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MueLu::CoalesceDropFactory_kokkos< Scalar, LocalOrdinal, GlobalOrdinal, Node > Class Template Reference

Factory for creating a graph based on a given matrix. More...

#include <MueLu_CoalesceDropFactory_kokkos_decl.hpp>

Detailed Description

template<class Scalar, class LocalOrdinal, class GlobalOrdinal, class Node>
class MueLu::CoalesceDropFactory_kokkos< Scalar, LocalOrdinal, GlobalOrdinal, Node >

Factory for creating a graph based on a given matrix.

Factory for creating graphs from matrices with entries selectively dropped. This factory combines the functionality of CoalesceDropFactory and FilteredAFactory from the non-Kokkos code path.

For an in-depth discussion, see https://github.com/trilinos/Trilinos/issues/1676.

Code paths

Both the classic dropping strategy as well as a coordinate-based distance laplacian method is implemented. For performance reasons there are four distinctive code paths for the classical method:

  • one DOF per node without dropping (i.e. "aggregation: drop tol" = 0.0)
  • one DOF per node with dropping (i.e. "aggregation: drop tol" > 0.0)
  • DOFs per node > 1 withouth dropping
  • DOFs per node > 1 with dropping

Additionally there is a code path for the distance-laplacian mode.

Input/output of CoalesceDropFactory_kokkos

User parameters of CoalesceDropFactory_kokkos

Parameter type default master.xml validated requested description
A Factory null * * Generating factory of the operator A
UnAmalgamationInfo Factory null * * Generating factory of type AmalgamationFactory which generates the variable 'UnAmalgamationInfo'. Do not change the default unless you know what you are doing.
Coordinates Factory null * (*) Generating factory for variable 'Coordinates'. The coordinates are only needed if "distance laplacian" is chosen for the parameter "aggregation: drop scheme"
"aggregation: drop scheme" std::string "classical" * * Coalescing algorithm. You can choose either "classical" (=default) or "distance laplacian"
"aggregation: drop tol" double 0.0 * * Threshold parameter for dropping small entries
"aggregation: Dirichlet threshold" double 0.0 * * Threshold for determining whether entries are zero during Dirichlet row detection
"lightweight wrap" bool true * hidden switch between fast implementation based on MueLu::LWGraph and a failsafe slower implementation based on Xpetra::Graph (for comparison). The user should not change the default value (=true)

The * in the master.xml column denotes that the parameter is defined in the master.xml file.
The * in the validated column means that the parameter is declared in the list of valid input parameters (see CoalesceDropFactory_kokkos::GetValidParameters).
The * in the requested column states that the data is requested as input with all dependencies (see CoalesceDropFactory_kokkos::DeclareInput).

Variables provided by UncoupledAggregationFactory

After CoalesceDropFactory_kokkos::Build the following data is available (if requested)

Parameter generated by description
Graph CoalesceDropFactory_kokkos Graph of matrix A
DofsPerNode CoalesceDropFactory_kokkos number of DOFs per node. Note, that we assume a constant number of DOFs per node for all nodes associated with the operator A.

Amalgamation process

The CoalesceDropFactory_kokkos is internally using the AmalgamationFactory for amalgamating the dof-based maps to node-based maps. The AmalgamationFactory creates the "UnAmalgamationInfo" container which basically stores all the necessary information for translating dof based data to node based data and vice versa. The container is used, since this way the amalgamation is only done once and later reused by other factories.

Of course, often one does not need the information from the "UnAmalgamationInfo" container since the same information could be extracted of the "Graph" or the map from the "Coordinates" vector. However, there are also some situations (e.g. when doing rebalancing based on HyperGraph partitioning without coordinate information) where one has not access to a "Graph" or "Coordinates" variable.

Definition at line 131 of file MueLu_CoalesceDropFactory_kokkos_decl.hpp.


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