Hi Jean,
It turns out that I did not configure dealii with ARPACK. So I followed the
readme instructions and installed and compiled ARPACK as suggested. I also
tried to run the examples in the ARPACK directory and they are running
without any errors. However, when I tried to reconfigure deallii using the
selfcompiled version, it says the following error.
Could not find the arpack library!
Please ensure that a suitable arpack library is installed on your
computer.
If the library is not at a default location, either provide some hints for
autodetection,
$ ARPACK_DIR="..." cmake <...>
$ cmake -DARPACK_DIR="..." <...>
or set the relevant variables by hand in ccmake.
I used the following cmake command to configure dealii again -
cmake -DDEAL_II_WITH_PETSC=ON
-DPETSC_DIR=/home/animesh/Documents/petsc-3.13.5
-DPETSC_ARCH=arch-linux-c-debug -DDEAL_II_WITH_METIS=ON
-DDEAL_II_WITH_MPI=ON -DDEAL_II_WITH_ARPACK=ON
-DARPACK_DIR=/home/animesh/Documents/ARPACK ..
I checked that the path of the directory of ARPACK that I am giving here is
correct.
I followed the instructions in this page -
https://www.dealii.org/current/external-libs/arpack.html.
Also, I couldn't figure out what it means when it says "For compilation of
ARPACK we emphasize adding the compiler flag -fPIC". What is -fPIC and
where should I use this flag?
Could you please help me with this and the question about identity matrix
asked in the previous mail of this thread?
Thanks a lot!
Animesh
On Thursday, September 24, 2020 at 11:56:24 AM UTC+5:30 Animesh Rastogi IIT
Gandhinagar wrote:
> Hi Jean,
>
> Thanks a lot for your response. I am trying as you suggested. I have added
> the following code inside the linear solver so that I can get the
> eigenvalues at every newton step.
>
> std::vector<std::complex<double>> eigenvalues;
> std::vector<Vector<double> > eigenvectors;
> SparseMatrix<double> identity (IdentityMatrix(u_dof));
> SparseDirectUMFPACK inverse;
> inverse.initialize (tangent_matrix.block(u_dof,u_dof));
> const int eigensolver_its = static_cast<unsigned int>(
> tangent_matrix.block(u_dof, u_dof).m()
> * parameters.max_iterations_lin);
> SolverControl solver_control(eigensolver_its, 1e-9);
> ArpackSolver::ArpackSolver eigensolver(solver_control);
> eigensolver.solve(tangent_matrix.block(u_dof,u_dof), identity,
> inverse, eigenvalues, eigenvectors);
>
> However, I am getting the follwing error while compiling.
>
> error: ‘ArpackSolver’ has not been declared
>
> I have included the header file #include <deal.II/lac/arpack_solver.h>.
>
> Also, could you please let me know if I have declared the identity matrix
> correctly? I am replacing the mass matrix B with the Identity matrix to
> compute the eigenvalues and eigenvectors.
>
> Thanks!
>
> Animesh
> On Thursday, September 24, 2020 at 1:10:35 AM UTC+5:30 Jean-Paul Pelteret
> wrote:
>
>> Hi Animesh,
>>
>> Although in that code-gallery example the system is assembled into a
>> BlockSparseMatrix<double>, the system actually has only one block. So you
>> can retrieve the underlying SparseMatrix<double> (and Vector<double> for
>> the RHS) via
>> tangent_matrix.block(u_dof, u_dof);
>> system_rhs.block(u_dof);
>> and use them with one of the standard eigensolvers (maybe ArpackSolver
>> <https://dealii.org/developer/doxygen/deal.II/classArpackSolver.html>,
>> since you want both the eigenvalues and eigenvectors).
>>
>> I hope that this helps you!
>>
>> Best,
>> Jean-Paul
>>
>> On 23 Sep 2020, at 20:53, Animesh Rastogi IIT Gandhinagar <
>> animesh...@alumni.iitgn.ac.in> wrote:
>>
>> Hi All,
>>
>> I am trying to play with the code of Quassi Static Finite Strain
>> Compressibility
>> <https://dealii.org/developer/doxygen/deal.II/code_gallery_Quasi_static_Finite_strain_Compressible_Elasticity.html>.
>>
>> I want to calculate the eigenvalues and eigenvectors of the System Tangent
>> Matrix (BlockSparseMatrix<double>
>> <https://dealii.org/developer/doxygen/deal.II/classBlockSparseMatrix.html>
>> tangent_matrix) that we get at every time step after the Newton method has
>> converged. However, I could not find any function to calculate the
>> eigenvalues and eigenvectors of the BlockSparse Matrix. Could someone
>> please help me with this?
>>
>> Thanks!
>>
>> AR
>>
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