alt Hacker NewsRe: your first paragraph, I don't get it, what does spatial locality have to do with recursion vs. iteration? And the blanket speed claim doesn't make sense either. I feel like you're thinking of a specific algorithm or access pattern or technology and overgeneralizing to the idea that it's somehow impossible for recursion to ever match the performance or be faster?
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vanviegen • yesterday at 10:04 PM
Yes, and a high-level scripting language can in some specific circumstances be made to run code faster than a low-level compiled language. Generally, it's the other way around though.
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maybe the wrong terminology, but non-tail-call-optimized recursions spray their state across space with each iteration consuming a new stack frame, where iterative algorithms live in one stack frame and can re-use temporaries. the state spraying results in consumption and spilling down the memory hierarchy, from registers through caches. i think of this as the memory hierarchy being designed to best perform when spatial locality of memory usage is maintained, but it's slightly different from what most people mean when they discuss spatial locality... maybe "cache efficiency" is the better term?