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

Public Types
using	WeightingFunction = std::function< unsigned int(const typename DoFHandler< dim, spacedim >::cell_iterator &, const FiniteElement< dim, spacedim > &)>

Public Member Functions
	CellWeights (const ::DoFHandler< dim, spacedim > &dof_handler, const WeightingFunction &weighting_function)

	~CellWeights ()

void	reinit (const DoFHandler< dim, spacedim > &dof_handler, const WeightingFunction &weighting_function)

Deprecated functions
	CellWeights (const ::DoFHandler< dim, spacedim > &dof_handler)

void	register_constant_weighting (const unsigned int factor=1000)

void	register_ndofs_weighting (const unsigned int factor=1000)

void	register_ndofs_squared_weighting (const unsigned int factor=1000)

void	register_custom_weighting (const std::function< unsigned int(const FiniteElement< dim, spacedim > &, const typename DoFHandler< dim, spacedim >::cell_iterator &)> custom_function)

Static Public Member Functions
static std::function< unsigned int(const typename ::Triangulation< dim, spacedim >::cell_iterator &cell, const typename ::Triangulation< dim, spacedim >::CellStatus status)>	make_weighting_callback (const DoFHandler< dim, spacedim > &dof_handler, const WeightingFunction &weighting_function)

Selection of weighting functions
static WeightingFunction	constant_weighting (const unsigned int factor=1000)

static WeightingFunction	ndofs_weighting (const std::pair< float, float > &coefficients)

static WeightingFunction	ndofs_weighting (const std::vector< std::pair< float, float > > &coefficients)

Static Private Member Functions
static unsigned int	weighting_callback (const typename ::Triangulation< dim, spacedim >::cell_iterator &cell, const typename ::Triangulation< dim, spacedim >::CellStatus status, const DoFHandler< dim, spacedim > &dof_handler, const parallel::TriangulationBase< dim, spacedim > &triangulation, const WeightingFunction &weighting_function)

Private Attributes
boost::signals2::connection	connection

Deprecated members
SmartPointer< const ::DoFHandler< dim, spacedim >, CellWeights >	dof_handler

SmartPointer< const parallel::TriangulationBase< dim, spacedim >, CellWeights >	triangulation

Detailed Description

template<int dim, int spacedim = dim>
class parallel::CellWeights< dim, spacedim >

Anytime a parallel::TriangulationBase is repartitioned, either upon request or by refinement/coarsening, cells will be distributed amongst all subdomains to achieve an equally balanced workload. If the workload per cell varies, which is in general the case for DoFHandler objects with hp-capabilities, we can take that into account by introducing individual weights for different cells.

This class allows computing these weights for load balancing by consulting the FiniteElement that is associated with each cell of a DoFHandler. One can choose from predefined weighting algorithms provided by this class or provide a custom one.

If the associated DoFHandler has not been initialized yet, i.e., its hp::FECollection is empty, all cell weights will be evaluated as zero.

This class offers two different ways of connecting the chosen weighting function to the corresponding signal of the linked parallel::TriangulationBase. The recommended way involves creating an object of this class which will automatically take care of registering the weighting function upon creation and de-registering it once destroyed. An object of this class needs to exist for every DoFHandler associated with the Triangulation we work on to achieve satisfying work balancing results. The connected weighting function may be changed anytime using the CellWeights::reinit() function. The following code snippet demonstrates how to achieve each cell being weighted by its current number of degrees of freedom. We chose a factor of 1000 that corresponds to the initial weight each cell is assigned to upon creation.

parallel::CellWeights<dim, spacedim> cell_weights(
  hp_dof_handler,
  parallel::CellWeights<dim, spacedim>::ndofs_weighting({1000, 1}));

On the other hand, you are also able to take care of handling the signal connection manually by using the static member function of this class. In this case, an analogous code example looks as follows.

boost::signals2::connection connection =
  hp_dof_handler.get_triangulation().signals.cell_weight.connect(
    parallel::CellWeights<dim, spacedim>::make_weighting_callback(
      hp_dof_handler,
      parallel::CellWeights<dim, spacedim>::ndofs_weighting(
        {1000, 1}));

The use of this class is demonstrated in step-75.

Note: See Triangulation::Signals::cell_weight for more information on weighting and load balancing.; Be aware that this class connects the weight function to the Triangulation during this class's constructor. If the Triangulation associated with the DoFHandler changes during the lifetime of the latter via DoFHandler::reinit(), an assertion will be triggered in the weight_callback() function. Use CellWeights::reinit() to deregister the weighting function on the old Triangulation and connect it to the new one.

