/*$Id: ex2.c,v 1.9 2000/01/11 20:59:51 bsmith Exp bsmith $*/ /* Program usage: mpirun ex2 [-help] [all PETSc options] */ static char help[] = "Synchronized printing.\n\n"; /*T Concepts: Introduction to PETSc; Concepts: printing^synchronized Concepts: printing^parallel Concepts: printf^synchronized Concepts: printf^parallel Processors: n T*/ #include "petsc.h" int main(int argc,char **argv) { int ierr,rank,size; /* Every PETSc routine should begin with the PetscInitialize() routine. argc, argv - These command line arguments are taken to extract the options supplied to PETSc and options supplied to MPI. help - When PETSc executable is invoked with the option -help, it prints the various options that can be applied at runtime. The user can use the "help" variable place additional help messages in this printout. */ ierr = PetscInitialize(&argc,&argv,PETSC_NULL,help);CHKERRA(ierr); /* The following MPI calls return the number of processes being used and the rank of this process in the group. */ ierr = MPI_Comm_size(PETSC_COMM_WORLD,&size);CHKERRA(ierr); ierr = MPI_Comm_rank(PETSC_COMM_WORLD,&rank);CHKERRA(ierr); /* Here we would like to print only one message that represents all the processes in the group. We use PetscPrintf() with the communicator PETSC_COMM_WORLD. Thus, only one message is printed representng PETSC_COMM_WORLD, i.e., all the processors. */ ierr = PetscPrintf(PETSC_COMM_WORLD,"Number of processors = %d, rank = %d\n",size,rank);CHKERRA(ierr); /* Here we would like to print info from each process such that output from process "n" appears after output from process "n-1". To do this we use a combination of PetscSynchronizedPrintf() and PetscSynchronizedFlush() with the communicator PETSC_COMM_WORLD. All the processes print the message, one after another. PetscSynchronizedFlush() indicates that the current process in the given communicator has concluded printing, so that the next process in the communicator can begin printing to the screen. */ ierr = PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] Synchronized Hello World.\n",rank);CHKERRA(ierr); ierr = PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] Synchronized Hello World - Part II.\n",rank);CHKERRA(ierr); ierr = PetscSynchronizedFlush(PETSC_COMM_WORLD);CHKERRA(ierr); /* Here a barrier is used to separate the two states. */ ierr = MPI_Barrier(PETSC_COMM_WORLD);CHKERRA(ierr); /* Here we simply use PetscPrintf() with the communicator PETSC_COMM_SELF (where each process is considered separately). Thus, this time the output from different processes does not appear in any particular order. */ ierr = PetscPrintf(PETSC_COMM_SELF,"[%d] Jumbled Hello World\n",rank);CHKERRA(ierr); /* Always call PetscFinalize() before exiting a program. This routine - finalizes the PETSc libraries as well as MPI - provides summary and diagnostic information if certain runtime options are chosen (e.g., -log_summary). See PetscFinalize() manpage for more information. */ ierr = PetscFinalize();CHKERRA(ierr); return 0; }