Thanks for both of your replies. Just to double check so that I don't have any misunderstanding, PARI is correctly determining whether my ideal is principal, and if it is, it is attempting to produce a generator. It may fail at that, but, since I never ask it for a generator, this produces no incorrect outputs. Is that where this warning comes from and what I should make of it?
EK On Thursday, January 5, 2017 at 10:45:32 AM UTC+1, John Cremona wrote: > > On 5 January 2017 at 09:27, Jeroen Demeyer <jdem...@cage.ugent.be > <javascript:>> wrote: > > Sorry, I was wrong. I actually looked at the PARI source code this time > and > > the warning comes from the bnfisprincipal() function to determine the > class > > of a given ideal in the class group (so, in particular, it can be used > to > > check whether an ideal is principal). This function can also compute a > > generator of the ideal, but it might fail doing that, giving the warning > > message. I believe this does not affect the correctness. > > That sounds correct to me too, so thanks for checking the source code. > When it determines that an ideal is principal it can reconstruct the > generator using some additional information stored which includes logs > of elements in the various embeddings (as explained in Henri COhen's > second book), and at this point there may not be sufficient precision. > As Jeroen says, the correctness of the class number should be > affected. > > > > > > > -- > > You received this message because you are subscribed to the Google > Groups > > "sage-support" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to sage-support...@googlegroups.com <javascript:>. > > To post to this group, send email to sage-s...@googlegroups.com > <javascript:>. > > Visit this group at https://groups.google.com/group/sage-support. > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
