The Computation of Pi to 29,360,000 Decimal Digits Using Borweins Quartically Convergent Algorithm

摘要

In a recent work, Borwein and Borwein derived a class of algorithms based on the theory of complete elliptic integrals that yield very rapidly convergent approximations to elementary constants. The author has implemented Borweins' quartically convergent algorithm for 1/pi, using a prime modulus transform multi-precision technique, to compute over 29,360,000 digits of the decimal expansion of pi. The result was checked by using a different algorithm, also due to the Borweins, that converges quadratically to pi. These computations were performed as a system test of the Cray-2 operated by the Numerical Aerodynamic Simulation (NAS) Program at NASA Ames Research Center. The calculations were made possible by the very large main memory of the Cray-2. Until recently the largest computation of the decimal expansion of pi was due to Kanada and Tamura of the University of Tokyo. In 1983 they computed approximately 16 million digits on a Hitachi S-810 computer. Late in 1985 Gosper reported computing 17 million digits using a Symbolics workstation. Since the computation described in this paper was performed, Kanada has reported extending the computation of pi to over 134 million digits (January 1987). This paper describes the algorithms and techniques used in the author's computation, both for converging to pi and for performing the required multi-precision arithmetic. The results of statistical analyses of the computed decimal expansion are also included.