Javascript code for making my browser slow down

Question

I'm writing a library for WebWorkers, and I want to test the difference between running a script in the main page thread, versus in one or more workers. The problem is: I can't find out of hand a short function which will strain my browser enough that I can observe the difference.

A quick search didn't return much, but it might just be that I don't really know what to search for; usually I try to optimise my code, not make it slower...

I'm looking for algorithms or patterns that can be easily implemented in pure Javascript, that do not depend on the DOM or XHR, and which can have an argument passed to limit or specify how far the calculation goes (no infinite algorithms); 1s < avg time < 10s.

Extra points if it can be built without recursion and if it does not incur a significant memory hog while still being as processor intensive as possible.

Answer 1

Try using the obvious (and bad) recursive implementation for the Fibonacci sequence:

function fib(x) {
  if (x <= 0) return 0;
  if (x == 1) return 1;
  return fib(x-1) + fib(x-2);
}

Calling it with values of ~30 to ~35 (depending entirely on your system) should produce good "slow down" times in the range you seek. The call stack shouldn't get very deep and the algorithm is something like O(2^n).