Comment (by Roland Haas):

Having approved and merged I now (naturally) notice this in cGH:

  /* unused */
  int *cctk_to;
  int *cctk_from;

which could have been used instead of tile_min and tile_max.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2446/cactus-new-cgh-fields-tile_min-tile_max