Architecture

ferroplan is data-oriented: states are bitsets of fact ids plus dense fluent vectors; operators are stored column-wise (CSR) so the hot loops stream contiguous memory and parallelize over immutable shared task data.

Pipeline:

1. Parse (parser, lexer) — PDDL domain + problem to an AST.
2. Ground (ground) — parallel per-action binding enumeration, DNF of preconditions, ADL expansion (forall/exists/when), negative-precondition compilation, relaxed-reachability pruning, CSR packing.
3. Search (search, heuristic) — weighted best-first (1·g + 5·h) with a delete-relaxation relaxed-plan heuristic; deferred (lazy) heuristic evaluation; parallel batch evaluation with order-preserving determinism.
4. Modes — classic FF, SGPlan-style partition+resolve, and PDDL3 pddl3 (Keyder–Geffner soft-goal compilation + anytime branch-and-bound).

Performance notes: an in-tree FxHash hasher, a compact relevant-only visited key, and size-gated parallelism (serial for small frontiers, capped threads) keep both small and large problems fast.