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git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@6277 6c8d7289-2bf4-0310-a012-ef5d649a1542
95 lines
2.8 KiB
Java
95 lines
2.8 KiB
Java
// ConcurrentARC.java
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// a Simple Adaptive Replacement Cache
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// (C) 2009 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
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// first published 17.04.2009 on http://yacy.net
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//
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// $LastChangedDate: 2006-04-02 22:40:07 +0200 (So, 02 Apr 2006) $
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// $LastChangedRevision: 1986 $
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// $LastChangedBy: orbiter $
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//
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// LICENSE
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program 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
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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package de.anomic.kelondro.index;
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/**
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* This is a simple cache using two generations of hashtables to store the content with a LFU strategy.
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* The Algorithm is described in a slightly more complex version as Adaptive Replacement Cache, "ARC".
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* For details see http://www.almaden.ibm.com/cs/people/dmodha/ARC.pdf
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* or http://en.wikipedia.org/wiki/Adaptive_Replacement_Cache
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* This version omits the ghost entry handling which is described in ARC, and keeps both cache levels
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* at the same size.
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*/
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public class ConcurrentARC<K, V> implements ARC<K, V> {
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protected int cacheSize;
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private int mask;
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private ARC<K, V> arc[];
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@SuppressWarnings("unchecked")
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public ConcurrentARC(final int cacheSize, int partitions) {
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this.mask = 1;
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while (this.mask < partitions) this.mask = this.mask * 2;
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this.arc = new SimpleARC[mask];
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for (int i = 0; i < this.arc.length; i++) this.arc[i] = new SimpleARC<K, V>(cacheSize / this.mask);
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this.mask -= 1;
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}
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/**
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* put a value to the cache.
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* @param s
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* @param v
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*/
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public void put(K s, V v) {
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this.arc[s.hashCode() & mask].put(s, v);
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}
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/**
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* get a value from the cache.
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* @param s
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* @return the value
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*/
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public V get(K s) {
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return this.arc[s.hashCode() & mask].get(s);
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}
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/**
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* check if the map contains the key
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* @param s
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* @return
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*/
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public boolean containsKey(K s) {
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return this.arc[s.hashCode() & mask].containsKey(s);
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}
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/**
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* remove an entry from the cache
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* @param s
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* @return the old value
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*/
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public V remove(K s) {
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return this.arc[s.hashCode() & mask].remove(s);
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}
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/**
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* clear the cache
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*/
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public void clear() {
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for (ARC<K, V> a: this.arc) a.clear();
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}
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}
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