third_party/WebKit/Source/wtf/HashTable.cpp

   1 /*
   2     Copyright (C) 2005 Apple Inc. All rights reserved.
   3
   4     This library is free software; you can redistribute it and/or
   5     modify it under the terms of the GNU Library General Public
   6     License as published by the Free Software Foundation; either
   7     version 2 of the License, or (at your option) any later version.
   8
   9     This library is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12     Library General Public License for more details.
  13
  14     You should have received a copy of the GNU Library General Public License
  15     along with this library; see the file COPYING.LIB.  If not, write to
  16     the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  17     Boston, MA 02110-1301, USA.
  18 */
  19
  20 #include "config.h"
  21 #include "HashTable.h"
  22 #include "DataLog.h"
  23
  24 namespace WTF {
  25
  26 #if DUMP_HASHTABLE_STATS
  27
  28 int HashTableStats::numAccesses;
  29 int HashTableStats::numCollisions;
  30 int HashTableStats::collisionGraph[4096];
  31 int HashTableStats::maxCollisions;
  32 int HashTableStats::numRehashes;
  33 int HashTableStats::numRemoves;
  34 int HashTableStats::numReinserts;
  35
  36 static Mutex& hashTableStatsMutex()
  37 {
  38     AtomicallyInitializedStaticReference(Mutex, mutex, new Mutex);
  39     return mutex;
  40 }
  41
  42 void HashTableStats::recordCollisionAtCount(int count)
  43 {
  44     MutexLocker lock(hashTableStatsMutex());
  45     if (count > maxCollisions)
  46         maxCollisions = count;
  47     numCollisions++;
  48     collisionGraph[count]++;
  49 }
  50
  51 void HashTableStats::dumpStats()
  52 {
  53     MutexLocker lock(hashTableStatsMutex());
  54
  55     dataLogF("\nWTF::HashTable statistics\n\n");
  56     dataLogF("%d accesses\n", numAccesses);
  57     dataLogF("%d total collisions, average %.2f probes per access\n", numCollisions, 1.0 * (numAccesses + numCollisions) / numAccesses);
  58     dataLogF("longest collision chain: %d\n", maxCollisions);
  59     for (int i = 1; i <= maxCollisions; i++) {
  60         dataLogF("  %d lookups with exactly %d collisions (%.2f%% , %.2f%% with this many or more)\n", collisionGraph[i], i, 100.0 * (collisionGraph[i] - collisionGraph[i+1]) / numAccesses, 100.0 * collisionGraph[i] / numAccesses);
  61     }
  62     dataLogF("%d rehashes\n", numRehashes);
  63     dataLogF("%d reinserts\n", numReinserts);
  64 }
  65
  66 #endif
  67
  68 } // namespace WTF