#include <deal.II/distributed/tria.h>

Inheritance diagram for parallel::distributed::Triangulation< dim, spacedim >:

Classes
struct	CellAttachedData

Public Types
enum	Settings { default_setting = 0x0, mesh_reconstruction_after_repartitioning = 0x1, construct_multigrid_hierarchy = 0x2, no_automatic_repartitioning = 0x4 }

typedef ::Triangulation< dim, spacedim >::cell_iterator	cell_iterator

typedef ::Triangulation< dim, spacedim >::active_cell_iterator	active_cell_iterator

Public Types inherited from Triangulation< dim, spacedim >
enum	MeshSmoothing { none = 0x0, limit_level_difference_at_vertices = 0x1, eliminate_unrefined_islands = 0x2, patch_level_1 = 0x4, coarsest_level_1 = 0x8, allow_anisotropic_smoothing = 0x10, eliminate_refined_inner_islands = 0x100, eliminate_refined_boundary_islands = 0x200, do_not_produce_unrefined_islands = 0x400, smoothing_on_refinement, smoothing_on_coarsening, maximum_smoothing = 0xffff ^ allow_anisotropic_smoothing }

typedef TriaIterator< CellAccessor< dim, spacedim > >	cell_iterator

typedef TriaActiveIterator< CellAccessor< dim, spacedim > >	active_cell_iterator

typedef TriaIterator< TriaAccessor< dim-1, dim, spacedim > >	face_iterator

typedef TriaActiveIterator< TriaAccessor< dim-1, dim, spacedim > >	active_face_iterator

typedef TriaIterator<::TriaAccessor< 0, dim, spacedim > >	vertex_iterator

typedef TriaActiveIterator<::TriaAccessor< 0, dim, spacedim > >	active_vertex_iterator

enum	CellStatus { CELL_PERSIST, CELL_REFINE, CELL_COARSEN, CELL_INVALID }

Public Member Functions
	Triangulation (MPI_Comm mpi_communicator, const typename ::Triangulation< dim, spacedim >::MeshSmoothing smooth_grid=(::Triangulation< dim, spacedim >::none), const Settings settings=default_setting)

virtual	~Triangulation ()

virtual void	clear ()

virtual void	copy_triangulation (const ::Triangulation< dim, spacedim > &other_tria)

virtual void	create_triangulation (const std::vector< Point< spacedim > > &vertices, const std::vector< CellData< dim > > &cells, const SubCellData &subcelldata)

virtual void	execute_coarsening_and_refinement ()

virtual bool	prepare_coarsening_and_refinement ()

void	repartition ()

void	communicate_locally_moved_vertices (const std::vector< bool > &vertex_locally_moved)

virtual bool	has_hanging_nodes () const

virtual std::size_t	memory_consumption () const

virtual std::size_t	memory_consumption_p4est () const

void	write_mesh_vtk (const char *file_basename) const

unsigned int	get_checksum () const

void	save (const char *filename) const

void	load (const char *filename, const bool autopartition=true)

unsigned int	register_data_attach (const std::size_t size, const std::function< void(const cell_iterator &, const CellStatus, void *)> &pack_callback)

void	notify_ready_to_unpack (const unsigned int handle, const std::function< void(const cell_iterator &, const CellStatus, const void *)> &unpack_callback)

const std::vector< types::global_dof_index > &	get_p4est_tree_to_coarse_cell_permutation () const

const std::vector< types::global_dof_index > &	get_coarse_cell_to_p4est_tree_permutation () const

virtual void	add_periodicity (const std::vector<::GridTools::PeriodicFacePair< cell_iterator > > &)

Public Member Functions inherited from parallel::Triangulation< dim, spacedim >
	Triangulation (MPI_Comm mpi_communicator, const typename ::Triangulation< dim, spacedim >::MeshSmoothing smooth_grid=(::Triangulation< dim, spacedim >::none), const bool check_for_distorted_cells=false)

virtual MPI_Comm	get_communicator () const

virtual void	copy_triangulation (const ::Triangulation< dim, spacedim > &old_tria)

const std::vector< unsigned int > &	n_locally_owned_active_cells_per_processor () const

unsigned int	n_locally_owned_active_cells () const

virtual types::global_dof_index	n_global_active_cells () const

virtual unsigned int	n_global_levels () const

types::subdomain_id	locally_owned_subdomain () const

const std::set< types::subdomain_id > &	ghost_owners () const

const std::set< types::subdomain_id > &	level_ghost_owners () const

Public Member Functions inherited from Triangulation< dim, spacedim >
	Triangulation (const MeshSmoothing smooth_grid=none, const bool check_for_distorted_cells=false)

	Triangulation (const Triangulation< dim, spacedim > &)=delete

	Triangulation (Triangulation< dim, spacedim > &&tria) noexcept

Triangulation &	operator= (Triangulation< dim, spacedim > &&tria) noexcept

virtual void	set_mesh_smoothing (const MeshSmoothing mesh_smoothing)

virtual const MeshSmoothing &	get_mesh_smoothing () const

void	set_boundary (const types::manifold_id number, const Boundary< dim, spacedim > &boundary_object)

void	set_boundary (const types::manifold_id number)

void	set_manifold (const types::manifold_id number, const Manifold< dim, spacedim > &manifold_object)

void	set_manifold (const types::manifold_id number)

void	reset_manifold (const types::manifold_id manifold_number)

void	reset_all_manifolds ()

void	set_all_manifold_ids (const types::manifold_id number)

void	set_all_manifold_ids_on_boundary (const types::manifold_id number)

void	set_all_manifold_ids_on_boundary (const types::boundary_id b_id, const types::manifold_id number)

const Boundary< dim, spacedim > &	get_boundary (const types::manifold_id number) const

const Manifold< dim, spacedim > &	get_manifold (const types::manifold_id number) const

std::vector< types::boundary_id >	get_boundary_ids () const

std::vector< types::manifold_id >	get_manifold_ids () const

virtual void	copy_triangulation (const Triangulation< dim, spacedim > &other_tria)

