At 07:43 PM 12/5/2007 -0700, Neil Toronto wrote: >Phillip J. Eby wrote: > > At 10:48 PM 12/5/2007 +0100, Georg Brandl wrote: > >> Neil Toronto schrieb: > >>> So Jim and PJE finally convinced me to do it the right way. :) Thanks > >>> guys - it turned out very nice. > >> How does this relate to Armin Rigo's method cache patch? > >> > >> (http://bugs.python.org/issue1685986) > > > > Interesting. Armin's approach uses a single global cache of up to > > 1024 descriptors. That seems a lot simpler than anything I thought > > of, and might perform better by encouraging the processor to keep the > > descriptors in cache. It has a lot less pointer indirection, and has > > a dirt-simple way of invalidating a class' entries when something changes. > >Hey, I took out all my extra pointer indirection. :p > >FWIW, I like it. Though the hash should really incorporate the hash of >the type name as well as the attribute's so that sometype.method calling >othertype.method doesn't invalidate the cache. Locality makes the global >cache work, but locality also often means re-using the same names.
Look at the patch more closely. The hash function uses a version number times the method name's hash. "Version" numbers are assigned one per class, so unless there are 2**32 classes in the system, they are uniquely numbered. The multiplication and use of the high bits should tend to spread the hash locations around and avoid same-name collisions. Of course, it's still always possible to have pathological cases, but even these shouldn't be much slower than the way things work now. _______________________________________________ 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
