1 static char help[] = "Introductory example that illustrates printing.\n\n";
2
3 #include <petscsys.h>
main(int argc,char ** argv)4 int main(int argc, char **argv)
5 {
6 PetscMPIInt rank, size;
7
8 /*
9 Every PETSc program should begin with the PetscInitialize() routine.
10 argc, argv - These command line arguments are taken to extract the options
11 supplied to PETSc and options supplied to MPI.
12 help - When PETSc executable is invoked with the option -help,
13 it prints the various options that can be applied at
14 runtime. The user can use the "help" variable to place
15 additional help messages in this printout.
16 */
17 PetscFunctionBeginUser;
18 PetscCall(PetscInitialize(&argc, &argv, NULL, help));
19
20 /*
21 The following MPI calls return the number of processes
22 being used and the rank of this process in the group.
23 */
24 PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
25 PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
26
27 /*
28 Here we would like to print only one message that represents
29 all the processes in the group. We use PetscPrintf() with the
30 communicator PETSC_COMM_WORLD. Thus, only one message is
31 printed representng PETSC_COMM_WORLD, i.e., all the processors.
32 */
33 PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Number of processors = %d, rank = %d\n", size, rank));
34
35 /*
36 Here a barrier is used to separate the two program states.
37 */
38 PetscCallMPI(MPI_Barrier(PETSC_COMM_WORLD));
39
40 /*
41 Here we simply use PetscPrintf() with the communicator PETSC_COMM_SELF,
42 where each process is considered separately and prints independently
43 to the screen. Thus, the output from different processes does not
44 appear in any particular order.
45 */
46
47 PetscCall(PetscPrintf(PETSC_COMM_SELF, "[%d] Jumbled Hello World\n", rank));
48
49 /*
50 Always call PetscFinalize() before exiting a program. This routine
51 - finalizes the PETSc libraries as well as MPI
52 - provides summary and diagnostic information if certain runtime
53 options are chosen (e.g., -log_view). See PetscFinalize()
54 manpage for more information.
55 */
56 PetscCall(PetscFinalize());
57 return 0;
58 }
59
60 /*TEST
61
62 test:
63
64 TEST*/
65