JavaEWAH

(c) Daniel Lemire,

http://lemire.me/en/

This is a word-aligned compressed variant of

the Java Bitset class. It uses a 64-bit RLE-like

compression scheme.

The goal of word-aligned compression is not to

achieve the best compression, but rather to

improve query processing time. Hence, we try

to save CPU cycles, maybe at the expense of

storage. However, the EWAH scheme we implemented

is always more efficient storage-wise than an

uncompressed bitmap (as implemented in the java

BitSet class by Sun).

For better performance, use a 64-bit JVM over

64-bit CPUs.

Among other possible open source licenses, this

code is licensed under Apache License, Version 2.0 (ASL2.0).

For more details, see the following paper:

Daniel Lemire, Owen Kaser, Kamel Aouiche, Sorting improves word-aligned bitmap indexes.

Data & Knowledge Engineering 69 (1), pages 3-28, 2010.

http://arxiv.org/abs/0901.3751

== Unit testing ==

As of October 2011, this packages relies on Maven. To

test it:

mvn test

See

http://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html

for details.

=== Usage ==

See example.java.

== Maven central repository ==

You can download JavaEWAH from the Maven central repository:

http://repo1.maven.org/maven2/com/googlecode/javaewah/JavaEWAH/

You can also specify the dependency in the Maven "pom.xml" file:

<dependencies>

<dependency>

<groupId>com.googlecode.javaewah</groupId>

<artifactId>JavaEWAH</artifactId>

<version>0.3.1</version>

</dependency>

</dependencies>