DUNE PDELab (git)
recipe-grid-function-operations.cc
See explanation at Operations on grid functions
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <iostream>
#include <dune/common/filledarray.hh>
#include <dune/common/parallel/mpihelper.hh>
#include <dune/grid/yaspgrid.hh>
#include <dune/pdelab.hh>
int main(int argc, char** argv)
{
// Initialize Mpi
Dune::MPIHelper::instance(argc, argv);
// need a grid in order to test grid functions
constexpr unsigned int dim = 2;
Dune::FieldVector<double,dim> L(5.0);
std::array<int,dim> N(Dune::filledArray<dim,int>(64));
Grid grid(L,N);
// [Defining functions]
auto analyticFunction1 = Dune::PDELab::makeGridFunctionFromCallable (grid.leafGridView(), [&](const auto& x){
return exp(-(x*x));
});
auto analyticFunction2 = Dune::PDELab::makeGridFunctionFromCallable (grid.leafGridView(), [&](const auto& x){
return x[0]*3.0;
});
{
// [Instantiating DifferenceSquaredAdapter]
Dune::PDELab::DifferenceSquaredAdapter<decltype(analyticFunction1),decltype(analyticFunction2)> difference(analyticFunction1, analyticFunction2);
// Note: Newer compiler versions do not require template arguments here!
std::cout << "Integral: " << integral << std::endl;
}
{
// [Defining operations]
auto difference = Dune::PDELab::makeGridFunctionFromCallable (grid.leafGridView(), [&](const auto& element, const auto& xlocal){
Dune::FieldVector<double,1> y1;
analyticFunction1.evaluate(element, xlocal, y1);
Dune::FieldVector<double,1> y2;
analyticFunction2.evaluate(element, xlocal, y2);
y2 -= y1;
return y2.two_norm2();
});
// [Compute integral]
auto integral = Dune::PDELab::integrateGridFunction(difference,10);
std::cout << "Integral: " << integral << std::endl;
}
}
static DUNE_EXPORT MPIHelper & instance(int &argc, char **&argv)
Get the singleton instance of the helper.
Definition: mpihelper.hh:252
Adapter returning ||f1(x)-f2(x)||^2 for two given grid functions.
Definition: gridfunctionadapter.hh:70
Utility to generate an array with a certain value.
GF::Traits::RangeType integrateGridFunction(const GF &gf, unsigned qorder=1)
Integrate a GridFunction.
Definition: functionutilities.hh:51
Helpers for dealing with MPI.
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