Reference documentation for deal.II version Git 5109843 20180321 23:56:40 +0700

#include <deal.II/dofs/dof_handler.h>
Classes  
class  MGVertexDoFs 
Public Types  
typedef ActiveSelector::active_cell_iterator  active_cell_iterator 
typedef ActiveSelector::cell_iterator  cell_iterator 
typedef ActiveSelector::face_iterator  face_iterator 
typedef ActiveSelector::active_face_iterator  active_face_iterator 
Public Member Functions  
DoFHandler ()  
DoFHandler (const Triangulation< dim, spacedim > &tria)  
DoFHandler (const DoFHandler &)=delete  
virtual  ~DoFHandler () 
DoFHandler &  operator= (const DoFHandler &)=delete 
void  initialize (const Triangulation< dim, spacedim > &tria, const FiniteElement< dim, spacedim > &fe) 
virtual void  distribute_dofs (const FiniteElement< dim, spacedim > &fe) 
virtual void  distribute_mg_dofs (const FiniteElement< dim, spacedim > &fe) 
virtual void  distribute_mg_dofs () 
bool  has_level_dofs () const 
bool  has_active_dofs () const 
void  initialize_local_block_info () 
virtual void  clear () 
void  renumber_dofs (const std::vector< types::global_dof_index > &new_numbers) 
void  renumber_dofs (const unsigned int level, const std::vector< types::global_dof_index > &new_numbers) 
unsigned int  max_couplings_between_dofs () const 
unsigned int  max_couplings_between_boundary_dofs () const 
Cell iterator functions  
cell_iterator  begin (const unsigned int level=0) const 
active_cell_iterator  begin_active (const unsigned int level=0) const 
cell_iterator  end () const 
cell_iterator  end (const unsigned int level) const 
active_cell_iterator  end_active (const unsigned int level) const 
level_cell_iterator  begin_mg (const unsigned int level=0) const 
level_cell_iterator  end_mg (const unsigned int level) const 
level_cell_iterator  end_mg () const 
Public Member Functions inherited from Subscriptor  
Subscriptor ()  
Subscriptor (const Subscriptor &)  
Subscriptor (Subscriptor &&) noexcept  
virtual  ~Subscriptor () 
Subscriptor &  operator= (const Subscriptor &) 
Subscriptor &  operator= (Subscriptor &&) noexcept 
void  subscribe (const char *identifier=nullptr) const 
void  unsubscribe (const char *identifier=nullptr) const 
unsigned int  n_subscriptions () const 
void  list_subscribers () const 
template<class Archive >  
void  serialize (Archive &ar, const unsigned int version) 
Static Public Attributes  
static const unsigned int  dimension = dim 
static const unsigned int  space_dimension = spacedim 
static const types::global_dof_index  invalid_dof_index = numbers::invalid_dof_index 
static const unsigned int  default_fe_index = 0 
Related Functions  
(Note that these are not member functions.)  
Functions to support code that generically uses both DoFHandler and hp::DoFHandler  
template<int dim, int spacedim>  
unsigned int  max_dofs_per_cell (const DoFHandler< dim, spacedim > &dh) 
template<int dim, int spacedim>  
unsigned int  max_dofs_per_face (const DoFHandler< dim, spacedim > &dh) 
template<int dim, int spacedim>  
unsigned int  max_dofs_per_vertex (const DoFHandler< dim, spacedim > &dh) 
template<int dim, int spacedim>  
unsigned int  n_components (const DoFHandler< dim, spacedim > &dh) 
template<int dim, int spacedim>  
bool  fe_is_primitive (const DoFHandler< dim, spacedim > &dh) 
Cell iterator functions returning ranges of iterators  
BlockInfo  block_info_object 
SmartPointer< const Triangulation< dim, spacedim >, DoFHandler< dim, spacedim > >  tria 
std::unique_ptr< const hp::FECollection< dim, spacedim > >  fe_collection 
std::unique_ptr<::internal::DoFHandlerImplementation::Policy::PolicyBase< dim, spacedim > >  policy 
::internal::DoFHandlerImplementation::NumberCache  number_cache 
std::vector<::internal::DoFHandlerImplementation::NumberCache >  mg_number_cache 
std::vector< types::global_dof_index >  vertex_dofs 
std::vector< MGVertexDoFs >  mg_vertex_dofs 
std::vector< std::unique_ptr<::internal::DoFHandlerImplementation::DoFLevel< dim > > >  levels 
std::vector< std::unique_ptr<::internal::DoFHandlerImplementation::DoFLevel< dim > > >  mg_levels 
std::unique_ptr<::internal::DoFHandlerImplementation::DoFFaces< dim > >  faces 
std::unique_ptr<::internal::DoFHandlerImplementation::DoFFaces< dim > >  mg_faces 
template<int , class , bool >  
class  DoFAccessor 
template<class , bool >  
class  DoFCellAccessor 
struct  ::internal::DoFAccessorImplementation::Implementation 
struct  ::internal::DoFCellAccessorImplementation::Implementation 
struct  ::internal::DoFHandlerImplementation::Implementation 
struct  ::internal::DoFHandlerImplementation::Policy::Implementation 
IteratorRange< cell_iterator >  cell_iterators () const 
