Actual source code: ex2.c
2: static char help[] = "Synchronized 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: */
18: PetscInitialize(&argc,&argv,NULL,help);
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: MPI_Comm_size(PETSC_COMM_WORLD,&size);
25: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
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 representing PETSC_COMM_WORLD, i.e., all the processors.
32: */
33: PetscPrintf(PETSC_COMM_WORLD,"Number of processors = %d, rank = %d\n",size,rank);
34: /*
35: Here we would like to print info from each process, such that
36: output from process "n" appears after output from process "n-1".
37: To do this we use a combination of PetscSynchronizedPrintf() and
38: PetscSynchronizedFlush() with the communicator PETSC_COMM_WORLD.
39: All the processes print the message, one after another.
40: PetscSynchronizedFlush() indicates that the current process in the
41: given communicator has concluded printing, so that the next process
42: in the communicator can begin printing to the screen.
43: */
44: PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] Synchronized Hello World.\n",rank);
45: PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] Synchronized Hello World - Part II.\n",rank);
46: PetscSynchronizedFlush(PETSC_COMM_WORLD,PETSC_STDOUT);
47: /*
48: Here a barrier is used to separate the two states.
49: */
50: MPI_Barrier(PETSC_COMM_WORLD);
52: /*
53: Here we simply use PetscPrintf() with the communicator PETSC_COMM_SELF
54: (where each process is considered separately). Thus, this time the
55: output from different processes does not appear in any particular order.
56: */
57: PetscPrintf(PETSC_COMM_SELF,"[%d] Jumbled Hello World\n",rank);
59: /*
60: Always call PetscFinalize() before exiting a program. This routine
61: - finalizes the PETSc libraries as well as MPI
62: - provides summary and diagnostic information if certain runtime
63: options are chosen (e.g., -log_view).
64: See the PetscFinalize() manpage for more information.
65: */
66: PetscFinalize();
67: return 0;
68: }
70: /*TEST
72: test:
74: TEST*/