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// Didasko Tutorial Package
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// this example creates a tridiagonal matrix of type
//
// | 2 -1 |
// | -1 2 -1 |
// A = | ... ... ... |
// | -1 2 |
#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"
int main(int argc, char *argv[])
{
#ifdef HAVE_MPI
MPI_Init(&argc, &argv);
Epetra_MpiComm Comm(MPI_COMM_WORLD);
#else
#endif
// set global dimension of the matrix to 5, could be any number
int NumGlobalElements = 5;
// create a map
Epetra_Map Map(NumGlobalElements,0,Comm);
// local number of rows
int NumMyElements = Map.NumMyElements();
// get update list
int * MyGlobalElements = Map.MyGlobalElements( );
// Create an integer vector NumNz that is used to build the Petra Matrix.
// NumNz[i] is the Number of OFF-DIAGONAL term for the ith global equation
// on this processor
int * NumNz = new int[NumMyElements];
// We are building a tridiagonal matrix where each row has (-1 2 -1)
// So we need 2 off-diagonal terms (except for the first and last equation)
for ( int i=0; i<NumMyElements; i++)
if (MyGlobalElements[i]==0 || MyGlobalElements[i] == NumGlobalElements-1)
NumNz[i] = 2;
else
NumNz[i] = 3;
// Create a Epetra_Matrix
Epetra_CrsMatrix A(Copy,Map,NumNz);
// (NOTE: constructor `Epetra_CrsMatrix A(Copy,Map,3);' was ok too.)
// Add rows one-at-a-time
// Need some vectors to help
// Off diagonal Values will always be -1, diagonal term 2
double *Values = new double[2];
Values[0] = -1.0; Values[1] = -1.0;
int *Indices = new int[2];
double two = 2.0;
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;
}
A.InsertGlobalValues(MyGlobalElements[i], NumEntries, Values, Indices);
// Put in the diagonal entry
A.InsertGlobalValues(MyGlobalElements[i], 1, &two, MyGlobalElements+i);
}
// Finish up, trasforming the matrix entries into local numbering,
// to optimize data transfert during matrix-vector products
A.FillComplete();
// build up two distributed vectors q and z, and compute
// q = A * z
Epetra_Vector q(A.RowMap());
Epetra_Vector z(A.RowMap());
// Fill z with 1's
z.PutScalar( 1.0 );
A.Multiply(false, z, q); // Compute q = A*z
double dotProduct;
z.Dot( q, &dotProduct );
if( Comm.MyPID() == 0 )
cout << "q dot z = " << dotProduct << endl;
#ifdef HAVE_MPI
MPI_Finalize();
#endif
delete[] NumNz;
return( EXIT_SUCCESS );
} /* 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