virtual void	create_triangulation_compatibility (const std::vector< Point< spacedim > > &vertices, const std::vector< CellData< dim > > &cells, const SubCellData &subcelldata)

void	flip_all_direction_flags ()

void	set_all_refine_flags ()

void	refine_global (const unsigned int times=1)

void	save_refine_flags (std::ostream &out) const

void	save_refine_flags (std::vector< bool > &v) const

void	load_refine_flags (std::istream &in)

void	load_refine_flags (const std::vector< bool > &v)

void	save_coarsen_flags (std::ostream &out) const

void	save_coarsen_flags (std::vector< bool > &v) const

void	load_coarsen_flags (std::istream &out)

void	load_coarsen_flags (const std::vector< bool > &v)

bool	get_anisotropic_refinement_flag () const

void	clear_user_flags ()

void	save_user_flags (std::ostream &out) const

void	save_user_flags (std::vector< bool > &v) const

void	load_user_flags (std::istream &in)

void	load_user_flags (const std::vector< bool > &v)

void	clear_user_flags_line ()

void	save_user_flags_line (std::ostream &out) const

void	save_user_flags_line (std::vector< bool > &v) const

void	load_user_flags_line (std::istream &in)

void	load_user_flags_line (const std::vector< bool > &v)

void	clear_user_flags_quad ()

void	save_user_flags_quad (std::ostream &out) const

void	save_user_flags_quad (std::vector< bool > &v) const

void	load_user_flags_quad (std::istream &in)

void	load_user_flags_quad (const std::vector< bool > &v)

void	clear_user_flags_hex ()

void	save_user_flags_hex (std::ostream &out) const

void	save_user_flags_hex (std::vector< bool > &v) const

void	load_user_flags_hex (std::istream &in)

void	load_user_flags_hex (const std::vector< bool > &v)

void	clear_user_data ()

void	save_user_indices (std::vector< unsigned int > &v) const

void	load_user_indices (const std::vector< unsigned int > &v)

void	save_user_pointers (std::vector< void *> &v) const

void	load_user_pointers (const std::vector< void *> &v)

void	save_user_indices_line (std::vector< unsigned int > &v) const

void	load_user_indices_line (const std::vector< unsigned int > &v)

void	save_user_indices_quad (std::vector< unsigned int > &v) const

void	load_user_indices_quad (const std::vector< unsigned int > &v)

void	save_user_indices_hex (std::vector< unsigned int > &v) const

void	load_user_indices_hex (const std::vector< unsigned int > &v)

void	save_user_pointers_line (std::vector< void *> &v) const

void	load_user_pointers_line (const std::vector< void *> &v)

void	save_user_pointers_quad (std::vector< void *> &v) const

void	load_user_pointers_quad (const std::vector< void *> &v)

void	save_user_pointers_hex (std::vector< void *> &v) const

void	load_user_pointers_hex (const std::vector< void *> &v)

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

cell_iterator	last () const

active_cell_iterator	last_active () const

IteratorRange< cell_iterator >	cell_iterators () const

IteratorRange< active_cell_iterator >	active_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

face_iterator	begin_face () const

active_face_iterator	begin_active_face () const

face_iterator	end_face () const

vertex_iterator	begin_vertex () const

active_vertex_iterator	begin_active_vertex () const

vertex_iterator	end_vertex () const

unsigned int	n_lines () const

unsigned int	n_lines (const unsigned int level) const

unsigned int	n_active_lines () const

unsigned int	n_active_lines (const unsigned int level) const

unsigned int	n_quads () const

unsigned int	n_quads (const unsigned int level) const

unsigned int	n_active_quads () const

unsigned int	n_active_quads (const unsigned int level) const

unsigned int	n_hexs () const

unsigned int	n_hexs (const unsigned int level) const

unsigned int	n_active_hexs () const

unsigned int	n_active_hexs (const unsigned int level) const

unsigned int	n_cells () const

unsigned int	n_cells (const unsigned int level) const

unsigned int	n_active_cells () const

unsigned int	n_active_cells (const unsigned int level) const

unsigned int	n_faces () const

unsigned int	n_active_faces () const

unsigned int	n_levels () const

unsigned int	n_vertices () const

const std::vector< Point< spacedim > > &	get_vertices () const

unsigned int	n_used_vertices () const

bool	vertex_used (const unsigned int index) const

const std::vector< bool > &	get_used_vertices () const

unsigned int	max_adjacent_cells () const

Triangulation< dim, spacedim > &	get_triangulation ()

const Triangulation< dim, spacedim > &	get_triangulation () const

unsigned int	n_raw_lines () const

unsigned int	n_raw_lines (const unsigned int level) const

unsigned int	n_raw_quads () const

unsigned int	n_raw_quads (const unsigned int level) const

unsigned int	n_raw_hexs (const unsigned int level) const

unsigned int	n_raw_cells (const unsigned int level) const

unsigned int	n_raw_faces () const

template<class Archive >
void	save (Archive &ar, const unsigned int version) const

template<class Archive >
void	load (Archive &ar, const unsigned int version)

virtual void	add_periodicity (const std::vector< GridTools::PeriodicFacePair< cell_iterator > > &)

const std::map< std::pair< cell_iterator, unsigned int >, std::pair< std::pair< cell_iterator, unsigned int >, std::bitset< 3 > > > &	get_periodic_face_map () 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)

Private Member Functions
virtual void	update_number_cache ()

typename ::internal::p4est::types< dim >::tree *	init_tree (const int dealii_coarse_cell_index) const

void	setup_coarse_cell_to_p4est_tree_permutation ()

void	copy_new_triangulation_to_p4est (std::integral_constant< int, 2 >)

void	copy_local_forest_to_triangulation ()

void	attach_mesh_data ()

std::vector< unsigned int >	get_cell_weights ()

virtual std::map< unsigned int, std::set<::types::subdomain_id > >	compute_vertices_with_ghost_neighbors () const

std::vector< bool >	mark_locally_active_vertices_on_level (const int level) const

