At 11:46 PM 8/15/2006 -0700, Neal Norwitz wrote: >On 8/15/06, "Martin v. Löwis" <[EMAIL PROTECTED]> wrote: >> >>That penalty is already paid today. Much code dealing with >>ints has a type test whether it's an int or a long. If >>int and long become subtypes of each other or of some abstract >>type, performance will decrease even more because a subtype >>test is quite expensive if the object is neither int nor >>long (it has to traverse the entire base type hierarchy to >>find out its not inherited from int). > >I was playing around with a little patch to avoid that penalty. It >doesn't take any additional memory, just a handful of bits we aren't >using. :-) > >For the more common builtin types, it stores whether it's a subclass >in tp_flags, so there's no function call necessary and it's a constant >time operation. It was faster when doing simple stuff. Haven't >thought much whether this is really worthwhile or not.
It seems to me that you could drop the FAST_SUBCLASS bit, since none of the other bits will be set if it is not a subclass of a builtin. That would free up one flag bit -- perhaps usable for that BaseException flag Guido wants. :) (Of course, if you can't inherit from both BaseException and one of the other builtin types, it can just be another enumeration value within the bit mask.) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
