RealType Solver::computeResidual(GridFunction& sourcegridfunction,
GridFunctionType& rhs,
const PointType& h){
//<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
// The pre-value to be returned (return sqrt(doubleSum)):
RealType doubleSum = 0.0;
/* We need to compute the derivatives p_xx and p_yy, therefore the stencil has to be applied.
*/
MultiIndexType dim = sourcegridfunction.GetGridDimension();
MultiIndexType bread (0,0);
MultiIndexType eread (dim[0]-1,dim[1]-1);
MultiIndexType bwrite (1,1);
MultiIndexType ewrite (dim[0]-2,dim[1]-2);
//Compute the needed derivations for the whole (inner?) area
Stencil stencil(3,h); // bzw. Kann man einfach const weitergeben? /Wie?
//Get the values for derivative in x-direction:
GridFunction Fxx(dim);
stencil.ApplyFxxStencilOperator(bread, eread, bwrite, ewrite, sourcegridfunction.GetGridFunction(), Fxx);
//Get the values for derivative in y-direction:
GridFunction Fyy(dim);
stencil.ApplyFyyStencilOperator(bread, eread, bwrite, ewrite, sourcegridfunction.GetGridFunction(), Fyy);
// Compute the residual: res = sqrt(Sum_i^I(Sum_j^J((p_xx+p_yy-rightHandSide)²/(I*J))))
RealType derivator;
for (IndexType i = 1; i <= dim[0]-2; i++)
{
for (IndexType j = 1; j <= dim[1]-2; j++)
{
derivator = Fxx.GetGridFunction()[i][j]+ Fyy.GetGridFunction()[i][j] - rhs[i][j];
doubleSum += derivator*derivator / (dim[0]-2) / (dim[1]-2);
}
}
//std::cout<<doubleSum<<std::endl;
return sqrt(doubleSum);
}
