I found that when doing lots of array code that needs to be fast, you cannot rely on the high-level abstractions of normal Swift. But even while staying in Swif

I found that when doing lots of array code that needs to be fast, you cannot rely on the high-level abstractions of normal Swift. But even while staying in Swift there are API's to drop down to, lower levels of array manipulation etc. where you get the speed of raw C (independent of your optimisation settings).