Mark Dickinson <dicki...@gmail.com> added the comment: Updated patch. Lots of cleanup, but only one significant change: the inner loop now uses signed arithmetic instead of unsigned arithmetic. This saves a negation and fixes a subtle bug: the previous inner loop code was incorrect when using 15-bit digits on machines with sizeof(short) == sizeof(long). Not that I know of any such machines: the Cray T3E famously has no 16-bit integer type, but there sizeof(short) is 4 and sizeof(long) is 8.
A few more timings, this time from doing a single huge integer division: 10**1000000//10**500000 (so this effectively times just the inner loop, since all else will be insignificant). All timings are best-of-5, from non-debug builds of py3k, on the same system: OS X 10.5.6/2.4 GHz Core 2 Duo. Times in brackets are the approximate per-inner-loop times (remembering that there are 4 times as many iterations of the inner loop for 15-bit digits). 32-bit build, 15-bit digits, unpatched: 92382.2 ms (~7.5 ns) 32-bit build, 15-bit digits, patched: 36473.3 ms (~3.0 ns) 64-bit build, 30-bit digits, unpatched: 14581.4 ms (~4.8 ns) 64-bit build, 30-bit digits, patched: 7385.1 ms (~2.4 ns) ... and just for fun, the other combinations: 64-bit build, 15-bit digits, unpatched: 61927.5 ms (~5.1 ns) 64-bit build, 15-bit digits, patched: 43632.9 ms (~3.6 ns) 32-bit build, 30-bit digits, unpatched: 62374.1 ms (~20.3 ns) 32-bit build, 30-bit digits, patched: 26928.3 ms (~8.8 ns) Thanks for the updated pidigits script, Victor! Maybe this is too small right now to be worth including in the Tools directory, but I hope we can fatten it up with some other benchmarks. What do you think? ---------- Added file: http://bugs.python.org/file13391/faster_integer_division2.patch _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue5512> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
