[jira] [Updated] (BEANUTILS-539) use ConcurrentHashMap insteadof WeakFastHashMap
[
https://issues.apache.org/jira/browse/BEANUTILS-539?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
JIN XU updated BEANUTILS-539:
-
Description:
Hi.
throughtout my performance test (using Jprofiler), I found out WeakHashMap is
far slower than ConcurrentHashMap.
Should we use ConcurrentHashMap instead of WeakHashMap?
I will attach my test codes here.
{code:java}
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.beanutils2;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.WeakHashMap;
/**
* A customized implementation of {@code java.util.HashMap} designed
* to operate in a multi-threaded environment where the large majority of
* method calls are read-only, instead of structural changes. When operating
* in "fast" mode, read calls are non-synchronized and write calls perform the
* following steps:
*
* Clone the existing collection
* Perform the modification on the clone
* Replace the existing collection with the (modified) clone
*
* When first created, objects of this class default to "slow" mode, where
* all accesses of any type are synchronized but no cloning takes place. This
* is appropriate for initially populating the collection, followed by a switch
* to "fast" mode (by calling {@code setFast(true)}) after initialization
* is complete.
*
* NOTE: If you are creating and accessing a
* {@code HashMap} only within a single thread, you should use
* {@code java.util.HashMap} directly (with no synchronization), for
* maximum performance.
*
* NOTE: This class is not cross-platform.
* Using it may cause unexpected failures on some architectures.
* It suffers from the same problems as the double-checked locking idiom.
* In particular, the instruction that clones the internal collection and the
* instruction that sets the internal reference to the clone can be executed
* or perceived out-of-order. This means that any read operation might fail
* unexpectedly, as it may be reading the state of the internal collection
* before the internal collection is fully formed.
* For more information on the double-checked locking idiom, see the
* http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html;>
* Double-Checked Locking Idiom Is Broken Declaration.
*
* @since Commons Collections 1.0
*/
public class WeakFastHashMap extends HashMap {
private static final long serialVersionUID = 1L;
/**
* The underlying map we are managing.
*/
private volatile Map map = null;
/**
* Are we currently operating in "fast" mode?
*/
private boolean fast = false;
// Constructors
/**
* Construct an empty map.
*/
public WeakFastHashMap() {
super();
this.map = createMap();
}
/**
* Construct an empty map with the specified capacity.
*
* @param capacity the initial capacity of the empty map
*/
public WeakFastHashMap(final int capacity) {
super();
this.map = createMap(capacity);
}
/**
* Construct an empty map with the specified capacity and load factor.
*
* @param capacity the initial capacity of the empty map
* @param factor the load factor of the new map
*/
public WeakFastHashMap(final int capacity, final float factor) {
super();
this.map = createMap(capacity, factor);
}
/**
* Construct a new map with the same mappings as the specified map.
*
* @param map the map whose mappings are to be copied
*/
public WeakFastHashMap(final Map map) {
super();
this.map = createMap(map);
}
// Property access
/**
* Returns true if this map is operating in fast mode.
*
* @return true if this map is operating in fast mode
*/
public boolean getFast() {
return this.fast;
}
/**
* Sets whether this map is operating in fast mode.
*
* @param fast true if this map should operate in fast mode
*/
public void setFast(final
[jira] [Updated] (BEANUTILS-539) use ConcurrentHashMap insteadof WeakFastHashMap
[
https://issues.apache.org/jira/browse/BEANUTILS-539?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
JIN XU updated BEANUTILS-539:
-
Description:
Hi.
throughtout my performance test (using Jprofiler), I found out WeakHashMap is
far slower than ConcurrentHashMap.
Should we use ConcurrentHashMap instead of WeakHashMap?
I will attach my test codes here.
{code:java}
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.beanutils2;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.WeakHashMap;
/**
* A customized implementation of {@code java.util.HashMap} designed
* to operate in a multi-threaded environment where the large majority of
* method calls are read-only, instead of structural changes. When operating
* in "fast" mode, read calls are non-synchronized and write calls perform the
* following steps:
*
* Clone the existing collection
* Perform the modification on the clone
* Replace the existing collection with the (modified) clone
*
* When first created, objects of this class default to "slow" mode, where
* all accesses of any type are synchronized but no cloning takes place. This
* is appropriate for initially populating the collection, followed by a switch
* to "fast" mode (by calling {@code setFast(true)}) after initialization
* is complete.
*
* NOTE: If you are creating and accessing a
* {@code HashMap} only within a single thread, you should use
* {@code java.util.HashMap} directly (with no synchronization), for
* maximum performance.
*
* NOTE: This class is not cross-platform.
* Using it may cause unexpected failures on some architectures.
* It suffers from the same problems as the double-checked locking idiom.
* In particular, the instruction that clones the internal collection and the
* instruction that sets the internal reference to the clone can be executed
* or perceived out-of-order. This means that any read operation might fail
* unexpectedly, as it may be reading the state of the internal collection
* before the internal collection is fully formed.
* For more information on the double-checked locking idiom, see the
* http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html;>
* Double-Checked Locking Idiom Is Broken Declaration.
*
* @since Commons Collections 1.0
*/
public class WeakFastHashMap extends HashMap {
private static final long serialVersionUID = 1L;
/**
* The underlying map we are managing.
*/
private volatile Map map = null;
/**
* Are we currently operating in "fast" mode?
*/
private boolean fast = false;
// Constructors
/**
* Construct an empty map.
*/
public WeakFastHashMap() {
super();
this.map = createMap();
}
/**
* Construct an empty map with the specified capacity.
*
* @param capacity the initial capacity of the empty map
*/
public WeakFastHashMap(final int capacity) {
super();
this.map = createMap(capacity);
}
/**
* Construct an empty map with the specified capacity and load factor.
*
* @param capacity the initial capacity of the empty map
* @param factor the load factor of the new map
*/
public WeakFastHashMap(final int capacity, final float factor) {
super();
this.map = createMap(capacity, factor);
}
/**
* Construct a new map with the same mappings as the specified map.
*
* @param map the map whose mappings are to be copied
*/
public WeakFastHashMap(final Map map) {
super();
this.map = createMap(map);
}
// Property access
/**
* Returns true if this map is operating in fast mode.
*
* @return true if this map is operating in fast mode
*/
public boolean getFast() {
return this.fast;
}
/**
* Sets whether this map is operating in fast mode.
*
* @param fast true if this map should operate in fast mode
*/
public void setFast(final
