That's a really hard thing for a compiler to predict though. I recently got a 2x performance boost just by switching to an array of struct of array representati

That's a really hard thing for a compiler to predict though. I recently got a 2x performance boost just by switching to an array of struct of array representation (making the cache lines have more data that actually matters), and the only reason it made a difference was the access pattern of a mildly non-trivial algorithm acting on that data (not hard per se, but definitely hard for a compiler to optimize through).