ported LF int-string map
Robinson
parent
dc45dcf0e5
commit
bc8edb8f4b
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@ -1,225 +0,0 @@
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package dorkbox.collections;
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import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
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/**
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* This class uses the "single-writer-principle" for lock-free publication.
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* <p>
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* Since there are only 2 methods to guarantee that modifications can only be called one-at-a-time (either it is only called by
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* one thread, or only one thread can access it at a time) -- we chose the 2nd option -- and use 'synchronized' to make sure that only
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* one thread can access this modification methods at a time. Getting or checking the presence of values can then happen in a lock-free
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* manner.
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* <p>
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* According to my benchmarks, this is approximately 25% faster than ConcurrentHashMap for (all types of) reads, and a lot slower for
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* contended writes.
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* <p>
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* This data structure is for many-read/few-write scenarios
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*
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* This is an unordered map that uses int keys. This implementation is a cuckoo hash map using 3 hashes, random walking, and a small stash
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* for problematic keys. Null values are allowed. No allocation is done except when growing the table size. <br>
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* <br>
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* This map performs very fast get, containsKey, and remove (typically O(1), worst case O(log(n))). Put may be a bit slower,
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* depending on hash collisions. Load factors greater than 0.91 greatly increase the chances the map will have to rehash to the
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* next higher POT size.
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*/
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@SuppressWarnings("unchecked")
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public
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class LockFreeIntStringMap<V> {
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public static final String version = Collections.version;
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private static final AtomicReferenceFieldUpdater<LockFreeIntStringMap, IntMap> mapREF = AtomicReferenceFieldUpdater.newUpdater(
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LockFreeIntStringMap.class,
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IntMap.class,
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"map");
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private volatile IntMap<V> map;
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public LockFreeIntStringMap() {
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this.map = new IntMap<V>();
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}
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/**
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* Constructs an empty <tt>IntMap</tt> with the specified initial
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* capacity and the default load factor (0.75).
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*
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* @param initialCapacity the initial capacity.
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*
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* @throws IllegalArgumentException if the initial capacity is negative.
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*/
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public
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LockFreeIntStringMap(int initialCapacity) {
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map = new IntMap<V>(initialCapacity);
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}
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/**
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* Constructs an empty <tt>IntMap</tt> with the specified initial
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* capacity and the default load factor (0.75).
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*
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* @throws IllegalArgumentException if the initial capacity is negative.
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*/
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public
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LockFreeIntStringMap(LockFreeIntStringMap map) {
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this.map = new IntMap<V>(map.map);
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}
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/**
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* Constructs an empty <tt>IntMap</tt> with the specified initial
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* capacity and load factor.
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*
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* @param initialCapacity the initial capacity
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* @param loadFactor the load factor
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*
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* @throws IllegalArgumentException if the initial capacity is negative
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* or the load factor is nonpositive
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*/
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public
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LockFreeIntStringMap(int initialCapacity, float loadFactor) {
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this.map = new IntMap<V>(initialCapacity, loadFactor);
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}
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public
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int size() {
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// use the SWP to get a lock-free get of the value
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return mapREF.get(this)
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.size;
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}
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public
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boolean isEmpty() {
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// use the SWP to get a lock-free get of the value
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return mapREF.get(this)
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.size == 0;
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}
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public
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boolean containsKey(final int key) {
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// use the SWP to get a lock-free get of the value
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return mapREF.get(this)
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.containsKey(key);
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}
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public
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boolean containsKey(final String key) {
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// use the SWP to get a lock-free get of the value
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return mapREF.get(this)
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.containsKey(key.hashCode());
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}
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/**
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* Returns true if the specified value is in the map. Note this traverses the entire map and compares every value, which may be
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* an expensive operation.
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*
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* @param identity If true, uses == to compare the specified value with values in the map. If false, uses
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* {@link #equals(Object)}.
