[petsc-users] Incorrect Eigenvalues when Setting KSP and PC types

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:

>   1) The test is definitely in the wrong place. If we are testing and erroring if using Cholesky and mat is not marked as symmetric or hermitian the test should be in MatGetFactor() not in a particular implementation.
>
>  2) It is a tough call if we should do this check or not.  There are good arguments in both directions. 
>
>    One thing we could do is if the matrix is not marked as symmetric/hermitian is we could just check at that point (but expensive) or we could just check in debug mode.
>
>  But I think we should require the user to set the flag (note for SBAIJ the flag for symmetric (or hermitian? which one) should be automatically set at creation).

So what's the approach if the user wants to do Cholesky on the nearby
symmetric matrix defined by the upper triangular part?  Now they'll need
to create that matrix explicitly?  It's certainly relevant for a
nearly-symmetric matrix, either due to a weak transport process or
implementation of boundary conditions.