Excessive flexibility for optimizers, schedulers, etc. adds a high price to debugging, and it’s not like we have perfect programs that can only be improved in t

Excessive flexibility for optimizers, schedulers, etc. adds a high price to debugging, and it’s not like we have perfect programs that can only be improved in these fancier ways. Programs are not all written by experts. Performance may be left on the table in areas that have nothing to do with optimizers or schedulers (e.g. picking an absolutely terrible algorithm or not noticing unnecessary memory allocations). If something must remain “unspecified”, I at least want a debugging tool for that behavior. If something “may” happen, give me a switch to make it happen. If something is data-dependent, show me the data that triggers a different outcome or give me a way to scramble data enough to increase the chance of triggering a change in behavior.