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
>
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