The gmp package contains GNU MP, a library for arbitrary precision arithmetic, signed integers operations, rational numbers and floating point numbers. GNU MP is designed for speed, for both small and very large operands. GNU MP is fast because it uses fullwords as the basic arithmetic type, it uses fast algorithms, it carefully optimizes assembly code for many CPUs' most common inner loops, and it generally emphasizes speed over simplicity/elegance in its operations. Install the gmp package if you need a fast arbitrary precision library.