Actual source code: ex4.c
1: static char help[] = "Introductory example that illustrates running PETSc on a subset of processes.\n\n";
3: #include <petscsys.h>
5: int main(int argc, char *argv[])
6: {
8: PetscMPIInt rank, size;
10: /* We must call MPI_Init() first, making us, not PETSc, responsible for MPI */
11: MPI_Init(&argc, &argv);if (ierr) return ierr;
12: #if defined(PETSC_HAVE_ELEMENTAL)
13: PetscElementalInitializePackage();if (ierr) return ierr;
14: #endif
15: /* We can now change the communicator universe for PETSc */
16: MPI_Comm_rank(MPI_COMM_WORLD, &rank);if (ierr) return ierr;
17: MPI_Comm_split(MPI_COMM_WORLD, rank%2, 0, &PETSC_COMM_WORLD);if (ierr) return ierr;
19: /*
20: Every PETSc routine should begin with the PetscInitialize() routine.
21: argc, argv - These command line arguments are taken to extract the options
22: supplied to PETSc and options supplied to MPI.
23: help - When PETSc executable is invoked with the option -help,
24: it prints the various options that can be applied at
25: runtime. The user can use the "help" variable place
26: additional help messages in this printout.
27: */
28: PetscInitialize(&argc, &argv, (char*) 0, help);
30: /*
31: The following MPI calls return the number of processes
32: being used and the rank of this process in the group.
33: */
34: MPI_Comm_size(PETSC_COMM_WORLD,&size);
35: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
37: /*
38: Here we would like to print only one message that represents
39: all the processes in the group. We use PetscPrintf() with the
40: communicator PETSC_COMM_WORLD. Thus, only one message is
41: printed representng PETSC_COMM_WORLD, i.e., all the processors.
42: */
43: PetscPrintf(PETSC_COMM_WORLD,"Number of processors = %d, rank = %d\n", size, rank);
45: /*
46: Always call PetscFinalize() before exiting a program. This routine
47: - finalizes the PETSc libraries as well as MPI
48: - provides summary and diagnostic information if certain runtime
49: options are chosen (e.g., -log_view). See PetscFinalize()
50: manpage for more information.
51: */
52: PetscFinalize();if (ierr) return ierr;
53: MPI_Comm_free(&PETSC_COMM_WORLD);if (ierr) return 0;
54: #if defined(PETSC_HAVE_ELEMENTAL)
55: PetscElementalFinalizePackage();if (ierr) return ierr;
56: #endif
57: /* Since we initialized MPI, we must call MPI_Finalize() */
58: MPI_Finalize();
59: return ierr;
60: }
62: /*TEST
64: test:
65: nsize: 5
66: args: -options_left no
67: filter: sort -b | grep -v saws_port_auto_selectcd
68: filter_output: sort -b
70: TEST*/