Ok, I see - it is that EPS_TARGET_MAGNITUDE flag that was missing. It works
now! Thanks a lot, Simon.
Anton.
On Tuesday, August 24, 2021 at 12:14:20 AM UTC-6 simon...@gmail.com wrote:
> Hi,
>
> I think you need to set both which eigen pair and the target value. For
> example, if you look for the eigenvalue closest in magnitude to 0, you need
> to set the following
>
> const double target_eigenvalue = 0;
> eigensolver.set_which_eigenpairs(EPS_TARGET_MAGNITUDE);
> eigensolver.set_target_eigenvalue(target_eigenvalue);
>
> Depending on slepc version it might be that you can only choose
> EPS_TARGET_MAGNITUDE. See question 8 here:
>
> https://slepc.upv.es/documentation/faq.htm
>
> Best,
> Simon
>
> On Tuesday, August 24, 2021 at 3:39:29 AM UTC+2 anton.i...@gmail.com
> wrote:
>
>> Dear All,
>>
>> I am trying to use a shift-invert transformation in step-36. I did
>> minimal changes in the solve function adding the following code that
>> describes what spectral transformation I need to do:
>>
>> SolverControl solver_control (dof_handler.n_dofs(), 1e-9);
>> SLEPcWrappers::SolverKrylovSchur eigensolver(solver_control);
>> eigensolver.set_which_eigenpairs (EPS_SMALLEST_REAL);
>> eigensolver.set_problem_type (EPS_GHEP);
>>
>> double eigen_shift = 1.0e-4;
>> SLEPcWrappers::TransformationShiftInvert::AdditionalData
>> additional_data(eigen_shift);
>> SLEPcWrappers::TransformationShiftInvert shift (MPI_COMM_WORLD,
>> additional_data);
>> eigensolver.set_transformation (shift);
>>
>> eigensolver.solve(stiffness_matrix,
>> mass_matrix,
>> eigenvalues,
>> eigenfunctions,
>> eigenfunctions.size());
>>
>> and it gives me the following error:
>>
>> [0]PETSC ERROR: Shift-and-invert requires a target 'which' (see
>> EPSSetWhichEigenpairs), for instance -st_type sinvert -eps_target 0
>> -eps_target_magnitude
>>
>> Any help to resolve this error is greatly appreciated. I also attached
>> the full code of modified step-36.
>>
>> Thank you,
>> Anton.
>>
>
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