Massively parallel & inverse matrix solver

[Hermes Sampedro]

Dear all,

I am trying to solve a similar problem as step-29 but including the massive parallel solution as presented in step-40.

I would like to ask how the solve() function would be in this case.

In step-29:

//LU decomposition and inverse matrix

SparseDirectUMFPACK A_direct;

A_direct.initialize(system_matrix);

//Solve with inverse matrix

A_direct.vmult(solution, system_rhs);

When applying massive parallel computations, my initial guess was:

LA::MPI::Vector    completely_distributed_solution(locally_owned_dofs,mpi_communicator);

//LU decomposition and inverse matrix

SparseDirectUMFPACK A_direct;

A_direct.initialize(system_matrix);

//Solve with inverse matrix

A_direct.vmult(completely_distributed_solution, system_rhs);

 locally_relevant_solution = completely_distributed_solution;

 However, I get a no matching member function for call to 'vmult' error. 

How can I use this LU decomposition and inverse matrix solver using MPI?

Thank you,

Regards,

H

[Daniel Arndt]

Hermes,

The SparseDirectUMFPACK solver doesn't work with MPI parallel matrices. You will need to find another solver based on the matrix class you are using. Standard choices would be GMRES or CG but I am assuming that your linear system might also be non-symmetric or indefinite.

Best,

Daniel

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[Hermes Sampedro]

Thank you for the answer. I am solving for real and imaginary parts.

What solver would you suggest using? Is it any example in any of the steps?

Thank you

Hermes.

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[Jean-Paul Pelteret]

Dear Hermes,

The equivalent classes to SparseDirectUMFPACK for parallel linear algebra would be:

- TrilinosWrappers::SolverDirect : You can choose the implementation through the AdditionalData struct that is passed into the class constructor.

- PETScWrappers::SparseDirectMUMPS

Best,

Jean-Paul

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