I've thought it would be extremely helpful for the procedural materials optimization to know the exact performance cost of each node in the Shader Editor, if not in the absolute values than at least in the comparison to each other. For example as far as I know some math operations are cheaper than the others: adding/subtraction are cheaper than multiplication which is much cheaper than division, etc. Do you have any idea of how to get this information about Blender nodes or at least where to start a search or how to formulate a request?
UPD. Everything I found out so far is that Math node uses math.h standard C library for computations. I haven't found exact computation costs for its particular functions, but found this wiki article about computational complexity, which seems like something that could be helpful... if I'd been familiar with calculus or whatever it is about.