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It was used in the world record calculations of 2.7 trillion digits of π in December 2009, [3] 10 trillion digits in October 2011, [4] [5] 22.4 trillion digits in November 2016, [6] 31.4 trillion digits in September 2018–January 2019, [7] 50 trillion digits on January 29, 2020, [8] 62.8 trillion digits on August 14, 2021, [9] 100 trillion ...
The Gauss–Legendre algorithm is an algorithm to compute the digits of π. It is notable for being rapidly convergent, with only 25 iterations producing 45 million correct digits of π . However, it has some drawbacks (for example, it is computer memory -intensive) and therefore all record-breaking calculations for many years have used other ...
where C is the circumference of a circle, d is the diameter, and r is the radius.More generally, = where L and w are, respectively, the perimeter and the width of any curve of constant width.
The same approach can be used to calculate digits of the binary expansion of ln(2) starting from an arbitrary nth position. The number of terms in the "head" sum increases linearly with n , but the complexity of each term only increases with the logarithm of n if an efficient method of modular exponentiation is used.
Start by setting [4] = = = + Then iterate + = + + = (+) + + = (+ +) + + + Then p k converges quadratically to π; that is, each iteration approximately doubles the number of correct digits.The algorithm is not self-correcting; each iteration must be performed with the desired number of correct digits for π 's final result.
For the first term in the Taylor series, all digits must be processed. In the last term of the Taylor series, however, there's only one digit remaining to be processed. In all of the intervening terms, the number of digits to be processed can be approximated by linear interpolation. Thus the total is given by:
The first belongs to a family of formulas which were rigorously proven by the Chudnovsky brothers in 1989 [11] and later used to calculate 10 trillion digits of π in 2011. [12] The second formula, and the ones for higher levels, was established by H.H. Chan and S. Cooper in 2012.
Today, this algorithm is used by Mathematica to calculate π, and has continued to be used by others who have achieved world records in pi calculation. The brothers also assisted the Metropolitan Museum of Art around 2003 in the merging of a series of digital photographs taken of The Hunt of the Unicorn tapestries during their cleaning. [7]