On Tue, Feb 10, 2009 at 11:50 PM, Simon King <k...@mathematik.uni-jena.de> wrote: > > Dear William, > > slightly OT: > > On Feb 10, 4:25 pm, William Stein <wst...@gmail.com> wrote: > ... >> On Tue, Feb 10, 2009 at 7:18 AM, Simon King <k...@mathematik.uni-jena.de> >> wrote: >> > It concerns multivariate factorization. I had p.factor() in my code, >> > but at some point I got a NotImplementedError. As Martin pointed out, >> > it is due to a bug in Singular that the default(!) case p.factor >> > (proof=True) can not be implemented. So I had to change my code into >> > p.factor(proof=False) >> >> Interesting. That API change was my doing, actually. At Sage Days in >> San diego, I discovered some new examples that shows that Singular's >> factorization gives wrong answers even in the case of GF(p) !! You >> might be actually *very* glad to find out about the above, since if >> your code depends on factor actually giving a complete factorization, >> it might have silently failed. > > Don't worry. I am happy if I find some factors, and it is no problem > for me if I get reducible factors. > > Only I found it strange that the default case is not implemented. > However, Martin said that the default in Sage must yield a provably > correct result, but Singular can't provide it, so, the default can't > be implemented.
Yes, in Sage there was a lot of discussion and it was decided that default implementations of algorithms should always be "proof=True", unless it is crystal clear from the function name (e.g., next_pseudoprime). <rant> The Singular documentation -- and me the authors of Singular (?) -- seem to claim that they have implemented an algorithm that is supposed to give a provably correct result. But it's not only not "provable correct", it's frequently not correct at all. </rant> -- William --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
