Just to add to the discussion: you're likely correct, based on this SO question: http://stackoverflow.com/questions/11227809/why-is-processing-a-sorted-array-f

Just to add to the discussion: you're likely correct, based on this SO question: http://stackoverflow.com/questions/11227809/why-is-processing-a-sorted-array-faster-than-an-unsorted-array http://stackoverflow.com/questions/11227809/why-is-processin... It will likely get faster the more duplicates you have, as it allows the CPU to predict a branch more reliably several times before being wrong and having to re-do some of its prediction stuff. (note that I'm not experienced with optimizing stuff, dealing with cache optimizations, etc., but I have read a decent amount, and I did take a class about CPU architecture) I would also suspect that hashing might end up messing with memory all over the place, causing the cache to be partly useless.