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

  4: /*T
  5:    Concepts: introduction to PETSc;
  6:    Concepts: printing^in parallel
  7:    Processors: n
  8: T*/



 12:  #include <petscsys.h>
 13: int main(int argc,char **argv)
 14: {
 16:   PetscMPIInt    rank,size;

 18:   /*
 19:     Every PETSc routine should begin with the PetscInitialize() routine.
 20:     argc, argv - These command line arguments are taken to extract the options
 21:                  supplied to PETSc and options supplied to MPI.
 22:     help       - When PETSc executable is invoked with the option -help,
 23:                  it prints the various options that can be applied at
 24:                  runtime.  The user can use the "help" variable place
 25:                  additional help messages in this printout.
 26:   */
 27:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;

 29:   /*
 30:      The following MPI calls return the number of processes
 31:      being used and the rank of this process in the group.
 32:    */
 33:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 34:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 36:   /*
 37:      Here we would like to print only one message that represents
 38:      all the processes in the group.  We use PetscPrintf() with the
 39:      communicator PETSC_COMM_WORLD.  Thus, only one message is
 40:      printed representng PETSC_COMM_WORLD, i.e., all the processors.
 41:   */
 42:   PetscPrintf(PETSC_COMM_WORLD,"Number of processors = %d, rank = %d\n",size,rank);

 44:   /*
 45:     Here a barrier is used to separate the two program states.
 46:   */
 47:   MPI_Barrier(PETSC_COMM_WORLD);

 49:   /*
 50:     Here we simply use PetscPrintf() with the communicator PETSC_COMM_SELF,
 51:     where each process is considered separately and prints independently
 52:     to the screen.  Thus, the output from different processes does not
 53:     appear in any particular order.
 54:   */

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

 58:   /*
 59:      Always call PetscFinalize() before exiting a program.  This routine
 60:        - finalizes the PETSc libraries as well as MPI
 61:        - provides summary and diagnostic information if certain runtime
 62:          options are chosen (e.g., -log_view).  See PetscFinalize()
 63:      manpage for more information.
 64:   */
 65:   PetscFinalize();
 66:   return ierr;
 67: }


 70: /*TEST

 72:    test:

 74: TEST*/