Set up to begin performance tests. The 'intermediates' is a
communication channel to send back intermediate performance numbers --
if you use it, you will probably want to ensure your test is only
executed once by returning 1. Otherwise, return 0 to allow the test
harness to decide the number of iterations.
If you return a non-zero iteration count, you should call
intermediates.endTiming to report the
duration of the test whose performance should actually be measured.