Original URL: http://www.theregister.co.uk/2010/01/06/very_long_pi/

Boffin calculates pi to 2.7 trillion digits

On a humble desktop PC

By Lester Haines

Posted in Science, 6th January 2010 11:14 GMT

Computer scientist Fabrice Bellard says he's calculated pi to a whopping 2.7 trillion digits - a Herculean task which took a humble desktop PC 131 days.

According to the BBC, the previous record of 2.6 trillion digits was held by Daisuke Takahashi of Japan's University of Tsukuba. That number-crunching exercise took just 29 hours, albeit on a T2K Open Supercomputer "2,000 times faster and thousands of times more expensive" than Bellard's bog-standard kit which cost "less than 2000 euros".

The Beeb explains that such exercises are known as "arbitrary-precision arithmetic", or "bignum arithmetic", wherein rather large numbers are calculated to a precision of digits limited only by the computer system's available memory.

In this case, pi to 2.7 trillion digits requires "over a terabyte" of disk storage space and is so long that if you fancy reciting one number a second, you'd be done in 49,000 years.

Bellard admitted he's "not especially interested in the digits of pi" and that "arbitrary-precision arithmetic with huge numbers has little practical use", although "some of the involved algorithms are interesting to do other things".

Ivars Peterson, director of publications at the Mathematical Association of America, explained to the BBC that an exceedingly long pi did indeed serve some purpose. He said: "People have used it as a vehicle for testing algorithms and for testing computers; pi has a precise sequence of digits, it's exactly that, and if your computer isn't operating flawlessly some of those digits will be wrong.

He concluded: "It's more than just for the fun of it - pi is a way of testing a method and then the method can be used for other purposes." ®

Bootnote

Bellard says he's planning to release Linux and Windows (64 bit only) versions of the program he used to do the calculation, and here's his kit list should you wish to give it a go:

Core i7 CPU at 2.93 GHz
6 GB of RAM
7.5 TB of disk storage using five 1.5 TB hard disks (Seagate Barracuda 7200.11 model)

Bellard notes: "The Linux Operating System was used with the 64 bit Red Hat Fedora 10 distribution. The 7.5 TB disk storage was managed using software RAID-0 and the ext4 filesystem. Files of up to 2.5 TB were manipulated during the computation."