Registering Coordinates and Coordinate Properties

The APIs described in this section are deprecated, and will probably be phased out fairly soon. New code should use the APIs provided by the CoordBase thorn instead (this lives in the CactusBase arrangement).

Coordinate systems and their properties can be registered at any time with the flesh. The registration utilities for thorns providing coordinates are:

CCTK_CoordRegisterSystem

Assigns a coordinate system with a chosen name and dimension. For example, a 3-dimensional Cartesian coordinate system could be registered with the name cart3d using the call from C

int ierr;
int dim=3;
ierr = CCTK_CoordRegisterSystem(dim,"cart3d");

CCTK_CoordRegisterData

Defines a coordinate in a given coordinate system, with a given direction and name, and optionally associates it to a grid variable. The directions of the coordinates range from 1 to the dimension of the coordinate system. For example, to register the grid variable grid::y3d to have the coordinate name y in the cart3d system

int ierr;
int dir=2;
ierr = CCTK_CoordRegisterData(dir,"grid::y3d","y","cart3d");

CCTK_CoordRegisterRange

Assigns the global computational maximum and minimum for a coordinate on a grid hierarchy, that is in a cctkGH. At this time the maximum and minimum values have to be of type CCTK_REAL. For example, if the y coordinate for the cart3d system ranges between zero and one

CCTK_REAL lower=0;
CCTK_REAL upper=1;
int ierr;
ierr = CCTK_CoordRegisterRange(cctkGH, lower, upper, -1, "y", "cart3d");

Note that the API allows either the coordinate name or the direction to be used, so that the following is also valid

CCTK_REAL lower=0;
CCTK_REAL upper=1;
int ierr;
ierr = CCTK_CoordRegisterRange(cctkGH, lower, upper, 2, NULL, "cart3d");

CCTK_CoordRegisterPhysIndex

Implementing such things as symmetry properties for a grid leads to the need to know the details of the physical section of a grid. Such information is typically needed by I/O thorns. The following call illustrates how to register the indices 3 and 25 as supplying the physical range of the y coordinate in the cart3d system

int loweri=3;
int upperi=25;
int ierr;
ierr = CCTK_CoordRegisterPhysIndex(cctkGH, loweri, upperi, -1, "y", "cart3d");