2: static char help[] = "Introductory example that illustrates printing.\n\n";

  4: #include <petscsys.h>
  5: int main(int argc, char **argv)
  6: {
  7:   PetscMPIInt rank, size;

  9:   /*
 10:     Every PETSc program should begin with the PetscInitialize() routine.
 11:     argc, argv - These command line arguments are taken to extract the options
 12:                  supplied to PETSc and options supplied to MPI.
 13:     help       - When PETSc executable is invoked with the option -help,
 14:                  it prints the various options that can be applied at
 15:                  runtime.  The user can use the "help" variable to place
 16:                  additional help messages in this printout.
 17:   */
 19:   PetscInitialize(&argc, &argv, (char *)0, help);

 21:   /*
 22:      The following MPI calls return the number of processes
 23:      being used and the rank of this process in the group.
 24:    */
 25:   MPI_Comm_size(PETSC_COMM_WORLD, &size);
 26:   MPI_Comm_rank(PETSC_COMM_WORLD, &rank);

 28:   /*
 29:      Here we would like to print only one message that represents
 30:      all the processes in the group.  We use PetscPrintf() with the
 31:      communicator PETSC_COMM_WORLD.  Thus, only one message is
 32:      printed representng PETSC_COMM_WORLD, i.e., all the processors.
 33:   */
 34:   PetscPrintf(PETSC_COMM_WORLD, "Number of processors = %d, rank = %d\n", size, rank);

 36:   /*
 37:     Here a barrier is used to separate the two program states.
 38:   */
 39:   MPI_Barrier(PETSC_COMM_WORLD);

 41:   /*
 42:     Here we simply use PetscPrintf() with the communicator PETSC_COMM_SELF,
 43:     where each process is considered separately and prints independently
 44:     to the screen.  Thus, the output from different processes does not
 45:     appear in any particular order.
 46:   */

 48:   PetscPrintf(PETSC_COMM_SELF, "[%d] Jumbled Hello World\n", rank);

 50:   /*
 51:      Always call PetscFinalize() before exiting a program.  This routine
 52:        - finalizes the PETSc libraries as well as MPI
 53:        - provides summary and diagnostic information if certain runtime
 54:          options are chosen (e.g., -log_view).  See PetscFinalize()
 55:      manpage for more information.
 56:   */
 57:   PetscFinalize();
 58:   return 0;
 59: }

 61: /*TEST

 63:    test:

 65: TEST*/