If you are familiar with TopCoder you know that your source-code gets a final "grade/points" this depends on time, how many compiles, etc, one of the highest weighted being performance. But how can they test that, is there some sort of simple code (java or c++) to do it that you could share for me to evaluate and hopefully write my own to test the programs I write for University?

This is sort of a follow up question to this one where I ask if shorter code results in best performance.

P.S: Im interested in both of how topcoders knows performance and writing code to test performance.