Author: manik.surtani(a)jboss.com Date: 2008-10-06 10:53:33 -0400 (Mon, 06 Oct 2008) New Revision: 6847 Modified: core/trunk/src/main/java/org/jboss/cache/lock/StripedLock.java core/trunk/src/main/java/org/jboss/cache/util/concurrent/locks/LockContainer.java Log: Better hashcode Modified: core/trunk/src/main/java/org/jboss/cache/lock/StripedLock.java =================================================================== --- core/trunk/src/main/java/org/jboss/cache/lock/StripedLock.java 2008-10-06 14:28:08 UTC (rev 6846) +++ core/trunk/src/main/java/org/jboss/cache/lock/StripedLock.java 2008-10-06 14:53:33 UTC (rev 6847) @@ -75,6 +75,9 @@ lockSegmentShift = 32 - tempLockSegShift; lockSegmentMask = numLocks - 1; + System.out.println("Lock Seg Shift = " + lockSegmentShift); + System.out.println("Lock Seg Mask = " + lockSegmentMask); + sharedLocks = new ReentrantReadWriteLock[numLocks]; for (int i = 0; i < numLocks; i++) sharedLocks[i] = new ReentrantReadWriteLock(); @@ -130,17 +133,22 @@ /** * Returns a hash code for non-null Object x. - * Uses the same hash code spreader as most other java.util hash tables, except that this uses the string representation - * of the object passed in. * * @param x the object serving as a key * @return the hash code */ final int hash(Object x) { + // Spread bits to regularize both segment and index locations, + // using variant of single-word Wang/Jenkins hash. int h = x.hashCode(); - h ^= (h >>> 20) ^ (h >>> 12); - return h ^ (h >>> 7) ^ (h >>> 4); + h += (h << 15) ^ 0xffffcd7d; + h ^= (h >>> 10); + h += (h << 3); + h ^= (h >>> 6); + h += (h << 2) + (h << 14); + h = h ^ (h >>> 16); + return h; } /** Modified: core/trunk/src/main/java/org/jboss/cache/util/concurrent/locks/LockContainer.java =================================================================== --- core/trunk/src/main/java/org/jboss/cache/util/concurrent/locks/LockContainer.java 2008-10-06 14:28:08 UTC (rev 6846) +++ core/trunk/src/main/java/org/jboss/cache/util/concurrent/locks/LockContainer.java 2008-10-06 14:53:33 UTC (rev 6847) @@ -67,9 +67,16 @@ */ final int hash(E object) { + // Spread bits to regularize both segment and index locations, + // using variant of single-word Wang/Jenkins hash. int h = object.hashCode(); - h ^= (h >>> 20) ^ (h >>> 12); - return h ^ (h >>> 7) ^ (h >>> 4); + h += (h << 15) ^ 0xffffcd7d; + h ^= (h >>> 10); + h += (h << 3); + h ^= (h >>> 6); + h += (h << 2) + (h << 14); + h = h ^ (h >>> 16); + return h; } protected abstract void initLocks(int numLocks);