Private Attributes
Settings	settings

bool	triangulation_has_content

typename ::internal::p4est::types< dim >::connectivity *	connectivity

typename ::internal::p4est::types< dim >::forest *	parallel_forest

typename ::internal::p4est::types< dim >::ghost *	parallel_ghost

std::vector< types::global_dof_index >	coarse_cell_to_p4est_tree_permutation

Additional Inherited Members
Static Public Member Functions inherited from Triangulation< dim, spacedim >
static ::ExceptionBase &	ExcInvalidLevel (int arg1)

static ::ExceptionBase &	ExcTriangulationNotEmpty (int arg1, int arg2)

static ::ExceptionBase &	ExcGridReadError ()

static ::ExceptionBase &	ExcFacesHaveNoLevel ()

static ::ExceptionBase &	ExcEmptyLevel (int arg1)

static ::ExceptionBase &	ExcNonOrientableTriangulation ()

static ::ExceptionBase &	ExcBoundaryIdNotFound (types::boundary_id arg1)

Static Public Member Functions inherited from Subscriptor
static ::ExceptionBase &	ExcInUse (int arg1, std::string arg2, std::string arg3)

static ::ExceptionBase &	ExcNoSubscriber (std::string arg1, std::string arg2)

Public Attributes inherited from Triangulation< dim, spacedim >
Signals	signals

Static Public Attributes inherited from Triangulation< dim, spacedim >
static const StraightBoundary< dim, spacedim >	straight_boundary = StraightBoundary<dim,spacedim>()

static const unsigned int	dimension = dim

static const unsigned int	space_dimension = spacedim

Protected Member Functions inherited from parallel::Triangulation< dim, spacedim >
void	fill_level_ghost_owners ()

Protected Member Functions inherited from Triangulation< dim, spacedim >
void	update_periodic_face_map ()

Static Protected Member Functions inherited from Triangulation< dim, spacedim >
static void	write_bool_vector (const unsigned int magic_number1, const std::vector< bool > &v, const unsigned int magic_number2, std::ostream &out)

static void	read_bool_vector (const unsigned int magic_number1, std::vector< bool > &v, const unsigned int magic_number2, std::istream &in)

Protected Attributes inherited from parallel::Triangulation< dim, spacedim >
MPI_Comm	mpi_communicator

types::subdomain_id	my_subdomain

types::subdomain_id	n_subdomains

Protected Attributes inherited from Triangulation< dim, spacedim >
MeshSmoothing	smooth_grid

Detailed Description

template<int dim, int spacedim = dim>
class parallel::distributed::Triangulation< dim, spacedim >

This class acts like the Triangulation class, but it distributes the mesh across a number of different processors when using MPI. The class's interface does not add a lot to the Triangulation class but there are a number of difficult algorithms under the hood that ensure we always have a load-balanced, fully distributed mesh. Use of this class is explained in step-40, step-32, the Parallel computing with multiple processors using distributed memory documentation module, as well as the distributed_paper. See there for more information. This class satisfies the MeshType concept.

Note: This class does not support anisotropic refinement, because it relies on the p4est library that does not support this. Attempts to refine cells anisotropically will result in errors.; There is currently no support for distributing 1d triangulations.

Interaction with boundary description

Refining and coarsening a distributed triangulation is a complicated process because cells may have to be migrated from one processor to another. On a single processor, materializing that part of the global mesh that we want to store here from what we have stored before therefore may involve several cycles of refining and coarsening the locally stored set of cells until we have finally gotten from the previous to the next triangulation. This process is described in more detail in the distributed_paper. Unfortunately, in this process, some information can get lost relating to flags that are set by user code and that are inherited from mother to child cell but that are not moved along with a cell if that cell is migrated from one processor to another.

An example are boundary indicators. Assume, for example, that you start with a single cell that is refined once globally, yielding four children. If you have four processors, each one owns one cell. Assume now that processor 1 sets the boundary indicators of the external boundaries of the cell it owns to 42. Since processor 0 does not own this cell, it doesn't set the boundary indicators of its ghost cell copy of this cell. Now, assume we do several mesh refinement cycles and end up with a configuration where this processor suddenly finds itself as the owner of this cell. If boundary indicator 42 means that we need to integrate Neumann boundary conditions along this boundary, then processor 0 will forget to do so because it has never set the boundary indicator along this cell's boundary to 42.

The way to avoid this dilemma is to make sure that things like setting boundary indicators or material ids is done immediately every time a parallel triangulation is refined. This is not necessary for sequential triangulations because, there, these flags are inherited from mother to child cell and remain with a cell even if it is refined and the children are later coarsened again, but this does not hold for distributed triangulations. It is made even more difficult by the fact that in the process of refining a parallel distributed triangulation, the triangulation may call Triangulation::execute_coarsening_and_refinement multiple times and this function needs to know about boundaries. In other words, it is not enough to just set boundary indicators on newly created faces only after calling distributed::parallel::Triangulation::execute_coarsening_and_refinement: it actually has to happen while that function is still running.

The way to do this is by writing a function that sets boundary indicators and that will be called by the Triangulation class. The triangulation does not provide a pointer to itself to the function being called, nor any other information, so the trick is to get this information into the function. C++ provides a nice mechanism for this that is best explained using an example:

#include <functional>
template <int dim>
void set_boundary_ids (parallel::distributed::Triangulation<dim> &triangulation)
{
  ... set boundary indicators on the triangulation object ...
}
template <int dim>
void
MyClass<dim>::
create_coarse_mesh (parallel::distributed::Triangulation<dim> &coarse_grid) const
{
  ... create the coarse mesh ...
  coarse_grid.signals.post_refinement.connect
    (std::bind (&set_boundary_ids<dim>,
                std::ref(coarse_grid)));
}

What the call to std::bind does is to produce an object that can be called like a function with no arguments. It does so by taking the address of a function that does, in fact, take an argument but permanently fix this one argument to a reference to the coarse grid triangulation. After each refinement step, the triangulation will then call the object so created which will in turn call set_boundary_ids<dim> with the reference to the coarse grid as argument.

