1c4762a1bSJed Brown 2c4762a1bSJed Brown static char help[] = "Synchronized printing.\n\n"; 3c4762a1bSJed Brown 4c4762a1bSJed Brown #include <petscsys.h> 5c4762a1bSJed Brown int main(int argc,char **argv) 6c4762a1bSJed Brown { 7c4762a1bSJed Brown PetscMPIInt rank,size; 8c4762a1bSJed Brown 9c4762a1bSJed Brown /* 10c4762a1bSJed Brown Every PETSc program should begin with the PetscInitialize() routine. 11c4762a1bSJed Brown argc, argv - These command line arguments are taken to extract the options 12c4762a1bSJed Brown supplied to PETSc and options supplied to MPI. 13c4762a1bSJed Brown help - When PETSc executable is invoked with the option -help, 14c4762a1bSJed Brown it prints the various options that can be applied at 15c87e60e8SJose E. Roman runtime. The user can use the "help" variable to place 16c4762a1bSJed Brown additional help messages in this printout. 17c4762a1bSJed Brown */ 18*327415f7SBarry Smith PetscFunctionBeginUser; 199566063dSJacob Faibussowitsch PetscCall(PetscInitialize(&argc,&argv,NULL,help)); 20c4762a1bSJed Brown 21c4762a1bSJed Brown /* 22c4762a1bSJed Brown The following MPI calls return the number of processes 23c4762a1bSJed Brown being used and the rank of this process in the group. 24c4762a1bSJed Brown */ 259566063dSJacob Faibussowitsch PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD,&size)); 269566063dSJacob Faibussowitsch PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD,&rank)); 27c4762a1bSJed Brown 28c4762a1bSJed Brown /* 29c4762a1bSJed Brown Here we would like to print only one message that represents 30c4762a1bSJed Brown all the processes in the group. We use PetscPrintf() with the 31c4762a1bSJed Brown communicator PETSC_COMM_WORLD. Thus, only one message is 32c4762a1bSJed Brown printed representing PETSC_COMM_WORLD, i.e., all the processors. 33c4762a1bSJed Brown */ 349566063dSJacob Faibussowitsch PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Number of processors = %d, rank = %d\n",size,rank)); 35c4762a1bSJed Brown /* 36c4762a1bSJed Brown Here we would like to print info from each process, such that 37c4762a1bSJed Brown output from process "n" appears after output from process "n-1". 38c4762a1bSJed Brown To do this we use a combination of PetscSynchronizedPrintf() and 39c4762a1bSJed Brown PetscSynchronizedFlush() with the communicator PETSC_COMM_WORLD. 40c4762a1bSJed Brown All the processes print the message, one after another. 41c4762a1bSJed Brown PetscSynchronizedFlush() indicates that the current process in the 42c4762a1bSJed Brown given communicator has concluded printing, so that the next process 43c4762a1bSJed Brown in the communicator can begin printing to the screen. 44c4762a1bSJed Brown */ 459566063dSJacob Faibussowitsch PetscCall(PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] Synchronized Hello World.\n",rank)); 469566063dSJacob Faibussowitsch PetscCall(PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] Synchronized Hello World - Part II.\n",rank)); 479566063dSJacob Faibussowitsch PetscCall(PetscSynchronizedFlush(PETSC_COMM_WORLD,PETSC_STDOUT)); 48c4762a1bSJed Brown /* 49c4762a1bSJed Brown Here a barrier is used to separate the two states. 50c4762a1bSJed Brown */ 519566063dSJacob Faibussowitsch PetscCallMPI(MPI_Barrier(PETSC_COMM_WORLD)); 52c4762a1bSJed Brown 53c4762a1bSJed Brown /* 54c4762a1bSJed Brown Here we simply use PetscPrintf() with the communicator PETSC_COMM_SELF 55c4762a1bSJed Brown (where each process is considered separately). Thus, this time the 56c4762a1bSJed Brown output from different processes does not appear in any particular order. 57c4762a1bSJed Brown */ 589566063dSJacob Faibussowitsch PetscCall(PetscPrintf(PETSC_COMM_SELF,"[%d] Jumbled Hello World\n",rank)); 59c4762a1bSJed Brown 60c4762a1bSJed Brown /* 61c4762a1bSJed Brown Always call PetscFinalize() before exiting a program. This routine 62c4762a1bSJed Brown - finalizes the PETSc libraries as well as MPI 63c4762a1bSJed Brown - provides summary and diagnostic information if certain runtime 64c4762a1bSJed Brown options are chosen (e.g., -log_view). 65c4762a1bSJed Brown See the PetscFinalize() manpage for more information. 66c4762a1bSJed Brown */ 679566063dSJacob Faibussowitsch PetscCall(PetscFinalize()); 68b122ec5aSJacob Faibussowitsch return 0; 69c4762a1bSJed Brown } 70c4762a1bSJed Brown 71c4762a1bSJed Brown /*TEST 72c4762a1bSJed Brown 73c4762a1bSJed Brown test: 74c4762a1bSJed Brown 75c4762a1bSJed Brown TEST*/ 76