IteratorRange< active_cell_iterator >  active_cell_iterators () const 
IteratorRange< level_cell_iterator >  mg_cell_iterators () const 
IteratorRange< cell_iterator >  cell_iterators_on_level (const unsigned int level) const 
IteratorRange< active_cell_iterator >  active_cell_iterators_on_level (const unsigned int level) const 
IteratorRange< level_cell_iterator >  mg_cell_iterators_on_level (const unsigned int level) const 
types::global_dof_index  n_dofs () const 
types::global_dof_index  n_dofs (const unsigned int level) const 
types::global_dof_index  n_boundary_dofs () const 
template<typename number >  
types::global_dof_index  n_boundary_dofs (const std::map< types::boundary_id, const Function< spacedim, number > * > &boundary_ids) const 
types::global_dof_index  n_boundary_dofs (const std::set< types::boundary_id > &boundary_ids) const 
const BlockInfo &  block_info () const 
unsigned int  n_locally_owned_dofs () const 
const IndexSet &  locally_owned_dofs () const 
const IndexSet &  locally_owned_mg_dofs (const unsigned int level) const 
const std::vector< IndexSet > &  locally_owned_dofs_per_processor () const 
const std::vector< types::global_dof_index > &  n_locally_owned_dofs_per_processor () const 
const std::vector< IndexSet > &  locally_owned_mg_dofs_per_processor (const unsigned int level) const 
const FiniteElement< dim, spacedim > &  get_fe (const unsigned int index=0) const 
const hp::FECollection< dim, spacedim > &  get_fe_collection () const 
const Triangulation< dim, spacedim > &  get_triangulation () const 
virtual std::size_t  memory_consumption () const 
template<class Archive >  
void  save (Archive &ar, const unsigned int version) const 
template<class Archive >  
void  load (Archive &ar, const unsigned int version) 
static::ExceptionBase &  ExcGridsDoNotMatch () 
static::ExceptionBase &  ExcInvalidBoundaryIndicator () 
static::ExceptionBase &  ExcNewNumbersNotConsecutive (types::global_dof_index arg1) 
static::ExceptionBase &  ExcInvalidLevel (int arg1) 
static::ExceptionBase &  ExcFacesHaveNoLevel () 
static::ExceptionBase &  ExcEmptyLevel (int arg1) 
void  clear_space () 
void  clear_mg_space () 
template<int structdim>  
types::global_dof_index  get_dof_index (const unsigned int obj_level, const unsigned int obj_index, const unsigned int fe_index, const unsigned int local_index) const 
template<int structdim>  
void  set_dof_index (const unsigned int obj_level, const unsigned int obj_index, const unsigned int fe_index, const unsigned int local_index, const types::global_dof_index global_index) const 
Additional Inherited Members  
Static Public Member Functions inherited from Subscriptor  
static::ExceptionBase &  ExcInUse (int arg1, char *arg2, std::string &arg3) 
static::ExceptionBase &  ExcNoSubscriber (char *arg1, char *arg2) 
Given a triangulation and a description of a finite element, this class enumerates degrees of freedom on all vertices, edges, faces, and cells of the triangulation. As a result, it also provides a basis for a discrete space \(V_h\) whose elements are finite element functions defined on each cell by a FiniteElement object. This class satisfies the MeshType concept requirements.
It is first used in the step2 tutorial program.
For each vertex, line, quad, etc, this class stores a list of the indices of degrees of freedom living on this object. These indices refer to the unconstrained degrees of freedom, i.e. constrained degrees of freedom are numbered in the same way as unconstrained ones, and are only later eliminated. This leads to the fact that indices in global vectors and matrices also refer to all degrees of freedom and some kind of condensation is needed to restrict the systems of equations to the unconstrained degrees of freedom only. The actual layout of storage of the indices is described in the internal::DoFHandlerImplementation::DoFLevel class documentation.
The class offers iterators to traverse all cells, in much the same way as the Triangulation class does. Using the begin() and end() functions (and companions, like begin_active()), one can obtain iterators to walk over cells, and query the degree of freedom structures as well as the triangulation data. These iterators are built on top of those of the Triangulation class, but offer the additional information on degrees of freedom functionality compared to pure triangulation iterators. The order in which dof iterators are presented by the ++
and –
operators is the same as that for the corresponding iterators traversing the triangulation on which this DoFHandler is constructed.
The spacedim
parameter has to be used if one wants to solve problems on surfaces. If not specified, this parameter takes the default value =dim
