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// Output a CRS matrix in MATLAB format

#include "Didasko_ConfigDefs.h"
#if defined(HAVE_DIDASKO_EPETRA)

#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[])
{
  puts("Please configure Didasko with:\n"
       "--enable-epetra");

  return 0;
}
#endif

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