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On Buffon Machines and Numbers

Philippe Flajolet 1 Maryse Pelletier 2 Michèle Soria 2
1 ALGORITHMS - Algorithms
Inria Paris-Rocquencourt
2 APR - Algorithmes, Programmes et Résolution
LIP6 - Laboratoire d'Informatique de Paris 6
Abstract : The well-know needle experiment of Buffon can be regarded as an analog (i.e., continuous) device that stochastically "computes" the number 2/pi ~ 0.63661, which is the experiment's probability of success. Generalizing the experiment and simplifying the computational framework, we consider probability distributions, which can be produced perfectly, from a discrete source of unbiased coin flips. We describe and analyse a few simple Buffon machines that generate geometric, Poisson, and logarithmic-series distributions. We provide human-accessible Buffon machines, which require a dozen coin flips or less, on average, and produce experiments whose probabilities of success are expressible in terms of numbers such as, exp(-1), log 2, sqrt(3), cos(1/4), aeta(5). Generally, we develop a collection of constructions based on simple probabilistic mechanisms that enable one to design Buffon experiments involving compositions of exponentials and logarithms, polylogarithms, direct and inverse trigonometric functions, algebraic and hypergeometric functions, as well as functions defined by integrals, such as the Gaussian error function.
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Contributor : Michèle Soria <>
Submitted on : Monday, December 20, 2010 - 8:06:23 PM
Last modification on : Thursday, March 21, 2019 - 1:00:33 PM
Document(s) archivé(s) le : Monday, March 21, 2011 - 3:42:30 AM


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  • HAL Id : hal-00548904, version 1


Philippe Flajolet, Maryse Pelletier, Michèle Soria. On Buffon Machines and Numbers. SODA'11 - ACM/SIAM Symposium on Discrete Algorithms, Jan 2011, San Francisco, United States. pp. 172--183. ⟨hal-00548904⟩



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