prepare_matrix_gather Subroutine

   subroutine prepare_matrix_gather(flow, ncomp, ncells, nlocal_comp)
      type(flow_mpi_t), intent(inout) :: flow
      integer, intent(in) :: ncomp, ncells
      integer, intent(out) :: nlocal_comp

      if (.not. allocated(flow%gather_matrix_sendbuf)) then
         call fatal_error('mpi_flow', 'owned matrix gather buffers are not initialized')
      end if

      if (ncomp > flow%gather_max_components) then
         call fatal_error('mpi_flow', 'owned matrix gather component count exceeds cached buffer size')
      end if

      if (sum(flow%gather_counts) /= ncells) then
         call fatal_error('mpi_flow', 'owned matrix gather cell count mismatch')
      end if

      nlocal_comp = flow%nlocal * ncomp
      flow%gather_matrix_counts = flow%gather_counts * ncomp
      flow%gather_matrix_displs = flow%gather_displs * ncomp
   end subroutine prepare_matrix_gather