, __unguarded_insertion_sort): Adjust for move-only
types.
(__unguarded_linear_insert): Assume always inserting value at __last.
(__unguarded_partition): Take pivot by reference.
(__introsort_loop, __introselect) : Use __unguarded_partition_pivot.
* testsuite/25_algorithms/nth_element/moveable.cc : Enable.
Index: include/bits/stl_algo.h
===================================================================
--- include/bits/stl_algo.h (revision 151053)
+++ include/bits/stl_algo.h (working copy)
@@ -136,6 +136,56 @@
return __b;
}
+ /// Swaps the median value of *__a, *__b and *__c to *__a
+ template<typename _Iterator>
+ void
+ __move_median_first(_Iterator __a, _Iterator __b, _Iterator __c)
+ {
+ // concept requirements
+ __glibcxx_function_requires(_LessThanComparableConcept<
+ typename iterator_traits<_Iterator>::value_type>)
+
+ if (*__a < *__b)
+ {
+ if (*__b < *__c)
+ std::iter_swap(__a, __b);
+ else if (*__a < *__c)
+ std::iter_swap(__a, __c);
+ }
+ else if (*__a < *__c)
+ return;
+ else if (*__b < *__c)
+ std::iter_swap(__a, __c);
+ else
+ std::iter_swap(__a, __b);
+ }
+
+ /// Swaps the median value of *__a, *__b and *__c under __comp to *__a
+ template<typename _Iterator, typename _Compare>
+ void
+ __move_median_first(_Iterator __a, _Iterator __b, _Iterator __c,
+ _Compare __comp)
+ {
+ // concept requirements
+ __glibcxx_function_requires(_BinaryFunctionConcept<_Compare, bool,
+ typename iterator_traits<_Iterator>::value_type,
+ typename iterator_traits<_Iterator>::value_type>)
+
+ if (__comp(*__a, *__b))
+ {
+ if (__comp(*__b, *__c))
+ std::iter_swap(__a, __b);
+ else if (__comp(*__a, *__c))
+ std::iter_swap(__a, __c);
+ }
+ else if (__comp(*__a, *__c))
+ return;
+ else if (__comp(*__b, *__c))
+ std::iter_swap(__a, __c);
+ else
+ std::iter_swap(__a, __b);
+ }
+
// for_each
/// This is an overload used by find() for the Input Iterator case.
@@ -2058,36 +2108,40 @@
}
/// This is a helper function for the sort routine.
- template<typename _RandomAccessIterator, typename _Tp>
+ template<typename _RandomAccessIterator>
void
- __unguarded_linear_insert(_RandomAccessIterator __last, _Tp __val)
+ __unguarded_linear_insert(_RandomAccessIterator __last)
{
+ typename iterator_traits<_RandomAccessIterator>::value_type
+ __val = _GLIBCXX_MOVE(*__last);
_RandomAccessIterator __next = __last;
--__next;
while (__val < *__next)
{
- *__last = *__next;
+ *__last = _GLIBCXX_MOVE(*__next);
__last = __next;
--__next;
}
- *__last = __val;
+ *__last = _GLIBCXX_MOVE(__val);
}
/// This is a helper function for the sort routine.
- template<typename _RandomAccessIterator, typename _Tp, typename _Compare>
+ template<typename _RandomAccessIterator, typename _Compare>
void
- __unguarded_linear_insert(_RandomAccessIterator __last, _Tp __val,
+ __unguarded_linear_insert(_RandomAccessIterator __last,
_Compare __comp)
{
+ typename iterator_traits<_RandomAccessIterator>::value_type
+ __val = _GLIBCXX_MOVE(*__last);
_RandomAccessIterator __next = __last;
--__next;
while (__comp(__val, *__next))
{
- *__last = *__next;
+ *__last = _GLIBCXX_MOVE(*__next);
__last = __next;
--__next;
}
- *__last = __val;
+ *__last = _GLIBCXX_MOVE(__val);
}
/// This is a helper function for the sort routine.
@@ -2101,15 +2155,15 @@
for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
{
- typename iterator_traits<_RandomAccessIterator>::value_type
- __val = *__i;
- if (__val < *__first)
+ if (*__i < *__first)
{
- std::copy_backward(__first, __i, __i + 1);
- *__first = __val;
+ typename iterator_traits<_RandomAccessIterator>::value_type
+ __val = _GLIBCXX_MOVE(*__i);
+ _GLIBCXX_MOVE_BACKWARD3(__first, __i, __i + 1);
+ *__first = _GLIBCXX_MOVE(__val);
}
else
- std::__unguarded_linear_insert(__i, __val);
+ std::__unguarded_linear_insert(__i);
}
}
@@ -2123,15 +2177,15 @@
for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
{
- typename iterator_traits<_RandomAccessIterator>::value_type
- __val = *__i;
- if (__comp(__val, *__first))
+ if (__comp(*__i, *__first))
{
- std::copy_backward(__first, __i, __i + 1);
- *__first = __val;
+ typename iterator_traits<_RandomAccessIterator>::value_type
+ __val = _GLIBCXX_MOVE(*__i);
+ _GLIBCXX_MOVE_BACKWARD3(__first, __i, __i + 1);
+ *__first = _GLIBCXX_MOVE(__val);
}
else
- std::__unguarded_linear_insert(__i, __val, __comp);
+ std::__unguarded_linear_insert(__i, __comp);
}
}
@@ -2145,7 +2199,7 @@
_ValueType;
for (_RandomAccessIterator __i = __first; __i != __last; ++__i)
- std::__unguarded_linear_insert(__i, _ValueType(*__i));
+ std::__unguarded_linear_insert(__i);
}
/// This is a helper function for the sort routine.
