[petsc-users] is something wrong with nnz ?

[Jed Brown]

On Wed, Nov 23, 2011 at 08:24, jean-frederic thebault <
jean-frederic at thebault-net.com> wrote:

> I'm wondering what's wrong in my code. I'm using PETSc to solve a linear
> system, and willing to use a multi-processor computer. 9 years ago, I used
> petsc-2.1.3 with success. Few weeks ago, I've update petsc with the 3.1-p8
> version and made the necessary changes to work with. No problem. And
> recently, I've migrate to petsc-3.2-p5. Compilation is OK. But when I do
> simulation, now, I have some PETSC-ERROR in the log file, even using only
> one processor (see the out.log file in this email).
>

You are calling MatSetOption() with the wrong number of arguments. C
compilers tell you about this, but Fortran compilers do not.

http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatSetOption.html


> However, I think I defined MatMPI and VecMPI correctly, according to the
> doc. The log file tell that something wrong with the nnz which should not
> be greater than row length (??).
>

The log you sent does not say anything about nnz. Fix the call to
MatSetOption().

And also, with the previous version of PETSc I've used, the were no problem
> using -pc_type bjacobi and -sub_pc_type sor, juste to solve linear system
> doing parallel computations and because SOR is not parallelized. But now,
> when I use -pc_type bjacobi and -sub_pc_type sor, with 3 rank, I experiment
> some convergence problem during my simulation.
>

These options should do the same thing they used to do. Make sure you are
assembling correctly. If it's still confusing, run the old and new code with

-ksp_monitor_true_residual -ksp_converged_reason -ksp_view -pc_type bjacobi
-sub_pc_type sor

and send the output of both for us to look at.

Also note that you can use -pc_type sor even in parallel. There are options
for local iterations and full iterations.
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