1c4762a1bSJed Brown! 2c4762a1bSJed Brown! This introductory example illustrates running PETSc on a subset 3c4762a1bSJed Brown! of processes 4c4762a1bSJed Brown! 5c4762a1bSJed Brown! ----------------------------------------------------------------------- 6c4762a1bSJed Brown#include <petsc/finclude/petscsys.h> 7*c5e229c2SMartin Diehlprogram main 88c8af28eSPedro Ricardo C. Souza use petscmpi ! or mpi or mpi_f08 9c4762a1bSJed Brown use petscsys 10c4762a1bSJed Brown implicit none 11c4762a1bSJed Brown 12c4762a1bSJed Brown PetscErrorCode ierr 134a713726SSatish Balay PetscMPIInt rank, size, zero, two 14c4762a1bSJed Brown 15c4762a1bSJed Brown! We must call MPI_Init() first, making us, not PETSc, responsible 16c4762a1bSJed Brown! for MPI 17c4762a1bSJed Brown 18f8402805SBarry Smith PetscCallMPIA(MPI_Init(ierr)) 19c4762a1bSJed Brown 20c4762a1bSJed Brown! We can now change the communicator universe for PETSc 21c4762a1bSJed Brown 224a713726SSatish Balay zero = 0 23c4762a1bSJed Brown two = 2 24f8402805SBarry Smith PetscCallMPIA(MPI_Comm_rank(MPI_COMM_WORLD, rank, ierr)) 25f8402805SBarry Smith PetscCallMPIA(MPI_Comm_split(MPI_COMM_WORLD, mod(rank, two), zero, PETSC_COMM_WORLD, ierr)) 26c4762a1bSJed Brown 27c4762a1bSJed Brown! Every PETSc routine should begin with the PetscInitialize() 28c4762a1bSJed Brown! routine. 29c4762a1bSJed Brown 30d8606c27SBarry Smith PetscCallA(PetscInitialize(ierr)) 31c4762a1bSJed Brown 32c4762a1bSJed Brown! The following MPI calls return the number of processes being used 33c4762a1bSJed Brown! and the rank of this process in the group. 34c4762a1bSJed Brown 35f8402805SBarry Smith PetscCallMPIA(MPI_Comm_size(PETSC_COMM_WORLD, size, ierr)) 36f8402805SBarry Smith PetscCallMPIA(MPI_Comm_rank(PETSC_COMM_WORLD, rank, ierr)) 37c4762a1bSJed Brown 38c4762a1bSJed Brown! Here we would like to print only one message that represents all 39c4762a1bSJed Brown! the processes in the group. 404820e4eaSBarry Smith if (rank == 0) write (6, 100) size, rank 41c4762a1bSJed Brown100 format('No of Procs = ', i4, ' rank = ', i4) 42c4762a1bSJed Brown 43c4762a1bSJed Brown! Always call PetscFinalize() before exiting a program. This 44c4762a1bSJed Brown! routine - finalizes the PETSc libraries as well as MPI - provides 45c4762a1bSJed Brown! summary and diagnostic information if certain runtime options are 46c4762a1bSJed Brown! chosen (e.g., -log_view). See PetscFinalize() manpage for more 47c4762a1bSJed Brown! information. 48c4762a1bSJed Brown 49f8402805SBarry Smith PetscCallA(PetscFinalize(ierr)) 50f8402805SBarry Smith PetscCallMPIA(MPI_Comm_free(PETSC_COMM_WORLD, ierr)) 51c4762a1bSJed Brown 52c4762a1bSJed Brown! Since we initialized MPI, we must call MPI_Finalize() 53c4762a1bSJed Brown 54f8402805SBarry Smith PetscCallMPIA(MPI_Finalize(ierr)) 55c4762a1bSJed Brownend 56c4762a1bSJed Brown 57c4762a1bSJed Brown! 58c4762a1bSJed Brown!/*TEST 59c4762a1bSJed Brown! 60c4762a1bSJed Brown! test: 61c4762a1bSJed Brown! 62c4762a1bSJed Brown!TEST*/ 63