`#include <Ifpack_Partitioner.h>`

Inheritance diagram for Ifpack_Partitioner:

## Public Member Functions | |

virtual | ~Ifpack_Partitioner () |

Destructor. | |

virtual int | NumLocalParts () const =0 |

Returns the number of computed local partitions. | |

virtual int | OverlappingLevel () const =0 |

Returns the overlapping level. | |

virtual int | operator() (int MyRow) const =0 |

Returns the local non-overlapping partition ID of the specified row. | |

virtual int | operator() (int i, int j) const =0 |

Returns the local overlapping partition ID of the j-th node in partition i. | |

virtual int | NumRowsInPart (const int Part) const =0 |

Returns the number of rows contained in specified partition. | |

virtual int | RowsInPart (const int Part, int *List) const =0 |

Copies into List the rows in the (overlapping) partition Part. | |

virtual const int * | NonOverlappingPartition () const =0 |

Returns a pointer to the integer vector containing the non-overlapping partition ID of each local row. | |

virtual int | SetParameters (Teuchos::ParameterList &List)=0 |

Sets all the parameters for the partitioner. | |

virtual int | Compute ()=0 |

Computes the partitions. Returns 0 if successful. | |

virtual bool | IsComputed ()=0 |

Returns true if partitions have been computed successfully. | |

virtual ostream & | Print (std::ostream &os) const =0 |

Prints basic information about the partitioning object. |

Class Ifpack_Partitioner enables the decomposition of a local Ifpack_Graph's. It is supposed that the graph refers to a localized matrix (that is, a matrix that has been filtered through Ifpack_LocalFilter).

The overloaded operator (int i) can be used to extract the local partition ID of local row i.

The partitions created by Ifpack_Partitioner derived clased are non-overlapping in graph sense. This means that each row (or, more approriately, vertex) of `G`

is assigned to exactly one partition.

Partitioner can be extended using the functionalities of class Ifpack_OverlappingPartitioner (itself derived from Ifpack_Partitioner. This class extends the non-overlapping partitions by the required amount of overlap, considering local nodes only (that is, this overlap do *not* modify the overlap among the processes).

Ifpack_Partitioner is a pure virtual class. Concrete implementations are:

- Ifpack_LinearPartitioner, which allows the decomposition of the rows of the graph in simple consecutive chunks;
- Ifpack_METISPartitioner, which calls METIS to decompose the graph (this requires the configuration option --enable-ifpack-metis);
- Ifpack_GreedyPartitioner, a simple greedy algorith;
- Ifpack_EquationPartitioner, which creates
`NumPDEEqns`

parts (where`NumPDEEqns`

is the number of equations in the linear system). It is supposed that all the equations referring to the same grid node are ordered consecutively. Besides, the number of equations per node must be constant in the domain.

Generically, a constructor requires an Ifpack_Graph object. Ifpack_Graph is a pure virtual class. Concrete implentations are:

- Ifpack_Graph_Epetra_CrsGraph, a light-weight class to wrap Epetra_CrsGraph objects as Ifpack_Graph objects;
- Ifpack_Graph_Epetra_RowMatrix, a light-weight class to wrap Epetra_RowMatrix objects as Ifpack_Graph objects.

An example of use is an Ifpack_Partitioner derived class is as follows:

#include "Ifpack_Partitioner.h" #include "Ifpack_LinearPartitioner.h" #include "Ifpack_Graph.h" #include "Ifpack_Graph_Epetra_CrsGraph.h" ... Epetra_CrsMatrix* A; // A is filled // create the wrapper from Epetra_CrsGraph Ifpack_Graph* Graph = new Ifpack_Graph_Epetra_CrsGraph(A); // we aim to create non-overlapping partitions only Ifpack_Partitioner Partitioner(Graph); Ifpack_Partitioner* Partitioner; Partitioner = new Ifpack_Graph_Epetra_CrsGraph(&A); // we want 16 local parts List.set("partitioner: local parts", 16); // and an overlap of 0 among the local parts (default option) List.set("partitioner: overlap", 0); // decompose the graph Partitioner.Create(List); // now Graph can be deleted, as Partitioner contains all the // necessary information to use the partitions delete Graph; // we can get the number of parts actually created... int NumParts = Partitioner.NumParts(); // ... and the number of rows in each of them for (int i = 0 ; i < NumParts ; ++i) { cout << "rows in " << i << "=" << Partitioner.RowsInPart(i); } // .. and, for non-overlapping partitions only, the partition ID // for each local row simply using: for (int i = 0 ; i < A->NumMyRows() ; ++i) cout << "Partition[" << i <<"] = " << Partitioner(i) << endl;

When overlapping partitiones are created, the user can get the row ID contained in each partition as follows:

for (int i = 0 ; i < NumParts ; ++i) { for (int j = 0 ; j < Partitioner.RowsInPart(i) ; ++j) { cout << "Partition " << i << ", contains local row " << Partitioner(i,j) << endl; } }

Ifpack_Partitioner is used to create the subblocks in Ifpack_BlockJacobi, Ifpack_BlockGaussSeidel, and Ifpack_BlockSymGaussSeidel.

**Author:**- Marzio Sala, SNL 9214.

**Date:**- Last modified on Nov-04.

Definition at line 119 of file Ifpack_Partitioner.h.

virtual int Ifpack_Partitioner::operator() | ( | int | MyRow |
) | const` [pure virtual]` |

Returns the local non-overlapping partition ID of the specified row.

Returns the non-overlapping partition ID of the specified row.

**Parameters:**-
*MyRow*- (In) local row numbe

**Returns:**- Local ID of non-overlapping partition for MyRow.

Implemented in Ifpack_OverlappingPartitioner.

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

Generated on Tue Oct 20 12:48:56 2009 for IFPACK by 1.4.7