implying that we want to solve problems in a domain whose dimension equals the dimension of the space in which it is embedded.
The degrees of freedom (`dofs') are distributed on the given triangulation by the function distribute_dofs(). It gets passed a finite element object describing how many degrees of freedom are located on vertices, lines, etc. It traverses the triangulation cell by cell and numbers the dofs of that cell if not yet numbered. For nonmultigrid algorithms, only active cells are considered. Active cells are defined to be those cells which have no children, i.e. they are the most refined ones.
Since the triangulation is traversed starting with the cells of the coarsest active level and going to more refined levels, the lowest numbers for dofs are given to the largest cells as well as their bounding lines and vertices, with the dofs of more refined cells getting higher numbers.
This numbering implies very large bandwidths of the resulting matrices and is thus vastly suboptimal for some solution algorithms. For this reason, the DoFRenumbering class offers several algorithms to reorder the dof numbering according. See there for a discussion of the implemented algorithms.
Upon construction, this class takes a reference to a triangulation object. In most cases, this will be a reference to an object of type Triangulation, i.e. the class that represents triangulations that entirely reside on a single processor. However, it can also be of type parallel::distributed::Triangulation (see, for example, step32, step40 and in particular the Parallel computing with multiple processors using distributed memory module) in which case the DoFHandler object will proceed to only manage degrees of freedom on locally owned and ghost cells. This process is entirely transparent to the used.
The DoFRenumbering class offers a number of renumbering schemes like the CuthillMcKee scheme. Basically, the function sets up an array in which for each degree of freedom we store the new index this DoF should have after renumbering. Using this array, the renumber_dofs() function of the present class is called, which actually performs the change from old DoF indices to the ones given in the array. In some cases, however, a user may want to compute her own renumbering order; in this case, one can allocate an array with one element per degree of freedom and fill it with the number that the respective degree of freedom shall be assigned. This number may, for example, be obtained by sorting the support points of the degrees of freedom in downwind direction. Then call the renumber_dofs(vector<types::global_dof_index>)
function with the array, which converts old into new degree of freedom indices.
Like many other classes in deal.II, the DoFHandler class can stream its contents to an archive using BOOST's serialization facilities. The data so stored can later be retrieved again from the archive to restore the contents of this object. This facility is frequently used to save the state of a program to disk for possible later resurrection, often in the context of checkpoint/restart strategies for long running computations or on computers that aren't very reliable (e.g. on very large clusters where individual nodes occasionally fail and then bring down an entire MPI job).
The model for doing so is similar for the DoFHandler class as it is for the Triangulation class (see the section in the general documentation of that class). In particular, the load() function does not exactly restore the same state as was stored previously using the save() function. Rather, the function assumes that you load data into a DoFHandler object that is already associated with a triangulation that has a content that matches the one that was used when the data was saved. Likewise, the load() function assumes that the current object is already associated with a finite element object that matches the one that was associated with it when data was saved; the latter can be achieved by calling DoFHandler::distribute_dofs() using the same kind of finite element before reloading data from the serialization archive.
Definition at line 29 of file block_info.h.
DoFHandler< dim, spacedim >::DoFHandler  (  ) 
Standard constructor, not initializing any data. After constructing an object with this constructor, use initialize() to make a valid DoFHandler.
Definition at line 675 of file dof_handler.cc.
DoFHandler< dim, spacedim >::DoFHandler  (  const Triangulation< dim, spacedim > &  tria  ) 
Constructor. Take tria
as the triangulation to work on.
Definition at line 653 of file dof_handler.cc.

