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Diffstat (limited to 'pi.c')
| -rw-r--r-- | pi.c | 78 |
1 files changed, 78 insertions, 0 deletions
@@ -0,0 +1,78 @@ +/* Copyright (C) 1991 1995 Free Software Foundation, Inc. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2, or (at your option) + * any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this software; see the file COPYING. If not, write to + * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. + * + * As a special exception, the Free Software Foundation gives permission + * for additional uses of the text contained in its release of GUILE. + * + * The exception is that, if you link the GUILE library with other files + * to produce an executable, this does not by itself cause the + * resulting executable to be covered by the GNU General Public License. + * Your use of that executable is in no way restricted on account of + * linking the GUILE library code into it. + * + * This exception does not however invalidate any other reasons why + * the executable file might be covered by the GNU General Public License. + * + * This exception applies only to the code released by the + * Free Software Foundation under the name GUILE. If you copy + * code from other Free Software Foundation releases into a copy of + * GUILE, as the General Public License permits, the exception does + * not apply to the code that you add in this way. To avoid misleading + * anyone as to the status of such modified files, you must delete + * this exception notice from them. + * + * If you write modifications of your own for GUILE, it is your choice + * whether to permit this exception to apply to your modifications. + * If you do not wish that, delete this exception notice. + */ + +/* "pi.c", program for computing digits of numerical value of PI. + Author: Aubrey Jaffer + +pi <n> <d> prints out <n> digits of pi in groups of <d> digits. + +'Spigot' algorithm origionally due to Stanly Rabinowitz. +This algorithm takes time proportional to the square of <n>/<d>. +This fact can make comparisons of computational speed between systems +of vastly differring performances quicker and more accurate. + +Try: pi 100 5 +The digit size <d> will have to be reduced for larger <n> or an +error due to overflow will occur. */ + +short *calloc(); +main(c,v) +int c;char **v;{ + int n=200,j=0,m,b=2,k=0,t,r=1,d=5; + long q; + short *a; + if(c>1)n=atoi(v[1]); + if(c>2)d=atoi(v[2]); + while(k++<d)r=r*10; + n=n/d+1; + k=m=3.322*n*d; + a=calloc(1+m,2); + while(k)a[--k]=2; + for(a[m]=4;j<n;b=q%r){ + q=0; + for(k=m;k;){ + q+=a[k]*r; + t=(2*k+1); + a[k]=q%t; + q=q/t; + q*=k--;} + printf("%0*d%s",d,b+q/r,++j%10?" ":"\n");} + puts("");} |