This approach can be generalized. In the example above, we have used a global function that will be called. However, sometimes it is necessary that this function is in fact a member function of the class that generates the mesh, for example because it needs to access run-time parameters. This can be achieved as follows: assuming the set_boundary_ids() function has been declared as a (non- static, but possibly private) member function of the MyClass class, then the following will work:

#include <functional>
template <int dim>
void
MyClass<dim>::
set_boundary_ids (parallel::distributed::Triangulation<dim> &triangulation) const
{
  ... set boundary indicators on the triangulation object ...
}
template <int dim>
void
MyClass<dim>::
create_coarse_mesh (parallel::distributed::Triangulation<dim> &coarse_grid) const
{
  ... create the coarse mesh ...
  coarse_grid.signals.post_refinement.connect
    (std::bind (&MyGeometry<dim>::set_boundary_ids,
                std::cref(*this),
                std::ref(coarse_grid)));
}

Here, like any other member function, set_boundary_ids implicitly takes a pointer or reference to the object it belongs to as first argument. std::bind again creates an object that can be called like a global function with no arguments, and this object in turn calls set_boundary_ids with a pointer to the current object and a reference to the triangulation to work on. Note that because the create_coarse_mesh function is declared as const, it is necessary that the set_boundary_ids function is also declared const.

Note:For reasons that have to do with the way the parallel::distributed::Triangulation is implemented, functions that have been attached to the post-refinement signal of the triangulation are called more than once, sometimes several times, every time the triangulation is actually refined.

Author: Wolfgang Bangerth, Timo Heister 2008, 2009, 2010, 2011

Definition at line 46 of file p4est_wrappers.h.

Member Enumeration Documentation

◆ Settings

template<int dim, int spacedim = dim>

enum parallel::distributed::Triangulation::Settings

Configuration flags for distributed Triangulations to be set in the constructor. Settings can be combined using bitwise OR.

Enumerator
default_setting	Default settings, other options are disabled.
mesh_reconstruction_after_repartitioning	If set, the deal.II mesh will be reconstructed from the coarse mesh every time a repartitioning in p4est happens. This can be a bit more expensive, but guarantees the same memory layout and therefore cell ordering in the deal.II mesh. As assembly is done in the deal.II cell ordering, this flag is required to get reproducible behaviour after snapshot/resume.
construct_multigrid_hierarchy	This flags needs to be set to use the geometric multigrid functionality. This option requires additional computation and communication. Note: geometric multigrid is still a work in progress.
no_automatic_repartitioning	Setting this flag will disable automatic repartitioning of the cells after a refinement cycle. It can be executed manually by calling repartition().

Definition at line 293 of file tria.h.

Constructor & Destructor Documentation

◆ Triangulation()

template<int dim, int spacedim>

Triangulation< dim, spacedim >::Triangulation	(	MPI_Comm	mpi_communicator,
		const typename ::Triangulation< dim, spacedim >::MeshSmoothing	smooth_grid = `(::Triangulation<dim,spacedim>::none)`,
		const Settings	settings = `default_setting`
	)

Constructor.

Parameters

mpi_communicator	denotes the MPI communicator to be used for the triangulation.
smooth_grid	Degree and kind of mesh smoothing to be applied to the mesh. See the Triangulation class for a description of the kinds of smoothing operations that can be applied.
settings	See the description of the Settings enumerator. Providing `construct_multigrid_hierarchy` enforces `Triangulation::limit_level_difference_at_vertices` for smooth_grid.

Note: This class does not currently support the check_for_distorted_cells argument provided by the base class.; While it is possible to pass all of the mesh smoothing flags listed in the base class to objects of this type, it is not always possible to honor all of these smoothing options if they would require knowledge of refinement/coarsening flags on cells not locally owned by this processor. As a consequence, for some of these flags, the ultimate number of cells of the parallel triangulation may depend on the number of processors into which it is partitioned. On the other hand, if no smoothing flags are passed, if you always mark the same cells of the mesh, you will always get the exact same refined mesh independent of the number of processors into which the triangulation is partitioned.

Definition at line 1287 of file tria.cc.

◆ ~Triangulation()

template<int dim, int spacedim>

Triangulation< dim, spacedim >::~Triangulation ( )

virtual

Destructor.

Reimplemented from parallel::Triangulation< dim, spacedim >.

Definition at line 1313 of file tria.cc.

Member Function Documentation

◆ clear()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::clear ( )

virtual

Reset this triangulation into a virgin state by deleting all data.

Note that this operation is only allowed if no subscriptions to this object exist any more, such as DoFHandler objects using it.

Reimplemented from Triangulation< dim, spacedim >.

Definition at line 1682 of file tria.cc.

◆ copy_triangulation()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::copy_triangulation ( const ::Triangulation< dim, spacedim > & other_tria )

virtual

Implementation of the same function as in the base class.

Note: This function cannot copy a triangulation that has been refined.; This function can be used to copy a serial Triangulation to a parallel::distributed::Triangulation but only if the serial Triangulation has never been refined.

Definition at line 3607 of file tria.cc.

◆ create_triangulation()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::create_triangulation	(	const std::vector< Point< spacedim > > &	vertices,
		const std::vector< CellData< dim > > &	cells,
		const SubCellData &	subcelldata
	)

virtual

Create a triangulation as documented in the base class.

This function also sets up the various data structures necessary to distribute a mesh across a number of processors. This will be necessary once the mesh is being refined, though we will always keep the entire coarse mesh that is generated by this function on all processors.

Reimplemented from Triangulation< dim, spacedim >.

Definition at line 1337 of file tria.cc.

◆ execute_coarsening_and_refinement()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::execute_coarsening_and_refinement ( )

virtual

Coarsen and refine the mesh according to refinement and coarsening flags set.

Since the current processor only has control over those cells it owns (i.e. the ones for which cell->subdomain_id() == this->locally_owned_subdomain()), refinement and coarsening flags are only respected for those locally owned cells. Flags may be set on other cells as well (and may often, in fact, if you call Triangulation::prepare_coarsening_and_refinement()) but will be largely ignored: the decision to refine the global mesh will only be affected by flags set on locally owned cells.

