I implemented it the following way:
Functions::InterpolatedTensorProductGridData<dim> interpolator(this->
coordinate_values,
this->data_storage);
VectorFunctionFromScalarFunctionObject<dim> interpolator_object(&
interpolator.value,
target_component,
n_components_to_use);
VectorTools::internal::project_matrix_free<n_components_to_use,
fe_degree_to_use>(MappingQGeneric<dim>(1),
dof_handler,
hanging_node_constraints,
INTERPOLATION_EQUATION<dim>(fe.degree + gauss_size),
interpolator_object,
present_solution,
false,
(dim > 1
?
INTERPOLATION_EQUATION<dim - 1>(fe_degree_to_use)
:
Quadrature<dim - 1>(0)),
false);
but the compilation fails with
error: ISO C++ forbids taking the address of a bound member function to
form a pointer to member function. Say
‘&dealii::Functions::InterpolatedTensorProductGridData<2>::value’.
Therefore, how can I approach that problem in a better way?
Thanks!
Am Donnerstag, 23. Januar 2020 15:39:23 UTC+1 schrieb Wolfgang Bangerth:
>
> On 1/23/20 7:29 AM, 'Maxi Miller' via deal.II User Group wrote:
> >
> > Why would you want to project when you can interpolate? That seems
> > unnecessarily expensive :-)
> >
> > I would like to have the input data (which is interpolated) as an
> additional
> > component, which then is printed together with the result of the other
> > calculations. Therefore I am not sure if there is a simpler approach
> (after
> > interpolation) to get the data into the component. I either can solve
> the
> > equation u = f for that, or use project(). Or is there another one?
>
> What I'm saying is that you can solve for u_h=f in many different ways,
> depending on how exactly you interpret the equality. In general, u_h is in
> some finite element space, but f is not, so the two will not be equal
> everywhere. Projection finds a u_h so that
> (u_h,v_h) = (f,v_h) for all v_h
> which is one way of interpreting the equality. Interpolation finds a u_h
> so that
> u_h(x_j) = f(x_j) at all node locations x_j
> which is another way of interpreting the equality. Neither is better than
> the
> other, but the second approach is *far* cheaper to compute.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bang...@colostate.edu
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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