On Oct 7, 2009, at 1:40 AM, ma...@mendelu.cz wrote: > Dear developers of Sage > > I'm working on trac http://trac.sagemath.org/sage_trac/ticket/6479
Thanks! We're really lacking in this area, and better exposing all that maxima has to offer will be a large step forward. > adn > the foloowing enahancements of desolve > * with parameter show_method=True Sage returns pair [solution, string > describing method (e.g. linear)] > * with parametr ode_contrib=True Sage tries to use ode2 first and if > this fails, then tries ode_contrib command, which allows to solve more > types of equations. This is False by default, since seems ode_contrib > sometimes to hang (more precisely, the computation is toooo long) > > I found a bug in maxima reported today at > http://news.gmane.org/gmane.comp.mathematics.maxima.general as > "Seriious bug in ic2" ( http://thread.gmane.org/ > gmane.comp.mathematics.maxima.general/28434 > ) > > I suppose to raise warning from Sage to the user that using bc2 > command for second order ODE equations which are not linear is > insecure. By insecure, I assume you mean it returns bogus answers? It depends on how severe it is--any time one uses a computer to do math there is a big implicit "warning: most software is not 100% bug free" that one needs to take into account anyways. > Is it O.K? Is it in harmony with customs used in Sage? And > how can send this message to the user, without producing error like > raise NotImplementedError, "Maxima was unable to solve this system." If Maxima was unable to solve it, that this seems like the right error to raise (perhaps with the hint if there's a flag you can pass to make it try harder). If you're wanting to warn the user, but still continue, you can raise a warning. http://docs.python.org/library/ warnings.html > > Thank you > Robert Marik > > On 4 říj, 00:22, "ma...@mendelu.cz" <ma...@mendelu.cz> wrote: >> Hello all, >> >> studying the problem related todesolveand discussed in sage-suppport >> (http://groups.google.cz/group/sage-support/browse_thread/thread/ >> b6f6b... >> ), I have one more question: >> The functiondesolveends with this: >> >> if soln.lhs() == dvar: >> soln = soln.rhs() >> >> So sometimesdesolveproduces expression (if the solution of ODE has >> been found in explicit form) and sometimes equation. >> >> What is the reason for this behavior? I think that it is confusing >> for >> the user, isn't it? >> >> Thank you >> >> Robert Marik > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
