On Tue, Apr 5, 2011 at 12:23 AM, Brian Granger <elliso...@gmail.com> wrote: > On Sun, Apr 3, 2011 at 11:17 PM, Andy Ray Terrel <andy.ter...@gmail.com> > wrote: >> On Mon, Apr 4, 2011 at 9:10 AM, Andy Ray Terrel <andy.ter...@gmail.com> >> wrote: >>> On Mon, Apr 4, 2011 at 8:58 AM, Frank K. <ylfch...@gmail.com> wrote: >>>> >>>>> > There's also the line somewhere in between numerical matrices and >>>>> > symbolic matrices, which is matrices with exact numeric values >>>>> > (instances of Rational), to consider. >>>>> >>>>> Not sure what you are getting at here. >>>>> >>>> >>>> There are some sparse matrix algorithms that are quite speedy, but >>>> give approximate answers (so you get a determinant with a little error >>>> bar, for example). These might be usable on a Rational matrix, but >>>> certainly not a symbolic one. >>>> >>>> Perhaps this is what Aaron is getting at, or just something I've made >>>> up! >>> >>> Only exact iterative methods, such as conjugate gradients, are >>> feasible in SymPy. SymPy expressions have no real way to do any >>> minimization or determine small fill-in so these methods are out from >>> the get go. >>> >> >> What I left out is that you won't in general be able to keep the >> rational syntax. Most complex operations such at sqrt will turn the >> Rational into an Expr. > > I have been confused by this and a few other comments. Won't the > sparse matrices work with *any* Expr subclass? >
It was in reference to the idea of getting speedy mathematics through Rationals. I wouldn't be thrilled with anything that didn't accept any Expr subclass. @Aaron: You are describing BLAS-like routines, LAPACK-like routines often require sqrt's. -- Andy > Brian > >> -- Andy >> >>> >>>> >>>> -- >>>> You received this message because you are subscribed to the Google Groups >>>> "sympy" group. >>>> To post to this group, send email to sympy@googlegroups.com. >>>> To unsubscribe from this group, send email to >>>> sympy+unsubscr...@googlegroups.com. >>>> For more options, visit this group at >>>> http://groups.google.com/group/sympy?hl=en. >>>> >>>> >>> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sympy" group. >> To post to this group, send email to sympy@googlegroups.com. >> To unsubscribe from this group, send email to >> sympy+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/sympy?hl=en. >> >> > > > > -- > Brian E. Granger > Cal Poly State University, San Luis Obispo > bgran...@calpoly.edu and elliso...@gmail.com > -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