@@ -2158,7 +2212,7 @@
_ValueType;
for (_RandomAccessIterator __i = __first; __i != __last; ++__i)
- std::__unguarded_linear_insert(__i, _ValueType(*__i), __comp);
+ std::__unguarded_linear_insert(__i, __comp);
}
/**
@@ -2202,7 +2256,7 @@
template<typename _RandomAccessIterator, typename _Tp>
_RandomAccessIterator
__unguarded_partition(_RandomAccessIterator __first,
- _RandomAccessIterator __last, _Tp __pivot)
+ _RandomAccessIterator __last, const _Tp& __pivot)
{
while (true)
{
@@ -2223,7 +2277,7 @@
_RandomAccessIterator
__unguarded_partition(_RandomAccessIterator __first,
_RandomAccessIterator __last,
- _Tp __pivot, _Compare __comp)
+ const _Tp& __pivot, _Compare __comp)
{
while (true)
{
@@ -2239,6 +2293,29 @@
}
}
+ /// This is a helper function...
+ template<typename _RandomAccessIterator>
+ inline _RandomAccessIterator
+ __unguarded_partition_pivot(_RandomAccessIterator __first,
+ _RandomAccessIterator __last)
+ {
+ _RandomAccessIterator __mid = __first + (__last - __first) / 2;
+ std::__move_median_first(__first, __mid, (__last - 1));
+ return std::__unguarded_partition(__first + 1, __last, *__first);
+ }
+
+
+ /// This is a helper function...
+ template<typename _RandomAccessIterator, typename _Compare>
+ inline _RandomAccessIterator
+ __unguarded_partition_pivot(_RandomAccessIterator __first,
+ _RandomAccessIterator __last, _Compare __comp)
+ {
+ _RandomAccessIterator __mid = __first + (__last - __first) / 2;
+ std::__move_median_first(__first, __mid, (__last - 1), __comp);
+ return std::__unguarded_partition(__first + 1, __last, *__first, __comp);
+ }
+
/// This is a helper function for the sort routine.
template<typename _RandomAccessIterator, typename _Size>
void
@@ -2246,9 +2323,6 @@
_RandomAccessIterator __last,
_Size __depth_limit)
{
- typedef typename iterator_traits<_RandomAccessIterator>::value_type
- _ValueType;
-
while (__last - __first > int(_S_threshold))
{
if (__depth_limit == 0)
@@ -2258,14 +2332,7 @@
}
--__depth_limit;
_RandomAccessIterator __cut =
- std::__unguarded_partition(__first, __last,
- _ValueType(std::__median(*__first,
- *(__first
- + (__last
- - __first)
- / 2),
- *(__last
- - 1))));
+ std::__unguarded_partition_pivot(__first, __last);
std::__introsort_loop(__cut, __last, __depth_limit);
__last = __cut;
}
@@ -2278,9 +2345,6 @@
_RandomAccessIterator __last,
_Size __depth_limit, _Compare __comp)
{
- typedef typename iterator_traits<_RandomAccessIterator>::value_type
- _ValueType;
-
while (__last - __first > int(_S_threshold))
{
if (__depth_limit == 0)
@@ -2290,15 +2354,7 @@
}
--__depth_limit;
_RandomAccessIterator __cut =
- std::__unguarded_partition(__first, __last,
- _ValueType(std::__median(*__first,
- *(__first
- + (__last
- - __first)
- / 2),
- *(__last - 1),
- __comp)),
- __comp);
+ std::__unguarded_partition_pivot(__first, __last, __comp);
std::__introsort_loop(__cut, __last, __depth_limit, __comp);
__last = __cut;
}
@@ -2349,14 +2405,7 @@
}
--__depth_limit;
_RandomAccessIterator __cut =
- std::__unguarded_partition(__first, __last,
- _ValueType(std::__median(*__first,
- *(__first
- + (__last
- - __first)
- / 2),
- *(__last
- - 1))));
+ std::__unguarded_partition_pivot(__first, __last);
if (__cut <= __nth)
__first = __cut;
else
@@ -2385,15 +2434,7 @@
}
--__depth_limit;
_RandomAccessIterator __cut =
- std::__unguarded_partition(__first, __last,
- _ValueType(std::__median(*__first,
- *(__first
- + (__last
- - __first)
- / 2),
- *(__last - 1),
- __comp)),
- __comp);
+ std::__unguarded_partition_pivot(__first, __last, __comp);
if (__cut <= __nth)
__first = __cut;
else
Index: testsuite/25_algorithms/nth_element/moveable.cc
===================================================================
--- testsuite/25_algorithms/nth_element/moveable.cc (revision 151053)
+++ testsuite/25_algorithms/nth_element/moveable.cc (working copy)
@@ -1,4 +1,3 @@
-// { dg-require-rvalref "" }
// { dg-options "-std=gnu++0x" }
// Copyright (C) 2005, 2007, 2009 Free Software Foundation, Inc.