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
  23 namespace WTF {
  24
  25 #if DUMP_HASHTABLE_STATS
  26
  27 int HashTableStats::numAccesses;
  28 int HashTableStats::numCollisions;
  29 int HashTableStats::collisionGraph[4096];
  30 int HashTableStats::maxCollisions;
  31 int HashTableStats::numRehashes;
  32 int HashTableStats::numRemoves;
  33 int HashTableStats::numReinserts;
  34
  35 static HashTableStats logger;
  36
  37 static Mutex& hashTableStatsMutex()
  38 {
  39     AtomicallyInitializedStatic(Mutex&, mutex = *new Mutex);
  40     return mutex;
  41 }
  42
  43 HashTableStats::~HashTableStats()
  44 {
  45     // Don't lock hashTableStatsMutex here because it can cause deadlocks at shutdown
  46     // if any thread was killed while holding the mutex.
  47     printf("\nWTF::HashTable statistics\n\n");
  48     printf("%d accesses\n", numAccesses);
  49     printf("%d total collisions, average %.2f probes per access\n", numCollisions, 1.0 * (numAccesses + numCollisions) / numAccesses);
  50     printf("longest collision chain: %d\n", maxCollisions);
  51     for (int i = 1; i <= maxCollisions; i++) {
  52         printf("  %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);
  53     }
  54     printf("%d rehashes\n", numRehashes);
  55     printf("%d reinserts\n", numReinserts);
  56 }
  57
  58 void HashTableStats::recordCollisionAtCount(int count)
  59 {
  60     MutexLocker lock(hashTableStatsMutex());
  61     if (count > maxCollisions)
  62         maxCollisions = count;
  63     numCollisions++;
  64     collisionGraph[count]++;
  65 }
  66
  67 #endif
  68
  69 } // namespace WTF