If you have time, begin with the physics. How many bits have to change, how many have to move, how many have to be computed? Do they really have to move? Do the

If you have time, begin with the physics. How many bits have to change, how many have to move, how many have to be computed? Do they really have to move? Do they really have to be computed? Do they really have to change? Do they have to change now and every time? Can they remain in-situ? Works on the CPU register scale, and on the availability region/continental/global scale. While modern hardware provides a wealth of capabilities WRT SIMD, multi threading, and of course the revolution in storage over the last 20 years… sometimes you can design-out a lot of the heavy lifting. My first program ran on a 2MHz CPU with 64KB RAM and (floppy) disk access time measured in seconds. I think something of the art and science has been lost when even a wonderful “toy” computer runs at 2.4GHz. Often when I ask “what is the system really doing when X is slow?” people (including developers who built it) have little idea.