Matthew, After all, the problem was mine. I had a bug in the code and I didn't notice it until this PETSc version.
Thanks once again. Keep up the good work. Billy. -----Original Message----- From: [email protected] on behalf of Billy Ara?jo Sent: Thu 2/5/2009 10:04 AM To: Matthew Knepley; PETSc users list Cc: petsc-maint Maintenance Subject: RE: Performance degradation after upgrade to 3.0.0 Thanks for the explanation. -----Original Message----- From: Matthew Knepley [mailto:[email protected]] Sent: Wed 2/4/2009 10:46 PM To: PETSc users list Cc: petsc-maint Maintenance; Billy Ara?jo Subject: Re: Performance degradation after upgrade to 3.0.0 On Tue, Feb 3, 2009 at 4:35 PM, Billy Araujo <billyaraujo at gmail.com> wrote: > "Can you send the matrix and rhs as PETSc binary output, and I will find out > what the difference is. It looks to me like the default ICC ordering > has changed. Okay, I have the explanation. The default factorization options changed in 3.0.0. No, by default, we use a diagonal shift to remedy zero diagonal elements, like -pc_factor_shift_positive_definite TRUE You do not have a zero per se, but you do have a singular matrix, which you can check using -ksp_type preonly -pc_type lu, so the last row has a zero diagonal. Since nothing is ever divided by it, it causes no problems if you do nothing. However, shifting generates a much poorer preconditioner. You can recover the original behavior using -pc_factor_shift_positive_definite FALSE However, I would also advise uncovering the source of the singularity. Thanks, Matt -- 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 -------------- A non-text attachment was scrubbed... Name: not available Type: application/ms-tnef Size: 3775 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090205/207267f8/attachment.bin>
