Grant Edwards <inva...@invalid> wrote: > On 2009-01-07, Steve Holden <st...@holdenweb.com> wrote: > > >> I use multiprocessing to compare more then one set of files. > >> > >> For comparison each set of files (i.e. Old file1 Vs New file1) > >> I create a process, > >> > >> Process(target=compare, args=(oldFile, newFile)).start() > >> > >> It takes 61 seconds execution time. > >> > >> When I do the same comparison without implementing > >> multiprocessing, it takes 52 seconds execution time. > > > My first suggestion would be: show us some code. We aren't > > psychic, you know. > > I am! > > He's only got one processor, and he's just been bit by Amdahl's > law when P<1 and S<1. > > There you have a perfectly "psychic" answer: an educated guess > camoflaged in plausible-sounding but mostly-bullshit buzzwords. > A better psychic would have avoided making that one falsifiable > statement (he's only got one processor).
;-) My guess would be that the job is IO bound rather than CPU bound, but that is covered by Amdahl's Law too where P is approx 0, N irrelevant... Being IO bound explains why it takes longer with multiprocessing - it causes more disk seeks to run an IO bound algorithm in parallel than running it sequentially. -- Nick Craig-Wood <n...@craig-wood.com> -- http://www.craig-wood.com/nick -- http://mail.python.org/mailman/listinfo/python-list