Thread: Problem printing a PI

First I must say that I'm new to C programming, a second sorry on my bad english!

My problem is that I try to print more then 1 milion didgits of PI. I'm using Gauss-Legendre algorithm that is used in program Super_pi. I was using Google for some time now, and only that I could find is that I need to use some non standard library! Any help is useful! Code is attached.

Code:

#include <stdio.h>
#include <math.h>


int main(){
	
int i;
float a = 1;
float b = a/sqrt(2);
float t = a/4;
float x = a;
float y;
float p;
for (i = 1; i <= 19; i++)
	{
		y = a;
		a = (a+b)/2;
		b = sqrt(b*y);
		t = t-x*(a-y)*(a-y);
		x = 2*x;
	}

p = (a+b)*(a+b)/(4*t);
printf("%.1000000f",p);

getch();
return 0;
}

Problem is that first 16 numbers have some value 0-9 then the rest are zeros.

Originally Posted by King Mir

the is no built in type to store 1 million digits of pi.

That is my problem, can this be solved in any way?!

Originally Posted by King Mir

Maybe if you used discriptive variable names

I used one from algoritham, its easyer for me! Here is original algoritham!

Gauss-Legendre algorithm

1. Initial value setting;

a=1
b=1/sqrt(2)
t=1/4
x=1

2. Repeat the following statements until the difference of a and b is within the desired accuracy;

y=a
a=(a+b)/2
b=sqrt(b*y)
t=t-x*(y-a)^2
x=2*x

3. Pi is approximated with a, b and t as;

PI=(a+b)^2/(4*t)

The algorithm has second order convergent nature. Then if you want to calculate up to n digits, iteration count of the order log2 n is sufficient. E.g. 19 times for 1 million decimal digits, 31 times for 3.2 billon decimal digits.