Marc-Andre Lemburg added the comment: On 04.04.2013 19:00, Eric Snow wrote: > > Eric Snow added the comment: > >> Marc-Andre Lemburg added the comment: >> Same here. The heuristic may work for short strings that easily fit >> into the CPU cache, but as soon as you use it on longer strings, >> this will result in much slower comparisons. > > When testing both, would it help to test the end of the string before the > beginning? I'd expect that be more likely to leave the beginning in the > cache for any subsequent memcmp() call.
Again: this depends a lot on what strings you are dealing with. If you are comparing strings that only vary in the first few characters, testing the last character first would not be ideal :-) Given that CPUs are optimized to read ahead in memory, it's always better to avoid jumping around too much when accessing memory. http://en.wikipedia.org/wiki/CPU_cache http://en.wikipedia.org/wiki/Locality_of_reference http://lwn.net/Articles/252125/ Ideally, you want to stay within a cache line, typically 64 bytes. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue17628> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
