Direct LU solver

[Amit.Itagi at seagate.com]

Matt/Hong/Satish,

My toy-problem would run with the command line options. However, the
in-code options were still giving a problem. I also found that I had a
Petsc version compiled with the debugging flag off. On recompiling Petsc by
turning the debugging flag on, the in-code options worked. I am wondering
about the cause for this behavior.

Thanks for your help. I will now fiddle around with the actual application.

Rgds,
Amit



                                                                           
             Satish Balay                                                  
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             02/28/2008 05:58                                              
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On Thu, 28 Feb 2008, Amit.Itagi at seagate.com wrote:

> Matt and Hong,
>
> I will try to customize the example. However, since my application
involves
> multiple ksp solvers (using different algorithms), I would really like to
> set the options with in the code, instead of on the command line. Is
there
> a way of doing this ?

-ksp_type preonly -pc_type lu -mat_type superlu_dist

There are 2 ways of doing this.

One is within the code:

    MatCreate(&mat);
    MatSetType(mat,MATSUPERLU_DIST);
    MatSetFromOptions(mat);

    KSPSetType(ksp,KSPPREONLY);
    KSPGetPC(ksp,&pc);
    PCSetType(pc,PCLU);
    KSPSetFromOptions(ksp);

etc..

Another way is to give each object a prefix [if you have multiple
objects of the same type. You can use this prefix with the command
line options.

For eg:

    KSPCreate(&ksp1)
    KSPCreate(&ksp2)

    KSPSetOptionsPrefix(ksp1,"a_")
    KSPSetOptionsPrefix(ksp2,"b_")

Now you can use -a_ksp_type gmres -b_ksp_type cg

etc..

Satish