On 27 August 2010 07:25, Dr. David Kirkby <david.kir...@onetel.net> wrote: > On 08/24/10 02:06 PM, kcrisman wrote: >> >> Anyway, I think (as you have correctly noted before) we have a bit of >> a culture clash between software engineering and mathematics. > > <SNIP> > > >> Just have patience with those of us who aren't from a software >> background - and trust that we are trying hard to internalize your >> lessons, but that we have more immediate needs to fill as well for our >> next course or paper. I think that just as Minh's messages about >> documentation are slowly taking hold in the whole ecosystem, so are >> yours about software engineering. >> >> - kcrisman > > > Just to make a point, my own background is not software engineering. My > first degree is in electrical and electronic engineering, my masters in > microwaves and optoelectronics and my PhD in medical physics. Apart from a > very brief spell (about 6 months), I have never worked in the IT industry. > > I first became aware of the subject of software engineering when an > Australian guy joined the department I worked at University College London. > Russel's task was to develop some hardware and software for a research > project. He quite rightly realised that developing software "by the seat of > your pants" as he called it was not the way to go about it. So before > starting to write the software, he purchased a book on the subject of > software engineering. > > I never gave this topic much more thought until I started working on Sage. I > then because to realise that Sage needs to take a more professional approach > to the development, as it seems a bit add-hock to me. > > My own view is I'd rather have something with less features, which I could > rely on, than lots of features I don't trust. When there is little in the > way of project management, and a culture of not doing anything properly, > then attitude tends to spread like a virus. > > I'm currently running the doctests 100 times on a machine, with the same > build of Sage that passed all doc tests. This is an interesting failure I > observed: > > sage -t -long devel/sage/doc/en/constructions/linear_algebra.rst > ********************************************************************** > File > "/export/home/drkirkby/sage-4.5.3.alpha2/devel/sage-main/doc/en/constructions/linear_algebra.rst", > line 202: > sage: A.eigenvalues() > Expected: > [3, 2, 1] > Got: > [3, 1] > ********************************************************************** >
That is very worrying. The matrix A here is [1 1 0] [0 2 0] [0 0 3] over the rationals, so if eigenvalues are being missed it is in finding the roots of a rational cubic whose roots are 1,2,3. I tried tracing through the call to A.eigenvalues() but that is hard to do since it spends ages doing things whose necessity is hard to understand (for example, there are calls to cputime()!). John > > The tests have been run 41 times now, and only once has that test failed. > The answer looks quite reasonable, but I assume is wrong, as the other 40 > times the code gave the expected value. It's these sorts of things that > concern me. Why should the same build of Sage, running exactly the same > doctests each time, not produce repeatable results? > > There's been a few failures, though that is the only one I've noticed where > the answer looks very reasonable, but is in fact incorrect. > > Dave > > -- > To post to this group, send an email to sage-devel@googlegroups.com > To unsubscribe from this group, send an email to > sage-devel+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/sage-devel > URL: http://www.sagemath.org > -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
