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. Was there any reason (aside from the usual lack of volunteers for review) why it didn't go in already?

On Dec 5, 2007 4:08 PM, Kevin Jacobs wrote:

On Dec 5, 2007 5:50 PM, 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)

...

Was there any reason (aside from the usual lack of volunteers for review) why it didn't go in already?

I'm not sure-- I think folks were waiting for Raymond H. to evaluate it. I did my part to update Armin's patch against 2.4 to HEAD at the time and put in what cleanups seemed sensible. FWIW, I've been using an interpreter with this patch ever since without problems.

I never even saw that one. I'm hoping Raymond will have another look. -- --Guido van Rossum (home page: http://www.python.org/~guido/)

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. Neil

Phillip J. Eby wrote:

At 07:43 PM 12/5/2007 -0700, Neil Toronto wrote:

...

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.

Good grief - how did I miss that? I plead parenthesis. They threw me off. So I've applied Armin's patch to 2.6 (it was nearly clean) and am playing with it. cls.name lookups are 15-20% faster than mine, and inst.name lookups are 5-10% faster. His is also winning on hasattr calls (succeeding and failing) on classes, but mine is winning on hasattr calls on instances. I want to poke at it a bit to find out why. On pybench, his is faster at BuiltinMethodLookups, significantly faster at CreateNewInstances, and a bit faster at almost everything else. BuiltinFunctionCalls is slower - slower than stock - it might need poking there, too. In all, it's a lovely piece of work. Neil

Kevin Jacobs wrote:

On Dec 6, 2007 1:35 AM, Neil Toronto mailto:ntoronto@cs.byu.edu> wrote:

So I've applied Armin's patch to 2.6 (it was nearly clean) and am playing with it. cls.name http://cls.name lookups are 15-20% faster than mine, and inst.name http://inst.name lookups are 5-10% faster. His is also winning on hasattr calls (succeeding and failing) on classes, but mine is winning on hasattr calls on instances. I want to poke at it a bit to find out why.

I hope folks have noticed that I've done some significant cleanup and forward porting some months ago at

http://bugs.python.org/issue1700288

Excellent. I tried this as well. This is guarding cache access with PyString_CheckExact (as it should) rather than asserting PyString_Check, plus a few other cleanups. It runs nearly as fast as Armin's, and still faster than mine and much faster than without. Neil