(CC gcc-patches)
On 25 July 2012 10:26, François Dumont wrote:
> Hi
>
> Here is a patch proposal for PR 54075. I also took the occasion to fix
> something that has been delay so far which is usage of std::max to get the
> number of buckets to use. The problem of using std::max when using the hash
> policy is that the hashtable might be using a number of buckets inconsistent
> with the hash policy.
>
> 2012-07-25 François Dumont <fdum...@gcc.gnu.org>
>
> PR libstdc++/54075
> * include/bits/hashtable.h
> (_Hashtable<>::_Hashtable(_InputIterator, _InputIterator,
> size_type, ...): Remove std::max usage to guaranty that hashtable
> state is consistent with hash policy state.
s/guaranty/guarantee/
> (_Hashtable<>::rehash): Likewise. Set _M_prev_resize to 0 to avoid
> the hashtable to be shrink on next insertion.
s/to be shrink/shrinking/
> * testsuite/23_containers/unordered_set/modifiers/reserve.cc: New.
> * testsuite/23_containers/unordered_multiset/modifiers/reserve.cc: New.
> * testsuite/23_containers/unordered_map/modifiers/reserve.cc: New.
> * testsuite/23_containers/unordered_multimap/modifiers/reserve.cc: New.
>
> Tested under Linux x86_64.
OK with the changelog edits above.
> I guess it will have to be apply to the 4.7 branch too, confirm please.
Yes, I think so, it's a regression from 4.6.
Thanks for dealing with it so quickly.
Index: include/bits/hashtable.h
===================================================================
--- include/bits/hashtable.h (revision 189626)
+++ include/bits/hashtable.h (working copy)
@@ -803,11 +803,11 @@
_M_element_count(0),
_M_rehash_policy()
{
- _M_bucket_count = std::max(_M_rehash_policy._M_next_bkt(__bucket_hint),
- _M_rehash_policy.
- _M_bkt_for_elements(__detail::
- __distance_fw(__f,
- __l)));
+ _M_bucket_count =
+ _M_rehash_policy._M_bkt_for_elements(__detail::__distance_fw(__f,
+ __l));
+ if (_M_bucket_count <= __bucket_hint)
+ _M_bucket_count = _M_rehash_policy._M_next_bkt(__bucket_hint);
// We don't want the rehash policy to ask for the hashtable to
// shrink on the first insertion so we need to reset its
@@ -1609,10 +1609,20 @@
rehash(size_type __n)
{
const __rehash_state& __saved_state = _M_rehash_policy._M_state();
- _M_rehash(std::max(_M_rehash_policy._M_next_bkt(__n),
- _M_rehash_policy._M_bkt_for_elements(_M_element_count
- + 1)),
- __saved_state);
+ std::size_t __buckets
+ = _M_rehash_policy._M_bkt_for_elements(_M_element_count + 1);
+ if (__buckets <= __n)
+ __buckets = _M_rehash_policy._M_next_bkt(__n);
+
+ if (__buckets != _M_bucket_count)
+ {
+ _M_rehash(__buckets, __saved_state);
+
+ // We don't want the rehash policy to ask for the hashtable to shrink
+ // on the next insertion so we need to reset its previous resize
+ // level.
+ _M_rehash_policy._M_prev_resize = 0;
+ }
}
template<typename _Key, typename _Value,
Index: testsuite/23_containers/unordered_multiset/modifiers/reserve.cc
===================================================================
--- testsuite/23_containers/unordered_multiset/modifiers/reserve.cc (revision 0)
+++ testsuite/23_containers/unordered_multiset/modifiers/reserve.cc (revision 0)
@@ -0,0 +1,48 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2012 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/>.
+
+#include <unordered_set>
+#include <testsuite_hooks.h>
+
+bool test __attribute__((unused)) = true;
+
+void test01()
+{
+ const int N = 1000;
+
+ typedef std::unordered_multiset<int> MSet;
+ MSet s;
+ s.reserve(N * 2);
+
+ std::size_t bkts = s.bucket_count();
+ for (int i = 0; i != N; ++i)
+ {
+ s.insert(i);
+ s.insert(i);
+ // As long as we insert less than the reserved number of elements we
+ // shouldn't experiment any rehash.
+ VERIFY( s.bucket_count() == bkts );
+ }
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
Index: testsuite/23_containers/unordered_map/modifiers/reserve.cc
===================================================================
--- testsuite/23_containers/unordered_map/modifiers/reserve.cc (revision 0)
+++ testsuite/23_containers/unordered_map/modifiers/reserve.cc (revision 0)
@@ -0,0 +1,47 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2012 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/>.
+
+#include <unordered_map>
+#include <testsuite_hooks.h>
+
+bool test __attribute__((unused)) = true;
+
+void test01()
+{
+ const int N = 1000;
+
+ typedef std::unordered_map<int, int> Map;
+ Map m;
+ m.reserve(N);
+
+ std::size_t bkts = m.bucket_count();
+ for (int i = 0; i != N; ++i)
+ {
+ m.insert(std::make_pair(i, i));
+ // As long as we insert less than the reserved number of elements we
+ // shouldn't experiment any rehash.
+ VERIFY( m.bucket_count() == bkts );
+ }
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
Index: testsuite/23_containers/unordered_multimap/modifiers/reserve.cc
===================================================================
--- testsuite/23_containers/unordered_multimap/modifiers/reserve.cc (revision 0)
+++ testsuite/23_containers/unordered_multimap/modifiers/reserve.cc (revision 0)
@@ -0,0 +1,48 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2012 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/>.
+
+#include <unordered_map>
+#include <testsuite_hooks.h>
+
+bool test __attribute__((unused)) = true;
+
+void test01()
+{
+ const int N = 1000;
+
+ typedef std::unordered_multimap<int, int> MMap;
+ MMap m;
+ m.reserve(N * 2);
+
+ std::size_t bkts = m.bucket_count();
+ for (int i = 0; i != N; ++i)
+ {
+ m.insert(std::make_pair(i, i));
+ m.insert(std::make_pair(i, i));
+ // As long as we insert less than the reserved number of elements we
+ // shouldn't experiment any rehash.
+ VERIFY( m.bucket_count() == bkts );
+ }
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
Index: testsuite/23_containers/unordered_set/modifiers/reserve.cc
===================================================================
--- testsuite/23_containers/unordered_set/modifiers/reserve.cc (revision 0)
+++ testsuite/23_containers/unordered_set/modifiers/reserve.cc (revision 0)
@@ -0,0 +1,47 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2012 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/>.
+
+#include <unordered_set>
+#include <testsuite_hooks.h>
+
+bool test __attribute__((unused)) = true;
+
+void test01()
+{
+ const int N = 1000;
+
+ typedef std::unordered_set<int> Set;
+ Set s;
+ s.reserve(N);
+
+ std::size_t bkts = s.bucket_count();
+ for (int i = 0; i != N; ++i)
+ {
+ s.insert(i);
+ // As long as we insert less than the reserved number of elements we
+ // shouldn't experiment any rehash.
+ VERIFY( s.bucket_count() == bkts );
+ }
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