Definition at line 91 of file cell_weights.h.

Member Typedef Documentation

◆ WeightingFunction

template<int dim, int spacedim = dim>

using parallel::CellWeights< dim, spacedim >::WeightingFunction = std::function< unsigned int(const typename DoFHandler<dim, spacedim>::cell_iterator &, const FiniteElement<dim, spacedim> &)>

An alias that defines the characteristics of a function that can be used for weighting cells during load balancing.

Such weighting functions take as arguments an iterator to a cell and the future finite element that will be assigned to it after repartitioning. They return an unsigned integer which is interpreted as the cell's weight or, in other words, the additional computational load associated with it.

Definition at line 104 of file cell_weights.h.

Constructor & Destructor Documentation

◆ CellWeights() [1/2]

template<int dim, int spacedim>

parallel::CellWeights< dim, spacedim >::CellWeights	(	const ::DoFHandler< dim, spacedim > &	dof_handler,
		const WeightingFunction &	weighting_function
	)

Constructor.

Parameters

[in]	dof_handler	The DoFHandler which will be used to determine each cell's finite element.
[in]	weighting_function	The function that determines each cell's weight during load balancing.

Definition at line 28 of file cell_weights.cc.

◆ ~CellWeights()

template<int dim, int spacedim>

parallel::CellWeights< dim, spacedim >::~CellWeights

Destructor.

Disconnects the function previously connected to the weighting signal.

Definition at line 38 of file cell_weights.cc.

◆ CellWeights() [2/2]

template<int dim, int spacedim>

parallel::CellWeights< dim, spacedim >::CellWeights ( const ::DoFHandler< dim, spacedim > & dof_handler )

Constructor.

Parameters

[in] dof_handler The DoFHandler which will be used to determine each cell's finite element.

Definition at line 225 of file cell_weights.cc.

Member Function Documentation

◆ reinit()

template<int dim, int spacedim = dim>

void parallel::CellWeights< dim, spacedim >::reinit	(	const DoFHandler< dim, spacedim > &	dof_handler,
		const WeightingFunction &	weighting_function
	)

Connect a different weighting_function to the Triangulation associated with the dof_handler.

Disconnects the function previously connected to the weighting signal.

Definition at line 47 of file cell_weights.cc.

◆ make_weighting_callback()

template<int dim, int spacedim = dim>

std::function< unsigned int(const typename::Triangulation< dim, spacedim >::cell_iterator &cell, const typename::Triangulation< dim, spacedim >::CellStatus status)> parallel::CellWeights< dim, spacedim >::make_weighting_callback	(	const DoFHandler< dim, spacedim > &	dof_handler,
		const WeightingFunction &	weighting_function
	)

static

Converts a weighting_function to a different type that qualifies as a callback function, which can be connected to a weighting signal of a Triangulation.

This function does not connect the converted function to the Triangulation associated with the dof_handler.

Definition at line 131 of file cell_weights.cc.

◆ constant_weighting()

template<int dim, int spacedim>

CellWeights< dim, spacedim >::WeightingFunction parallel::CellWeights< dim, spacedim >::constant_weighting ( const unsigned int factor = 1000 )

static

Choose a constant weight factor on each cell.

Definition at line 65 of file cell_weights.cc.

◆ ndofs_weighting() [1/2]

template<int dim, int spacedim>

CellWeights< dim, spacedim >::WeightingFunction parallel::CellWeights< dim, spacedim >::ndofs_weighting ( const std::pair< float, float > & coefficients )

static

The pair of floating point numbers \((a,b)\) provided via coefficients determines the weight \(w_K\) of each cell \(K\) with \(n_K\) degrees of freedom in the following way:

\[ w_K = a \, n_K^b \]

The right hand side will be rounded to the nearest integer since cell weights are required to be integers.

Definition at line 77 of file cell_weights.cc.

◆ ndofs_weighting() [2/2]

template<int dim, int spacedim>

CellWeights< dim, spacedim >::WeightingFunction parallel::CellWeights< dim, spacedim >::ndofs_weighting ( const std::vector< std::pair< float, float > > & coefficients )

static

The container coefficients provides pairs of floating point numbers \((a_i, b_i)\) that determine the weight \(w_K\) of each cell \(K\) with \(n_K\) degrees of freedom in the following way:

\[ w_K = \sum_i a_i \, n_K^{b_i} \]

The right hand side will be rounded to the nearest integer since cell weights are required to be integers.

Definition at line 101 of file cell_weights.cc.

