How to access solution values at DoFs of a cell?

[Junchao Zhang]

 Hi,

 In matrix assembly, I need to access solution values of the previous time-step at DoFs of the current cell. Is my following code correct? I could not find an example. Thanks.

 std::vector<types::global_dof_index> local_dof_indices (dofs_per_cell);

 ...

  for(; cell!=endc; ++cell) {

    if (cell->is_locally_owned()) {

      

      cell->get_dof_indices (local_dof_indices);

      fe_values.reinit (cell);

       ... += old_locally_relevant_solution(local_dof_indices[i]);

    }

  }

--Junchao Zhang

[Wolfgang Bangerth]

No. You typically need to access the old solution at *quadrature points*, not
at the node points. You can find how this is typically done in many tutorial
programs, e.g., in steps 21, 26, 15. To evaluate a solution at the quadrature
points, you'll have to do something like
fe_values.get_function_values (old_solution,
old_solution_values);

Best
W.

--
------------------------------------------------------------------------
Wolfgang Bangerth email: bang...@math.tamu.edu
www: http://www.math.tamu.edu/~bangerth/

[Junchao Zhang]

You are right. I only need values or grad values at the quadrature points.  Thanks a lot.

--Junchao Zhang

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