Reference documentation for deal.II version Git 8ba89c874e 20210804 22:06:33 0600

#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) 
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 
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 hpcapabilities, 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 deregistering 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.
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.
The use of this class is demonstrated in step75.
Definition at line 91 of file cell_weights.h.
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 106 of file cell_weights.h.
parallel::CellWeights< dim, spacedim >::CellWeights  (  const ::DoFHandler< dim, spacedim > &  dof_handler, 
const WeightingFunction &  weighting_function  
) 
Constructor.
[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.
parallel::CellWeights< dim, spacedim >::~CellWeights  (  ) 
Destructor.
Disconnects the function previously connected to the weighting signal.
Definition at line 38 of file cell_weights.cc.
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.

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.

static 
Choose a constant weight factor
on each cell.
Definition at line 65 of file cell_weights.cc.

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.

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.

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.

private 
A connection to the corresponding cell_weight signal of the Triangulation which is attached to the DoFHandler.
Definition at line 194 of file cell_weights.h.