Actual source code: ex1.c
2: static char help = "Introductory example that illustrates printing.\n\n";
5: Concepts: introduction to PETSc;
6: Concepts: printing^in parallel
7: Processors: n
12: #include <petscsys.h>
13: int main(int argc,char **argv)
16: PetscMPIInt rank,size;
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.
27: PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
30: The following MPI calls return the number of processes
31: being used and the rank of this process in the group.
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.
42: PetscPrintf(PETSC_COMM_WORLD,"Number of processors = %d, rank = %d\n",size,rank);
45: Here a barrier is used to separate the two program states.
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.
56: PetscPrintf(PETSC_COMM_SELF,"[%d] Jumbled Hello World\n",rank);
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_summary). See PetscFinalize()
63: manpage for more information.
66: return ierr;