On Tuesday, September 2, 2014 12:23:31 PM UTC-7, Joachim Durchholz wrote: > > The makers of RUBI insist that no two rules of a rule set can ever apply > to the same subexpression. > That's draconic, and verifying that would be, erm, "interesting". > > I'm not sure whether that's worth it, but they do have a point if they > say it's the only way to be sure that no rule is applied in an > unexpected way, which is what I get is the main point behind most of the > problems you mentioned. > Also, it would force rule writers to investigate into which rule's turf > they are breaking, and reconsider whether their addition is actually an > improvement over what's already there. > > I can't say what's the best approach, I'm just collecting potentially > relevant arguments here and hope somebody has enough breadth of vision > to properly weigh them all. >
Having tried to use Rubi (not the latest version) I can attest to the problem that the ruleset as I used it did lots of problems but failed on some of them in somewhat mysterious ways. (I think I reported these to Albert Rich). Here's my suspicion, and it is sort of different from your concern about rule independence. That is, the rules need to terminate -- either each rule must show progress towards some goal, or some collection of them converge (hill-climbing as necessary) towards a termination. Some of these conditions are delicately dependent on particular simplifications. I was running Rubi using the Mathematica-syntax rules, using MockMMA. The pattern syntax and semantics are essentially the same as Mathematica, but the forms for (my version of) FullSimplify are different. I'm not sure how much more of Mathematica beyond what I wrote might actually be necessary to run all of the Rubi test suite. I think I kind of gave up after repeated "infinite loops" about 180 examples in to the tests. RJF -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/80e41827-9caa-4a00-ae99-d7d8b1215ac6%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