Note: This function by default partitions the mesh in such a way that the number of cells on all processors is roughly equal. If you want to set weights for partitioning, e.g. because some cells are more expensive to compute than others, you can use the signal cell_weight as documented in the Triangulation class. This function will check whether a function is connected to the signal and if so use it. If you prefer to repartition the mesh yourself at user-defined intervals only, you can create your triangulation object by passing the parallel::distributed::Triangulation::no_automatic_repartitioning flag to the constructor, which ensures that calling the current function only refines and coarsens the triangulation, but doesn't partition it. You can then call the repartition() function manually. The usage of the cell_weights signal is identical in both cases, if a function is connected to the signal it will be used to balance the calculated weights, otherwise the number of cells is balanced.

Reimplemented from Triangulation< dim, spacedim >.

Definition at line 2792 of file tria.cc.

◆ prepare_coarsening_and_refinement()

template<int dim, int spacedim>

bool Triangulation< dim, spacedim >::prepare_coarsening_and_refinement ( )

virtual

Override the implementation of prepare_coarsening_and_refinement from the base class. This is necessary if periodic boundaries are enabled and the level difference over vertices over the periodic boundary must be not more than 2:1.

Reimplemented from Triangulation< dim, spacedim >.

Definition at line 2452 of file tria.cc.

◆ repartition()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::repartition ( )

Manually repartition the active cells between processors. Normally this repartitioning will happen automatically when calling execute_coarsening_and_refinement() (or refine_global()) unless the no_automatic_repartitioning is set in the constructor. Setting the flag and then calling repartition() gives the same result.

If you want to transfer data (using SolutionTransfer or manually with register_data_attach() and notify_ready_to_unpack()), you need to set it up twice: once when calling execute_coarsening_and_refinement(), which will handle coarsening and refinement but obviously won't ship any data between processors, and a second time when calling repartition(). Here, no coarsening and refinement will be done but information will be packed and shipped to different processors. In other words, you probably want to treat a call to repartition() in the same way as execute_coarsening_and_refinement() with respect to dealing with data movement (SolutionTransfer, etc.).

Note: If no function is connected to the cell_weight signal described in the Triangulation class, this function will balance the number of cells on each processor. If one or more functions are connected, it will calculate the sum of the weights and balance the weights across processors. The only requirement on the weights is that every cell's weight is positive and that the sum over all weights on all processors can be formed using a 64-bit integer. Beyond that, it is your choice how you want to interpret the weights. A common approach is to consider the weights proportional to the cost of doing computations on a cell, e.g., by summing the time for assembly and solving. In practice, determining this cost is of course not trivial since we don't solve on isolated cells, but on the entire mesh. In such cases, one could, for example, choose the weight equal to the number of unknowns per cell (in the context of hp finite element methods), or using a heuristic that estimates the cost on each cell depending on whether, for example, one has to run some expensive algorithm on some cells but not others (such as forming boundary integrals during the assembly only on cells that are actually at the boundary, or computing expensive nonlinear terms only on some cells but not others, e.g., in the elasto-plastic problem in step-42).

Definition at line 3005 of file tria.cc.

◆ communicate_locally_moved_vertices()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::communicate_locally_moved_vertices ( const std::vector< bool > & vertex_locally_moved )

When vertices have been moved locally, for example using code like

cell->vertex(0) = new_location;

then this function can be used to update the location of vertices between MPI processes.

All the vertices that have been moved and might be in the ghost layer of a process have to be reported in the vertex_locally_moved argument. This ensures that that part of the information that has to be send between processes is actually sent. Additionally, it is quite important that vertices on the boundary between processes are reported on exactly one process (e.g. the one with the highest id). Otherwise we could expect undesirable results if multiple processes move a vertex differently. A typical strategy is to let processor \(i\) move those vertices that are adjacent to cells whose owners include processor \(i\) but no other processor \(j\) with \(j<i\); in other words, for vertices at the boundary of a subdomain, the processor with the lowest subdomain id "owns" a vertex.

Note: It only makes sense to move vertices that are either located on locally owned cells or on cells in the ghost layer. This is because you can be sure that these vertices indeed exist on the finest mesh aggregated over all processors, whereas vertices on artificial cells but not at least in the ghost layer may or may not exist on the globally finest mesh. Consequently, the vertex_locally_moved argument may not contain vertices that aren't at least on ghost cells.; This function moves vertices in such a way that on every processor, the vertices of every locally owned and ghost cell is consistent with the corresponding location of these cells on other processors. On the other hand, the locations of artificial cells will in general be wrong since artificial cells may or may not exist on other processors and consequently it is not possible to determine their location in any way. This is not usually a problem since one never does anything on artificial cells. However, it may lead to problems if the mesh with moved vertices is refined in a later step. If that's what you want to do, the right way to do it is to save the offset applied to every vertex, call this function, and before refining or coarsening the mesh apply the opposite offset and call this function again.

Parameters

vertex_locally_moved A bitmap indicating which vertices have been moved. The size of this array must be equal to Triangulation::n_vertices() and must be a subset of those vertices flagged by GridTools::get_locally_owned_vertices().

See also: This function is used, for example, in GridTools::distort_random().

Definition at line 3074 of file tria.cc.

◆ has_hanging_nodes()

template<int dim, int spacedim>

bool Triangulation< dim, spacedim >::has_hanging_nodes ( ) const

virtual

Return true if the triangulation has hanging nodes.

In the context of parallel distributed triangulations, every processor stores only that part of the triangulation it locally owns. However, it also stores the entire coarse mesh, and to guarantee the 2:1 relationship between cells, this may mean that there are hanging nodes between cells that are not locally owned or ghost cells (i.e., between ghost cells and artificial cells, or between artificial and artificial cells; see the glossary). One is not typically interested in this case, so the function returns whether there are hanging nodes between any two cells of the "global" mesh, i.e., the union of locally owned cells on all processors.

Reimplemented from Triangulation< dim, spacedim >.

Definition at line 1716 of file tria.cc.

