Problem Solving BlockSparsematrix system blockwise

[Gabriel Peters]

Hey everyone,

I have a problem at solving a blocksystem.

I have a matrix called "system_matrix" in Blockform M =  [[A,0],[B,C]]

and I want to solve classical Mx = F. (F = [f,0], x = [x1,x2])

I proceed according to the LinearSolvers class in the step-32 tutorial.

so by blockwise solving the system I want to solve A*x1 = f for x1

and later on I want to solve

C*x2 = 0 - B*x1 for x2.

In the code I use:

std::shared_ptr<TrilinosWrappers::PreconditionJacobi> Mp_preconditioner;

and compute

    TrilinosWrappers::SolverGMRES solver_gmres(solver_control_gmres);

    solver_gmres.solve(system_matrix.block(0,0),distributed_solution.block(0),
                rhs.block(0),Mp_preconditioner);

But when I compile this I get the error

 error: no matching function for call to ‘dealii::TrilinosWrappers::SolverGMRES::solve(dealii::BlockMatrixBase<dealii::TrilinosWrappers::SparseMatrix>::BlockType&, dealii::BlockVectorBase<dealii::TrilinosWrappers::MPI::Vector>::BlockType&, dealii::BlockVectorBase<dealii::TrilinosWrappers::MPI::Vector>::BlockType&, std::shared_ptr<dealii::TrilinosWrappers::PreconditionJacobi>&)’
     rhs.block(0),Mp_preconditioner);

This error also comes up at solving the lower right block

TrilinosWrappers::SolverCG solver_cg(solver_control_cg);   
    solver_cg.solve(system_matrix.block(1,1),
            distributed_solution.block(1),
            u_tmp_p,
            Amg_preconditioner);

Can somebody tell me what actually went wrong? I think I did everything quite similar to the LinearSolvers class which works finely.

Thanks a lot and best regards

Gabriel

[Jean-Paul Pelteret]

Dear Gabriel,

It looks to me like you forgot to dereference the shared pointer for the preconditioner. So,

solver_gmres.solve(

  system_matrix.block(0,0),

  distributed_solution.block(0),
  rhs.block(0),

  *Mp_preconditioner); // <— here

You probably have the same problem for the other call.

I hope this was the correct observation to help sole the issue!

Best,

Jean-Paul

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[Gabriel Peters]

Hey Jean-Paul
Thanks a lot, Now it works finely.
Best regards

Gabriel




Gabriel Peters
Endenicher Str. 310
53121 Bonn
00491525/5478185
Gabriel...@koeln.de

Am 20.05.19 um 15:01 schrieb Jean-Paul Pelteret

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