Why is this faster on 64 bit than 32 bit?

Question

I\'ve been doing some performance testing, mainly so I can understand the difference between iterators and simple for loops. As part of this I created a simple set of tests

Answer 1

As others said, doing 64-bit arithmetic on a 32-bit machine is going to take some extra manipulation, more-so if doing multiplication or division.

Back to your concern about iterators vs. simple for loops, iterators can have fairly complex definitions, and they will only be fast if inlining and compiler-optimization is capable of replacing them with the equivalent simple form. It really depends on the type of iterator and the underlying container implementation. The simplest way to tell if it has been optimized reasonably well is to examine the generated assembly code. Another way is to put it in a long-running loop, pause it, and look at the stack to see what it's doing.