On Aug 29, 12:28 pm, "John Cremona" <[EMAIL PROTECTED]> wrote: > Thanks, Nick and Carl, that is very helpful! > > Now I am not sure whether to use QQbar just to determine which > embeddings are (and are not) real, and then revert to > RealField(precision) and ComplexField(Precision); or whether to try > to do everything using QQbar. That sounds worth a try, despite Carl's > warning about comparing real parts.
Computing in QQ[alpha], where alpha is some algebraic number, should be at most a (large) constant factor slower in QQbar than in the corresponding number field; so if this is what you're doing, I'd definitely give QQbar a try. The problem is that the sorting involves computation in QQ[alpha,beta], where alpha and beta are two different roots of the polynomial; QQbar is not very fast at computing the compositum of number fields. (I would be happy for somebody to take a look at it; I'm using Pari to do the computation, but perhaps there's a faster method.) Carl --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
