The compiler could have heuristics and profiling data to replace optimal but "small" reductions with cheap recomputation with even less locking where it seems l

The compiler could have heuristics and profiling data to replace optimal but "small" reductions with cheap recomputation with even less locking where it seems like a good idea; it's an additional level of improvement rather than a competing choice. As the Python documentation says, "practicality beats purity", particularly when the sacrificed purity is only the pride of using an universal solution. In a similar vein, if typical strategies for unstable sorting of arrays in place use quicksort splitting for long spans and insertion sort for short spans it doesn' mean that either algorithm is "better".