On Mon, Sep 26, 2016 at 11:52 PM, William Stein <wst...@gmail.com> wrote:
> On Mon, Sep 26, 2016 at 3:27 PM, Jonathan Bober <jwbo...@gmail.com> wrote: > > In the matrix_integer_dense charpoly() function, there is a note in the > > docstring which says "Linbox charpoly disabled on 64-bit machines, since > it > > hangs in many cases." > > > > As far as I can tell, that is not true, in the sense that (1) I have > 64-bit > > machines, and Linbox charpoly is not disabled, (2) > > charpoly(algorithm='flint') is so horribly broken that if it were ever > used > > it should be quickly noticed that it is broken, and (3) I can't see > anywhere > > where it is actually disabled. > > > > So I actually just submitted a patch which removes this note while fixing > > point (2). (Trac #21596). > > > > However... > > > > In some testing I'm noticing problems with charpoly(), so I'm wondering > > where that message came from, and who knows something about it. > > Do you know about "git blame", or the "blame" button when viewing any > file here: https://github.com/sagemath/sage/tree/master/src Ah, yes. Of course I know about that. And it was you! You added that message here: https://github.com/sagemath/sage/commit/ce8c59b53cb46c338ca89cebc50e26ff0e0643cc and didn't remove it here: https://github.com/sagemath/sage/commit/7030ad944f6023825fbd4a30e1c800d18a2c0b4c (though it isn't completely clear to me that the second commit really comes after the first, since date's might not tell the full story.) Anyway, it seems likely that this comment is ancient history. Using flint to compute the characteristic polynomial has only been broken for 2 years (though not because of brokenness in filnt). I'll have to keep testing to see if linbox is broken. > > > > > > The problems seem the likely cause of #21579, though I haven't actually > been > > able to conclusively blame that on linbox yet. I'm also not sure I've > seen > > linbox's charpoly() hang, exactly, but I do see very erratic behavior in > how > > long it takes: on a fixed matrix I have it typically takes 30 seconds, > but > > I've also seen it return the correct answer after 50 minutes. > > > > (I've also got the wrong answer sometimes, but there are some conversions > > going on, and I've so far only seen the wrong answer for rational > matrices, > > which is why I've not get blamed linbox, though I am certainly leaning > > towards blaming it.) > > > > Note: I'm currently testing on 7.4.beta6, so this is after the recent > linbox > > upgrade. But I was also having some problems before that. It is possible > > that the recent upgrade made errors less likely, though. > > > > -- > > 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 https://groups.google.com/group/sage-devel. > > For more options, visit https://groups.google.com/d/optout. > > > > -- > William (http://wstein.org) > > -- > 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 https://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 https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
