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Date: Fri, 5 Nov 2010 14:25:19 -0500
From: Alex Stangl <alex@stangl.us>
To: Arthur Bela <jozsi.avadkan@gmail.com>
Message-ID: <20101105192519.GA78113@scout.stangl.us>
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Cc: FreeBSD Mailing list <freebsd-questions@freebsd.org>
Subject: Re: how to generate pi in c
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On Fri, Nov 05, 2010 at 05:40:39PM +0100, Arthur Bela wrote:
> Does anyone has a "generate-pi.c" source code?

Search for pi spigot algorithm.

Here is a tiny C program from Jeremy Gibbon's Unbounded Spigot paper
(due to Dik Winter and Achim Flammenkamp):

a[52514],b,c=52514,d,e,f=1e4,g,h;main(){for(;b=c-=14;h=printf("%04d",
e+d/f))for(e=d%=f;g=--b*2;d/=g)d=d*b+f*(h?a[b]:f/5),a[b]=d%--g;}

This produces the first 15,000 digits concisely, but is obfuscated.
If you need an unbounded number of digits, search out the spigot
algorithm papers.

Alex