You will need to tell the MeshWorker to compute the values with something like
info.cell_selector.add("solution", true, ..., ...);
On Mon, Oct 12, 2020 at 8:18 AM Gregor Pfau <gregor2....@gmail.com> wrote:
>
> Dear Timo,
>
> first of all thank you for your reply and advice.
>
> As you suspected, info.values[0][0] and info.values[0] are both of size
> zero. I have tried this with the example given in my previous question, as
> well as with the original code.
>
> Since the original problem is time dependent, the goal was to get the
> solution values of the previous timestep at the quadrature points.
> Could it be, that I need to use a different approach, at least for the first
> time step ?
>
> I have tried get_function_values, but even with the workaround proposed here:
> https://groups.google.com/g/dealii/c/pjUBPbaZgxg/m/lSPLgiTtAgAJ , I still get
> the same error.
>
> To be honest, I am not shure how to tackle either apporach.
>
> Thank you very much.
>
> Best regards,
> Gregor
>
>
>
>
>
>
>
>
> Timo Heister schrieb am Samstag, 26. September 2020 um 21:44:05 UTC+2:
>>
>> Hi Gregor,
>>
>> I would suggest that you grab a debugger (inside an IDE like
>> QtCreator, VS Code, etc.) or gdb directly and inspect the types and
>> content of "info", "info.values", and "info.values[0]" in that order
>> to see if they are all valid objects and have a non-zero size. From
>> the error message, it sounds like that this is not the case.
>>
>> Best,
>> Timo
>>
>> On Sat, Sep 26, 2020 at 8:25 AM Gregor Pfau <grego...@gmail.com> wrote:
>> >
>> > Dear Deal.II community,
>> >
>> > currently I am trying to solve a nonlinear problem with Newtons Method
>> > using MeshWorker.
>> >
>> > However during this, I encounter an error while using the public attribute
>> > value of
>> > MeshWorker::IntegrationInfo.
>> > I get a segmentation fault, whenever I call it. (A concrete example will
>> > be given)
>> >
>> > My current code is heavily based on Step-12( Version 9.1.1). To exclude as
>> > many errors as possible, as an experiment I decided to modify Step-12 and
>> > see, wether I could reprodue the error. It turns out I can.
>> >
>> > The modification of Step-12 is just three lines of code added in
>> > integrate_cell_term, where values is called analogously to Step-39
>> > (version 9.1.1).
>> >
>> > template <int dim>
>> > void AdvectionProblem<dim>::integrate_cell_term(DoFInfo & dinfo,
>> > CellInfo &info)
>> > {
>> > const FEValuesBase<dim> & fe_values = info.fe_values();
>> > FullMatrix<double> & local_matrix = dinfo.matrix(0).matrix;
>> > const std::vector<double> &JxW = fe_values.get_JxW_values();
>> >
>> > std::cout << "Checkpoint1" << std::endl;
>> > const std::vector<double> &uh = info.values[0][0];
>> > std::cout << "Checkpoint2" << std::endl;
>> >
>> > for (unsigned int point = 0; point < fe_values.n_quadrature_points;
>> > ++point)
>> > {
>> > const Tensor<1, dim> beta_at_q_point =
>> > beta(fe_values.quadrature_point(point));
>> >
>> > for (unsigned int i = 0; i < fe_values.dofs_per_cell; ++i)
>> > for (unsigned int j = 0; j < fe_values.dofs_per_cell; ++j)
>> > local_matrix(i, j) += -beta_at_q_point * //
>> > fe_values.shape_grad(i, point) * //
>> > fe_values.shape_value(j, point) * //
>> > JxW[point];
>> > }
>> > }
>> >
>> >
>> >
>> > Usually the compiler just shuld give me a warning, that uh is an unused
>> > variable, but the program itself should run smoothly.
>> > However when I run the program, I get the following message:
>> >
>> > Checkpoint1Checkpoint1
>> > Checkpoint1
>> > CMakeFiles/run.dir/build.make:57: recipe for target 'CMakeFiles/run' failed
>> > make[3]: *** [CMakeFiles/run] Segmentation fault (core dumped)
>> > CMakeFiles/Makefile2:131: recipe for target 'CMakeFiles/run.dir/all' failed
>> > make[2]: *** [CMakeFiles/run.dir/all] Error 2
>> > CMakeFiles/Makefile2:138: recipe for target 'CMakeFiles/run.dir/rule'
>> > failed
>> > make[1]: *** [CMakeFiles/run.dir/rule] Error 2
>> > Makefile:144: recipe for target 'run' failed
>> > make: *** [run] Error 2
>> >
>> > Double checking this with gdb I get the following:
>> >
>> > Thread 3 "step-12" received signal SIGSEGV, Segmentation fault.
>> > [Switching to Thread 0x7fffe0553700 (LWP 2417)]
>> > 0x00005555556864d2 in std::vector<std::vector<double,
>> > std::allocator<double> >, std::allocator<std::vector<double,
>> > std::allocator<double> > > >::operator[] (
>> > this=0x0, __n=0) at /usr/include/c++/7/bits/stl_vector.h:798
>> > 798 return *(this->_M_impl._M_start + __n);
>> >
>> > when trying to run the program beyond
>> > const std::vector<double> &uh = info.values[0][0]
>> >
>> > In both cases the program was run in debug-mode.
>> >
>> > I feel it helps with identifying the problem, that Step-39 runs perfectly
>> > smooth on my computer.
>> >
>> > I hope this is enough information to find the error in my approach.
>> >
>> > Thank you very much.
>> >
>> > Best regards,
>> > Gregor
>> >
>> > --
>> > The deal.II project is located at http://www.dealii.org/
>> > For mailing list/forum options, see
>> > https://groups.google.com/d/forum/dealii?hl=en
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>>
>>
>>
>> --
>> Timo Heister
>> http://www.math.clemson.edu/~heister/
>
> --
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--
Timo Heister
http://www.math.clemson.edu/~heister/
--
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