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- From: alopez-o@neumann.uwaterloo.ca (Alex Lopez-Ortiz)
- Subject: sci.math FAQ: How to compute Pi?
- Summary: Part 12 of many, New version,
- Originator: alopez-o@neumann.uwaterloo.ca
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- Date: Fri, 17 Nov 1995 17:14:38 GMT
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- Archive-Name: sci-math-faq/specialnumbers/computePi
- Last-modified: December 8, 1994
- Version: 6.2
-
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- How to compute digits of pi ?
-
-
-
- Symbolic Computation software such as Maple or Mathematica can compute
- 10,000 digits of pi in a blink, and another 20,000-1,000,000 digits
- overnight (range depends on hardware platform).
-
- It is possible to retrieve 1.25+ million digits of pi via anonymous
- ftp from the site wuarchive.wustl.edu, in the files pi.doc.Z and
- pi.dat.Z which reside in subdirectory doc/misc/pi. New York's
- Chudnovsky brothers have computed 2 billion digits of pi on a homebrew
- computer.
-
- There are essentially 3 different methods to calculate pi to many
- decimals.
-
- 1. One of the oldest is to use the power series expansion of atan(x)
- = x - x^3/3 + x^5/5 - ... together with formulas like pi =
- 16*atan(1/5) - 4*atan(1/239) . This gives about 1.4 decimals per
- term.
-
- 2. A second is to use formulas coming from Arithmetic-Geometric mean
- computations. A beautiful compendium of such formulas is given in
- the book pi and the AGM, (see references). They have the advantage
- of converging quadratically, i.e. you double the number of
- decimals per iteration. For instance, to obtain 1 000 000
- decimals, around 20 iterations are sufficient. The disadvantage is
- that you need FFT type multiplication to get a reasonable speed,
- and this is not so easy to program.
-
- 3. The third, and perhaps the most elegant in its simplicity, arises
- from the construction of a large circle with known radius. The
- length of the circumference is then divided by twice the radius
- and pi is evaluated to the required accuracy. The most ambitious
- use of this method was successfully completed in 1993, when
- H. G. Smythe produced 1.6 million decimals using high-precision
- measuring equipment and a circle with a radius of a staggering
- nine hundred and fifty miles.
-
-
-
- References
-
- P. B. Borwein, and D. H. Bailey. Ramanujan, Modular Equations, and
- Approximations to pi American Mathematical Monthly, vol. 96, no. 3
- (March 1989), p. 201-220.
-
-
-
- J.M. Borwein and P.B. Borwein. The arithmetic-geometric mean and fast
- computation of elementary functions. SIAM Review, Vol. 26, 1984, pp.
- 351-366.
-
-
-
- J.M. Borwein and P.B. Borwein. More quadratically converging
- algorithms for pi . Mathematics of Computation, Vol. 46, 1986, pp.
- 247-253.
-
-
-
- Shlomo Breuer and Gideon Zwas Mathematical-educational aspects of the
- computation of pi Int. J. Math. Educ. Sci. Technol., Vol. 15, No. 2,
- 1984, pp. 231-244.
-
-
-
- David Chudnovsky and Gregory Chudnovsky. The computation of classical
- constants. Columbia University, Proc. Natl. Acad. Sci. USA, Vol. 86,
- 1989.
-
-
-
- Y. Kanada and Y. Tamura. Calculation of pi to 10,013,395 decimal
- places based on the Gauss-Legendre algorithm and Gauss arctangent
- relation. Computer Centre, University of Tokyo, 1983.
-
-
-
- Morris Newman and Daniel Shanks. On a sequence arising in series for
- pi . Mathematics of computation, Vol. 42, No. 165, Jan 1984, pp.
- 199-217.
-
-
-
- E. Salamin. Computation of pi using arithmetic-geometric mean.
- Mathematics of Computation, Vol. 30, 1976, pp. 565-570
-
-
-
- David Singmaster. The legal values of pi . The Mathematical
- Intelligencer, Vol. 7, No. 2, 1985.
-
-
-
- Stan Wagon. Is pi normal? The Mathematical Intelligencer, Vol. 7, No.
- 3, 1985.
-
-
-
-
-
- A history of pi . P. Beckman. Golem Press, CO, 1971 (fourth edition
- 1977)
-
-
-
- pi and the AGM - a study in analytic number theory and computational
- complexity. J.M. Borwein and P.B. Borwein. Wiley, New York, 1987.
-
-
-
-
- _________________________________________________________________
-
-
-
- alopez-o@barrow.uwaterloo.ca
- Tue Apr 04 17:26:57 EDT 1995
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