Y-Cruncher is a program that computes Pi and other constants to billions/trillions of digits. It currently holds the world record for the most digits of Pi ever computed (13.3 trillion digits) as well as a bunch of other less popular constants.

Y-Cruncher is also the first Pi computing program that can a) use multiple threads for a worthwhile speedup, b) use (and stress) an unlimited amount of memory and c) utilize ISA extensions (SSE, AVX, etc...) for nearly all modern processors. Y-Cruncher owner Mysticial developed a GUI that can run and submit results to HWBOT. This competition is to best test the submitter. More information in the forum thread.