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MGTwoLevelTransfer (p): add fallback FE case #12924

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MGTwoLevelTransfer (p): add fallback FE case #12924

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ffa826f
Enabel FETools::get_projection_matrix() for multiple components
peterrum Nov 7, 2021
468444d
MGTwoLevelTransfer (p): add fallback FE case
peterrum Nov 7, 2021
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34 changes: 15 additions & 19 deletions include/deal.II/fe/fe_tools.templates.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1454,19 +1454,19 @@ namespace FETools
const FiniteElement<dim, spacedim> &fe2,
FullMatrix<number> & matrix)
{
Assert(fe1.n_components() == 1, ExcNotImplemented());
Assert(fe1.n_components() == fe2.n_components(),
ExcDimensionMismatch(fe1.n_components(), fe2.n_components()));
Assert(matrix.m() == fe2.n_dofs_per_cell() &&
matrix.n() == fe1.n_dofs_per_cell(),
ExcMatrixDimensionMismatch(matrix.m(),
matrix.n(),
fe2.n_dofs_per_cell(),
fe1.n_dofs_per_cell()));
AssertDimension(fe1.n_components(), fe2.n_components());

matrix = 0;

const unsigned int n1 = fe1.n_dofs_per_cell();
const unsigned int n2 = fe2.n_dofs_per_cell();
const unsigned int nd = fe1.n_components();

const ReferenceCell reference_cell = fe1.reference_cell();

Expand All @@ -1486,6 +1486,8 @@ namespace FETools
const auto quadrature =
reference_cell.get_gauss_type_quadrature<dim>(degree + 1);

const unsigned int nq = quadrature.size();

// Set up FEValues.
const UpdateFlags flags =
update_values | update_quadrature_points | update_JxW_values;
Expand All @@ -1498,16 +1500,13 @@ namespace FETools
// Integrate and invert mass matrix. This happens in the target space
FullMatrix<double> mass(n2, n2);

for (unsigned int k = 0; k < quadrature.size(); ++k)
{
const double dx = val2.JxW(k);
for (unsigned int i = 0; i < n2; ++i)
{
const double v = val2.shape_value(i, k);
for (unsigned int j = 0; j < n2; ++j)
mass(i, j) += v * val2.shape_value(j, k) * dx;
}
}
for (unsigned int i = 0; i < n2; ++i)
for (unsigned int j = 0; j < n2; ++j)
for (unsigned int d = 0; d < nd; ++d)
for (unsigned int k = 0; k < nq; ++k)
mass(i, j) += val2.JxW(k) * val2.shape_value_component(i, k, d) *
val2.shape_value_component(j, k, d);

// Invert the matrix. Gauss-Jordan should be sufficient since we expect
// the mass matrix to be well-conditioned
mass.gauss_jordan();
Expand All @@ -1522,12 +1521,9 @@ namespace FETools
b = 0.;
for (unsigned int i = 0; i < n2; ++i)
for (unsigned int k = 0; k < quadrature.size(); ++k)
{
const double dx = val2.JxW(k);
const double u = val1.shape_value(j, k);
const double v = val2.shape_value(i, k);
b(i) += u * v * dx;
}
for (unsigned int d = 0; d < nd; ++d)
b(i) += val1.shape_value_component(j, k, d) *
val2.shape_value_component(i, k, d) * val2.JxW(k);

// Multiply by the inverse
mass.vmult(x, b);
Expand Down