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//
// EpetraExt: Epetra Extended - Linear Algebra Services Package
// Copyright (2001) Sandia Corporation
//
// Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive
// license for use of this work by or on behalf of the U.S. Government.
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// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as
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//
// This library is distributed in the hope that it will be useful, but
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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// Questions? Contact Michael A. Heroux (maherou@sandia.gov)
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#ifndef EpetraExt_PERMUTATION_H
#define EpetraExt_PERMUTATION_H
#include <Epetra_IntVector.h>
#include <EpetraExt_Transform.h>
namespace EpetraExt {
/** 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.
<pre>
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);
</pre>
Questions and comments about this class may be directed to Alan Williams.
*/
template<typename T>
class Permutation : public Epetra_IntVector,
public EpetraExt::StructuralSameTypeTransform<T> {
public:
/** Constructor
@param CV Set to either Copy or View.
@param map Defines the index space to be permuted.
@param 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.
*/
Permutation(Epetra_DataAccess CV,
const Epetra_BlockMap& map,
int* permutation);
/** Constructor. This constructor creates an empty permutation object.
The contents must then be set using regular Epetra_IntVector methods.
@param map Defines the index space to be permuted.
*/
Permutation(const Epetra_BlockMap& map);
/** Copy Constructor */
Permutation(const Permutation<T>& src);
/** Destructor */
virtual ~Permutation();
typedef typename EpetraExt::SameTypeTransform<T>::TransformTypeRef OutputRef;
typedef typename EpetraExt::SameTypeTransform<T>::TransformTypeRef InputRef;
typedef typename EpetraExt::SameTypeTransform<T>::TransformTypePtr OutputPtr;
typedef typename EpetraExt::SameTypeTransform<T>::TransformTypePtr InputPtr;
/** This method creates a new object which is a permuted copy of
the input argument.
Notes:
<ul>
<li> 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.)
<li> 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.
<li> The new object will be destroyed by this permutation object,
so the caller should not delete it.
</ul>
@param orig Input Object to be permuted.
*/
OutputRef operator()( InputRef orig );
/** 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.
@param orig Input Object to be permuted.
@param 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).
*/
OutputRef operator()( InputRef orig,
bool column_permutation );
private:
Permutation<T>& operator=(const Permutation<T>& src)
{
//not currently supported
abort();
return(*this);
}
bool isTypeSupported();
OutputPtr newObj_;
InputPtr origObj_;
};
}//namespace EpetraExt
#include <EpetraExt_Permutation_impl.h>
#endif
