Antoine Pitrou <[EMAIL PROTECTED]> added the comment: This is a preliminary patch to speedup for and while loops (it will also be able to speedup list comps and gen comps, if I get to do it). The patch works by putting the loop condition test at the end of loop, which allows removing one JUMP_ABSOLUTE byte code out of the critical path.
For this two new opcodes are introduced: - FOR_ITER2 is the same as FOR_ITER except that it does an /absolute/ jump if the iterator is /not/ exhausted (when other uses of FOR_ITER are replaced with FOR_ITER2, we can of course restore the original naming) - JUMP_ABS_IF_TRUE /pops/ the top of the stack and does an absolute jump if its value is true Some micro-benchmarks: ./python -m timeit "for x in xrange(10000): pass" Before: 1000 loops, best of 3: 782 usec per loop After: 1000 loops, best of 3: 412 usec per loop ./python -m timeit "x=100" "while x: x -= 1" Before: 10000 loops, best of 3: 22.1 usec per loop After: 100000 loops, best of 3: 16.6 usec per loop ./python Tools/pybench/pybench.py -t ForLoops Before: 365ms per round After: 234ms per round Also, pystone gets 5% faster (from 43300 to 45800). Now for the less shiny things: 1. I'm having problems modifying the pure Python compiler module. For some reasons it seems to have stricter requirements than compile.c itself does (!); I get some assertion error in compiler.pyassem.FlowGraph.fixupOrderHonorNext as soon as a loop gets non-trivial. 2. Line numbers probably need to be fixed. The lnotab format may even have to be adapted in order to accomodate non-monotonically increasing line numbers. Is there some interest in this patch? If yes, I'd like to have your input on the two bullet points above :) __________________________________ Tracker <[EMAIL PROTECTED]> <http://bugs.python.org/issue2459> __________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
