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hashtable_policy.h (_Prime_rehash_policy): Use __builtin_floor rather than __builtin_ceil to compute next resize value.

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2011-07-24  François Dumont  <francois.cppdevs@free.fr>

        * include/bits/hashtable_policy.h (_Prime_rehash_policy): Use
        __builtin_floor rather than __builtin_ceil to compute next resize
        value.
        * testsuite/23_containers/unordered_set/hash_policy/load_factor.cc:
        New.

From-SVN: r176717
This commit is contained in:
François Dumont 2011-07-24 21:20:26 +02:00 committed by François Dumont
parent 7d5997c66c
commit 4f7b188f20
3 changed files with 75 additions and 9 deletions
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8
libstdc++-v3/ChangeLog
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@ -1,3 +1,11 @@
2011-07-24 François Dumont <francois.cppdevs@free.fr>
* include/bits/hashtable_policy.h (_Prime_rehash_policy): Use
__builtin_floor rather than __builtin_ceil to compute next resize
value.
* testsuite/23_containers/unordered_set/hash_policy/load_factor.cc:
New.
2011-07-22 Benjamin Kosnik <bkoz@redhat.com>
Daniel Krugler <daniel.kruegler@googlemail.com>

18
libstdc++-v3/include/bits/hashtable_policy.h
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@ -427,10 +427,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_Prime_rehash_policy::
_M_next_bkt(std::size_t __n) const
{
const unsigned long* __p = std::lower_bound(__prime_list, __prime_list
const unsigned long __p = *std::lower_bound(__prime_list, __prime_list
+ _S_n_primes, __n);
_M_next_resize =
static_cast<std::size_t>(__builtin_ceil(*__p * _M_max_load_factor));
static_cast<std::size_t>(__builtin_floor(__p * _M_max_load_factor));
return *__p;
}
@ -441,10 +441,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_bkt_for_elements(std::size_t __n) const
{
const float __min_bkts = __n / _M_max_load_factor;
const unsigned long* __p = std::lower_bound(__prime_list, __prime_list
const unsigned long __p = *std::lower_bound(__prime_list, __prime_list
+ _S_n_primes, __min_bkts);
_M_next_resize =
static_cast<std::size_t>(__builtin_ceil(*__p * _M_max_load_factor));
static_cast<std::size_t>(__builtin_floor(__p * _M_max_load_factor));
return *__p;
}
@ -469,17 +469,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (__min_bkts > __n_bkt)
{
__min_bkts = std::max(__min_bkts, _M_growth_factor * __n_bkt);
const unsigned long* __p =
std::lower_bound(__prime_list, __prime_list + _S_n_primes,
__min_bkts);
const unsigned long __p =
*std::lower_bound(__prime_list, __prime_list + _S_n_primes,
__min_bkts);
_M_next_resize = static_cast<std::size_t>
(__builtin_ceil(*__p * _M_max_load_factor));
(__builtin_floor(__p * _M_max_load_factor));
return std::make_pair(true, *__p);
}
else
{
_M_next_resize = static_cast<std::size_t>
(__builtin_ceil(__n_bkt * _M_max_load_factor));
(__builtin_floor(__n_bkt * _M_max_load_factor));
return std::make_pair(false, 0);
}
}

58
libstdc++-v3/testsuite/23_containers/unordered_set/hash_policy/load_factor.cc Normal file
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@ -0,0 +1,58 @@
// Copyright (C) 2011 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-options "-std=gnu++0x" }
#include <unordered_set>
#include <testsuite_hooks.h>
void test01()
{
bool test __attribute__((unused)) = true;
{
std::unordered_set<int> us;
for (int i = 0; i != 100000; ++i)
{
us.insert(i);
VERIFY( us.load_factor() <= us.max_load_factor() );
}
}
{
std::unordered_set<int> us;
us.max_load_factor(3.f);
for (int i = 0; i != 100000; ++i)
{
us.insert(i);
VERIFY( us.load_factor() <= us.max_load_factor() );
}
}
{
std::unordered_set<int> us;
us.max_load_factor(.3f);
for (int i = 0; i != 100000; ++i)
{
us.insert(i);
VERIFY( us.load_factor() <= us.max_load_factor() );
}
}
}
int main()
{
test01();
return 0;
}