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*/
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public
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boolean containsValue(final Object value, boolean identity) {
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// use the SWP to get a lock-free get of the value
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return mapREF.get(this)
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.containsValue(value, identity);
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}
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public
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V get(final int key) {
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// use the SWP to get a lock-free get of the value
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return (V) mapREF.get(this)
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.get(key);
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}
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public
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V get(final String key) {
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// use the SWP to get a lock-free get of the value
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return (V) mapREF.get(this)
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.get(key.hashCode());
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}
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public synchronized
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V put(final int key, final V value) {
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return map.put(key, value);
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}
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public synchronized
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V put(final String key, final V value) {
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return map.put(key.hashCode(), value);
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}
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public synchronized
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V remove(final int key) {
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return map.remove(key);
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}
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public synchronized
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V remove(final String key) {
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return map.remove(key.hashCode());
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}
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public synchronized
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void putAll(final IntMap<V> map) {
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this.map.putAll(map);
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}
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/**
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* DO NOT MODIFY THE MAP VIA THIS (unless you synchronize around it!) It will result in unknown object visibility!
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*
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* Returns an iterator for the keys in the map. Remove is supported. Note that the same iterator instance is returned each
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* time this method is called. Use the {@link IntMap.Entries} constructor for nested or multi-threaded iteration.
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*/
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public
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IntMap.Keys keys() {
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return mapREF.get(this)
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.keys();
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}
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/**
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* DO NOT MODIFY THE MAP VIA THIS (unless you synchronize around it!) It will result in unknown object visibility!
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*
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* Returns an iterator for the values in the map. Remove is supported. Note that the same iterator instance is returned each
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* time this method is called. Use the {@link IntMap.Entries} constructor for nested or multi-threaded iteration.
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*/
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public
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IntMap.Values<V> values() {
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return mapREF.get(this)
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.values();
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}
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/**
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* DO NOT MODIFY THE MAP VIA THIS (unless you synchronize around it!) It will result in unknown object visibility!
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*
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* Returns an iterator for the entries in the map. Remove is supported. Note that the same iterator instance is returned each
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* time this method is called. Use the {@link IntMap.Entries} constructor for nested or multi-threaded iteration.
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*/
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public
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IntMap.Entries<V> entries() {
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return mapREF.get(this)
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.entries();
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}
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public synchronized
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void clear() {
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map.clear();
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}
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/**
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* Identity equals only!
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*/
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@Override
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public
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boolean equals(final Object o) {
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return this == o;
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}
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@Override
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public
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int hashCode() {
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return mapREF.get(this)
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.hashCode();
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}
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@Override
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public
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String toString() {
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return mapREF.get(this)
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.toString();
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}
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}
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@ -0,0 +1,209 @@
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/*
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* Copyright 2023 dorkbox, llc
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dorkbox.collections
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import java.io.Serializable
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import java.util.concurrent.atomic.*
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/**
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* This class uses the "single-writer-principle" for lock-free publication.
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*
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*
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* Since there are only 2 methods to guarantee that modifications can only be called one-at-a-time (either it is only called by
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* one thread, or only one thread can access it at a time) -- we chose the 2nd option -- and use 'synchronized' to make sure that only
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* one thread can access this modification methods at a time. Getting or checking the presence of values can then happen in a lock-free
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* manner.
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*
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*
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* According to my benchmarks, this is approximately 25% faster than ConcurrentHashMap for (all types of) reads, and a lot slower for
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* contended writes.
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*
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*
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* This data structure is for many-read/few-write scenarios
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*/
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class LockFreeIntStringMap : MutableMap<Int, String?>, Cloneable, Serializable {
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@Volatile
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private var hashMap: IntMap<String?>
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// synchronized is used here to ensure the "single writer principle", and make sure that ONLY one thread at a time can enter this
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// section. Because of this, we can have unlimited reader threads all going at the same time, without contention (which is our
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// use-case 99% of the time)
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/**
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* Constructs an empty <tt>HashMap</tt> with the default initial capacity
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* (16) and the default load factor (0.75).
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*/
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constructor() {
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hashMap = IntMap()
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}
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/**
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* Constructs an empty <tt>HashMap</tt> with the specified initial
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* capacity and the default load factor (0.75).
