Patches item #1624059, was opened at 2006-12-29 01:01 Message generated for change (Comment added) made by gvanrossum You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=305470&aid=1624059&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Core (C code) Group: Python 2.6 Status: Open Resolution: None Priority: 5 Private: No Submitted By: Neal Norwitz (nnorwitz) Assigned to: Guido van Rossum (gvanrossum) Summary: fast subclasses of builtin types Initial Comment: This is similar to a patch posted on python-dev a few months ago (or more). I modified it to also handle subclassing exceptions which should speed up exception handling a bit. (This was proposed by Guido based on the original patch.) I also dropped an extra bit that was going to indicate if it was a builtin type or a subclass of a builtin type. ---------------------------------------------------------------------- >Comment By: Guido van Rossum (gvanrossum) Date: 2007-01-03 22:59 Message: Logged In: YES user_id=6380 Originator: NO This looks fine, but I have some questions about alternative implementations: - Why does the typical PyFoo_Check() macro first call PyFoo_CheckExact() before calling the fast bit checking macro? Did you measure that this is in fact faster? True, it means always a pointer deref, so maybe it is -- but OTOH it is more instructions. - Why not have a separate bit for each type? Then you could make the fast macro test for (flags & mask) != 0 instead of testing for (flag & mask) == value. It would use up all the remaining bits, but I suspect there are some unused (or reusable) bits in lower positions: 1L<<2 is unused (was GC), and 1L<<11 also seems unused. And bits 18 through 23! And I'm guessing that INPLACEOPS (1L<<3) isn't all that interesting any more they were introduced in 2.0... So it really looks like you have plenty of bits. Of course I don't know if it matters; would be worth it perhaps to look at the machine code. - Oops, it looks like your comment is off. You claim to be using bits 24-27, leaving 28-31 free, but in fact you're using bits 28-31! BTW You're inroducing quite a few lines over 80 chars. Perhaps cut back a bit? ---------------------------------------------------------------------- Comment By: Neal Norwitz (nnorwitz) Date: 2006-12-29 01:04 Message: Logged In: YES user_id=33168 Originator: YES I forgot to mention this patch works by using unused bits in tp_flags. This saves a function call when checking for a subclass of a builtin type. There's one funky thing about this patch, the change to Objects/exceptions.c. I didn't investigate why this was necessary, or more likely I did why when I added it and forgot. I know that without adding BASE_EXC_SUBCLASS to tp_flags, test_exceptions fails. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=305470&aid=1624059&group_id=5470 _______________________________________________ Patches mailing list Patches@python.org http://mail.python.org/mailman/listinfo/patches
