The evaluation spine's run #
The run theorem of DescriptiveComplexity.Draw.Data.evalRule: from the
checkpoint before the first variable to the checkpoint after the last, one
abstract sub-machinery run per position – the spine contributes only its
dispatches and walk-backs, so it needs to know nothing about a machinery's
internals beyond its entry phase, its control transform and its tape
transform.
The run comes with its cost (eval_reachesIn): one machinery's width plus
its dispatch and its walk back, once per variable. eval_run is it with the
budget forgotten.
The two boundary steps at the last checkpoint – erase the marker rightwards
into the sweep's advance, or into the post-sweep reset at the ltp cell –
are separate single-step lemmas, consumed by the outer composition.
The spine's run, on a clock: from the checkpoint before the first variable at the marker to the checkpoint after the last, one machinery run per position, each with its dispatch and its walk back.
Dependency graph
The spine's run, the budget forgotten: what a space-bounded caller reads, its machineries' runs carrying no count.