Dear all
I am working on a model in which the system matrix is a
TrilinosWrappers::BlockSparseMatrix with 2*2 blocks. I set the precondition
as:
{
LA::MPI::PreconditionAMG::AdditionalData data;
data.constant_modes = constant_modes;
data.elliptic = *true*;
data.higher_order_elements = *true*;
data.smoother_sweeps = 2;
data.aggregation_threshold = 0.02;
preconditioner_solid.*initialize*(system_pde_matrix.block(0, 0), data);
}
{
LA::MPI::PreconditionAMG::AdditionalData data;
//data.constant_modes = constant_modes;
data.elliptic = *true*;
data.higher_order_elements = *true*;
data.smoother_sweeps = 2;
data.aggregation_threshold = 0.02;
preconditioner_second.*initialize*(system_pde_matrix.block(1, 1), data);
}
and the solve template function is:
*template* <*int* *dim*>
*unsigned* *int*
*FEM<dim>::solve* ()
{
newton_update = 0;
*if* (direct_solver)
{
SolverControl cn;
TrilinosWrappers::SolverDirect solver(cn);
solver.*solve*(system_pde_matrix.block(0,0),
newton_update.block(0), system_pde_residual.block(0));
constraints_update.distribute(newton_update);
*return* 1;
}
*else*
{
SolverControl solver_control(200, system_pde_residual.l2_norm() * 1e-8);
SolverGMRES<LA::MPI::BlockVector> solver(solver_control);
BlockDiagonalPreconditioner_two<LA::MPI::PreconditionAMG,LA::MPI::
PreconditionAMG>
preconditioner(system_pde_matrix,preconditioner_solid,
preconditioner_second);
solver.solve(system_pde_matrix, newton_update,
system_pde_residual, preconditioner);
*return* solver_control.*last_step*();
}
}
in which BlockDiagonalPreconditioner_two is defined as:
*template* <*class* *PreconditionerA*, *class* *PreconditionerC*>
*class* BlockDiagonalPreconditioner_two
{
*public*:
*BlockDiagonalPreconditioner_two*(*const* LA::MPI::BlockSparseMatrix &M,
*const* *PreconditionerA* &pre_A, *const* *PreconditionerC* &pre_C)
: matrix(M),
prec_A (pre_A),
prec_C (pre_C)
{
}
*void* *vmult* (LA::MPI::BlockVector &dst,
*const* LA::MPI::BlockVector &src) *const*
{
prec_A.vmult(dst.block(0), src.block(0));
prec_C.vmult(dst.block(1), src.block(1));
}
*const* LA::MPI::BlockSparseMatrix &matrix;
*const* *PreconditionerA* &prec_A;
*const* *PreconditionerC* &prec_C;
};
The system is solved perfectly when all blocks is solved simultaneously.
However I want to test split method. So I need to solve each block
separately but I don't know how. Is it possible to solve each block
separately when the system matrix is a TrilinosWrappers::BlockSparseMatrix?how?
Please help me.
Best,
Pasha
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