> The main source of slowness in modern software is memory access I don't think it is. Memory access patterns matters a lot when you want to squeeze every last

> The main source of slowness in modern software is memory access I don't think it is. Memory access patterns matters a lot when you want to squeeze every last bit of performance, or when you want to update old code that was optimized for different assumptions. But I think most slowness comes from not having looked at what could make your software slow. Maybe you forgot to compile a regex before a loop, maybe you're copying a whole array at each of the 100 000 iterations, maybe your algorithm is accidentally n^2.