// @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) // // *********************************************************************** // @HEADER // Basic definition of communicator. // This code should be run with at least two processes // However, note that the SAME code works even if Epetra // has been configured without MPI! #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 int main(int argc, char *argv[]) { #ifdef HAVE_MPI MPI_Init(&argc, &argv); // define an Epetra communicator Epetra_MpiComm Comm(MPI_COMM_WORLD); #else Epetra_SerialComm Comm; #endif // get the proc ID of this process int MyPID = Comm.MyPID(); // get the total number of processes int NumProc = Comm.NumProc(); // output some information to std output cout << Comm << endl; // ======================== // // now some basic MPI calls // // ------------------------ // int ivalue; double dvalue, dvalue2; double* dvalues; dvalues = new double[NumProc]; double* dvalues2; dvalues2 = new double[NumProc]; int root = 0; // equivalent to MPI_Barrier Comm.Barrier(); if (MyPID == root) dvalue = 12.0; // On input, the root processor contains the list of values // (in this case, a single value). On exit, all processes will // have he same list of values. Note that all values must be allocated // vefore the broadcast // equivalent to MPI_Broadcast Comm.Broadcast(&dvalue, 1, root); // as before, but with integer values. As C++ can bind to the appropriate // interface based on argument typing, the type of data is not required. Comm.Broadcast(&ivalue, 1, root); // equivalent MPI_Allgather Comm.GatherAll(dvalues, dvalues2, 1); // equivalent to MPI_Allreduce with MPI_SUM dvalue = 1.0*MyPID; Comm.SumAll( &dvalue, dvalues, 1); // equivalent to MPI_Allreduce with MPI_SUM Comm.MaxAll( &dvalue, dvalues, 1); // equiavant to MPI_Scan with MPI_SUM dvalue = 1.0 * MyPID; Comm.ScanSum(&dvalue, &dvalue2, 1); cout << "On proc " << MyPID << " dvalue2 = " << dvalue2 << endl; delete[] dvalues; delete[] dvalues2; // ======================= // // Finalize MPI and return // // ----------------------- // #ifdef HAVE_MPI MPI_Finalize(); #endif return( EXIT_SUCCESS ); } /* main */ #else #include <stdlib.h> #include <stdio.h> #ifdef HAVE_MPI #include "mpi.h" #endif int main(int argc, char *argv[]) { #ifdef HAVE_MPI MPI_Init(&argc,&argv); #endif puts("Please configure Didasko with:\n" "--enable-epetra"); #ifdef HAVE_MPI MPI_Finalize(); #endif return 0; } #endif