--------------------------------------------------------------------------------
Apfloat is a high performance arbitrary precision package. That means you can do calculations involving millions of digits with it. It uses Number Theoretic Transforms. It's simple to use. It's fast. It's freeware.
A Java version is also available.
Apfloat could be compiled in general with most C++ compilers, however gcc is recommended. It has assembler optimizations for x86, Alpha and MIPS processors.
A sample program for calculating pi is included in the package. Calculating one million digits of pi takes less than half a minute with an Athlon XP computer. This makes it one of the fastest programs for calculating pi (faster than the Japanese super_pi program).
Compiled executables for calculating pi are available for download. The fastest versions of the program can calculate up to 226 million decimal digits of pi. A machine with at least 256 MB of RAM would be needed for such a calculation. A version, which can calculate up to 1.9 billion digits (if you have at least two gigabytes of memory) is also provided, but it is somewhat slower.