Stack performance in programming languages

Question

Just for fun, I tried to compare the stack performance of a couple of programming languages calculating the Fibonacci series using the naive recursive algorithm. The code is

Answer 1

One possibility is that the C compiler is optimizing on the guess that the first branch (n < 2) is the one more frequently taken. It has to do that purely at compile time: make a guess and stick with it.

Hotspot gets to run the code, see what actually happens more often, and reoptimize based on that data.

You may be able to see a difference by inverting the logic of the if:

public static int fib(int n) {
 if (n >= 2) return fib(n-1) + fib(n-2);
 return 1;
}

It's worth a try, anyway :)

As always, check the optimization settings for all platforms, too. Obviously the compiler settings for C - and on Java, try using the client version of Hotspot vs the server version. (Note that you need to run for longer than a second or so to really get the full benefit of Hotspot... it might be interesting to put the outer call in a loop to get runs of a minute or so.)