SummationByPart's Diff_gv aliased function does ont document which part of the grid the computed derivative is valid

[Roland Haas]

Looking at the code in SummationByParts

  case (0) direction
    if ( bb(1) == 0 ) then
      il = 1 + gsize                                                                                        else
      ol = offset(1)
!$omp parallel workshare
      dvar(1+ol,:,:) = ( q(1,1) * var(1+ol,:,:) + q(2,1) * var(2+ol,:,:) ) * idel
      dvar(2+ol,:,:) = ( q(1,2) * var(1+ol,:,:) + q(3,2) * var(3+ol,:,:) ) * idel
!$omp end parallel workshare
      il = 3 + ol
    end if

seems to indicate that for non-boundary ends of a grid component (bb == 0) derivatives are computed only in the interior (from il = 1+gsize) while for boundary ends some (larger) area is valid.

This does not seem to be documented though, at least I could not find it in either documentation.tex nor interface.ccl.