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Re: goops and memoization
From: |
Tom Lord |
Subject: |
Re: goops and memoization |
Date: |
Tue, 3 Dec 2002 18:49:59 -0800 (PST) |
> Have you considered the approach of writing a custom optimizer (not O,
> but another optimizer) that can do a good job of "compiling" (scheme
> to scheme):
>
>
> (lambda (ms) (M (O (U ms))))
>
> ?
Hmm... could you please clarify this suggestion. What is the
core idea? To specify O in a custom language and compile it?
To optimize the composition of M O and U? Something else that
I have missed?
O, I am presuming, optimizes method selection, presumbably by ordering
tests of argument types in favorable orders and by generating
special-case tests where, otherwise, a generic search would be
required. Have I missed something?
So, O is a fairly straightforward scheme->scheme transform. It can
almost certainly be expressed in very regular form (a "custom
language" (such as a pattern-matching macro plus quasiquote) -- or
simply a narrow Scheme subset).
M and U are similar.
You can write them as three separate functions, and write a customized
optimizer that folds them together. It might even be able to take
advantage of non-general optimizations that apply only to these
functions.
You could look at the custom optimizer as a constant-folding exercise,
an abstract-evaluation exercize, or a partial-evaluation exercize
(where you are partially evaluating "(apply (compose M O U)
free-ms)").
The reason I think this is a plausible approach is just that the three
transforms involved (M O and U) don't need to be arbitrary code -- you
can do very well here just by thinking of them as pattern-matching
rewrite systems -- and such systems compose cleanly and should be easy
to optimize.
Clearer? or did I just make it worse :-)
(I used to suspect that Aubrey secretly generated `eval' using
techniques along these lines but eventually concluded: nah, he just
writes very consistent code. :-)
-t
Re: goops and memoization, Mikael Djurfeldt, 2002/12/03
Re: goops and memoization, Mikael Djurfeldt, 2002/12/03