Reference documentation for deal.II version GIT 6da2e5d553 2022-07-01 18:55:02+00:00
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dof_accessor_get.cc
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15 
19 
20 #include <deal.II/fe/fe.h>
21 
23 #include <deal.II/grid/tria_iterator.templates.h>
24 
28 #include <deal.II/lac/la_vector.h>
36 #include <deal.II/lac/vector.h>
37 
38 #include <vector>
39 
41 
42 
43 template <int dim, int spacedim, bool lda>
44 template <class InputVector, typename number>
45 void
47  const InputVector &values,
48  Vector<number> & interpolated_values,
49  const unsigned int fe_index_) const
50 {
51  const unsigned int fe_index =
52  (this->dof_handler->hp_capability_enabled == false &&
55  fe_index_;
56 
57  if (this->is_active())
58  // If this cell is active: simply return the exact values on this
59  // cell unless the finite element we need to interpolate to is different
60  // than the one we have on the current cell
61  {
62  if ((this->dof_handler->hp_capability_enabled == false) ||
63  // for hp-DoFHandlers, we need to require that on
64  // active cells, you either don't specify an fe_index,
65  // or that you specify the correct one
66  (fe_index == this->active_fe_index()) ||
68  this->get_dof_values(values, interpolated_values);
69  else
70  {
71  // well, here we need to first get the values from the current
72  // cell and then interpolate it to the element requested. this
73  // can clearly only happen for DoFHandler objects in hp-mode
74  const unsigned int dofs_per_cell = this->get_fe().n_dofs_per_cell();
75  if (dofs_per_cell == 0)
76  {
77  interpolated_values = 0;
78  }
79  else
80  {
81  Vector<number> tmp(dofs_per_cell);
82  this->get_dof_values(values, tmp);
83 
84  FullMatrix<double> interpolation(
85  this->dof_handler->get_fe(fe_index).n_dofs_per_cell(),
86  this->get_fe().n_dofs_per_cell());
87  this->dof_handler->get_fe(fe_index).get_interpolation_matrix(
88  this->get_fe(), interpolation);
89  interpolation.vmult(interpolated_values, tmp);
90  }
91  }
92  }
93  else
94  // The cell is not active; we need to obtain data them from
95  // children recursively.
96  {
97  // we are on a non-active cell. these do not have any finite
98  // element associated with them in the hp-context (in the non-hp-
99  // context, we can simply assume that the FE space to which we
100  // want to interpolate is the same as for all elements in the
101  // mesh). consequently, we cannot interpolate from children's FE
102  // space to this cell's (unknown) FE space unless an explicit
103  // fe_index is given
104  Assert((this->dof_handler->hp_capability_enabled == false) ||
106  ExcMessage(
107  "You cannot call this function on non-active cells "
108  "of DoFHandler objects unless you provide an explicit "
109  "finite element index because they do not have naturally "
110  "associated finite element spaces associated: degrees "
111  "of freedom are only distributed on active cells for which "
112  "the active FE index has been set."));
113 
114  const FiniteElement<dim, spacedim> &fe =
115  this->get_dof_handler().get_fe(fe_index);
116  const unsigned int dofs_per_cell = fe.n_dofs_per_cell();
117 
118  Assert(this->dof_handler != nullptr,
119  typename BaseClass::ExcInvalidObject());
120  Assert(interpolated_values.size() == dofs_per_cell,
121  typename BaseClass::ExcVectorDoesNotMatch());
122  Assert(values.size() == this->dof_handler->n_dofs(),
123  typename BaseClass::ExcVectorDoesNotMatch());
124 
125 
126  // see if the finite element we have on the current cell has any
127  // degrees of freedom to begin with; if not (e.g., when
128  // interpolating FE_Nothing), then simply skip all of the
129  // following since the output vector would be of size zero
130  // anyway (and in fact is of size zero, see the assertion above)
131  if (fe.n_dofs_per_cell() > 0)
132  {
133  Vector<number> tmp1(dofs_per_cell);
134  Vector<number> tmp2(dofs_per_cell);
135 
136  interpolated_values = 0;
137 
138  // later on we will have to push the values interpolated from the
139  // child to the mother cell into the output vector. unfortunately,
140  // there are two types of elements: ones where you add up the
141  // contributions from the different child cells, and ones where you
142  // overwrite.
143  //
144  // an example for the first is piecewise constant (and discontinuous)
145  // elements, where we build the value on the coarse cell by averaging
146  // the values from the cell (i.e. by adding up a fraction of the
147  // values of their values)
148  //
149  // an example for the latter are the usual continuous elements. the
150  // value on a vertex of a coarse cell must there be the same,
151  // irrespective of the adjacent cell we are presently on. so we always
152  // overwrite. in fact, we must, since we cannot know in advance how
153  // many neighbors there will be, so there is no way to compute the
154  // average with fixed factors
155  //
156  // so we have to find out to which type this element belongs. the
157  // difficulty is: the finite element may be a composed one, so we can
158  // only hope to do this for each shape function individually. in fact,
159  // there are even weird finite elements (for example the
160  // Raviart-Thomas element) which have shape functions that are
161  // additive (interior ones) and others that are overwriting (face
162  // degrees of freedom that need to be continuous across the face).
163  for (unsigned int child = 0; child < this->n_children(); ++child)
164  {
165  // get the values from the present child, if necessary by
166  // interpolation itself either from its own children or
167  // by interpolating from the finite element on an active
168  // child to the finite element space requested here
169  this->child(child)->get_interpolated_dof_values(values,
170  tmp1,
171  fe_index);
172  // interpolate these to the mother cell
173  fe.get_restriction_matrix(child, this->refinement_case())
174  .vmult(tmp2, tmp1);
175 
176  // and add up or set them in the output vector
177  for (unsigned int i = 0; i < dofs_per_cell; ++i)
178  if (fe.restriction_is_additive(i))
179  interpolated_values(i) += tmp2(i);
180  else if (tmp2(i) != number())
181  interpolated_values(i) = tmp2(i);
182  }
183  }
184  }
185 }
186 
187 
188 // --------------------------------------------------------------------------
189 // explicit instantiations
190 #include "dof_accessor_get.inst"
191 
void get_interpolated_dof_values(const InputVector &values, Vector< number > &interpolated_values, const unsigned int fe_index=DoFHandler< dimension_, space_dimension_ >::invalid_fe_index) const
unsigned int n_dofs_per_cell() const
bool restriction_is_additive(const unsigned int index) const
virtual const FullMatrix< double > & get_restriction_matrix(const unsigned int child, const RefinementCase< dim > &refinement_case=RefinementCase< dim >::isotropic_refinement) const
void vmult(Vector< number2 > &w, const Vector< number2 > &v, const bool adding=false) const
Definition: vector.h:109
#define DEAL_II_NAMESPACE_OPEN
Definition: config.h:442
#define DEAL_II_NAMESPACE_CLOSE
Definition: config.h:443
#define Assert(cond, exc)
Definition: exceptions.h:1473
static ::ExceptionBase & ExcMessage(std::string arg1)
size_type size() const