One should never loose to the complier, after all you can see it's output and it can't see yours. Also, the programmer can "cheat" by doing things the compiler

One should never loose to the complier, after all you can see it's output and it can't see yours. Also, the programmer can "cheat" by doing things the compiler would consider invalid but are known to be ok given the larger context of the application. The restrict keyword in c gives an example of how one can optimize code by knowing the larger context. https://cellperformance.beyond3d.com/articles/2006/05/demystifying-the-restrict-keyword.html https://cellperformance.beyond3d.com/articles/2006/05/demyst... The problem is the ROI is usually pretty bad as these assumptions rarely hold as the code evolves, in my experience, and the optimization usually only lasts for finite (sometimes shockingly short) amount of time. i.e. OS changes, hardware changes, memory changes, etc. etc. etc.