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// Example of Epetra_MultiVector; use of ExtractView on MultiVector.

#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_MultiVector.h"

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

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

  // Total number of elements in the vector
  int NumElements = 10;

  // Construct a Map with NumElements and index base of 0
  Epetra_Map Map(NumElements, 0, Comm);

  // Create x as a 2-component multi-vector
  Epetra_MultiVector x(Map,2);

  // get the local size of the vector
  int MyLength = x.MyLength();

  /* First way to define the vector:   */
  /* use the [] operator on the object */

  for( int c=0 ; c<x.NumVectors() ; ++c )
    for( int i=0 ; i<MyLength ; ++i ) x[c][i] = 1.0*i+1000*c;

  // need a double pointer because this works with multi-vectors
  double ** pointer;

  x.ExtractView( &pointer );

  for( int c=0 ; c<x.NumVectors() ;++c )
    for( int i=0 ; i<MyLength ; ++i )
      cout << "on proc " << Comm.MyPID() << ", x["
        << i << "] = " << pointer[c][i] << endl;

  // now modify the values
  for( int c=0 ; c<x.NumVectors() ;++c )
    for( int i=0 ; i<MyLength ; ++i )
      pointer[c][i] *= 10;

  cout << x;

#ifdef HAVE_MPI
  MPI_Finalize();
#endif

  return(0);

} /* main */

#else

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

int main(int argc, char *argv[])
{
  puts("Please configure Didasko with:\n"
      "--enable-epetra");

  return 0;
}

#endif