[petsc-users] Use boomeramg to solve system of PDEs

[Thomas Witkowski]

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
>>