module petsc_mod
#include "petsc/finclude/petscsys.h"
#include "petsc/finclude/petsc.h"
  implicit none
  
  private
  public :: init_petsc, stop_petsc
  public :: petsc_initialized
  public :: petsc_mpi_comm
  
  logical, save, protected :: petsc_initialized = .false.
  MPI_Comm, allocatable, save, protected :: petsc_mpi_comm
  
contains
  subroutine init_petsc
    use petscsys, only: PETSC_COMM_SELF, PETSC_NULL_CHARACTER
    
    PetscErrorCode :: ierr
    
    if (petsc_initialized) error stop 'init_petsc: module already initialized'
    
    call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
    if (ierr /= 0) error stop 'init_petsc: Cannot initialize PETSc'
    
    allocate(petsc_mpi_comm,source=PETSC_COMM_SELF)
    petsc_initialized = .true.
  end subroutine init_petsc
  
  subroutine stop_petsc
    PetscErrorCode :: ierr
    
    if (.not. petsc_initialized) error stop 'stop_petsc: uninitialized module'
    
    call PetscFinalize(ierr)
    if (ierr /= 0) error stop 'stop_petsc: Cannot finalize PETSc'
    
    petsc_initialized = .false.
  end subroutine stop_petsc
  
end module petsc_mod