◆ register_constant_weighting()

template<int dim, int spacedim>

void parallel::CellWeights< dim, spacedim >::register_constant_weighting ( const unsigned int factor = 1000 )

Choose a constant weight factor on each cell.

Deprecated:: Use CellWeights::constant_weighting() instead.

Definition at line 244 of file cell_weights.cc.

◆ register_ndofs_weighting()

template<int dim, int spacedim>

void parallel::CellWeights< dim, spacedim >::register_ndofs_weighting ( const unsigned int factor = 1000 )

Choose a weight for each cell that is proportional to its number of degrees of freedom with a factor factor.

Deprecated:: Use CellWeights::ndofs_weighting() instead.

Definition at line 266 of file cell_weights.cc.

◆ register_ndofs_squared_weighting()

template<int dim, int spacedim>

void parallel::CellWeights< dim, spacedim >::register_ndofs_squared_weighting ( const unsigned int factor = 1000 )

Choose a weight for each cell that is proportional to its number of degrees of freedom squared with a factor factor.

Deprecated:: Use CellWeights::ndofs_weighting() instead.

Definition at line 288 of file cell_weights.cc.

◆ register_custom_weighting()

template<int dim, int spacedim>

void parallel::CellWeights< dim, spacedim >::register_custom_weighting ( const std::function< unsigned int(const FiniteElement< dim, spacedim > &, const typename DoFHandler< dim, spacedim >::cell_iterator &)> custom_function )

Register a custom weight for each cell by providing a function as a parameter.

Parameters

[in] custom_function The custom weighting function returning the weight of each cell as an unsigned integer. It is required to have two arguments, namely the FiniteElement that will be active on the particular cell, and the cell itself of type DoFHandler::cell_iterator. We require both to make sure to get the right active FiniteElement on each cell in case that we coarsen the Triangulation.

Definition at line 310 of file cell_weights.cc.

◆ weighting_callback()

template<int dim, int spacedim = dim>

unsigned int parallel::CellWeights< dim, spacedim >::weighting_callback	(	const typename ::Triangulation< dim, spacedim >::cell_iterator &	cell,
		const typename ::Triangulation< dim, spacedim >::CellStatus	status,
		const DoFHandler< dim, spacedim > &	dof_handler,
		const parallel::TriangulationBase< dim, spacedim > &	triangulation,
		const WeightingFunction &	weighting_function
	)

staticprivate

A callback function that will be connected to the cell_weight signal of the triangulation, to which the dof_handler is attached. Ultimately returns the weight for each cell, determined by the weighting_function provided as a parameter. Returns zero if dof_handler has not been initialized yet.

Definition at line 164 of file cell_weights.cc.

Member Data Documentation

◆ dof_handler

template<int dim, int spacedim = dim>

SmartPointer<const ::DoFHandler<dim, spacedim>, CellWeights> parallel::CellWeights< dim, spacedim >::dof_handler

private

Pointer to the degree of freedom handler.

Definition at line 263 of file cell_weights.h.

◆ triangulation

template<int dim, int spacedim = dim>

SmartPointer<const parallel::TriangulationBase<dim, spacedim>, CellWeights> parallel::CellWeights< dim, spacedim >::triangulation

private

Pointer to the Triangulation associated with the degree of freedom handler.

We store both to make sure to always work on the correct combination of both.

Definition at line 274 of file cell_weights.h.

◆ connection

template<int dim, int spacedim = dim>

boost::signals2::connection parallel::CellWeights< dim, spacedim >::connection

private

A connection to the corresponding cell_weight signal of the Triangulation which is attached to the DoFHandler.

Definition at line 284 of file cell_weights.h.

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

include/deal.II/distributed/cell_weights.h
source/distributed/cell_weights.cc

Public Types

Public Member Functions

Static Public Member Functions

Static Private Member Functions

Private Attributes

Detailed Description

Member Typedef Documentation

◆ WeightingFunction

Constructor & Destructor Documentation

◆ CellWeights() [1/2]

◆ ~CellWeights()

◆ CellWeights() [2/2]

Member Function Documentation

◆ reinit()

◆ make_weighting_callback()

◆ constant_weighting()

◆ ndofs_weighting() [1/2]

◆ ndofs_weighting() [2/2]

◆ register_constant_weighting()

◆ register_ndofs_weighting()

◆ register_ndofs_squared_weighting()

◆ register_custom_weighting()

◆ weighting_callback()

Member Data Documentation

◆ dof_handler

◆ triangulation

◆ connection