Added LockFreeIntMap
Robinson
parent
7f1b1c0c0c
commit
f3855bed38
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@ -54,7 +54,7 @@ import java.util.*
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* @author Nathan Sweet
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* @author Tommy Ettinger
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*/
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class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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open class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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companion object {
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const val version = Collections.version
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}
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@ -198,14 +198,14 @@ class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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return null
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}
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fun putAll(map: IntMap<out V>) {
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ensureCapacity(map.size_)
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if (map.hasZeroValue) {
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put(0, map.zeroValue!!)
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open fun putAll(from: IntMap<out V>) {
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ensureCapacity(from.size_)
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if (from.hasZeroValue) {
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put(0, from.zeroValue!!)
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}
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val keyTable = map.keyTable
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val valueTable = map.valueTable
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val keyTable = from.keyTable
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val valueTable = from.valueTable
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var i = 0
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val n = keyTable.size
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while (i < n) {
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@ -306,7 +306,7 @@ class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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* nothing is done. If the map contains more items than the specified capacity, the next highest power of two capacity is used
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* instead.
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*/
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fun shrink(maximumCapacity: Int) {
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open fun shrink(maximumCapacity: Int) {
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require(maximumCapacity >= 0) { "maximumCapacity must be >= 0: $maximumCapacity" }
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val tableSize = tableSize(maximumCapacity, loadFactor)
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if (keyTable.size > tableSize) resize(tableSize)
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@ -315,7 +315,7 @@ class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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/**
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* Clears the map and reduces the size of the backing arrays to be the specified capacity / loadFactor, if they are larger.
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* */
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fun clear(maximumCapacity: Int) {
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open fun clear(maximumCapacity: Int) {
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val tableSize = tableSize(maximumCapacity, loadFactor)
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if (keyTable.size <= tableSize) {
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clear()
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@ -357,7 +357,7 @@ class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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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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* [.equals].
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*/
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fun containsValue(value: Any?, identity: Boolean = false): Boolean {
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open fun containsValue(value: Any?, identity: Boolean): Boolean {
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val valueTable = valueTable
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if (value == null) {
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if (hasZeroValue && zeroValue == null) return true
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@ -503,7 +503,7 @@ class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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* Uses == for comparison of each value.
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*/
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@Suppress("UNCHECKED_CAST")
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fun equalsIdentity(other: Any?): Boolean {
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open fun equalsIdentity(other: Any?): Boolean {
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if (other === this) return true
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if (other !is IntMap<*>) return false
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other as IntMap<V>
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@ -568,7 +568,7 @@ class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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* Use the [Entries] constructor for nested or multithreaded iteration.
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*/
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@Suppress("UNCHECKED_CAST")
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fun entries(): Entries<V?> {
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open fun entries(): Entries<V?> {
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if (allocateIterators) return Entries(this as IntMap<V?>)
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if (entries1 == null) {
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entries1 = Entries(this as IntMap<V?>)
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@ -592,7 +592,7 @@ class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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* If [Collections.allocateIterators] is false, the same iterator instance is returned each time this method is called.
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* Use the [Entries] constructor for nested or multithreaded iteration.
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*/
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fun values(): Values<V> {
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open fun values(): Values<V> {
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if (allocateIterators) return Values(this)
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if (values1 == null) {
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values1 = Values(this)
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@ -616,7 +616,7 @@ class IntMap<V> : MutableMap<Int, V>, MutableIterable<IntMap.Entry<V?>> {
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* If [Collections.allocateIterators] is false, the same iterator instance is returned each time this method is called.
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* Use the [Entries] constructor for nested or multithreaded iteration.
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*/
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fun keys(): Keys {
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open fun keys(): Keys {
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if (allocateIterators) return Keys(this)
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if (keys1 == null) {
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keys1 = Keys(this)
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@ -1,230 +0,0 @@
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/*
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* Copyright 2018 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.AtomicReferenceFieldUpdater;
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import dorkbox.collections.IntMap.Entries;
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import dorkbox.collections.IntMap.Keys;
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import dorkbox.collections.IntMap.Values;
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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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* @author Nathan Sweet
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*/
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@SuppressWarnings("unchecked")
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public final
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class LockFreeIntMap<V> implements Cloneable, Serializable {
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public static final String 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 static final AtomicReferenceFieldUpdater<LockFreeIntMap, IntMap> mapREF = AtomicReferenceFieldUpdater.newUpdater(
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LockFreeIntMap.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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// 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>LockFreeIntMap</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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public
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LockFreeIntMap() {
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map = new IntMap<V>();
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}
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/**
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* Constructs a copy of an <tt>LockFreeIntMap</tt>
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*/
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public
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LockFreeIntMap(LockFreeIntMap 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>LockFreeIntMap</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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LockFreeIntMap(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>LockFreeIntMap</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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LockFreeIntMap(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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/**
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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 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 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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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 Entries} constructor for nested or multithreaded iteration.