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*
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* @param initialCapacity the initial capacity.
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*
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* @throws IllegalArgumentException if the initial capacity is negative.
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*/
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constructor(initialCapacity: Int) {
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hashMap = IntMap(initialCapacity)
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}
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/**
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* Constructs a new <tt>HashMap</tt> with the same mappings as the
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* specified <tt>Map</tt>. The <tt>HashMap</tt> is created with
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* default load factor (0.75) and an initial capacity sufficient to
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* hold the mappings in the specified <tt>Map</tt>.
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*
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* @param map the map whose mappings are to be placed in this map
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*
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* @throws NullPointerException if the specified map is null
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*/
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constructor(map: Map<Int, String?>) {
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hashMap = IntMap(map.size)
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map.forEach { (index, key) ->
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hashMap.put(index, key)
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}
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}
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constructor(map: LockFreeIntStringMap) {
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hashMap = IntMap(map.hashMap)
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}
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/**
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* Constructs an empty <tt>HashMap</tt> with the specified initial
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* capacity and load factor.
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*
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* @param initialCapacity the initial capacity
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* @param loadFactor the load factor
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*
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* @throws IllegalArgumentException if the initial capacity is negative
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* or the load factor is nonpositive
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*/
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constructor(initialCapacity: Int, loadFactor: Float) {
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hashMap = IntMap(initialCapacity, loadFactor)
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}
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val map: IntMap<String>
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get() {
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@Suppress("UNCHECKED_CAST")
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return mapREF[this] as IntMap<String>
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}
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override val size: Int
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get() {
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// use the SWP to get a lock-free get of the value
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return mapREF[this].size
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}
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override val keys: MutableSet<Int>
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get() {
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return map.keys()
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}
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override val values: MutableCollection<String?>
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get() {
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@Suppress("UNCHECKED_CAST")
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return map.values() as MutableCollection<String?>
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}
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override val entries: MutableSet<MutableMap.MutableEntry<Int, String?>>
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get() {
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@Suppress("UNCHECKED_CAST")
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return map.entries() as MutableSet<MutableMap.MutableEntry<Int, String?>>
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}
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override fun isEmpty(): Boolean {
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// use the SWP to get a lock-free get of the value
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return mapREF[this].isEmpty()
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}
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override fun containsKey(key: Int): Boolean {
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// use the SWP to get a lock-free get of the value
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return mapREF[this].containsKey(key)
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}
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override fun containsValue(value: String?): Boolean {
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// use the SWP to get a lock-free get of the value
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return mapREF[this].containsValue(value)
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}
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override operator fun get(key: Int): String? {
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return mapREF[this][key] as String?
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}
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@Synchronized
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override fun put(key: Int, value: String?): String? {
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return hashMap.put(key, value)
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}
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@Synchronized
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override fun putAll(from: Map<out Int, String?>) {
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hashMap.putAll(from)
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}
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@Synchronized
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override fun remove(key: Int): String? {
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return hashMap.remove(key)
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}
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@Synchronized
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fun removeAllValues(value: String) {
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val iterator = hashMap.entries().iterator()
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while (iterator.hasNext()) {
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val value1 = iterator.next()
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if (value1.value == value) {
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iterator.remove()
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}
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}
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}
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@Synchronized
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fun replaceAll(hashMap: IntMap<String?>) {
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this.hashMap.clear()
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this.hashMap.putAll(hashMap)
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}
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@Synchronized
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override fun clear() {
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hashMap.clear()
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}
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override fun equals(other: Any?): Boolean {
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return (mapREF[this] == other)
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}
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override fun hashCode(): Int {
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return mapREF[this].hashCode()
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}
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override fun toString(): String {
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return mapREF[this].toString()
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}
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// this must be at the end of the file!
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companion object {
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const val version = Collections.version
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// Recommended for best performance while adhering to the "single writer principle". Must be static-final
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private val mapREF = AtomicReferenceFieldUpdater.newUpdater(
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LockFreeIntStringMap::class.java, IntMap::class.java, "hashMap"
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)
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}
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}
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Reference in New Issue