Checkpointing is useful for saving the state of the simulator,
which allows one to interrupt and resume long simulations,
and also examine points of failure in detail.
— Command: save ckpt
Saves the current state of the production rules and nodes into
a checkpoint file ckpt. The checkpoint file can be loaded to
resume or replay a simulation later.
— Command: load ckpt
Loads a ipple checkpoint file into the simulator state.
Loading a checkpoint will not overwrite the current status of
the auto-save file, the previous autosave command will keep effect.
Loading a checkpoint, however, will close any open tracing streams.