Shigeru Kondo, a systems engineer in his 50s at a food company in the central Japanese prefecture of Nagano, in August calculated pi -- the ratio of a circle’s circumference to its diameter -- to five trillion digits, almost doubling the accuracy of the previous world record. Last week, the calculation was recognized by Guinness World Records with a certificate mailed to Kondo, who said he began the calculations simply as a hobby. “I really want to praise my computer, which calculated continuously for three months without complaint,” Kondo told the Chunichi Shimbun daily. He shared the honor with a US. computer science student, Alexander Yee, who programmed the application software and liaised with Kondo by e-mail. Calculating a more accurate pi, which is believed to go on forever, has been a challenge for scholars for thousands of years, ever since the parameter was used in ancient Egypt.