◆ memory_consumption()

template<int dim, int spacedim>

std::size_t Triangulation< dim, spacedim >::memory_consumption ( ) const

virtual

Return the local memory consumption in bytes.

Reimplemented from parallel::Triangulation< dim, spacedim >.

Definition at line 3575 of file tria.cc.

◆ memory_consumption_p4est()

template<int dim, int spacedim>

std::size_t Triangulation< dim, spacedim >::memory_consumption_p4est ( ) const

virtual

Return the local memory consumption contained in the p4est data structures alone. This is already contained in memory_consumption() but made available separately for debugging purposes.

Definition at line 3596 of file tria.cc.

◆ write_mesh_vtk()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::write_mesh_vtk ( const char * file_basename ) const

A collective operation that produces a sequence of output files with the given file base name that contain the mesh in VTK format.

More than anything else, this function is useful for debugging the interface between deal.II and p4est.

Definition at line 1762 of file tria.cc.

◆ get_checksum()

template<int dim, int spacedim>

unsigned int Triangulation< dim, spacedim >::get_checksum ( ) const

Produce a check sum of the triangulation. This is a collective operation and is mostly useful for debugging purposes.

Definition at line 1926 of file tria.cc.

◆ save()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::save ( const char * filename ) const

Save the refinement information from the coarse mesh into the given file. This file needs to be reachable from all nodes in the computation on a shared network file system. See the SolutionTransfer class on how to store solution vectors into this file. Additional cell-based data can be saved using register_data_attach().

Definition at line 1775 of file tria.cc.

◆ load()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::load	(	const char *	filename,
		const bool	autopartition = `true`
	)

Load the refinement information saved with save() back in. The mesh must contain the same coarse mesh that was used in save() before calling this function.

You do not need to load with the same number of MPI processes that you saved with. Rather, if a mesh is loaded with a different number of MPI processes than used at the time of saving, the mesh is repartitioned appropriately. Cell-based data that was saved with register_data_attach() can be read in with notify_ready_to_unpack() after calling load().

If you use p4est version > 0.3.4.2 the autopartition flag tells p4est to ignore the partitioning that the triangulation had when it was saved and make it uniform upon loading. If autopartition is set to false, the triangulation is only repartitioned if needed (i.e. if a different number of MPI processes is encountered).

Definition at line 1835 of file tria.cc.

◆ register_data_attach()

template<int dim, int spacedim>

unsigned int Triangulation< dim, spacedim >::register_data_attach	(	const std::size_t	size,
		const std::function< void(const cell_iterator &, const CellStatus, void *)> &	pack_callback
	)

Register a function that can be used to attach data of fixed size to cells. This is useful for two purposes: (i) Upon refinement and coarsening of a triangulation (in parallel::distributed::Triangulation::execute_coarsening_and_refinement()), one needs to be able to store one or more data vectors per cell that characterizes the solution values on the cell so that this data can then be transferred to the new owning processor of the cell (or its parent/children) when the mesh is re-partitioned; (ii) when serializing a computation to a file, it is necessary to attach data to cells so that it can be saved (in parallel::distributed::Triangulation::save()) along with the cell's other information and, if necessary, later be reloaded from disk with a different subdivision of cells among the processors.

The way this function works is that it allows any number of interest parties to register their intent to attach data to cells. One example of classes that do this is parallel::distributed::SolutionTransfer where each parallel::distributed::SolutionTransfer object that works on the current Triangulation object then needs to register its intent. Each of these parties registers a call-back function (the second argument here, pack_callback) that will be called whenever the triangulation's execute_coarsening_and_refinement() or save() functions are called. The first argument here specifies the number of bytes the interest party will want to store per cell. (This needs to be a constant per cell.)

The current function then returns an integer handle that corresponds to the number of data set that the callback provided here will attach. While this number could be given a precise meaning, this is not important: You will never actually have to do anything with this number except return it to the notify_ready_to_unpack() function. In other words, each interested party (i.e., the caller of the current function) needs to store their respective returned handle for later use when unpacking data in the callback provided to notify_ready_to_unpack().

Whenever pack_callback is then called by execute_coarsening_and_refinement() or load() on a given cell, it receives a number of arguments. In particular, the first argument passed to the callback indicates the cell for which it is supposed to attach data. This is always an active cell.

The second, CellStatus, argument provided to the callback function will tell you if the given cell will be coarsened, refined, or will persist as is. (This status may be different than the refinement or coarsening flags set on that cell, to accommodate things such as the "one hanging node per edge" rule.). Specifically, the values for this argument mean the following:

CELL_PERSIST: The cell won't be refined/coarsened, but might be moved to a different processor. If this is the case, the callback will want to pack up the data on this cell into an array and store it at the provided address for later unpacking wherever this cell may land.
CELL_REFINE: this cell will be refined into 4 or 8 cells (in 2d and 3d, respectively). However, because these children don't exist yet, you cannot access them at the time when the callback is called. If the callback is called with this value, the callback will want to pack up the data on this cell into an array and store it at the provided address for later unpacking in a way so that it can then be transferred to the children of the cell that will then be available. In other words, if the data the callback will want to pack up corresponds to a finite element field, then the prolongation from parent to (new) children will have to happen during unpacking.
CELL_COARSEN: the children of this cell will be coarsened into the given cell. These children still exist, so if this is the value given to the callback as second argument, the callback will want to transfer data from the children to the current parent cell and pack it up so that it can later be unpacked again on a cell that then no longer has any children (and may also be located on a different processor). In other words, if the data the callback will want to pack up corresponds to a finite element field, then it will need to do the restriction from children to parent at this point.

Note: If this function is used for serialization of data using save() and load(), then the cell status argument with which the callback is called will always CELL_PERSIST.

The third argument given to the callback is a pointer to a memory location at which the callback can store its data. It is allowed to store exactly as many bytes as were passed to the current function via the size argument.