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*/
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public
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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 Entries} constructor for nested or multithreaded iteration.
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*/
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public
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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 Entries} constructor for nested or multithreaded iteration.
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*/
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public
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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 +1,217 @@
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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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*
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* An unordered map. This implementation is a cuckoo hash map using 3 hashes, random walking, and a small stash for problematic
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* keys. Null keys are not allowed. Null values are allowed. No allocation is done except when growing the table size. <br></br>
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*
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*
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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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*
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* Iteration can be very slow for a map with a large capacity. [.clear] and [.shrink] can be used to reduce
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* the capacity. [OrderedMap] provides much faster iteration.
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*/
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class LockFreeIntMap<V> : IntMap<V>, Cloneable, Serializable {
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@Volatile
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private var hashMap: IntMap<V>
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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 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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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 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].size == 0
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}
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@Suppress("UNCHECKED_CAST")
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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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val value = mapREF[this] as IntMap<V>
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return value.containsKey(key)
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}
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override fun containsValue(value: Any?, identity: Boolean): 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, identity)
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}
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@Suppress("UNCHECKED_CAST")
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override operator fun get(key: Int): V? {
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// use the SWP to get a lock-free get of the value
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val value = mapREF[this] as IntMap<V>
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return value.get(key)
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}
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@Synchronized
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override fun put(key: Int, value: V): V? {
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return hashMap.put(key, value)
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}
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@Synchronized
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override fun remove(key: Int): V? {
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return hashMap.remove(key)
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}
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@Synchronized
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override fun putAll(from: IntMap<out V>) {
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hashMap.putAll(from)
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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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/**
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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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*
|
||||
* Returns an iterator for the keys in the map. Remove is supported. Note that the same iterator instance is returned each
|
||||
* time this method is called. Use the [ObjectMap.Entries] constructor for nested or multithreaded iteration.
|
||||
*/
|
||||
override fun keys(): Keys {
|
||||
return mapREF[this].keys()
|
||||
}
|
||||
|
||||
/**
|
||||
* DO NOT MODIFY THE MAP VIA THIS (unless you synchronize around it!) It will result in unknown object visibility!
|
||||
*
|
||||
* Returns an iterator for the values in the map. Remove is supported. Note that the same iterator instance is returned each
|
||||
* time this method is called. Use the [ObjectMap.Entries] constructor for nested or multithreaded iteration.
|
||||
*/
|
||||
@Suppress("UNCHECKED_CAST")
|
||||
override fun values(): Values<V> {
|
||||
return mapREF[this].values() as Values<V>
|
||||
}
|
||||
|
||||
/**
|
||||
* DO NOT MODIFY THE MAP VIA THIS (unless you synchronize around it!) It will result in unknown object visibility!
|
||||
*
|
||||
* Returns an iterator for the entries in the map. Remove is supported. Note that the same iterator instance is returned each
|
||||
* time this method is called. Use the [ObjectMap.Entries] constructor for nested or multithreaded iteration.
|
||||
*/
|
||||
@Suppress("UNCHECKED_CAST")
|
||||
override fun entries(): Entries<V?> {
|
||||
return mapREF[this].entries() as Entries<V?>
|
||||
}
|
||||
|
||||
override fun equals(other: Any?): Boolean {
|
||||
return mapREF[this] == other
|
||||
}
|
||||
|
||||
override fun equalsIdentity(other: Any?): Boolean {
|
||||
return mapREF[this].equalsIdentity(other)
|
||||
}
|
||||
|
||||
override fun hashCode(): Int {
|
||||
return mapREF[this].hashCode()
|
||||
}
|
||||
|
||||
override fun toString(): String {
|
||||
return mapREF[this].toString()
|
||||
}
|
||||
|
||||
/**
|
||||
* Clears the map and reduces the size of the backing arrays to be the specified capacity, if they are larger. The reduction
|
||||
* is done by allocating new arrays, though for large arrays this can be faster than clearing the existing array.
|
||||
*/
|
||||
@Synchronized
|
||||
override fun clear(maximumCapacity: Int) {
|
||||
mapREF[this].clear(maximumCapacity)
|
||||
}
|
||||
|
||||
/**
|
||||
* Reduces the size of the backing arrays to be the specified capacity or less. If the capacity is already less, nothing is
|
||||
* done.
|
||||
* If the map contains more items than the specified capacity, the next highest power of two capacity is used instead.
|
||||
*/
|
||||
@Synchronized
|
||||
override fun shrink(maximumCapacity: Int) {
|
||||
mapREF[this].shrink(maximumCapacity)
|
||||
}
|
||||
|
||||
companion object {
|
||||
const val version = Collections.version
|
||||
|
||||
// Recommended for best performance while adhering to the "single writer principle". Must be static-final
|
||||
private val mapREF = AtomicReferenceFieldUpdater.newUpdater(
|
||||
LockFreeIntMap::class.java, IntMap::class.java, "hashMap"
|
||||
)
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue