Accessing

multiple fields (for future multi-field support)

class CoupledIC : public pfc::FieldModifier {
public:
  void apply(pfc::Model& model, double time) override {
    // Current: single field via get_field_name()
    auto& density = model.get_real_field(get_field_name());
 
    // Future: access multiple fields
    // auto& temperature = model.get_real_field("temperature");
 
    // Set coupled initial state
    std::fill(density.begin(), density.end(), 0.5);
  }
};

Usage in Simulator:

• Initial conditions: Applied once before time integration via Simulator::add_initial_condition()
• Boundary conditions: Applied every time step (or at intervals) via Simulator::add_boundary_condition()
• Application order: ICs first, then BCs, in the order added

Performance Considerations:

• Boundary conditions are in the hot path (applied every step)
• Minimize allocations in apply()
• Consider caching computed values if expensive
• Use direct indexing (avoid coordinate transformations when possible)

Known Limitations:

• Currently designed for single-field access via get_field_name()
• TODO: Support modifying multiple fields in one modifier (see TODO comment)
• No built-in support for parallel reduction operations

Note

The time parameter allows implementing time-dependent boundary conditions, but most initial conditions ignore it (t=0 at IC application)

Warning

Modifiers have direct mutable access to model state. Ensure your apply() implementation maintains physical correctness and doesn't violate model invariants.

See also

Model::get_real_field() for field access

Model::get_complex_field() for k-space operations

Simulator::add_initial_condition() for IC registration

Simulator::add_boundary_condition() for BC registration

initial_conditions/ for built-in IC implementations

boundary_conditions/ for built-in BC implementations