Comment by zmmmmm

I feel torn about the "premature optimization" stuff. On the one hand it's clearly true that we're terrible at predicting bottlenecks and it makes no real sense to second guess them at any fine level of detail. On the other hand, I think about products that I love to use and they are all fast. I think about the first iPhone and how utterly crucial that first user experience was. Did they achieve that by just writing giant gobs of code and then circling back afterwards to fix a few hotspots? I think about how Chrome was such a delight after FireFox got slower and slower and more bogged down. Clearly, Chrome was written from the ground up to avoid that. I am not so sure you can really optimise for performance after the fact, at least not universally. There are times when you have to build it into the very fabric of a project right from the start. Once a project has a giant mass of moderately slow code, there's nothing you can do except rewrite it to get better performance.