3+1 Variables

It is highly recommended that all thorns which inherit from ADMBase check the value of the metric_type parameter in a routine scheduled at CCTK_PARAMCHECK and signal an error if the metric type is not recognised. (See the source file ParamCheck.c in any of the thorns in the CactusEinstein arrangement for examples of this, and note that the PARAMCHECK time bin is a good place to check for illegal/bad combinations of parameters, and also to inform the user of any relevent details of the parameters she has chosen).

ADMBase allocates one timelevel of memory for all variables, except the shift, which is only allocated if the initial_shift parameter is set to a value other than `none'. (`none' is the default.) The state of the shift storage is indicated by the shift_state grid scalar. This is 1 if there is storage for the shift, and 0 otherwise.

The thorn provides, on request, initial data to set the metric and extrinsic curvature to flat space in cartesian coordinates, to set the initial lapse to one and the initial shift to zero.