Performance

ferroplan is data-oriented by design, but a fast layout only pays off if the hot paths don't do redundant work. This session landed three optimizations that turn instances which were previously un-finishable or un-scoreable into routine ones — each measured, each correctness-preserving.

Grounding — static-precondition parameter-domain restriction

Untyped domains used to enumerate the full cartesian product of every parameter and string-match almost all of it away. gripper's pick(?obj ?room ?gripper) was generating 154³ ≈ 3.6M bindings per action and discarding 99.98% of them.

The fix restricts each parameter's domain by its static unary preconditions before enumerating — so ?gripper only ever ranges over the grippers, not every object — collapsing the blowup at the source. The produced ground ops are bit-identical; only the work to find them shrinks.

(crates/ferroplan/src/ground.rs)

EHC work cap — scaled by operator count

Enforced hill-climbing carried a fixed work cap. Large-but-easy instances would exhaust it and bail into the unpruned best-first arm, doing millions of evaluations on a problem EHC's near-greedy descent would have walked straight through. Scaling the cap by operator count lets those instances finish in the cheap arm; the heuristic is untouched and the plan stays valid.

Small and genuinely-hard instances are unchanged — they never hit the old cap, or they legitimately need the fallback (deep plateaus are still on the backlog; see perf-notes). (crates/ferroplan/src/search.rs)

Metric optimizer — monotone numeric-term folding

The metric optimizer drives an anytime branch-and-bound over the :metric. Previously it could only see the preference-violation terms, so on domains whose metric also charges a monotone numeric quantity — like rovers' (sum-traverse-cost) — it scored a bogus 0: the numeric part was invisible and the search had nothing to optimize.

It now folds monotone numeric metric terms into total-cost, so it optimizes the full metric. rovers went from un-scoreable to a real metric of 935.3 — which is what unlocked the sixth IPC-5 domain (see Metric quality). (crates/ferroplan/src/pddl3.rs)

How the wins are measured

Two harnesses, with a deliberate division of labor:

• cargo bench -p ferroplan --bench planning (criterion) is the reference for wall-time deltas. Its solve/ group covers small typed/numeric instances (gripper, blocks, rovers) and solve_large/ covers the scale-sensitive grounding- and search-dominated cases. Criterion is the only noise-robust timer on a loaded machine.
• benchmarks/perf.py reports deterministic evaluated-state counts. A constant-factor win leaves these bit-identical (proof the work, not the strategy, shrank); a search-strategy win changes them and must be re-baselined.

Raw wall-clock here is noise-dominated below ~15% — the same binary has ranged 11.5–14 s under background load — so treat any single timed run with suspicion and let criterion arbitrate.

The ranked backlog of remaining optimizations (generation-counter Scratch reset, preferred-operator best-first, apply_into clone-on-survival) lives in docs/perf-notes.md, along with the methodology caveats learned the hard way (notably: atos mis-attributes inlined hot code on optimized builds — trust the de-noised profile, not the raw top symbols).