FastIntegerCompression

This is an integer compression library in JavaScript, useful for work on indexes. Given an array of small integers, it produces an ArrayBuffer that uses far fewer bytes than the original (using VByte compression). It assumes a modern JavaScript engine with typed arrays.

From the compressed data, you can later recover the original array quickly (at a rate of millions of integers per second).

   // var FastIntegerCompression = require("fastintcompression");// if you use node
   var array = [10,100000,65999,10,10,0,1,1,2000,0xFFFFFFFF];
   var buf = FastIntegerCompression.compress(array);
   var back = FastIntegerCompression.uncompress(buf); // gets back [10,100000,65999,10,10,0,1,1,2000]

By default, non-negative 32-bit integers are expected. If you have signed (negative and positive) 32-bit integers, then you must use distinct functions since we need to code the sign bit:

   // var FastIntegerCompression = require("fastintcompression");// if you use node
   var array = [10,100000,65999,10,10,0,-1,-1,-2000];
   var buf = FastIntegerCompression.compressSigned(array);
   var back = FastIntegerCompression.uncompressSigned(buf); // gets back [10,100000,65999,10,10,0,-1,-1,-2000]

You can install the library under node with the command line

   npm install fastintcompression

This code is made available under the Apache License 2.0.

Suitability

This library is meant to compress arrays of small integers. It is not meant to compress text documents or arrays of large (or random) integers.

Performance numbers

Go to benchmark repository (check the README.md file) and run the benchmark:

$ node test.js
Platform: linux 3.13.0-91-generic x64
Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz
Node version 4.5.0, v8 version 4.5.103.37

input size: 7.813K compressed size: 1000B
FastIntegerCompression.compress x 337,845 ops/sec ±0.93% (92 runs sampled)
Fastest is FastIntegerCompression.compress
FastIntegerCompression.uncompress x 187,694 ops/sec ±0.72% (93 runs sampled)
Fastest is FastIntegerCompression.uncompress

These numbers means that we can uncompress 187,694 1000-integer arrays per second. That's 187 millions of integers per second.

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• https://github.com/lemire/FastPriorityQueue.js
• https://github.com/lemire/StablePriorityQueue.js
• https://github.com/lemire/FastBitSet.js