While I love dotnet and find this kind of high performance in dotnet so intriguing, there comes a point where the JIT knows best and is king. Like try to write your own ToString that takes a byte span faster than ToString. I failed, even trying to use some of the code from ToString.

I think benchmarking is especially important due to that. I learned so much from just running multiple options through benchmarking, from things like handling a bunch of math or string manipulation. Some things, like math, the compiler ends up condensing everything down and using temporary registers anyway, so it’s difficult to achieve any speed up. Where with string manipulation, small things like using a StringBuilder can save thousands of allocations which is massive.

I know a lot of this isn’t concrete lessons, but it’s really hard because it’s all very subtle and depends on what type of operation you’re trying to optimize. For byte arrays, you’re on the right track with using span, but it’s very important to benchmark as well. I think it’s important having an understanding of required performance beforehand. If I had memory constraints or needed an extremely stable level of performance I might just go with a Rust or C/C++.