Colt HashMap

Extension of Colt HashMap using Generics for storage of Objects

This is based on part of the code from Colt Project: http://acs.lbl.gov/software/colt/ The Colt Project is made before generics was introduced in Java. This means that the HashMap from Colt Project cannot be used as a drop-in replacement for Java's HashMap.

This version contains only the HashMap part of Colt Project (version 1.2.0) and adds the support for generics, so that it can now be used as a drop-in replacement for Java's HashHamp

Download

JAR also contains source code

Date	Version	File	Description
22. June 2013	1.01	http://files.subsecret.dk/ColtHashMap101.jar	Benchmark code updated
16. June 2013	1.00	http://files.subsecret.dk/ColtHashMap100.jar	Initial release

Changes to original code

• Removed all non-hashmap relevant code
• Fixed bug where OpenLongObjectHashMap.indexOfValue(...) and OpenIntObjectHashMap.indexOfValue(...) used "==" rather than equals for Object types.
• Created new interfaces and classes for wrapping Colt Project HashMap in Java's Map<K,V> interface.

Usage

Class	Key type	Value type
ColtIntHashMap	Int	Object
ColtIntIntHashMap	Int	Int
ColtQuickIntIntHashMap	Int	Int
ColtIntDoubleHashMap	Int	Double
ColtLongHashMap	Long	Object
ColtDoubleIntHashMap	Double	Int

Existing code can easily be changed to use new HashMaps's. By changing to Colt's HashMap there will be a memory saving because of more efficient storage of keys and possibly values. However the penalty for autoboxing is still present unless using put(...) and get(...) on the native type.

//From
Map<Integer, String> map = new HashMap<Integer,String>();
map.put(3,"test");

//To
ColtIntHashMap<String> native = new ColtIntHashMap<String>();
Map<Integer, String> map = native;
map.put(3,"test");

//For maximum performance, its necessary to use the original type when putting and retrieving from the map.
native.put(3,"test"); 
//Caveat: When using ColtIntHashMap<Integer> the compiler cannot infer which of the two put methods you want, and you need to use putNative(...) method
native.putNative(3,"test");

Benchmark

JVM options: -Xms8g -Xmx8g Insertions: 20 million (7 million duplicates) get(...) 13 million Contains key: 20 million Removals: 6 million containsValue(): 100

JVM 1.6

Map	Memory usage (mb)	Insertion	get(...) (sec.)
Java HashMap	2485	8	8
Colt HashMap	1711	7	4
Colt (Native) HashMap	1706	6.1	2.6
Colt (IntInt) HashMap	1304	4.7	1.9
Colt (Quick IntInt) HashMap	1304	4.8	1.9