You are doing the right thing, but AA (and QQbar) are very slow at testing equality -- and hence also at division since the denominator must be tested for equality with 0.
In this case since el1.minpoly() and el2.minpoly() are the same, and the roots in RR are very different: sage: el1.minpoly() x^4 - 2238072*x^2 + 44133904 sage: el2.minpoly() x^4 - 2238072*x^2 + 44133904 sage: el2.minpoly().roots(RR) [(-1496.01212569203, 1), (-4.44069616336440, 1), (4.44069616336440, 1), (1496.01212569203, 1)] it is hard to believe that there is not a quicker way of doing the test. (It is also relevant that sage: el1.minpoly().is_irreducible() True here, since in general during a computation in AA/QQbar, the polynomials carried around are not factored. i think.) Also note that sage: el1.minpoly()(el2) ==0 True ! John On 17 September 2014 15:40, Jonas Jermann <jjerma...@gmail.com> wrote: > Hi > > How can I do exact comparison of numbers in AA? > I noticed that this doesn't work very reliably: > > el1 = AA((x^4 - 2238072*x^2 + 44133904).roots()[1][0]) > el2 = (791264*AA(2*cos(pi/8))^2 - 463492).sqrt() > el1 == el2 > > ^- This fails for me (resp. never stops) > [el1-el2 gives "0.?e-15"] > > > Best > Jonas > > -- > 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 post to this group, send email to sage-devel@googlegroups.com. > Visit this group at http://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/d/optout. -- 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 post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
