On 8/28/08, Moshe Looks <madscience at google.com> wrote:
> I have recently begun playing around with maxima for a probabilistic
> program evolution project that requires simplification of random
> expressions.
Hmm, neat. I like hearing about stuff that people are working on with Maxima.
> Some of these expressions use the absolute-value function
> (abs) in a way that seems to lead to bad behavior by the default
> simplifier. For example, doing
>
> abs(-0.2+x^0.70086);
>
> at the maxima prompt gives "MAKE-ARRAY: dimensions (7905 7905)
> produce too large total-size" under clisp, and launches into a long
> (> 10 min) computation under sbcl.
Well, it looks like Maxima's method for factoring is very inefficient for
fractional exponents. I really have no idea how to do it better.
Is there some way to prove that there is no nontrivial factorization for
some class of expressions? (Which includes stuff like -0.2 + x^0.70086.)
Maybe there are better ways to approach the sign determination
problem, but I'm not yet ready to give up factoring.
best
Robert Dodier