Skip to content

radCAD and cadCAD

radCAD and cadCAD implement the same modelling paradigm, the Generalised Dynamical Systems model, but differ in API ergonomics and performance. This page explains the relationship so you can choose between them and move between them.

Shared foundations

Both frameworks describe a system as State Variables, Policy Functions, State Update Functions, and Partial State Update Blocks, and both produce results with the same simulation/subset/run/substep/timestep structure. Crucially, your model logic is portable: the policy and state update functions you write for cadCAD work in radCAD unchanged.

What radCAD changes

A leaner configuration API. cadCAD configures a run through several steps: config_sim, append_configs, an ExecutionContext, an Executor, and a global configs list. radCAD collapses this into three explicit classes: Model, Simulation, and Experiment. (Note the one rename: partial_state_update_blocks to state_update_blocks.)

Performance focus. radCAD runs faster, so you can fit more runs, larger sweeps, and bigger models in the same time. It exposes performance levers directly on the Engine: pluggable backends, a configurable deepcopy strategy, and substep dropping.

Extensibility. Hooks provide a stable API for extending behaviour without modifying the core, models are iterable for in-the-loop use, and System Parameters can be typed dataclasses.

Distributed execution. The Ray backend scales runs across a cluster.

Compatibility mode

For existing cadCAD codebases, radCAD ships a compatibility mode that re-exports the cadCAD configuration and execution API under radcad.compat.cadCAD.*, translating it into radCAD behind the scenes. Repoint your imports and an existing cadCAD model runs on radCAD with no further changes. It doesn't promise to cover every cadCAD option, but handles most models.

See Migrate from cadCAD for both the rewrite path and the compatibility-mode path.

Which should I use?

  • New project? Start with radCAD's native API; it's simpler and faster.
  • Existing cadCAD model? Use compatibility mode to run it on radCAD immediately, then migrate the configuration incrementally if you wish.
  • Learning the paradigm? The concepts are identical; cadCAD.education teaches both.