Compressed bitmaps in C#
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CSharpEWAH (c) 2012 Kemal Erdogan, Daniel Lemire and Ciaran Jessup, This code is licensed under the Apache License, Version 2.0 (ASL2.0) This is a compressed variant of the standard bitarray class. It uses a 64-bit RLE-like compression scheme. It can be used to implement bitmap indexes. 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 bitarray. For more details regarding the compressed format, see Section 3 of 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 (The PDF file is freely available on the arXiv site.) == Unit testing == Building using Mono You can build CSharpEWAH using the open source Mono toolchain using the xbuild command. Just type xbuild in the main directory. This should build a C# executable file that you will then find in a newly created bin directory. $ xbuild Then you can run the executable using the mono command: $ mono ./EWAH.RunTests/bin/Debug/EWAH.RunTests.exe This will run unit tests. === Usage == See example.cs.