re PR libstdc++/54075 ([4.7.1] unordered_map insert still slower than 4.6.2)

2012-07-26  François Dumont  <fdumont@gcc.gnu.org>

	PR libstdc++/54075
	* include/bits/hashtable.h
	(_Hashtable<>::_Hashtable(_InputIterator, _InputIterator,
	size_type, ...): Remove std::max usage to guarantee that hashtable
	state is consistent with hash policy state.
	(_Hashtable<>::rehash): Likewise. Set _M_prev_resize to 0 to avoid
	the hashtable shrinking on next insertion.
	* 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.

From-SVN: r189889

libstdc++-v3/ChangeLog

@@ -1,3 +1,17 @@
+2012-07-26  François Dumont  <fdumont@gcc.gnu.org>
+
+	PR libstdc++/54075
+	* include/bits/hashtable.h
+	(_Hashtable<>::_Hashtable(_InputIterator, _InputIterator,
+	size_type, ...): Remove std::max usage to guarantee that hashtable
+	state is consistent with hash policy state.
+	(_Hashtable<>::rehash): Likewise. Set _M_prev_resize to 0 to avoid
+	the hashtable shrinking on next insertion.
+	* 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.
+
 2012-07-20  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* testsuite/30_threads/thread/adl.cc: Add missing dg-requires.

libstdc++-v3/include/bits/hashtable.h

@@ -760,11 +760,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_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 previous resize
 	// level.
@@ -1582,10 +1583,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     rehash(size_type __n)
     {
       const _RehashPolicyState& __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,

libstdc++-v3/testsuite/23_containers/unordered_map/modifiers/reserve.cc

@@ -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;
+}

libstdc++-v3/testsuite/23_containers/unordered_multimap/modifiers/reserve.cc

@@ -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;
+}

libstdc++-v3/testsuite/23_containers/unordered_multiset/modifiers/reserve.cc

@@ -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;
+}

libstdc++-v3/testsuite/23_containers/unordered_set/modifiers/reserve.cc

@@ -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;
+}