Note: The purpose of this function is to register intent to attach data for a single, subsequent call to execute_coarsening_and_refinement() and notify_ready_to_unpack(), save(), load(). Consequently, notify_ready_to_unpack(), save(), and load() all forget the registered callbacks once these callbacks have been called, and you will have to re-register them with a triangulation if you want them to be active for another call to these functions.

Definition at line 3224 of file tria.cc.

◆ notify_ready_to_unpack()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::notify_ready_to_unpack	(	const unsigned int	handle,
		const std::function< void(const cell_iterator &, const CellStatus, const void *)> &	unpack_callback
	)

This function is the opposite of register_data_attach(). It is called after the execute_coarsening_and_refinement() or save()/load() functions are done when classes and functions that have previously attached data to a triangulation for either transfer to other processors, across mesh refinement, or serialization of data to a file are ready to receive that data back. The important part about this process is that the triangulation cannot do this right away from the end of execute_coarsening_and_refinement() or load() via a previously attached callback function (as the register_data_attach() function does) because the classes that eventually want the data back may need to do some setup between the point in time where the mesh has been recreated and when the data can actually be received. An example is the parallel::distributed::SolutionTransfer class that can really only receive the data once not only the mesh is completely available again on the current processor, but only after a DoFHandler has been reinitialized and distributed degrees of freedom. In other words, there is typically a significant amount of set up that needs to happen in user space before the classes that can receive data attached to cell are ready to actually do so. When they are, they use the current function to tell the triangulation object that now is the time when they are ready by calling the current function.

The supplied callback function is then called for each newly locally owned cell. The first argument to the callback is an iterator that designated the cell; the second argument indicates the status of the cell in question; and the third argument points to a memory area that contains the data that was previously saved from the callback provided to register_data_attach().

The CellStatus will indicate if the cell was refined, coarsened, or persisted unchanged. The cell_iterator argument to the callback will then either be an active, locally owned cell (if the cell was not refined), or the immediate parent if it was refined during execute_coarsening_and_refinement(). Therefore, contrary to during register_data_attach(), you can now access the children if the status is CELL_REFINE but no longer for callbacks with status CELL_COARSEN.

The first argument to this function, handle, corresponds to the return value of register_data_attach(). (The precise meaning of what the numeric value of this handle is supposed to represent is neither important, nor should you try to use it for anything other than transmit information between a call to register_data_attach() to the corresponding call to notify_ready_to_unpack().)

Definition at line 3248 of file tria.cc.

◆ get_p4est_tree_to_coarse_cell_permutation()

template<int dim, int spacedim>

const std::vector< types::global_dof_index > & Triangulation< dim, spacedim >::get_p4est_tree_to_coarse_cell_permutation ( ) const

Return a permutation vector for the order the coarse cells are handed off to p4est. For example the value of the \(i\)th element in this vector is the index of the deal.II coarse cell (counting from begin(0)) that corresponds to the \(i\)th tree managed by p4est.

Definition at line 3329 of file tria.cc.

◆ get_coarse_cell_to_p4est_tree_permutation()

template<int dim, int spacedim>

const std::vector< types::global_dof_index > & Triangulation< dim, spacedim >::get_coarse_cell_to_p4est_tree_permutation ( ) const

Return a permutation vector for the mapping from the coarse deal cells to the p4est trees. This is the inverse of get_p4est_tree_to_coarse_cell_permutation.

Definition at line 3338 of file tria.cc.

◆ add_periodicity()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::add_periodicity ( const std::vector<::GridTools::PeriodicFacePair< cell_iterator > > & periodicity_vector )

virtual

In addition to the action in the base class Triangulation, this function joins faces in the p4est forest for periodic boundary conditions. As a result, each pair of faces will differ by at most one refinement level and ghost neighbors will be available across these faces.

The vector can be filled by the function GridTools::collect_periodic_faces.

For more information on periodic boundary conditions see GridTools::collect_periodic_faces, DoFTools::make_periodicity_constraints and step-45.

Note: Before this function can be used the Triangulation has to be initialized and must not be refined. Calling this function more than once is possible, but not recommended: The function destroys and rebuilds the p4est forest each time it is called.

Definition at line 3427 of file tria.cc.

◆ update_number_cache()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::update_number_cache ( )

privatevirtual

Override the function to update the number cache so we can fill data like level_ghost_owners.

Reimplemented from parallel::Triangulation< dim, spacedim >.

Definition at line 1938 of file tria.cc.

◆ init_tree()

template<int dim, int spacedim>

typename::internal::p4est::types< dim >::tree * Triangulation< dim, spacedim >::init_tree ( const int dealii_coarse_cell_index ) const

private

Return a pointer to the p4est tree that belongs to the given dealii_coarse_cell_index()

Definition at line 1951 of file tria.cc.

◆ setup_coarse_cell_to_p4est_tree_permutation()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::setup_coarse_cell_to_p4est_tree_permutation ( )

private

The function that computes the permutation between the two data storage schemes.

Definition at line 1745 of file tria.cc.

◆ copy_new_triangulation_to_p4est()

template<int dim, int spacedim = dim>

void parallel::distributed::Triangulation< dim, spacedim >::copy_new_triangulation_to_p4est ( std::integral_constant< int, 2 > )

private

Take the contents of a newly created triangulation we are attached to and copy it to p4est data structures.

This function exists in 2d and 3d variants.

◆ copy_local_forest_to_triangulation()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::copy_local_forest_to_triangulation ( )

private

Copy the local part of the refined forest from p4est into the attached triangulation.

Definition at line 2483 of file tria.cc.

◆ attach_mesh_data()

template<int dim, int spacedim>

void Triangulation< dim, spacedim >::attach_mesh_data ( )

private

Internal function notifying all registered classes to attach their data before repartitioning occurs. Called from execute_coarsening_and_refinement() and save(). The function recursively visits all deal.II cells and corresponding p4est quadrants and calls the callbacks registered via register_data_attach() on the ones where data needs to be stored.

This function is odd in that it is called on a p4est triangulation and a deal.II triangulation that may not be in sync when it is called from execute_coarsening_and_refinement(). Specifically, the p4est trees have already been refined and coarsened, but the deal.II triangulation has not. Consequently, when walking the two recursively, it can reason about which cells will remain after the deal.II triangulation has been brought up to date with regard to the p4est trees.

