Dear Bruno,
Thank you very much for the comments. The problem was that I was running in
Debug mode without knowing. Now, after changing to Release the assembling
time is considerably reduced.
Moreover, I am experiencing another issue that I would like to ask. My mesh
is done with hyper_cube() in 3D and 5 refinements. The dof is around 3
million. When running, I always get a memory issue and the program stops. I
realized that the problem is in the line that executes
*solver.solve(system_matrix,
completely_distributed_solution, system_rhs);*
I am using SparseMatrix and I do not fully understand where the problem
could come from. The matrices are initialized beforehand, what reason do
you think It could produce a memory issue in the solver?
Below is the full solver function:
* template <int dim>*
* void LaplaceProblem<dim>::solve()*
* {*
* PETScWrappers::MPI::Vector
completely_distributed_solution(locally_owned_dofs,mpi_communicator);*
* SolverControl cn;*
* PETScWrappers::SparseDirectMUMPS solver(cn, mpi_communicator);*
* solver.solve(system_matrix, completely_distributed_solution, system_rhs);*
* constraints.distribute(completely_distributed_solution);*
* locally_relevant_solution = completely_distributed_solution;*
*}*
Thank you again for your help
Regards
H.
El jueves, 3 de marzo de 2022 a las 15:13:30 UTC+1, bruno.t...@gmail.com
escribió:
> Hermes,
>
> There is a couple of things that you could do but it probably won't give
> you a significant speed up. Are you sure that you are running in Release
> mode and not in Debug? Do you evaluate complicated functions in the
> assembly?
> A couple changes that could help:
> - don't use *fe.system_to_component_index(i).first *and
> f*e.system_to_component_index(j).first
> *everywhere. Just define const k = ... and const m = ... and use k and m.
> That might help the compiler with some optimizations
> - move the two if for the cell assembly outside the for loop on the
> quadrature point, similar to what you did for the boundaries. This could
> potentially help quite a bit if the cpu often gets the branch prediction
> wrong
>
> Best,
>
> Bruno
>
> On Thursday, March 3, 2022 at 4:31:04 AM UTC-5 hermes...@gmail.com wrote:
>
>> Dear all,
>>
>> I am experiencing long times when computing the assembling and I would
>> like to ask if this is common or there is something wrong with my
>> implementation.
>>
>> My model is built in a similar way as step-29 and step-40 (using complex
>> values ad solving with a direct solver using distributed parallel
>> implementation).
>> Now I am running larger systems with 3.5million dof and the assembling
>> took 16h, while the solver function took much less.
>>
>> I can show the structure of my assembly_system() function to ask if
>> there is something that can be done in order to speed up the process:
>>
>>
>> *void Problem<dim>::assemble_system()*
>> *{*
>> * for (unsigned int i = 0; i < dofs_per_cell; ++i) {*
>> * for (unsigned int j = 0; j < dofs_per_cell; ++j)*
>> * {*
>> * for (unsigned int q_point = 0; q_point < n_q_points; ++q_point)*
>> * { *
>> * if (fe.system_to_component_index(i).first ==
>> fe.system_to_component_index(j).first)*
>> * {*
>> * cell_matrix(i, j) += ....*
>>
>> * }*
>> * if (fe.system_to_component_index(i).first !=
>> fe.system_to_component_index(j).first)*
>> * {*
>> * cell_matrix(i, j) += ....*
>> * }*
>>
>> * }*
>>
>> // Boundaries
>> * if (fe.system_to_component_index(i).first ==
>> fe.system_to_component_index(j).first)*
>> * {*
>> * for (unsigned int face_no : GeometryInfo<dim>::face_indices())*
>> * if (cell->face(face_no)->at_boundary() &&
>> (cell->face(face_no)->boundary_id() == 0))*
>> * {*
>> * fe_face_values.reinit(cell, face_no);*
>> * for (unsigned int q_point = 0; q_point < n_face_q_points; ++q_point)*
>> * cell_matrix(i, j) += ....*
>> * }*
>> * }*
>> * if (fe.system_to_component_index(i).first !=
>> fe.system_to_component_index(j).first)*
>> * {*
>> * for (unsigned int face_no : GeometryInfo<dim>::face_indices())*
>> * {*
>> * if (cell->face(face_no)->at_boundary() &&
>> (cell->face(face_no)->boundary_id() == 0))*
>> * {*
>> * fe_face_values.reinit(cell, face_no);*
>> * for (unsigned int q_point = 0; q_point < n_face_q_points;++q_point)*
>> * cell_matrix(i, j) += ....*
>> * }*
>> * }*
>>
>> * }*
>>
>> * } *
>> *}*
>>
>>
>> Thank you very much.
>> Regards,
>> Hermes
>>
>
--
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see
https://groups.google.com/d/forum/dealii?hl=en
---
You received this message because you are subscribed to the Google Groups
"deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to dealii+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/dealii/d80cbd1c-7d1f-4042-a9e8-e8382a721790n%40googlegroups.com.
