EpetraExt::Permutation< T > Class Template Reference

Permutation stores and describes a permutation matrix P. More...

#include <EpetraExt_Permutation.h>

Inheritance diagram for EpetraExt::Permutation< T >:
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List of all members.

Public Types

typedef
EpetraExt::SameTypeTransform
< T >::TransformTypeRef 
OutputRef
typedef
EpetraExt::SameTypeTransform
< T >::TransformTypeRef 
InputRef
typedef
EpetraExt::SameTypeTransform
< T >::TransformTypePtr 
OutputPtr
typedef
EpetraExt::SameTypeTransform
< T >::TransformTypePtr 
InputPtr

Public Member Functions

 Permutation (Epetra_DataAccess CV, const Epetra_BlockMap &map, int *permutation)
 Constructor.
 Permutation (const Epetra_BlockMap &map)
 Constructor.
 Permutation (const Permutation< T > &src)
 Copy Constructor.
virtual ~Permutation ()
 Destructor.
OutputRef operator() (InputRef orig)
 This method creates a new object which is a permuted copy of the input argument.
OutputRef operator() (InputRef orig, bool column_permutation)
 This method creates a new object which is a permuted copy of the input argument.

Detailed Description

template<typename T>
class EpetraExt::Permutation< T >

Permutation stores and describes a permutation matrix P.

As described in "Matrix Computations" (Golub and Van Loan), a permutation matrix is the identity matrix with its rows re-ordered. The permutation is internally stored as an integer vector p, where p[i] is the column-index of the "1" in P's i-th row. Consider the example of permuting a matrix A by applying the permutation matrix P to form the result B. i.e., B = PA. If p[i] = j, then row j of A becomes row i of B.

This Permutation class is templated on the type of the object to be permuted. However, not all objects are eligible to be template parameters. Currently the following objects may be used: Epetra_CrsMatrix, Epetra_CrsGraph and Epetra_MultiVector.

A test program which exercises this Permutation class is located in the directory packages/epetraext/test/Permutation.

    Implementation Notes:
    Permutation currently inherits StructuralSameTypeTransform, which in turn
    inherits Transform through SameTypeTransform. Permutation, and its base classes,
    are templates. A couple of noteworthy consequences result from this:
       1. A separate instantiation of Permutation must be created for each type
       of object to be permuted. Example:
         Epetra_CrsGraph& graph = ...
         Epetra_CrsMatrix& A = ...
         Permutation<Epetra_CrsGraph> graph_perm(...);
         Permutation<Epetra_CrsMatrix> matrix_perm(...);
         Epetra_CrsMatrix& PA = matrix_perm(A);
	 Epetra_CrsGraph& Pgraph = graph_perm(graph);
       2. Following the semantics of Transform, when the Permutation class is used
       to create a new permuted copy of an object, ownership of the new copy is
       retained by Permutation. Permutation will destroy the new object. This means
       that only one object should be permuted by a Permutation instance.
    It is not clear that these are desirable behaviors for permutations. It is
    possible that Permutation will be altered to remove these limitations, as
    follows:
       1. If Permutation doesn't inherit Transform, then Permutation need not be
       a template and instead we could either overload or template-ize the
       operator() method member. This would allow a single instantiation of
       Permutation to be used for permuting all of the eligible target types.
       2. Allowing the caller (user) to take ownership of the newly-produced
       permuted objects would allow a single Permutation instance to be used
       repeatedly since it would no longer need to hold a pointer to the new object
       for later deletion.
       Then, example usage could look like this:
         Epetra_CrsMatrix& A = ...
	 Epetra_MultiVector& v = ...
         Permutation P(...);
	 Epetra_CrsMatrix PA = P(A);
	 Epetra_MultiVector Pv = P(v);

Questions and comments about this class may be directed to Alan Williams.

Definition at line 103 of file EpetraExt_Permutation.h.


Member Typedef Documentation

Definition at line 134 of file EpetraExt_Permutation.h.

Definition at line 135 of file EpetraExt_Permutation.h.

Definition at line 136 of file EpetraExt_Permutation.h.

Definition at line 137 of file EpetraExt_Permutation.h.


Constructor & Destructor Documentation

template<typename T >
EpetraExt::Permutation< T >::Permutation ( Epetra_DataAccess  CV,
const Epetra_BlockMap map,
int *  permutation 
) [inline]

Constructor.

Parameters:
CV Set to either Copy or View.
map Defines the index space to be permuted.
permutation Array defining the permutation. The length of this array must be 'map.NumMyElements()'. This array is the local portion of the 'p' vector described in the 'Detailed Description' section.

Definition at line 363 of file EpetraExt_Permutation_impl.h.

template<typename T >
EpetraExt::Permutation< T >::Permutation ( const Epetra_BlockMap map  )  [inline]

Constructor.

This constructor creates an empty permutation object. The contents must then be set using regular Epetra_IntVector methods.

Parameters:
map Defines the index space to be permuted.

Definition at line 377 of file EpetraExt_Permutation_impl.h.

template<typename T >
EpetraExt::Permutation< T >::Permutation ( const Permutation< T > &  src  )  [inline]

Copy Constructor.

Definition at line 389 of file EpetraExt_Permutation_impl.h.

template<typename T >
EpetraExt::Permutation< T >::~Permutation (  )  [inline, virtual]

Destructor.

Definition at line 401 of file EpetraExt_Permutation_impl.h.


Member Function Documentation

template<typename T>
OutputRef EpetraExt::Permutation< T >::operator() ( InputRef  orig  ) 

This method creates a new object which is a permuted copy of the input argument.

Notes:

  • This is a collective function, so in a parallel setting it must be called by all processors before any will complete it. (This is because map objects are being created, and import/export operations are being performed.)
  • The new object that is created, if it is a graph or matrix, has already had FillComplete() called before it is returned to the user.
  • The new object will be destroyed by this permutation object, so the caller should not delete it.
Parameters:
orig Input Object to be permuted.
template<typename T>
OutputRef EpetraExt::Permutation< T >::operator() ( InputRef  orig,
bool  column_permutation 
)

This method creates a new object which is a permuted copy of the input argument.

The same notes apply to this method (regarding collective communications etc.) as to the row-permutation operator method above.

Parameters:
orig Input Object to be permuted.
column_permutation Optional Input, defaults to false if not provided. A value of false means that a row-permutation will be performed (result = P*orig), a value of true means that a column-permutation will be performed (result = orig*P).

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