delete 
Copy constructor. DoFHandler objects are large and expensive. They should not be copied, in particular not by accident, but rather deliberately constructed. As a consequence, this constructor is explicitly removed from the interface of this class.

virtual 
Destructor.
Definition at line 683 of file dof_handler.cc.

delete 
Copy operator. DoFHandler objects are large and expensive. They should not be copied, in particular not by accident, but rather deliberately constructed. As a consequence, this operator is explicitly removed from the interface of this class.
void DoFHandler< dim, spacedim >::initialize  (  const Triangulation< dim, spacedim > &  tria, 
const FiniteElement< dim, spacedim > &  fe  
) 
Assign a Triangulation and a FiniteElement to the DoFHandler and compute the distribution of degrees of freedom over the mesh.
Definition at line 701 of file dof_handler.cc.

virtual 
Go through the triangulation and "distribute" the degrees of freedoms needed for the given finite element. "Distributing" degrees of freedom involves allocating memory to store the indices on all entities on which degrees of freedom can be located (e.g., vertices, edges, faces, etc.) and to then enumerate all degrees of freedom. In other words, while the mesh and the finite element object by themselves simply define a finite element space \(V_h\), the process of distributing degrees of freedom makes sure that there is a basis for this space and that the shape functions of this basis are enumerated in an indexable, predictable way.
The exact order in which degrees of freedom on a mesh are ordered, i.e., the order in which basis functions of the finite element space are enumerated, is something that deal.II treats as an implementation detail. By and large, degrees of freedom are enumerated in the same order in which we traverse cells, but you should not rely on any specific numbering. In contrast, if you want a particular ordering, use the functions in namespace DoFRenumbering.
This function is first discussed in the introduction to the step2 tutorial program.
Definition at line 995 of file dof_handler.cc.

virtual 
Distribute level degrees of freedom on each level for geometric multigrid. The active DoFs need to be distributed using distribute_dofs() before calling this function and the fe
needs to be identical to the finite element passed to distribute_dofs().
Definition at line 1041 of file dof_handler.cc.

virtual 
Distribute level degrees of freedom on each level for geometric multigrid. The active DoFs need to be distributed using distribute_dofs() before calling this function.
Definition at line 1049 of file dof_handler.cc.
bool DoFHandler< dim, spacedim >::has_level_dofs  (  )  const 
This function returns whether this DoFHandler has DoFs distributed on each multigrid level or in other words if distribute_mg_dofs() has been called.
bool DoFHandler< dim, spacedim >::has_active_dofs  (  )  const 
This function returns whether this DoFHandler has active DoFs. This is equivalent to asking whether (i) distribute_dofs() has been called and (ii) the finite element for which degrees of freedom have been distributed actually has degrees of freedom (which is not the case for FE_Nothing, for example).
If this object is based on a parallel::distributed::Triangulation, then the current function returns true if any partition of the parallel DoFHandler object has any degrees of freedom. In other words, the function returns true even if the Triangulation does not own any active cells on the current MPI process, but at least one process owns cells and at least this one process has any degrees of freedom associated with it.
void DoFHandler< dim, spacedim >::initialize_local_block_info  (  ) 
After distribute_dofs() with an FESystem element, the block structure of global and level vectors is stored in a BlockInfo object accessible with block_info(). This function initializes the local block structure on each cell in the same object.
Definition at line 1087 of file dof_handler.cc.

