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/* "pi.c", program for computing digits of numerical value of PI.
* 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 3 of the
* License, 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 program. If not, see
* <http://www.gnu.org/licenses/>.
*/
/* 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("");}
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