Putting the wxmaxima stuff in a hash table might be a way to get it off the
property list so that other programs more intensively using the property
list would not have to shuffle through wxmaxima properties.
I'm not entirely convinced that running the test suite is a good test of
whether the move-to-front heuristic for the simplifier is worth doing or
not. The cost to run this heuristic is zero at runtime, so any runtime
speedup is pure gain.
The length of the plist for %sin in wxmaxima is 46. To say that it is just
as fast to get item 1 as item 46 is clearly false. Why does it seem that in
the larger benchmark of the test suite that it makes no difference? Perhaps
the test is not doing anything particularly time-consuming with respect to
simplification, or just doing (+,*,expt) simplification most of the time,
and/or this is just a minor enhancement on a very clumsy program. Consider
this:
g(x):=if x=0 then z else sin(g(x-1));
How long should it take to compute g(15)? Would you believe my computer
takes about 28 seconds?
How much faster is it to compute if the operators property is moved to the
front? My computer takes maybe 1/3 second less.
Why is g(15) so slow? Why does g(16) take time 3X ?
.... Note that simplification of + and * and expt expressions are not done
by looking for their simplification operators on their property list,
because it was considered to be inefficient, and the program simplifya has a
hack to avoid this property-list access. But that was in 1966.
RJF
> -----Original Message-----
> From: maxima-bounces at math.utexas.edu [mailto:maxima-
> bounces at math.utexas.edu] On Behalf Of Raymond Toy
> Sent: Saturday, February 17, 2007 10:17 AM
> To: Barton Willis
> Cc: fateman at cs.berkeley.edu; maxima at math.utexas.edu
> Subject: Re: [Maxima] speeding up the simplifier
>
> Barton Willis wrote:
> > I suppose a nice solution would be to move all this property list
> > stuff into CL hash tables. In trigi.lisp, you'll see that a hash
> > table is used to store functions for floating point evaluation
> > of trig functions (I think this innovation is due to Raymond).
> >
> >
> I'm guessing, but I think a hash table lookup would be slower than the
> finding the first symbol in the property list.
> > Maxima has functions (I'm going on memory, so some names might be wrong)
> > mget, zl-get, putprop, and getprop that all access property list data.
> > I sure would be nice to unify all this junk into hash tables with one
> > programming interface to this data.
> >
> >
> I had given a little thought about this some time ago. It seemed like
> an all or nothing change (that is, I couldn't think of a way to only do
> a small set of changes, preserving the original parts). Thus, I didn't
> try it.
> Plus, the hashed array stuff is also stored in the plist, and arranged
> in a very confusing way.
>
> Ray
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