JvarMapInterface

The JvarMapKernelInterface and JvarMapIntegratedBCInterface interface classes (veneers), for Kernels and integrated boundary conditions respectively, provide a mapping from the value of the jvar parameter passed into computeQpOffDiagJacobian method to

  • an index into the _coupled_moose_vars vector

  • a coupledValue(var_name, i) index i for a given var_name using the getParameterJvarMap method

This class is useful in conjunction with DerivativeMaterialInterface, where vectors of material property derivatives with respect to coupled variables are pulled in.

Mapping jvar to a _coupled_moose_vars index

In case an index into the vector of all coupled variables for the current object (_coupled_moose_vars vector) is requested


  unsigned int cvar = mapJvarToCvar(jvar);

should be used. When called from computeQpOffDiagJacobian with the method's jvar parameter passed in, mapJvarToCvar is guaranteed to return a valid index into _coupled_moose_vars. The off diagonal Jacobian method is only called for variable numbers that are found in the _coupled_moose_vars vector, and those are mapped in the global jvar map which the JvarMapInterface classes construct automatically.

Mapping jvar to a coupledValue(parameter_name, index) index

In case an index is requested that can be passed into coupledValue for a given input parameter name (vector variable coupling), a parameter specific map has to be obtained. This map can be build and fetched (by reference) in the initializer list of the class constructor using


  _myvar_map(getParameterJvarMap("myvar"))

where the class should have a member


  const JvarMap & _myvar_map;

and an input parameter


  params.addCoupledValue("myvar", "Vector of coupled variables");

The index into a specific coupled variable vector for a given jvar can then be obtained using


  int pvar = mapJvarToCvar(jvar, _myvar_map);
  if (pvar >= 0)
  {
    // jvar points to an entry in the myvar vector
  }

A negative return value indicates that the jvar value does not point to a variable in the couple variable vector corresponding to the mapped parameter.