! Introductory example that illustrates printing: Fortran Example
#include <petsc/finclude/petscsys.h>
program main
  use petscsys

  implicit none
  PetscErrorCode    :: ierr
  PetscMPIInt       :: rank, size
  character(len=80) :: outputString

  ! Every PETSc routine should begin with the PetscInitialize() routine.
  PetscCallA(PetscInitialize(ierr))

  ! We can now change the communicator universe for PETSc
  PetscCallMPIA(MPI_Comm_size(PETSC_COMM_WORLD, size, ierr))
  PetscCallMPIA(MPI_Comm_rank(PETSC_COMM_WORLD, rank, 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.

  write (outputString, *) 'No of Processors = ', size, ', rank = ', rank, '\n'
  PetscCallA(PetscPrintf(PETSC_COMM_WORLD, outputString, ierr))

  ! Here a barrier is used to separate the two program states.
  PetscCallMPIA(MPI_Barrier(PETSC_COMM_WORLD, ierr))

  ! Here we simply use PetscPrintf() with the communicator PETSC_COMM_SELF,
  ! where each process is considered separately and prints independently
  ! to the screen.  Thus, the output from different processes does not
  ! appear in any particular order.

  write (outputString, *) rank, 'Jumbled Hello World\n'
  PetscCallA(PetscPrintf(PETSC_COMM_SELF, outputString, 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_view).  See PetscFinalize()
  !  manpage for more information.

  PetscCallA(PetscFinalize(ierr))

end program main
!/*TEST
!
!   test:
!
!TEST*/