On Thu, Aug 10, 2000 at 04:54:25PM -0400, Dan Sugalski wrote:
> At 08:31 PM 8/10/00 +0000, Nick Ing-Simmons wrote:
> >You just re-invented "look up the name in a hash table" ;-)
> >
> >You now have one big hash table rather than several small ones.
> >Which _may_ give side benefits - but I doubt it.
>
> If we prefigure a bunch of things (hash values of method names, store
> package stash pointers in objects, and pre-lookup CVs for objects that are
> typed) it'll save us maybe one level of pointer indirection and a type
> comparison. If the object isn't the same type we pay for a type comparison
> and hashtable lookup.
>
> Not free, but not expensive either. 'Specially if we get way too clever and
> cache the new CV and type in the opcode for the next time around, presuming
> we'll have the same type the next time through.
Or if someone has defined a new sub, you don't know it was not the
one you stashed.
IMO, what perl5 does not is "quite" close to optimal as you will get
given the dynamic nature of the language (ie namespaces changing
at runtime etc)
I am not sure it got into perl5, but pre-computing the hash value of
the method name and storing it in the op is one thing. Maybe also trying
a bit harder to keep package hashes more flat.
Another thing that may help is if all the keys in package hashes are shared
and also shared with constant method names in the op tree. Then when
scanning the chain you only need do a pointer comparison and not a
string compare.
Graham.
