On Sun, Jul 22, 2012 at 9:31 AM, Aaron Meurer <[email protected]> wrote: > On Jul 16, 2012, at 4:36 AM, Sergiu Ivanov <[email protected]> wrote: > >> On Mon, Jul 16, 2012 at 1:19 PM, [email protected] >> <[email protected]> wrote: >>> With all the issues surrounding ordering, hashes and hash >>> randomization I was left with the impression that we should rewrite >>> tests in such a way that they test for mathematical correctness but >>> not for specific ordering of args, etc. >> >> Since we are discussing this, I would like to state that not forcing >> the ordering in some cases leads to an unpleasant variety of results. >> For example, in computing eigenvectors, this leads to _different_ >> eigenvectors at different runs. They are not essentially different, >> of course, but they are still different and this sounds a lot like a >> concealed bomb. > > I'm curious, do these eigenvectors differ only by constants, or is it > a case of completely different linear combinations with some > eigenvalues of high geometric degree?
I can't produce the exact example off-hand (I can do that, however, should the need be), but from what I remember, the eigenvectors would have components in different order, i.e., something like [0, 1, 2] in one run and [2, 0, 1] in another. Sergiu -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
