| \u001B[1mSYNOPSIS\u001B[0m |
| ${project.description} |
| |
| Original Maven URL: |
| \u001B[33mmvn:${pkgGroupId}/${pkgArtifactId}/${pkgVersion}\u001B[0m |
| |
| \u001B[1mDESCRIPTION\u001B[0m |
| The bit array data structure is implemented in Java as the BitSet class. Unfortunately, this fails to scale |
| without compression. |
| |
| JavaEWAH is a word-aligned compressed variant of the Java bitset class. It uses a 64-bit run-length encoding (RLE) |
| compression scheme. We trade-off some compression for better processing speed. We also have a 32-bit version which |
| compresses better, but is not as fast. |
| |
| In general, 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 BitSet class). |
| Unlike some alternatives, javaewah does not rely on a patented scheme. |
| |
| It includes exhaustive unit testing. As of November 2011, Apache Maven is used to build and validate the releases. |
| (Building the source code with javac remains trivial). |
| |
| Usage: |
| |
| // set bits at pos. 0, 2, 64, and 1<<30 to value "true" (others are false) |
| EWAHCompressedBitmap ewahBitmap1 = EWAHCompressedBitmap.bitmapOf(0,2,64,1<<30); |
| EWAHCompressedBitmap ewahBitmap2 = EWAHCompressedBitmap.bitmapOf(1,3,64,1<<30); |
| EWAHCompressedBitmap xorbitmap = EWAHCompressedBitmap.xor(ewahBitmap1,ewahBitmap2); |
| int[] setbits = xorbitmap.toArray();// which bits are set? |
| |
| \u001B[1mSEE ALSO\u001B[0m |
| \u001B[36mhttp://code.google.com/p/javaewah/\u001B[0m |
