I agree.. if you ask any kind of question on code optimisation on stackoverflow you’ll be bombarded with “profile and see” responses, or “don’t bother, your com

I agree.. if you ask any kind of question on code optimisation on stackoverflow you’ll be bombarded with “profile and see” responses, or “don’t bother, your compiler can do a better job” or “use an existing library”, but... profiling will only tell me what’s best on my current hardware, not in the general case. It doesn’t help me understand typical performance characteristics of common operating systems or hardware. It also doesn’t help me with coming up with new better approaches that I don’t know about (which is why I’m asking the question in the first place, to learn what I don’t know). The compiler can do a decent job, but it’s not magic and it often pretty easy to beat the compiler or at least helping it (eg by following Mike Actons advice - compiler can’t make cache inefficient code cache efficient often). Finally, regarding using libraries, sure, in production code I probably will, but I want to learn! If nobody learns, who will write tomorrow’s libraries?