Michael Orlitzky wrote:
>> It's messy the instant you type it in with decimal points > > Not the end user's fault. > > >> it starts using floating point numbers internally. > > I didn't tell it to do that. > I think there are several points here: 1. The moment Sage sees a decimal, it starts using approximate, floating point arithmetic. If you don't want that, then don't use decimals; use fractions. This is consistent with most mathematical software (though other software may have better algorithms that minimize the effect of the round-off errors). 2. Sage currently does not deal very well with round-off error in linear algebra. This needs to be fixed. Furthermore, Sage doesn't tell you (like matlab *sometimes* does) when round-off error might be a big issue. For your matrix, Sage probably should have warned you that round-off error might lead to an incorrect response. I've opened up http://trac.sagemath.org/sage_trac/ticket/7392 and http://trac.sagemath.org/sage_trac/ticket/7391 to address specific issues that came up in this thread. Implementing numerically stable arbitrary precision linear algebra is a much bigger project, so I'm holding off on opening up a ticket until someone starts making it happen. > Ok, but (assuming it can be done) how do you propose I convert my > problem to an exact field? By hand? If only there were some sort of > program... > Don't use decimals; use fractions. Then Sage does everything exactly, with no round-off error. Thanks, Jason --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
