A compressed alternative to the Java BitSet class
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JavaEWAH (c) Daniel Lemire, http://www.daniel-lemire.com/ 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). Unlike the similar compressedbitset, it does not implement a patented scheme (to D. Lemire's knowledge). http://code.google.com/p/compressedbitset/ For better performance, use a 64-bit JVM over 64-bit CPUs. Among other possible open source licenses, this code is licensed under GPL version 3 and 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. === Warning == Don't trust software you downloaded off the internet. When in doubt, run the unit tests (javaewah/unit.java). Report bugs when you find them.