Reference documentation for deal.II version Git 6abe6d7889 2020-08-12 13:30:05 -0400
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dof_accessor_get.cc
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5 // This file is part of the deal.II library.
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15 
19 
20 #include <deal.II/fe/fe.h>
21 
23 #include <deal.II/grid/tria_iterator.templates.h>
24 
25 #include <deal.II/hp/dof_handler.h>
26 
30 #include <deal.II/lac/la_vector.h>
38 #include <deal.II/lac/vector.h>
39 
40 #include <vector>
41 
43 
44 
45 template <int dim, int spacedim, bool lda>
46 template <class InputVector, typename number>
47 void
49  const InputVector &values,
50  Vector<number> & interpolated_values,
51  const unsigned int fe_index_) const
52 {
53  const unsigned int fe_index =
54  (this->dof_handler->hp_capability_enabled == false &&
57  fe_index_;
58 
59  if (this->is_active())
60  // If this cell is active: simply return the exact values on this
61  // cell unless the finite element we need to interpolate to is different
62  // than the one we have on the current cell
63  {
64  if ((this->dof_handler->hp_capability_enabled == false) ||
65  // for hp-DoFHandlers, we need to require that on
66  // active cells, you either don't specify an fe_index,
67  // or that you specify the correct one
68  (fe_index == this->active_fe_index()) ||
70  this->get_dof_values(values, interpolated_values);
71  else
72  {
73  // well, here we need to first get the values from the current
74  // cell and then interpolate it to the element requested. this
75  // can clearly only happen for hp::DoFHandler objects
76  const unsigned int dofs_per_cell = this->get_fe().n_dofs_per_cell();
77  if (dofs_per_cell == 0)
78  {
79  interpolated_values = 0;
80  }
81  else
82  {
83  Vector<number> tmp(dofs_per_cell);
84  this->get_dof_values(values, tmp);
85 
86  FullMatrix<double> interpolation(
87  this->dof_handler->get_fe(fe_index).n_dofs_per_cell(),
88  this->get_fe().n_dofs_per_cell());
89  this->dof_handler->get_fe(fe_index).get_interpolation_matrix(
90  this->get_fe(), interpolation);
91  interpolation.vmult(interpolated_values, tmp);
92  }
93  }
94  }
95  else
96  // The cell is not active; we need to obtain data them from
97  // children recursively.
98  {
99  // we are on a non-active cell. these do not have any finite
100  // element associated with them in the hp context (in the non-hp
101  // context, we can simply assume that the FE space to which we
102  // want to interpolate is the same as for all elements in the
103  // mesh). consequently, we cannot interpolate from children's FE
104  // space to this cell's (unknown) FE space unless an explicit
105  // fe_index is given
106  Assert((this->dof_handler->hp_capability_enabled == false) ||
108  ExcMessage(
109  "You cannot call this function on non-active cells "
110  "of hp::DoFHandler objects unless you provide an explicit "
111  "finite element index because they do not have naturally "
112  "associated finite element spaces associated: degrees "
113  "of freedom are only distributed on active cells for which "
114  "the active_fe_index has been set."));
115 
116  const FiniteElement<dim, spacedim> &fe =
117  this->get_dof_handler().get_fe(fe_index);
118  const unsigned int dofs_per_cell = fe.n_dofs_per_cell();
119 
120  Assert(this->dof_handler != nullptr,
121  typename BaseClass::ExcInvalidObject());
122  Assert(interpolated_values.size() == dofs_per_cell,
123  typename BaseClass::ExcVectorDoesNotMatch());
124  Assert(values.size() == this->dof_handler->n_dofs(),
125  typename BaseClass::ExcVectorDoesNotMatch());
126 
127 
128  // see if the finite element we have on the current cell has any
129  // degrees of freedom to begin with; if not (e.g., when
130  // interpolating FE_Nothing), then simply skip all of the
131  // following since the output vector would be of size zero
132  // anyway (and in fact is of size zero, see the assertion above)
133  if (fe.n_dofs_per_cell() > 0)
134  {
135  Vector<number> tmp1(dofs_per_cell);
136  Vector<number> tmp2(dofs_per_cell);
137 
138  interpolated_values = 0;
139 
140  // later on we will have to push the values interpolated from the
141  // child to the mother cell into the output vector. unfortunately,
142  // there are two types of elements: ones where you add up the
143  // contributions from the different child cells, and ones where you
144  // overwrite.
145  //
146  // an example for the first is piecewise constant (and discontinuous)
147  // elements, where we build the value on the coarse cell by averaging
148  // the values from the cell (i.e. by adding up a fraction of the
149  // values of their values)
150  //
151  // an example for the latter are the usual continuous elements. the
152  // value on a vertex of a coarse cell must there be the same,
153  // irrespective of the adjacent cell we are presently on. so we always
154  // overwrite. in fact, we must, since we cannot know in advance how
155  // many neighbors there will be, so there is no way to compute the
156  // average with fixed factors
157  //
158  // so we have to find out to which type this element belongs. the
159  // difficulty is: the finite element may be a composed one, so we can
160  // only hope to do this for each shape function individually. in fact,
161  // there are even weird finite elements (for example the
162  // Raviart-Thomas element) which have shape functions that are
163  // additive (interior ones) and others that are overwriting (face
164  // degrees of freedom that need to be continuous across the face).
165  for (unsigned int child = 0; child < this->n_children(); ++child)
166  {
167  // get the values from the present child, if necessary by
168  // interpolation itself either from its own children or
169  // by interpolating from the finite element on an active
170  // child to the finite element space requested here
171  this->child(child)->get_interpolated_dof_values(values,
172  tmp1,
173  fe_index);
174  // interpolate these to the mother cell
175  fe.get_restriction_matrix(child, this->refinement_case())
176  .vmult(tmp2, tmp1);
177 
178  // and add up or set them in the output vector
179  for (unsigned int i = 0; i < dofs_per_cell; ++i)
180  if (fe.restriction_is_additive(i))
181  interpolated_values(i) += tmp2(i);
182  else if (tmp2(i) != number())
183  interpolated_values(i) = tmp2(i);
184  }
185  }
186  }
187 }
188 
189 
190 // --------------------------------------------------------------------------
191 // explicit instantiations
192 #include "dof_accessor_get.inst"
193 
bool restriction_is_additive(const unsigned int index) const
Definition: fe.h:3241
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
void vmult(Vector< number2 > &w, const Vector< number2 > &v, const bool adding=false) const
static ::ExceptionBase & ExcMessage(std::string arg1)
#define Assert(cond, exc)
Definition: exceptions.h:1411
virtual const FullMatrix< double > & get_restriction_matrix(const unsigned int child, const RefinementCase< dim > &refinement_case=RefinementCase< dim >::isotropic_refinement) const
Definition: fe.cc:335
#define DEAL_II_NAMESPACE_CLOSE
Definition: config.h:363
unsigned int n_dofs_per_cell() const
#define DEAL_II_NAMESPACE_OPEN
Definition: config.h:362
size_type size() const