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// ***********************************************************************
//
//
// 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.
//
// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 2.1 of the
//
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// 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
// USA
//
//
// ***********************************************************************

// Use of Epetra_Operator.
// This code must be run with one process

#include "Epetra_ConfigDefs.h"
#ifdef HAVE_MPI
#include "mpi.h"
#include "Epetra_MpiComm.h"
#else
#include "Epetra_SerialComm.h"
#endif
#include "Epetra_Map.h"
#include "Epetra_Vector.h"
#include "Epetra_MultiVector.h"
#include "Epetra_Operator.h"

// ==================== //
// TriDiagonal Operator //
// -------------------- //

class TriDiagonalOperator : public Epetra_Operator
{

public:

// constructor
TriDiagonalOperator( double diag_minus_one,
double diag,
double diag_plus_one,
Epetra_Map & Map) :
Map_(Map),
diag_minus_one_(diag_minus_one),
diag_(diag),
diag_plus_one_(diag_plus_one)
{}

// application of the tridiagonal operator
int Apply( const Epetra_MultiVector & X,
Epetra_MultiVector & Y ) const
{
int Length = X.MyLength();

// maybe some error checks on MultiVector Lenghts
// for the future...

for( int vec=0 ; vec<X.NumVectors() ; ++vec ) {

// one-dimensional problems here
if( Length == 1 ) {
Y[vec][0] = diag_ * X[vec][0];
break;
}

// more general case (Lenght >= 2)

// first row
Y[vec][0] = diag_ * X[vec][0] + diag_plus_one_ * X[vec][1];

// intermediate rows
for( int i=1 ; i<Length-1 ; ++i ) {
Y[vec][i] = diag_ * X[vec][i] + diag_plus_one_ * X[vec][i+1]
+ diag_minus_one_ * X[vec][i-1];
}
// final row
Y[vec][Length-1] = diag_ * X[vec][Length-1]
+ diag_minus_one_ * X[vec][Length-2];
}

return true;
}

// other function
int SetUseTranspose( bool UseTranspose)
{
return(-1); // not implemented
}

int ApplyInverse( const Epetra_MultiVector & X,
Epetra_MultiVector & Y ) const
{
return(-1); // not implemented
}

double NormInf() const
{
return(abs(diag_) + abs(diag_minus_one_) + abs(diag_plus_one_));
}

const char * Label () const
{
return("TriDiagonalOperator");
}

bool UseTranspose() const
{
return(false);
}

bool HasNormInf () const
{
return(true);
}

const Epetra_Comm & Comm() const
{
return(Map_.Comm());
}

const Epetra_Map & OperatorDomainMap() const
{
return(Map_);
}

const Epetra_Map & OperatorRangeMap() const
{
return(Map_);
}

private:

Epetra_Map Map_;
double diag_minus_one_;   // value in the sub-diagonal
double diag_;             // value in the diagonal
double diag_plus_one_;    // value in the super-diagonal

};

// =========== //
// main driver //
// ----------- //

int main(int argc, char *argv[]) {

#ifdef HAVE_MPI
MPI_Init(&argc, &argv);
Epetra_MpiComm Comm(MPI_COMM_WORLD);
#else
Epetra_SerialComm Comm;
#endif

if( Comm.NumProc() != 1 ) {
if( Comm.MyPID() == 0 ) {
cerr << "This is mono-process example\n"
<< "Please run with one processo only\n";
}
#ifdef HAVE_MPI
MPI_Finalize();
#endif
exit(EXIT_SUCCESS);
}

// global dimension of the problem, could be any positive number
int NumGlobalElements( 5 );

// linear decomposition (for simplicity, could be general)
Epetra_Map Map(NumGlobalElements,0,Comm );

// define two vectors based on Map
Epetra_Vector x(Map);
Epetra_Vector y(Map);
x.PutScalar(1.0);

// define a linear operator, as previously defined in class
// TriDiagonalOperator

TriDiagonalOperator TriDiagOp(-1.0,2.0,-1.0,Map);

TriDiagOp.Apply(x,y);

cout << x;
cout << y;

#ifdef HAVE_MPI
MPI_Finalize();
#endif

return( EXIT_SUCCESS );

}

#else

#include <stdlib.h>
#include <stdio.h>

int main(int argc, char *argv[])
{