virtual 
Clear all data of this object.
Definition at line 1095 of file dof_handler.cc.
void DoFHandler< dim, spacedim >::renumber_dofs  (  const std::vector< types::global_dof_index > &  new_numbers  ) 
Renumber degrees of freedom based on a list of new DoF indices for each of the degrees of freedom.
This function is called by the functions in DoFRenumbering function after computing a new ordering of the degree of freedom indices. However, it can of course also be called from user code.
i
is currently locally owned, then new_numbers[locally_owned_dofs().index_within_set(i)]
returns the new global DoF index of i
. Since the IndexSet of locally_owned_dofs() is complete in the sequential case, the latter convention for the content of the array reduces to the former in the case that only one processor participates in the mesh.true
) are of course affected by the exact renumbering performed here. For example, while the initial numbering of DoF indices done in distribute_dofs() yields a contiguous numbering, the renumbering performed by DoFRenumbering::component_wise() will, in general, not yield contiguous locally owned DoF indices. Definition at line 1109 of file dof_handler.cc.
void DoFHandler< dim, spacedim >::renumber_dofs  (  const unsigned int  level, 
const std::vector< types::global_dof_index > &  new_numbers  
) 
The same function as above, but renumber the degrees of freedom of a single level of a multigrid hierarchy.
Definition at line 1158 of file dof_handler.cc.
unsigned int DoFHandler< dim, spacedim >::max_couplings_between_dofs  (  )  const 
Return the maximum number of degrees of freedom a degree of freedom in the given triangulation with the given finite element may couple with. This is the maximum number of entries per line in the system matrix; this information can therefore be used upon construction of the SparsityPattern object.
The returned number is not really the maximum number but an estimate based on the finite element and the maximum number of cells meeting at a vertex. The number holds for the constrained matrix as well.
The determination of the number of couplings can be done by simple picture drawing. An example can be found in the implementation of this function.
Definition at line 1193 of file dof_handler.cc.
unsigned int DoFHandler< dim, spacedim >::max_couplings_between_boundary_dofs  (  )  const 
Return the number of degrees of freedom located on the boundary another dof on the boundary can couple with.
The number is the same as for max_couplings_between_dofs() in one dimension less.
Definition at line 1202 of file dof_handler.cc.
DoFHandler< dim, spacedim >::cell_iterator DoFHandler< dim, spacedim >::begin  (  const unsigned int  level = 0  )  const 
Iterator to the first used cell on level level
.
Definition at line 725 of file dof_handler.cc.
DoFHandler< dim, spacedim >::active_cell_iterator DoFHandler< dim, spacedim >::begin_active  (  const unsigned int  level = 0  )  const 
Iterator to the first active cell on level level
. If the given level does not contain any active cells (i.e., all cells on this level are further refined, then this function returns end_active(level)
so that loops of the kind
have zero iterations, as may be expected if there are no active cells on this level.
Definition at line 737 of file dof_handler.cc.
DoFHandler< dim, spacedim >::cell_iterator DoFHandler< dim, spacedim >::end  (  )  const 
Iterator past the end; this iterator serves for comparisons of iterators with pasttheend or beforethebeginning states.
Definition at line 753 of file dof_handler.cc.
DoFHandler< dim, spacedim >::cell_iterator DoFHandler< dim, spacedim >::end  (  const unsigned int  level  )  const 
Return an iterator which is the first iterator not on the given level. If level
is the last level, then this returns end()
.
Definition at line 764 of file dof_handler.cc.
DoFHandler< dim, spacedim >::active_cell_iterator DoFHandler< dim, spacedim >::end_active  (  const unsigned int  level  )  const 
Return an active iterator which is the first active iterator not on the given level. If level
is the last level, then this returns end()
.
Definition at line 775 of file dof_handler.cc.
DoFHandler< dim, spacedim >::level_cell_iterator DoFHandler< dim, spacedim >::begin_mg  (  const unsigned int  level = 0  )  const 
