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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166e.extra; |
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package jsr166e; |
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|
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import jsr166e.LongAdder; |
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import java.util.concurrent.ConcurrentHashMap; |
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import java.util.Map; |
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import java.util.Set; |
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import java.io.Serializable; |
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/** |
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* A keyed table of adders, that may be useful in computing frequency |
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* counts and histograms, or may be used a form of multiset. A {@link |
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* LongAdder} is associated with each key. Keys are added to the table |
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* implicitly upon any attempt to update, or may be added explicitly |
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* using method {@link #install}. |
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* counts and histograms, or may be used as a form of multiset. A |
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* {@link LongAdder} is associated with each key. Keys are added to |
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* the table implicitly upon any attempt to update, or may be added |
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* explicitly using method {@link #install}. |
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* |
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* <p><em>jsr166e note: This class is targeted to be placed in |
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* java.util.concurrent.atomic<em> |
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* java.util.concurrent.atomic.</em> |
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* |
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* @since 1.8 |
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* @author Doug Lea |
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*/ |
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public class LongAdderTable<K> implements Serializable { |
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/** Relies on default serialization */ |
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private static final long serialVersionUID = 7249369246863182397L; |
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|
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/** Concurrency parameter for map -- we assume high contention */ |
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private static final int MAP_SEGMENTS = |
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Math.max(16, Runtime.getRuntime().availableProcessors()); |
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|
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/** The underlying map */ |
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private final ConcurrentHashMap<K, LongAdder> map; |
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private final ConcurrentHashMapV8<K, LongAdder> map; |
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|
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static final class CreateAdder |
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implements ConcurrentHashMapV8.Fun<Object, LongAdder> { |
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public LongAdder apply(Object unused) { return new LongAdder(); } |
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} |
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|
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private static final CreateAdder createAdder = new CreateAdder(); |
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/** |
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* Creates a new empty table. |
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*/ |
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public LongAdderTable() { |
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map = new ConcurrentHashMap<K, LongAdder>(16, 0.75f, MAP_SEGMENTS); |
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map = new ConcurrentHashMapV8<K, LongAdder>(); |
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} |
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/** |
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* @return the adder associated with the key |
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*/ |
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public LongAdder install(K key) { |
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LongAdder a = map.get(key); |
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if (a == null) { |
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LongAdder r = new LongAdder(); |
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if ((a = map.putIfAbsent(key, r)) == null) |
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a = r; |
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} |
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return a; |
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return map.computeIfAbsent(key, createAdder); |
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} |
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/** |
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* @param x the value to add |
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*/ |
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public void add(K key, long x) { |
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LongAdder a = map.get(key); |
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if (a == null) { |
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LongAdder r = new LongAdder(); |
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if ((a = map.putIfAbsent(key, r)) == null) |
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a = r; |
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} |
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a.add(x); |
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map.computeIfAbsent(key, createAdder).add(x); |
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} |
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/** |
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/** |
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* Returns the sum totalled across all keys. |
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* |
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* @return the sum totalled across all keys. |
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* @return the sum totalled across all keys |
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*/ |
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public long sumAll() { |
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long sum = 0L; |
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/** |
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* Totals, then resets, the sums associated with all keys. |
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* |
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* @return the sum totalled across all keys. |
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* @return the sum totalled across all keys |
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*/ |
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public long sumThenResetAll() { |
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long sum = 0L; |
