Shift Vector

It is only relatively recently that numerical relativists have started to use a shift vector in 3D calculations, and previously, to save space, storage for the shift vector was not allocated. If the parameter initial_shift is set to none, ADMBase does not allocate storage for betax, betay, betaz and sets the grid scalar shift_state to 0. In all other cases the shift_state parameter is set to 1.

Thorns using the shift should always check that storage for the shift is allocated before using it.