Since this seems more like a math question than programming, I'm placing it here instead of on SO
I'm trying to find $x$ when $c$ and $d$ are known constants (user input and iteration counter, respectively) in the equation $c=d^x$ in a program I'm making. How can I find this without using complex methods? (this operation must be done several thousand times per second, at least)
Please use pseudocode for any examples.