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Copyright (C) 2005 Apple Inc. All rights reserved.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public License
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along with this library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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#include "HashTable.h"
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#if DUMP_HASHTABLE_STATS
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int HashTableStats::numAccesses;
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int HashTableStats::numCollisions;
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int HashTableStats::collisionGraph[4096];
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int HashTableStats::maxCollisions;
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int HashTableStats::numRehashes;
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int HashTableStats::numRemoves;
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int HashTableStats::numReinserts;
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static HashTableStats logger;
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static Mutex& hashTableStatsMutex()
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AtomicallyInitializedStatic(Mutex&, mutex = *new Mutex);
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HashTableStats::~HashTableStats()
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// Don't lock hashTableStatsMutex here because it can cause deadlocks at shutdown
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// if any thread was killed while holding the mutex.
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printf("\nWTF::HashTable statistics\n\n");
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printf("%d accesses\n", numAccesses);
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printf("%d total collisions, average %.2f probes per access\n", numCollisions, 1.0 * (numAccesses + numCollisions) / numAccesses);
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printf("longest collision chain: %d\n", maxCollisions);
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for (int i = 1; i <= maxCollisions; i++) {
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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);
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printf("%d rehashes\n", numRehashes);
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printf("%d reinserts\n", numReinserts);
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void HashTableStats::recordCollisionAtCount(int count)
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MutexLocker lock(hashTableStatsMutex());
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if (count > maxCollisions)
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maxCollisions = count;
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collisionGraph[count]++;