[petsc-dev] PaStiX solution

Alexander Grayver agrayver at gfz-potsdam.de
Wed Dec 28 08:11:37 CST 2011


I tried LU, the result is the same (attached). The matrix is recognized 
as a symmetric, even though I put in the code:
     ierr = MatSetOption(A,MAT_SYMMETRIC,PETSC_FALSE);
     ierr = MatSetOption(A,MAT_SPD,PETSC_FALSE);

Seems like internal check?
I checked positive-definiteness of the matrix in matlab (using [L,p,s] = 
chol(A); test) and it's not SPD.
So it seems like PaStiX is not very robust. This case is not one inch 
close to the bad cases I used MUMPS with.


On 28.12.2011 14:11, Jed Brown wrote:
> On Wed, Dec 28, 2011 at 07:02, Alexander Grayver 
> <agrayver at gfz-potsdam.de <mailto:agrayver at gfz-potsdam.de>> wrote:
>     Hi Jed,
>     If you mean input parameters they are as following:
>     -ksp_view -ksp_monitor -mat_type mpisbaij -ksp_type preonly
>     -pc_type cholesky -pc_factor_mat_solver_package pastix
>     -mat_pastix_verbose 2
>>         The output is attached.
>>         The matrix is SPD and has condition number of 16, there
>>         should be no problem.
>>         I use petsc-dev.
>>         How could I figure out where is the problem?
>>     This sounds like a small example matrix. Can you -ksp_view_binary
>>     and send us the output file ('binaryoutput').
>     Maybe it was too preliminary to say that it is positive definite
>     since CG diverges with reason DIVERGED_INDEFINITE_MAT,
> Oh, I also see in the PaStiX output that it is reporting an error (but 
> just a number). If you run with -ksp_converged_reason, it should say 
> that it diverged. You should always run with -ksp_converged_reason 
> -ksp_monitor_true_residual when investigating whether a solver is 
> converging. From code, call KSPGetConvergedReason().
>     however GMRES with default parameters converges successfully.
>     Matrix is ~200000x200000, not so small, but zipped occupies 4.5
>     Mb. Shall I send it?
> Try solving with LU instead. It sounds like Cholesky is just breaking 
> down, maybe because it does a slightly different method than the other 
> direct solver packages.

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