On Tue, Aug 21, 2012 at 11:25 AM, Alexander Grayver <agrayver at gfz-potsdam.de > wrote:
> On 21.08.2012 18:14, Hong Zhang wrote: > > Alexander : > > Testing your matrix A.dat > using petsc-3.3/src/ksp/ksp/examples/tutorials/ex10.c, > I find that A is numerically singular: > > > Hong, > > Sorry, but I forgot to mention that this is double complex symmetric > matrix. Did you load and treat it like that? > > I'm convinced that matrix A is corrupted or obtained from an incorrect > numerical model. > Also note, your matrix A has size of approx. 60k, which is too large for > sequential direct solver. > > > MUMPS takes only several minutes and 6 GB of memory to factorize it. > This factorization gives residual on the order of 10e-12 and solution is > indeed correct. > > Nevertheless, you're right, there is numerical null-space in this matrix > since it comes > from the discretization of equation that contains curl curl operator, but > practically this > case is not really the worst one. > This makes no sense whatsoever. How can you LU factor a matrix that has a null space? Matt > > The error on MatMatSolve() when calling > ' -pc_type cholesky -pc_factor_mat_solver_package mumps' > is a bug in our petsc-mumps interface. I've pushed a fix to petsc-3.3 > http://petsc.cs.iit.edu/petsc/releases/petsc-3.3/rev/8badc49a596e > > Thanks for your report. > > > Thank you for the patch. > > -- > Regards, > Alexander > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120821/b617d1de/attachment.html>
