Adding new grid functions

A grid function is a discretization of a variable (a "field") which is defined on every point of a given grid. Examples are the components of the metric tensor in GR, or the rest-mass density of a fluid which is defined in all cells within a given domain.

Instructions to add a new grid function for the field gf

• add the identifier gf to an enumeration in the fld namespace

• (optionally) add gf to a list passed to GridInitialData::gridFunction()

• (optionally) add gf to a list passed to GridOutputWriter::gridFunction()

• (optionally) add gf to a list passed to MoLIntegrator::keepConstant() or to MoLIntegrator::keepEvolved()

• to be able to access gf's values using gf(m,n), add emitField(gf) inside the declaration.

You will also need to:

• (optionally) add emitDerivative_r(gf) and/or emitDerivative_rr(gf) (in case you need the spatial derivatives of the field).

• (optionally) define the RHS of the evolution equation Real eq_gf_t( Int m, Int n ) and then assign the RHS to gf_t in BimetricEvolve::integStep_Prepare.

• setup the behavior of 'gf' at boundaries in the IntegFace interface methods IntegFace::applyLeftBoundaryCondition and IntegFace::applyRightBoundaryCondition.