I sometimes get Nan output values in computed eigenvectors for the generalized symmetric eigenvalue problem produced by slepc. Is this a known issue, and is it related to the conditioning of the matrix pair (A,B)? Is there some way to compute a "condition number" of the matrix pair ahead of time to see if i have a good chance of getting stable eigenvectors out?
In a possibly related issue, i am finding that petsc/slepc compiled with debugging vs optimization can produce very different eigenvectors for the same problem, while the eigenvalues are the same. The eigenvectors seem more accurate when I use the debugging version of the libraries. Could this be also a conditioning problem with the matrix pair?
