[PEAK] PEAK-Rules indexing performance

[Phillip J. Eby]

At 09:25 PM 1/10/2009 +0100, Alberto Valverde wrote:
>Phillip J. Eby wrote:
>>At 09:12 PM 1/9/2009 +0100, Alberto Valverde wrote:
>>
>>>After some peeking at peak.rules internals, motivated by the meta 
>>>function recipe you posted some months ago to optimize the 
>>>"isclass" test, I thought about using them to simplify some rules 
>>>by "wrapping" several related checks under a function without 
>>>incurring in performance penalties due to non-statically analyzable predicates.
>>
>>You can't really do that; meta-functions have to expand back into 
>>statically-analyzable predicates, and so will these "predicate 
>>functions".  Essentially, both meta-functions are like macros, and 
>>predicate functions will be like macros that take effect at runtime 
>>instead of compile time.  ;-)
>
>Yeah, I understand that the need to expand to statically analyzable 
>predicates, I must have expressed myself wrong. What I meant is to 
>wrap several statically analyzable checks like: "(isclass(obj) and 
>issubclass(obj, Foo)) or isinstance(obj, Foo)" into something nicer 
>like: "issubclass_or_instance(obj, Foo)". Mainly to clean up the 
>hairy code in here [1]. Anyway, I think this could probably be done 
>with a meta function (right?) but first I need to study the source better...

Yes, static (i.e. non-generic) predicate functions can be inlined 
using meta-functions.  You would do something like:

def issubclass_or_instance(ob, cls):
     """This is the "regular" function"""
     return isclass(obj) and issubclass(ob, cls) or isinstance(ob, cls)

@meta_function(issubclass_or_instance)
def compile_issubclass_or_instance(__builder__, ob, cls):
     """This is the compiled version"""
     __builder__.push({'ob':ob, 'cls':cls, 
'classtypes':classtypes})  # temporarily bind vars
     result = __builder__.parse("isinstance(obj, classtypes) and 
issubclass(ob, cls) or isinstance(ob, cls)")
     __builder__.pop()
     return result

I've left the definition of 'classtypes' as an exercise for the 
reader.  ;-)  (Also, technically speaking, for this to be correct one 
should include isinstance and issubclass in the push, so as to ensure 
that the caller didn't change or mask them.  That is a downside of 
macros in general, of course.)