Iterator to the first used cell on level level
. This returns a level_cell_iterator that returns level dofs when dof_indices() is called.
Definition at line 787 of file dof_handler.cc.
DoFHandler< dim, spacedim >::level_cell_iterator DoFHandler< dim, spacedim >::end_mg  (  const unsigned int  level  )  const 
Iterator past the last cell on level level
. This returns a level_cell_iterator that returns level dofs when dof_indices() is called.
Definition at line 800 of file dof_handler.cc.
DoFHandler< dim, spacedim >::level_cell_iterator DoFHandler< dim, spacedim >::end_mg  (  )  const 
Iterator past the end; this iterator serves for comparisons of iterators with pasttheend or beforethebeginning states.
Definition at line 813 of file dof_handler.cc.
types::global_dof_index DoFHandler< dim, spacedim >::n_dofs  (  )  const 
Return the global number of degrees of freedom. If the current object handles all degrees of freedom itself (even if you may intend to solve your linear system in parallel, such as in step17 or step18), then this number equals the number of locally owned degrees of freedom since this object doesn't know anything about what you want to do with it and believes that it owns every degree of freedom it knows about.
On the other hand, if this object operates on a parallel::distributed::Triangulation object, then this function returns the global number of degrees of freedom, accumulated over all processors.
In either case, included in the returned number are those DoFs which are constrained by hanging nodes, see Constraints on degrees of freedom.
Mathematically speaking, the number returned by this function equals the dimension of the finite element space (without taking into account constraints) that corresponds to (i) the mesh on which it is defined, and (ii) the finite element that is used by the current object. It also, of course, equals the number of shape functions that span this space.
types::global_dof_index DoFHandler< dim, spacedim >::n_dofs  (  const unsigned int  level  )  const 
The (global) number of multilevel degrees of freedom on a given level.
If no level degrees of freedom have been assigned to this level, returns numbers::invalid_dof_index. Else returns the number of degrees of freedom on this level.
types::global_dof_index DoFHandler< dim, spacedim >::n_boundary_dofs  (  )  const 
Return the number of degrees of freedom located on the boundary.
Definition at line 891 of file dof_handler.cc.
types::global_dof_index DoFHandler< dim, spacedim >::n_boundary_dofs  (  const std::map< types::boundary_id, const Function< spacedim, number > * > &  boundary_ids  )  const 
Return the number of degrees of freedom located on those parts of the boundary which have a boundary indicator listed in the given set. The reason that a map
rather than a set
is used is the same as described in the documentation of that variant of DoFTools::make_boundary_sparsity_pattern() that takes a map. To this end, the type of the boundary_ids
argument is the same as typename FunctionMap<spacedim,number>::type.
There is, however, another overload of this function that takes a set
argument (see below).
types::global_dof_index DoFHandler< dim, spacedim >::n_boundary_dofs  (  const std::set< types::boundary_id > &  boundary_ids  )  const 
Return the number of degrees of freedom located on those parts of the boundary which have a boundary indicator listed in the given set. The
Definition at line 930 of file dof_handler.cc.
const BlockInfo& DoFHandler< dim, spacedim >::block_info  (  )  const 
Access to an object informing of the block structure of the dof handler.
If an FESystem is used in distribute_dofs(), degrees of freedom naturally split into several blocks. For each base element as many blocks appear as its multiplicity.
At the end of distribute_dofs(), the number of degrees of freedom in each block is counted, and stored in a BlockInfo object, which can be accessed here. If you have previously called distribute_mg_dofs(), the same is done on each level of the multigrid hierarchy. Additionally, the block structure on each cell can be generated in this object by calling initialize_local_block_info().
unsigned int DoFHandler< dim, spacedim >::n_locally_owned_dofs  (  )  const 
Return the number of degrees of freedom that belong to this process.