Definition at line 3666 of file tria.cc.

◆ get_cell_weights()

template<int dim, int spacedim>

std::vector< unsigned int > Triangulation< dim, spacedim >::get_cell_weights ( )

private

Internal function notifying all registered slots to provide their weights before repartitioning occurs. Called from execute_coarsening_and_refinement() and repartition().

Returns: A vector of unsigned integers representing the weight or computational load of every cell after the refinement/coarsening/ repartition cycle. Note that the number of entries does not need to be equal to either n_active_cells or n_locally_owned_active_cells, because the triangulation is not updated yet. The weights are sorted in the order that p4est will encounter them while iterating over them.

Definition at line 3715 of file tria.cc.

◆ compute_vertices_with_ghost_neighbors()

template<int dim, int spacedim>

std::map< unsigned int, std::set<::types::subdomain_id > > Triangulation< dim, spacedim >::compute_vertices_with_ghost_neighbors ( ) const

privatevirtual

Override the implementation in parallel::Triangulation because we can ask p4est about ghost neighbors across periodic boundaries.

Specifically, this function determines the neighboring subdomains that are adjacent to each vertex.

Reimplemented from parallel::Triangulation< dim, spacedim >.

Definition at line 3347 of file tria.cc.

◆ mark_locally_active_vertices_on_level()

template<int dim, int spacedim>

std::vector< bool > Triangulation< dim, spacedim >::mark_locally_active_vertices_on_level ( const int level ) const

private

This method returns a bit vector of length tria.n_vertices() indicating the locally active vertices on a level, i.e., the vertices touched by the locally owned level cells for use in geometric multigrid (possibly including the vertices due to periodic boundary conditions) are marked by true.

Used by DoFHandler::Policy::ParallelDistributed.

ensure that if one of the two vertices on a periodic face is marked as active (i.e., belonging to an owned level cell), also the other one is active

Definition at line 3361 of file tria.cc.

Member Data Documentation

◆ settings

template<int dim, int spacedim = dim>

Settings parallel::distributed::Triangulation< dim, spacedim >::settings

private

store the Settings.

Definition at line 816 of file tria.h.

◆ triangulation_has_content

template<int dim, int spacedim = dim>

bool parallel::distributed::Triangulation< dim, spacedim >::triangulation_has_content

private

A flag that indicates whether the triangulation has actual content.

Definition at line 821 of file tria.h.

◆ connectivity

template<int dim, int spacedim = dim>

typename ::internal::p4est::types<dim>::connectivity* parallel::distributed::Triangulation< dim, spacedim >::connectivity

private

A data structure that holds the connectivity between trees. Since each tree is rooted in a coarse grid cell, this data structure holds the connectivity between the cells of the coarse grid.

Definition at line 828 of file tria.h.

◆ parallel_forest

template<int dim, int spacedim = dim>

typename ::internal::p4est::types<dim>::forest* parallel::distributed::Triangulation< dim, spacedim >::parallel_forest

private

A data structure that holds the local part of the global triangulation.

Definition at line 834 of file tria.h.

◆ parallel_ghost

template<int dim, int spacedim = dim>

typename ::internal::p4est::types<dim>::ghost* parallel::distributed::Triangulation< dim, spacedim >::parallel_ghost

private

A data structure that holds some information about the ghost cells of the triangulation.

Definition at line 840 of file tria.h.

◆ coarse_cell_to_p4est_tree_permutation

template<int dim, int spacedim = dim>

std::vector<types::global_dof_index> parallel::distributed::Triangulation< dim, spacedim >::coarse_cell_to_p4est_tree_permutation

private

Two arrays that store which p4est tree corresponds to which coarse grid cell and vice versa. We need these arrays because p4est goes with the original order of coarse cells when it sets up its forest, and then applies the Morton ordering within each tree. But if coarse grid cells are badly ordered this may mean that individual parts of the forest stored on a local machine may be split across coarse grid cells that are not geometrically close. Consequently, we apply a hierarchical preordering according to SparsityTools::reorder_hierarchical() to ensure that the part of the forest stored by p4est is located on geometrically close coarse grid cells.

Definition at line 898 of file tria.h.

The documentation for this class was generated from the following files:

deal.II/distributed/p4est_wrappers.h
deal.II/distributed/tria.h
source/distributed/tria.cc

Classes

Public Types

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

template<int dim, int spacedim = dim> class parallel::distributed::Triangulation< dim, spacedim >

Interaction with boundary description

Member Enumeration Documentation

◆ Settings

Constructor & Destructor Documentation

◆ Triangulation()

◆ ~Triangulation()

Member Function Documentation

◆ clear()

◆ copy_triangulation()

◆ create_triangulation()

◆ execute_coarsening_and_refinement()

◆ prepare_coarsening_and_refinement()

◆ repartition()

◆ communicate_locally_moved_vertices()

◆ has_hanging_nodes()

◆ memory_consumption()

◆ memory_consumption_p4est()

◆ write_mesh_vtk()

◆ get_checksum()

◆ save()

◆ load()

◆ register_data_attach()

◆ notify_ready_to_unpack()

◆ get_p4est_tree_to_coarse_cell_permutation()

◆ get_coarse_cell_to_p4est_tree_permutation()

◆ add_periodicity()

◆ update_number_cache()

◆ init_tree()

◆ setup_coarse_cell_to_p4est_tree_permutation()

◆ copy_new_triangulation_to_p4est()

◆ copy_local_forest_to_triangulation()

◆ attach_mesh_data()

◆ get_cell_weights()

◆ compute_vertices_with_ghost_neighbors()

◆ mark_locally_active_vertices_on_level()

Member Data Documentation

◆ settings

◆ triangulation_has_content

◆ connectivity

◆ parallel_forest

◆ parallel_ghost

◆ coarse_cell_to_p4est_tree_permutation

template<int dim, int spacedim = dim>
class parallel::distributed::Triangulation< dim, spacedim >