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cpi

Basic pi searcher in C, whats wrong?

So I tried making a basic pi searcher based on the Gregory-Leibniz series. My problem is it returns 3.0000, and I don't have a clue why...

This is the basic program:

int i = 1, j = 1;
double pi = 0;

for (i; i < 1000; i++)
{
    if(i % 2 != 0)
    {
        pi = pi + (4 / j);
    }
    else
    {
        pi = pi - (4 / j);
    }


    j = j + 2;
}
Solution

  • The 4/j is entirely integer math, which means it will round down to an integer before being added. Some options are 4.0 / j and (double)4 / j.

    The MSDN has an article on C floating-point constants that explains the notation you should use to ensure a literal value is treated as a float or a double.