silo_obj_CreateGroups Subroutine

    impure subroutine silo_obj_CreateGroups(this)
      !> Sets up silo groups for poor man's IO.
      ! Splits MPI ranks into groups of size nproc_node.
      ! Each group writes squentially to its own file.
      implicit none
      class(silo_obj),  intent(inout) :: this                                  !! A silo object
      !Work variables
      integer :: ierr,n

      ! Set the IDs of the different silo groups
      allocate(this%group_ids(this%parallel%nproc))

      do n=1,this%parallel%nproc
        this%group_ids(n)=ceiling(real(n,wp)/real(this%nproc_node,wp))
      end do

      ! Create a new MPI communicator for each silo group
      call MPI_COMM_SPLIT(this%parallel%comm%g,this%group_ids(this%parallel%rank%mine),0,this%silo_comm,ierr)

      ! Return rank within this communicator
      call MPI_COMM_RANK (this%silo_comm,this%silo_rank,ierr)

      ! Adjust rank numbering Fortran style
      this%silo_rank=this%silo_rank+1

      return
    end subroutine silo_obj_CreateGroups