Re: pmc_type

Nicholas Clark wrote:
> On Fri, Oct 29, 2004 at 05:19:35PM +0200, Leopold Toetsch wrote:
>
>
> > The method_lookup doesn't have a vtable indirection. And having a direct
> > array lookup doesn't really scale. So the actual code is a bit more
> > complicated (and in no way optimized).
>
>
> Something that just struck me reading this whole thread - can we take
> advantage of the lazy approach the prederef cores use? Prime all the slots
> in the vtable array with pointers to the same function that actually does
> the real work of the method lookup. So we take the lookup hit only when
> we call the method. 

First, while Paolo named the thing vtable, that term collides with 
pmc->table. So let's call the thing method_table. Second, I've to revise 
my above sentence, method lookup *is* a vtable call. We have:

  method_pmc = object->vtable->find_method(... "the_method_str")

The find_method calls the method lookup, which is a hash lookup in the 
objects class, and likely some more hash lookups in the classes parents.

So back to your idea. We'd need a list of the top N methods of all 
objects and generate a sparse array of index <-> method_str mappings per 
object primed with the actual lookup function. For all top N methods, 
we'd replace the keyed find_method with an indexed find_method.

Then after a successful lookup, we could replace the lookup-function 
with a function that returns the real method. Sounds doable, yes.

leo