Great answer, thanks Jed.

-J

On Thu, Apr 10, 2008 at 7:27 AM, Jed Brown <[EMAIL PROTECTED]> wrote:
> On Thu 2008-04-10 14:09, [EMAIL PROTECTED] wrote:
>  > Hi,
>  > How can I use a direct solver to solve a linear system of equations?
>  > Thanks in advance,
>  > Paulo
>
>  You can do this entirely with PETSc command line arguments.  For instance
>
>  -ksp_type preonly -pc_type lu
>
>  will solve the system using LU decomposition.  If your matrix is symmetric, 
> you
>  can try -pc_type cholesky.  You can select different direct solvers by 
> changing
>  the matrix type with -mat_type.  Run the program with -help and you will see 
> the
>  supported types (such as umfpack, superlu, aijspooles, sbaijmumps).  
> Depending
>  on the problem, you may want to try preconditioning with algebraic multigrid.
>  You can build PETSc with libraries like Hypre, ML, and Prometheus, then use
>  -pc_type hypre.  For 3D problems, I find this starts beating a direct method
>  for quite small sizes.
>
>  Jed
>
>
>
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