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Emma Haruka Iwao grew up fascinated by pi. Now she is calculated over 31 trillion of the numbers.
Iwao puts the newest Guinness World Record for the most accurate value of pi on Thursday. The Google employee and her team calculated 31 415 926 535 897 digits pi – crushing a 2016 record with trillion digits.
And everything traces back to its infancy of the mathematical constant – the relationship between the circumference of a circle and its diameter.
"I liked computers when I was a child," she tells NPR Here & Now . "And I learned that some people use computers to calculate millions and billions of digits in pi. It seemed so fascinating to me."
Pi was estimated for the first time thousands of years ago, and in the mid-20th century, mathematicians had calculated 1000 digits in the number, using a gear-driven counter. But the digital computer's birth in the 20's overloaded efforts to estimate pi more accurately. By 2009, Daisuke Takahashi at the University of Tsukuba told about 2.6 trillion pi with a supercomputer.
Iwao knew about Takahashi when she was a child, she says, because he held the world record at that time, along with Japanese mathematician Yasumasa Canada. Iwao was inspired by her work, and she would continue to study with Takahashi at the university. When she later told her own attempt to calculate the numbers in pi, "he shared his advice and some technical strategies," she said in a Google blog post.
But when Iwao broke the record herself, she didn't use a supercomputer. Instead, she used y-cruncher, an application that everyone can download, runs on 25 virtual Google Cloud machines.
Even with Google's infrastructure on her side, it wasn't easy to determine trillion numbers. The calculation took about four months and about 170 terabytes of data to complete, according to Google, or "roughly equal to the amount of data in the entire library's congressional print."
Is her result useful? Not in practical sense, Iwao recognizes. "For technical and scientific applications," she says, "You probably don't need more than 100 numbers." NASA, for example, only needs to use pi rounded to the 15 decimal number to send spacecraft to the moon.
But she says that it will be beneficial for anyone who studies the functions of pi to better understand the number through statistical analysis. And for her and her colleagues at her Tokyo office, she adds, it was worth celebrating with "a real pie".
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