Re: C Program confused me

[ivan <ivan@freddie.vianet.net.au>]

Check out sci.math & the sci.math FAQ (lost the url-sorry) - the faq has
extensive descriptions of several different algorithms for calculating pi.

At 06:47 PM 3/12/99 +0800, Bal K. Paudyal wrote:
>Hello Friends,
>
>I encountered following program in one of the Linux Howtos. This calculates
>the value of pai. But how does it do this? I am not asking the programming
>details, but on what theory the formula is based on. Can anybody help? Is
>there any better place to look for help?
>
>
> 
>---------------------------------------
>#include <stdlib.h>;
> #include <stdio.h>;
>
>  main(int argc, char **argv)
>  {
>    register double width, sum;
>    register int intervals, i;
>
>    /* get the number of intervals */
>    intervals = atoi(argv[1]);
>    width = 1.0 / intervals;
>
>    /* do the computation */
>    sum = 0;
>    for (i=0; i<intervals; ++i) {
>      register double x = (i + 0.5) * width;
>      sum += 4.0 / (1.0 + x * x);
>    }
>    sum *= width;
>
>    printf("Estimation of pi is %f\n", sum);
>
>    return(0);
>  }
>--------------------------------
>
>
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