Google bakes world's largest pi

Google developer Emma Iwao has claimed a Guiness World Record for calculating pi to 31.4 trillion digits using Google Cloud

Pi, the ratio of the circumference of a circle to its diameter, which starts as 3.1415 and just keeps going, has many applications. Engineers use it to measure the circular velocity of things like wheels, motor shafts, engine parts and gears. It can measure things like ocean, light and sound waves, river bends and radioactive particle distribution. NASA even uses it to calculate space flights.

Most of these applications don't need pi to more than a few hundred digits, but that hasn't stopped mathematicians from continually setting and breaking records using calculators specifically built for the task.

For the first time ever, Google senior developer advocate Emma Iwao has turned away from physical machines and used the cloud to calculate pi - to more than 31.4 trillion digits (31,415,926,535,897, to be exact), which we can't reproduce here because bits would start falling off the Computing site.

Iwao set a new Guinness World Record with her work, which used y-cruncher (a Pi-benchmark program developed by Alexander Yee) on a Google Compute Engine cluster of 25 virtual machines.

She turned to the cloud because of Chudnovky's formula - a common algorithm for computing π. Basically, it states that the time and resources necessary to calculate digits increase more rapidly than the digits themselves, and it gets harder to survive a potential hardware outage or failure as the computation goes on.

The cloud, says Iwao, solved both problems. It has scalable and powerful compute, and a live migration feature to keep infrastructure up to date. Over the course of the four months (121 days) it took to finish the calculations, Google Cloud performed ‘thousands' of these migrations/

The biggest challenge in calculating pi to such extreme lengths is the massive storage and memory requirements. Iwao's work required 170TB of data to complete: about the same as housed in all of the print collections in the US Library of Congress: or about 2,833.33 (repeating, of course) copies of World of Warcraft.

One of the uses of these gigantic calculations of pi is using them to test supercomputers. Iwao said, "When I was a kid, I didn't have access to supercomputers. But even if you don't work for Google, you can apply for various scholarships and programs to access computing resources," she says. "I was very fortunate that there were Japanese world record holders that I could relate to. I'm really happy to be one of the few women in computer science holding the record, and I hope I can show more people who want to work in the industry what's possible."