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PR libstdc++/81476 Optimise vector insertion from input iterators

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PR libstdc++/81476
	* include/bits/vector.tcc (vector::_M_range_insert<_InputIterator>):
	Only insert elements one-by-one when inserting at the end.
	* testsuite/performance/23_containers/insert/81476.cc: New.

From-SVN: r250366
This commit is contained in:
Jonathan Wakely 2017-07-19 20:32:15 +01:00 committed by Jonathan Wakely
parent 6cdcce60ff
commit 304a15ec64
3 changed files with 103 additions and 3 deletions
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7
libstdc++-v3/ChangeLog
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@ -1,3 +1,10 @@
2017-07-19 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/81476
* include/bits/vector.tcc (vector::_M_range_insert<_InputIterator>):
Only insert elements one-by-one when inserting at the end.
* testsuite/performance/23_containers/insert/81476.cc: New.
2017-07-19 Volker Reichelt <v.reichelt@netcologne.de>
* libsupc++/new (bad_array_new_length): Remove redundant

13
libstdc++-v3/include/bits/vector.tcc
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@ -617,10 +617,17 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_range_insert(iterator __pos, _InputIterator __first,
_InputIterator __last, std::input_iterator_tag)
{
for (; __first != __last; ++__first)
if (__pos == end())
{
__pos = insert(__pos, *__first);
++__pos;
for (; __first != __last; ++__first)
insert(end(), *__first);
}
else if (__first != __last)
{
vector __tmp(__first, __last, _M_get_Tp_allocator());
insert(__pos,
_GLIBCXX_MAKE_MOVE_ITERATOR(__tmp.begin()),
_GLIBCXX_MAKE_MOVE_ITERATOR(__tmp.end()));
}
}

86
libstdc++-v3/testsuite/performance/23_containers/insert/81476.cc Normal file
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@ -0,0 +1,86 @@
// Copyright (C) 2012-2017 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 3, 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 COPYING3. If not see
// <http://www.gnu.org/licenses/>.
// { dg-do run { target c++11 } }
#include <random>
#include <vector>
#include <testsuite_hooks.h>
#include <testsuite_performance.h>
int main()
{
using namespace __gnu_test;
std::default_random_engine eng;
std::uniform_int_distribution<unsigned> r(0, 127);
time_counter time;
resource_counter resource;
std::vector<std::vector<char>> vecs(10000);
for (auto& v : vecs)
{
v.resize(1000);
for (auto& c : v)
c = r(eng);
}
start_counters(time, resource);
std::vector<char> res;
for (auto& v : vecs)
res.insert(res.begin(), v.begin(), v.end());
stop_counters(time, resource);
report_performance(__FILE__, "insert pointers", time, resource);
struct input_iterator : std::vector<char>::iterator
{
using iterator_category = std::input_iterator_tag;
using base = std::vector<char>::iterator;
input_iterator(base it) : base(it) { }
};
start_counters(time, resource);
std::vector<char> res2;
for (auto& v : vecs)
{
auto begin = input_iterator(v.begin());
auto end = input_iterator(v.end());
res2.insert(res2.begin(), begin, end);
}
stop_counters(time, resource);
report_performance(__FILE__, "insert input iterators", time, resource);
start_counters(time, resource);
std::vector<char> res3;
for (auto rev = vecs.rbegin(); rev != vecs.rend(); ++rev)
res3.insert(res3.end(), rev->begin(), rev->end());
stop_counters(time, resource);
report_performance(__FILE__, "insert pointers end", time, resource);
start_counters(time, resource);
std::vector<char> res4;
for (auto rev = vecs.rbegin(); rev != vecs.rend(); ++rev)
res4.insert(res4.end(), rev->begin(), rev->end());
stop_counters(time, resource);
report_performance(__FILE__, "insert input iterators end", time, resource);
VERIFY(res2 == res);
VERIFY(res3 == res);
VERIFY(res4 == res);
}