Hi Sudip,
this is the only place in assemble_system() in which you call
SparseMatrix<double>::operator()
/*std::cout << "Before applying boundary conditions" << std::endl;*/
for (unsigned int i = 0; i < dof_handler.n_dofs(); i++) {
for (unsigned int j = 0; j < dof_handler.n_dofs(); j++) {
text_output_file << system_matrix(i, j) << " ";
} text_output_file << std::endl;
}
/* std::cout << solution(i) << " " << system_rhs(i) << std::endl;*/
system_matrix is a Sparse Matrix which does not store all elements. You are
asking for elements in the matrix that do not exist, and the function
throws an exception.
See also:
https://dealii.org/developer/doxygen/deal.II/classSparseMatrix.html#a97b95d2e38fe6a38a2af59155a6892d7
Best,
Marc
On Monday, August 5, 2024 at 1:57:20 PM UTC+2 sudip...@gmail.com wrote:
> Hi all,
>
> I have a code that works fine for one element, but won't compile for even
> one level of refinement (8 elements). It solves a small deformation problem
> of elastic compression of a cube of side length 1. The edges of the cube
> are parallel to the coordinate axes and three of its faces are on the
> coordinate planes. The code assumes that the Young's modulus, Poisson's
> ratio and the speed at which the "top" surface of the cube is moving are
> defined in a parameters.h file.
>
> I have attached my code to this message. When I try to refine the mesh
> (say 8 elements) I get the following message from the compiler
>
> --------------------------------------------------------
> An error occurred in line <2014> of file
> </home/skunda/built-programs/dealii-9.2.0/install/include/deal.II/lac/sparse_matrix.h>
>
> in function
> number&
> dealii::SparseMatrix<number>::operator()(dealii::SparseMatrix<number>::size_type,
>
> dealii::SparseMatrix<number>::size_type) [with number = double;
> dealii::SparseMatrix<number>::size_type = unsigned int]
> The violated condition was:
> cols->operator()(i, j) != SparsityPattern::invalid_entry
> Additional information:
> You are trying to access the matrix entry with index <0,24>, but this
> entry does not exist in the sparsity pattern of this matrix.
>
> The most common cause for this problem is that you used a method to build
> the sparsity pattern that did not (completely) take into account all of the
> entries you will later try to write into. An example would be building a
> sparsity pattern that does not include the entries you will write into due
> to constraints on degrees of freedom such as hanging nodes or periodic
> boundary conditions. In such cases, building the sparsity pattern will
> succeed, but you will get errors such as the current one at one point or
> other when trying to write into the entries of the matrix.
>
> Stacktrace:
> -----------
> #0 ./main: dealii::SparseMatrix<double>::operator()(unsigned int,
> unsigned int)
> #1 ./main: Problem<3>::assemble_system()
> #2 ./main: Problem<3>::run()
> #3 ./main: main
> --------------------------------------------------------
>
> I am using the following 4 lines to make the sparsity pattern and the
> system matrix
>
> DynamicSparsityPattern dsp(dof_handler.n_dofs(), dof_handler.n_dofs());
> DoFTools::make_sparsity_pattern(dof_handler, dsp);
> sparsity_pattern.copy_from(dsp);
> system_matrix.reinit(sparsity_pattern);
>
> I cannot see the mistake I am making while building the sparsity pattern.
> Any help is appreciated.
>
> Best Regards,
> Sudip Kunda
>
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