A landmark factory specification is either a newly created instance or a landmark factory that has been defined previously. This page describes how one can specify a new landmark factory instance. For re-using landmark factories, see Landmark Predefinitions.

This feature type can be bound to variables using let(variable_name, variable_definition, expression) where expression can use variable_name. Predefinitions using --evaluator, --heuristic, and --landmarks are automatically transformed into let-expressions but are deprecated.

Exhaustive Landmarks

Exhaustively checks for each fact if it is a landmark.This check is done using relaxed planning.

lm_exhaust(verbosity=normal, only_causal_landmarks=false)

Supported language features:

h^m Landmarks

The landmark generation method introduced by Keyder, Richter & Helmert (ECAI 2010).

lm_hm(m=2, conjunctive_landmarks=true, verbosity=normal, use_orders=true)

Supported language features:

Merged Landmarks

Merges the landmarks and orderings from the parameter landmarks

lm_merged(lm_factories, verbosity=normal)

Precedence: Fact landmarks take precedence over disjunctive landmarks, orderings take precedence in the usual manner (gn > nat > reas > o_reas).

Note: Does not currently support conjunctive landmarks

Supported language features:

HPS Orders

Adds reasonable orders described in the following paper

lm_reasonable_orders_hps(lm_factory, verbosity=normal)

Obedient-reasonable orders: Hoffmann et al. (2004) suggest obedient-reasonable orders in addition to reasonable orders. Obedient-reasonable orders were later also used by the LAMA planner (Richter and Westphal, 2010). They are "reasonable orders" under the assumption that all (non-obedient) reasonable orders are actually "natural", i.e., every plan obeys the reasonable orders. We observed experimentally that obedient-reasonable orders have minimal effect on the performance of LAMA (Büchner et al., 2023) and decided to remove them in issue1089.

Supported language features:

RHW Landmarks

The landmark generation method introduced by Richter, Helmert and Westphal (AAAI 2008).

lm_rhw(disjunctive_landmarks=true, verbosity=normal, use_orders=true, only_causal_landmarks=false)

Supported language features:

Zhu/Givan Landmarks

The landmark generation method introduced by Zhu & Givan (ICAPS 2003 Doctoral Consortium).

lm_zg(verbosity=normal, use_orders=true)

Supported language features:

FastDownward: Doc/LandmarkFactory (last edited 2024-01-11 22:26:37 by XmlRpcBot)