Re: [eigen] Bug in SelfAdjointEigenSolver<>, or am I missing something important?

[Benoit Jacob <jacob.benoit.1@xxxxxxxxx>]

2010/11/3 Jose Luis Blanco <joseluisblancoc@xxxxxxxxx>:
> Hello all,
>
> I attach a little test program. It basically takes a square symmetric
> matrix and computes its eigen{vectors,values} with
> SelfAdjointEigenSolver<>, then reconstruct the original matrix with
> EVEC * diag(EVALS) * EVEC^T.
>
> The point is, that works for a ColMajor ordering, but not with a
> RowMajor, so, for these two tests:
>
>        myTest< Eigen::Matrix<double,4,4,ColMajor> >();
>        myTest< Eigen::Matrix<double,4,4,RowMajor> >();
>
> it fails in the latter.
>
> From what I've learned of Eigen, everything is prepared so users can
> use or even mix ColMajor & RowMajor matrices and everything is smart
> enough to handle it.. but in this case.

Indeed, the storage order is semantically transparent as long as you
don't directly address the array of coeffs.

In your test program, you actually do address it by using the Matrix
constructor taking a pointer, but that still shouldn't make any
difference in your case since your matrix is symmetric.

So yes you found a bug. Thanks to your great test case I'm sure it'll
be fixed soon, the best thing you could do is file a bug and attach
your test case.

Benoit

>
> Please, let me know if I'm missing something. I managed to solve it by
> setting the template argument of SelfAdjointEigenSolver<> to a
> ColMajor version of the input matrix, but I guess that implies a
> (transparent from my viewpoint) conversion, which may be an avoidable
> delay for big matrices if there's a better way.
>
> Best,
> Jose Luis
>
> btw: Huge congrats to you all developers for this *absolutely
> marvelous* library!
>