1c4762a1bSJed Brown static char help[] = "Introductory example that illustrates running PETSc on a subset of processes.\n\n"; 2c4762a1bSJed Brown 3c4762a1bSJed Brown /*T 4c4762a1bSJed Brown Concepts: introduction to PETSc; 5c4762a1bSJed Brown Concepts: process^subset set PETSC_COMM_WORLD 6c4762a1bSJed Brown Processors: 2 7c4762a1bSJed Brown 8c4762a1bSJed Brown Note that this example is not checking the error codes from the MPI calls with CHKERRQ() before PETSc is initialized 9c4762a1bSJed Brown and after PETSc is finalized. This is because the PETSc macro CHKERRQ() will not work in those circumstances. 10c4762a1bSJed Brown T*/ 11c4762a1bSJed Brown #include <petscsys.h> 12c4762a1bSJed Brown 13c4762a1bSJed Brown int main(int argc, char *argv[]) 14c4762a1bSJed Brown { 15c4762a1bSJed Brown PetscErrorCode ierr; 16c4762a1bSJed Brown PetscMPIInt rank, size; 17c4762a1bSJed Brown 18c4762a1bSJed Brown /* We must call MPI_Init() first, making us, not PETSc, responsible for MPI */ 19c4762a1bSJed Brown ierr = MPI_Init(&argc, &argv);if (ierr) return ierr; 20540e20f2SPierre Jolivet #if defined(PETSC_HAVE_ELEMENTAL) 21540e20f2SPierre Jolivet ierr = PetscElementalInitializePackage();if (ierr) return ierr; 22540e20f2SPierre Jolivet #endif 23c4762a1bSJed Brown /* We can now change the communicator universe for PETSc */ 24c4762a1bSJed Brown ierr = MPI_Comm_rank(MPI_COMM_WORLD, &rank);if (ierr) return ierr; 25c4762a1bSJed Brown ierr = MPI_Comm_split(MPI_COMM_WORLD, rank%2, 0, &PETSC_COMM_WORLD);if (ierr) return ierr; 26c4762a1bSJed Brown 27c4762a1bSJed Brown /* 28c4762a1bSJed Brown Every PETSc routine should begin with the PetscInitialize() routine. 29c4762a1bSJed Brown argc, argv - These command line arguments are taken to extract the options 30c4762a1bSJed Brown supplied to PETSc and options supplied to MPI. 31c4762a1bSJed Brown help - When PETSc executable is invoked with the option -help, 32c4762a1bSJed Brown it prints the various options that can be applied at 33c4762a1bSJed Brown runtime. The user can use the "help" variable place 34c4762a1bSJed Brown additional help messages in this printout. 35c4762a1bSJed Brown */ 36*b122ec5aSJacob Faibussowitsch CHKERRQ(PetscInitialize(&argc, &argv, (char*) 0, help)); 37c4762a1bSJed Brown 38c4762a1bSJed Brown /* 39c4762a1bSJed Brown The following MPI calls return the number of processes 40c4762a1bSJed Brown being used and the rank of this process in the group. 41c4762a1bSJed Brown */ 425f80ce2aSJacob Faibussowitsch CHKERRMPI(MPI_Comm_size(PETSC_COMM_WORLD,&size)); 435f80ce2aSJacob Faibussowitsch CHKERRMPI(MPI_Comm_rank(PETSC_COMM_WORLD,&rank)); 44c4762a1bSJed Brown 45c4762a1bSJed Brown /* 46c4762a1bSJed Brown Here we would like to print only one message that represents 47c4762a1bSJed Brown all the processes in the group. We use PetscPrintf() with the 48c4762a1bSJed Brown communicator PETSC_COMM_WORLD. Thus, only one message is 49c4762a1bSJed Brown printed representng PETSC_COMM_WORLD, i.e., all the processors. 50c4762a1bSJed Brown */ 515f80ce2aSJacob Faibussowitsch CHKERRQ(PetscPrintf(PETSC_COMM_WORLD,"Number of processors = %d, rank = %d\n", size, rank)); 52c4762a1bSJed Brown 53c4762a1bSJed Brown /* 54c4762a1bSJed Brown Always call PetscFinalize() before exiting a program. This routine 55c4762a1bSJed Brown - finalizes the PETSc libraries as well as MPI 56c4762a1bSJed Brown - provides summary and diagnostic information if certain runtime 57c4762a1bSJed Brown options are chosen (e.g., -log_view). See PetscFinalize() 58c4762a1bSJed Brown manpage for more information. 59c4762a1bSJed Brown */ 60*b122ec5aSJacob Faibussowitsch CHKERRQ(PetscFinalize();if (ierr) return ierr); 61*b122ec5aSJacob Faibussowitsch ierr = MPI_Comm_free(&PETSC_COMM_WORLD);if (ierr) return 0; 62540e20f2SPierre Jolivet #if defined(PETSC_HAVE_ELEMENTAL) 63540e20f2SPierre Jolivet ierr = PetscElementalFinalizePackage();if (ierr) return ierr; 64540e20f2SPierre Jolivet #endif 65c4762a1bSJed Brown /* Since we initialized MPI, we must call MPI_Finalize() */ 66c4762a1bSJed Brown ierr = MPI_Finalize(); 67c4762a1bSJed Brown return ierr; 68c4762a1bSJed Brown } 69c4762a1bSJed Brown 70c4762a1bSJed Brown /*TEST 71c4762a1bSJed Brown 72c4762a1bSJed Brown test: 73c4762a1bSJed Brown nsize: 5 74c4762a1bSJed Brown args: -options_left no 75c4762a1bSJed Brown filter: sort -b | grep -v saws_port_auto_selectcd 76c4762a1bSJed Brown filter_output: sort -b 77c4762a1bSJed Brown 78c4762a1bSJed Brown TEST*/ 79