> Also the moving of shared pointers is just an optimization to avoid increasing and then immediately decreasing the ref count, no UB there since its passed by value in the argument, so it gets copied before being moved

I saw that, that function is probably completely inlined by the optimiser as well so likely the move doesn't even happen there.

Just wanted to make sure since I know a lot of devs not super proficient in C++ just sticks a shared pointer on things to get around worries about ownership and don't concider the tradeoffs.

For me I concider using a unique_ptr a form of compile time check for how I'm thinking about the code. I find shared_ptr to be a smell. It's not necessarily wrong but probably needs some reasoning about.

Another note, I saw some comments somewhere about SIMD vectorisation that needs to be implemented. I would check whether the compiler isn't already doing that and if it isn't I would see about changing the code to make if possible for the optimiser to generate vectorised code.

I still haven't been at a PC so haven't been able to properly look through the code but it is nice to at least see modern C++ being used in a codebase