If this is a sequential DoFHandler, then the result equals that produced by n_dofs(). (Here, "sequential" means that either the whole program does not use MPI, or that it uses MPI but only uses a single MPI process, or that there are multiple MPI processes but the Triangulation on which this DoFHandler builds works only on one MPI process.) On the other hand, if we are operating on a parallel::distributed::Triangulation or parallel::shared::Triangulation, then it includes only the degrees of freedom that the current processor owns. Note that in this case this does not include all degrees of freedom that have been distributed on the current processor's image of the mesh: in particular, some of the degrees of freedom on the interface between the cells owned by this processor and cells owned by other processors may be theirs, and degrees of freedom on ghost cells are also not necessarily included.
const IndexSet& DoFHandler< dim, spacedim >::locally_owned_dofs  (  )  const 
Return an IndexSet describing the set of locally owned DoFs as a subset of 0..n_dofs(). The number of elements of this set equals n_locally_owned_dofs().
const IndexSet& DoFHandler< dim, spacedim >::locally_owned_mg_dofs  (  const unsigned int  level  )  const 
Return an IndexSet describing the set of locally owned DoFs used for the given multigrid level as a subset of 0..n_dofs(level).
const std::vector<IndexSet>& DoFHandler< dim, spacedim >::locally_owned_dofs_per_processor  (  )  const 
Return a vector that stores the locally owned DoFs of each processor. If you are only interested in the number of elements each processor owns then n_locally_owned_dofs_per_processor() is a better choice.
If this is a sequential DoFHandler, then the vector has a single element that equals the IndexSet representing the entire range [0,n_dofs()]. (Here, "sequential" means that either the whole program does not use MPI, or that it uses MPI but only uses a single MPI process, or that there are multiple MPI processes but the Triangulation on which this DoFHandler builds works only on one MPI process.)
const std::vector<types::global_dof_index>& DoFHandler< dim, spacedim >::n_locally_owned_dofs_per_processor  (  )  const 
Return a vector that stores the number of degrees of freedom each processor that participates in this triangulation owns locally. The sum of all these numbers equals the number of degrees of freedom that exist globally, i.e. what n_dofs() returns.
Each element of the vector returned by this function equals the number of elements of the corresponding sets returned by global_dof_indices().
If this is a sequential DoFHandler, then the vector has a single element equal to n_dofs(). (Here, "sequential" means that either the whole program does not use MPI, or that it uses MPI but only uses a single MPI process, or that there are multiple MPI processes but the Triangulation on which this DoFHandler builds works only on one MPI process.)
const std::vector<IndexSet>& DoFHandler< dim, spacedim >::locally_owned_mg_dofs_per_processor  (  const unsigned int  level  )  const 
Return a vector that stores the locally owned DoFs of each processor on the given level level
.
If this is a sequential DoFHandler, then the vector has a single element that equals the IndexSet representing the entire range [0,n_dofs()]. (Here, "sequential" means that either the whole program does not use MPI, or that it uses MPI but only uses a single MPI process, or that there are multiple MPI processes but the Triangulation on which this DoFHandler builds works only on one MPI process.)
const FiniteElement<dim,spacedim>& DoFHandler< dim, spacedim >::get_fe  (  const unsigned int  index = 0  )  const 
Return a constant reference to the selected finite element object. Since there is only one FiniteElement index
must be equal to zero which is also the default value.
const hp::FECollection<dim,spacedim>& DoFHandler< dim, spacedim >::get_fe_collection  (  )  const 
Return a constant reference to the set of finite element objects that are used by this DoFHandler
. Since this object only contains one FiniteElement, only this one object is returned wrapped in a hp::FECollection.
const Triangulation<dim,spacedim>& DoFHandler< dim, spacedim >::get_triangulation  (  )  const 
Return a constant reference to the triangulation underlying this object.

