On Mon, Apr 17, 2023 at 12:20 PM Michael Orlitzky <mich...@orlitzky.com> wrote: > > On Sun, 2023-04-16 at 19:46 -0700, aw wrote: > > > > Unbelievable. > > This is failing a basic consistency check: if x==y, then we should have > > f(x)==f(y) for any function f. > > > > The problem here is that float literals are being mishandled. The string > > "0.5" should be interpreted as 1/2, unless the user overrides that. > > > > Can you post the other "permabugs" you know of that involve float literals? > > > > They're all variations on a theme. Floating point sucks, and Sage > inherits that: > > sage: (0.1 + 0.2) + 0.3 == 0.1 + (0.2 + 0.3) > False > > Whenever you perform an operation with two different types of "number," > Sage essentially picks the worst of the two and performs the operation > there. Every example is basically, > > 1. Something returns a float where you don't expect it > 2. You use that result with some other object > 3. Now the other object is made of float > 4. Nothing works in floating point > > The conversion to float is consistent with all of the other intelligent > coercions that Sage can do (embedding ZZ into QQ, for example), so it > goes off silently. But floating point is a uniquely bad base ring for > most of Sage.
for some tasks, at least, built-in RBF and CBF does wonders, e.g. for the example earlier in the thread: sage: A = matrix([[-3, 2, 1 ], ....: [ 2,-4, 4 ], ....: [ 1, 2,-5 ]]) sage: B = (2 * 0.5 * A) sage: B.rank() # bad 3 sage: matrix(RBF,B).rank() # right! 2 sage: type(matrix(RBF,B)) # this is not even using what's available in arb for matrices <class 'sage.matrix.matrix_generic_dense.Matrix_generic_dense'> > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sage-devel/44b14f57528ac06463e2294fa52cf3a661cc2cc0.camel%40orlitzky.com. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/CAAWYfq38u9%3DdEX0xcY0rHyOgHTfXr%2BFVu0GfF6SKbbK7VpZ79g%40mail.gmail.com.
