[petsc-users] Use boomeramg to solve system of PDEs
Thomas Witkowski
thomas.witkowski at tu-dresden.de
Fri Feb 3 06:34:33 CST 2012
I did it, but gmres with boomeramg diverges. The system has three
unknowns per mesh node. Each block operator is either a Laplace or the
mass matrix. So each block by-itself is solvable with amg. Thus it
follows that the overall system is solvable? In my case the system is
not symmetric and indefinite. The boundary conditions are Neuman
everywhere, but the global matrix has an empty null space. As the local
blocks (in the case of the discrete Laplace) have constant null space I
set -pc_hypre_boomeramg_relax_type_coarse Jacobi for boomeramg not to
make direct solves on coarse grid. Is there any theoretical reason that
AMG cannot work in this case or is it a question of just the right
settings for the solver?
Thomas
Am 02.02.2012 14:43, schrieb Mark F. Adams:
> Use MatSetBlockSize(mat,ndof); and that info will get passed down to HYPRE.
> Mark
>
> On Feb 2, 2012, at 7:09 AM, Thomas Witkowski wrote:
>
>> The documentation of boomeramg mention that it's possible to solve also matrices arising from the discretization of system of PDEs. But there is no more information on it. What should I do to make use of it in PETSc?
>>
>> Thomas
>>
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