virtual 
Determine an estimate for the memory consumption (in bytes) of this object.
This function is made virtual, since a dof handler object might be accessed through a pointers to this base class, although the actual object might be a derived class.
Definition at line 966 of file dof_handler.cc.
void DoFHandler< dim, spacedim >::save  (  Archive &  ar, 
const unsigned int  version  
)  const 
Write the data of this object to a stream for the purpose of serialization.
void DoFHandler< dim, spacedim >::load  (  Archive &  ar, 
const unsigned int  version  
) 
Read the data of this object from a stream for the purpose of serialization.

private 
Free all memory used for nonmultigrid data structures.
Definition at line 1240 of file dof_handler.cc.

private 
Free all memory used for multigrid data structures.
Definition at line 1073 of file dof_handler.cc.
Make accessor objects friends.
Definition at line 1190 of file dof_handler.h.

related 
Maximal number of degrees of freedom on a cell.
dh.get_fe_collection().max_dofs_per_cell()
.

related 
Maximal number of degrees of freedom on a face.
This function exists for both nonhp and hp DoFHandlers, to allow for a uniform interface to query this property.
dh.get_fe_collection().max_dofs_per_face()
.

related 
Maximal number of degrees of freedom on a vertex.
This function exists for both nonhp and hp DoFHandlers, to allow for a uniform interface to query this property.
dh.get_fe_collection().max_dofs_per_vertex()
.

related 
Number of vector components in the finite element object used by this DoFHandler.
This function exists for both nonhp and hp DoFHandlers, to allow for a uniform interface to query this property.
dh.get_fe_collection().n_components()
.

related 
Find out whether the first FiniteElement used by this DoFHandler is primitive or not.
This function exists for both nonhp and hp DoFHandlers, to allow for a uniform interface to query this property.
dh.get_fe(0).is_primitive()
.

static 
Make the dimension available in function templates.
Definition at line 300 of file dof_handler.h.

static 
Make the space dimension available in function templates.
Definition at line 305 of file dof_handler.h.

static 
When the arrays holding the DoF indices are set up, but before they are filled with actual values, they are set to an invalid value, in order to monitor possible problems. This invalid value is the constant defined here.
Please note that you should not rely on it having a certain value, but rather take its symbolic name.
Definition at line 319 of file dof_handler.h.

static 
The default index of the finite element to be used on a given cell. Since the present class only supports the same finite element to be used on all cells, the index of the finite element needs to be the same on all cells anyway, and by convention we pick zero for this value. The situation is different for hp objects (i.e. the hp::DoFHandler class) where different finite element indices may be used on different cells, and the default index there corresponds to an invalid value.
Definition at line 330 of file dof_handler.h.

private 
An object containing information on the block structure.
Definition at line 1027 of file dof_handler.h.

private 
Address of the triangulation to work on.
Definition at line 1033 of file dof_handler.h.

private 
Store a pointer to a hp::FECollection object containing the (one) FiniteElement this object is initialized with.
Definition at line 1040 of file dof_handler.h.

private 
An object that describes how degrees of freedom should be distributed and renumbered.
Definition at line 1046 of file dof_handler.h.

private 
A structure that contains all sorts of numbers that characterize the degrees of freedom this object works on.
For most members of this structure, there is an accessor function in this class that returns its value.
Definition at line 1055 of file dof_handler.h.

private 
Data structure like number_cache, but for each multigrid level.
Definition at line 1060 of file dof_handler.h.

private 
Array to store the indices for degrees of freedom located at vertices.
Definition at line 1162 of file dof_handler.h.

private 
An array to store the indices for level degrees of freedom located at vertices.
Definition at line 1168 of file dof_handler.h.

private 
Space to store the DoF numbers for the different levels. Analogous to the levels[]
tree of the Triangulation objects.
Definition at line 1174 of file dof_handler.h.

private 
Space to store DoF numbers of faces. They are not stored in levels
since faces are not organized hierarchically, but in a flat array.
Definition at line 1183 of file dof_handler.h.