```// @HEADER
// ***********************************************************************
//
//                      Didasko Tutorial Package
//                 Copyright (2005) 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.
//
// 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
// License, or (at your option) any later version.
//
// 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
//
// Questions about Didasko? Contact Marzio Sala (marzio.sala _AT_ gmail.com)
//
// ***********************************************************************

// Output a CRS matrix in MATLAB format

#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_CrsMatrix.h"

// ============================================================
// define a class, derived from Epetra_CrsMatrix, which
// initializes the matrix entires. User has to provide
// a valid Epetra_Map in the constructor, plus the diagonal
// value, and the sub- and super-diagonal values.
// ============================================================

class TridiagonalCrsMatrix : public Epetra_CrsMatrix {

public:
TridiagonalCrsMatrix(const Epetra_Map & Map,
double a,
double diag, double c) :
Epetra_CrsMatrix(Copy,Map,3)
{

// global number of rows
int NumGlobalElements = Map.NumGlobalElements();
// local number of rows
int NumMyElements = Map.NumMyElements();
// get update list
int * MyGlobalElements = new int [NumMyElements];
Map.MyGlobalElements( MyGlobalElements );

// Add  rows one-at-a-time
// Need some vectors to help
// Off diagonal Values will always be -1

double *Values = new double[2];
Values[0] = a; Values[1] = c;
int *Indices = new int[2];
int NumEntries;

for( int i=0 ; i<NumMyElements; ++i ) {
if (MyGlobalElements[i]==0) {
Indices[0] = 1;
NumEntries = 1;
} else if (MyGlobalElements[i] == NumGlobalElements-1) {
Indices[0] = NumGlobalElements-2;
NumEntries = 1;
} else {
Indices[0] = MyGlobalElements[i]-1;
Indices[1] = MyGlobalElements[i]+1;
NumEntries = 2;
}
InsertGlobalValues(MyGlobalElements[i], NumEntries, Values, Indices);
// Put in the diagonal entry
InsertGlobalValues(MyGlobalElements[i], 1, &diag, MyGlobalElements+i);
}

FillComplete();
}

};

/* ======== ================ *
* function CrsMatrix2MATLAB *
* ======== ================ *
*
* Print out a CrsMatrix in a MATLAB format. Each processor prints out
* its part, starting from proc 0 to proc NumProc-1. The first line of
* each processor's output states the number of local rows and of
* local nonzero elements. Output is finished by "End of Matrix Output".
*
*
* Return code:        true if matrix has been printed out
* -----------         false otherwise
*
* Parameters:
* ----------
*
* - Epetra_CrsMatrix  reference to the ditributed CrsMatrix to
*                     print out
*/

bool CrsMatrix2MATLAB( const Epetra_CrsMatrix & A )

{

int MyPID = A.Comm().MyPID();
int NumProc = A.Comm().NumProc();

// work only on transformed matrices;
if( A.IndicesAreLocal() == false ) {
if( MyPID == 0 ) {
cerr << "ERROR in "<< __FILE__ << ", line " << __LINE__ << endl;
cerr << "Function CrsMatrix2MATLAB accepts\n";
cerr << "transformed matrices ONLY. Please call A.FillComplete()\n";
cerr << "on your matrix A to that purpose.\n";
cerr << "Now returning...\n";
}
return false;
}

int NumMyRows = A.NumMyRows(); // number of rows on this process
int NumNzRow;   // number of nonzero elements for each row
int NumEntries; // number of extracted elements for each row
int NumGlobalRows; // global dimensio of the problem
int GlobalRow;  // row in global ordering
int NumGlobalNonzeros; // global number of nonzero elements

NumGlobalRows = A.NumGlobalRows();
NumGlobalNonzeros = A.NumGlobalNonzeros();

// print out on cout if no filename is provided

int IndexBase = A.IndexBase(); // MATLAB start from 0
if( IndexBase == 0 ) IndexBase = 1;

// write on file the dimension of the matrix

if( MyPID==0 ) {
cout << "A = spalloc(";
cout << NumGlobalRows << ',' << NumGlobalRows;
cout << ',' << NumGlobalNonzeros << ");\n";
}

for( int Proc=0 ; Proc<NumProc ; ++Proc ) {

if( MyPID == Proc ) {

cout << "% On proc " << Proc << ": ";
cout << NumMyRows << " rows and ";
cout << A.NumMyNonzeros() << " nonzeros\n";

// cycle over all local rows to find out nonzero elements
for( int MyRow=0 ; MyRow<NumMyRows ; ++MyRow ) {

GlobalRow = A.GRID(MyRow);

NumNzRow = A.NumMyEntries(MyRow);
double *Values = new double[NumNzRow];
int *Indices = new int[NumNzRow];

A.ExtractMyRowCopy(MyRow, NumNzRow,
NumEntries, Values, Indices);
// print out the elements with MATLAB syntax
for( int j=0 ; j<NumEntries ; ++j ) {
cout << "A(" << GlobalRow  + IndexBase
<< "," << A.GCID(Indices[j]) + IndexBase
<< ") = " << Values[j] << ";\n";
}

delete Values;
delete Indices;
}

}
A.Comm().Barrier();
if( MyPID == 0 ) {
cout << " %End of Matrix Output\n";
}
}

return true;

}

// =========== //
// 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

// set global dimension to 5, could be any number
int NumGlobalElements = 5;

// define a linear map
Epetra_Map Map(NumGlobalElements,0,Comm);

// create the matrix
TridiagonalCrsMatrix A( Map, -1.0, 2.0, -1.0);

// output informationto stdout
CrsMatrix2MATLAB( A );

#ifdef HAVE_MPI
MPI_Finalize();
#endif

return( EXIT_SUCCESS );

}

#else

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

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