Contents
Alternation open list
alternates between several open lists.
alt(sublists, boost=0)
sublists (list of OpenList): sub open lists
boost (int): boost value for sub-open-lists that are restricted to preferred operator nodes
Preferred operators: Preferred operators are only taken from sub-open-lists that do not consider the evaluated state a dead end.
Dead ends: A state is considered a dead end if either all alternated open lists agree that it is a dead end or at least one reliable open list considers it a dead end. A state is never inserted into a sub-open-list that considers it a dead end.
Note: The treatment of dead ends is different from the one described in the technical report "The More, the Merrier: Combining Heuristic Estimators for Satisficing Planning (Extended Version)" (Department of Computer Science at Freiburg University, No. 258, 2010)
Pareto open list
Selects one of the Pareto-optimal (regarding the sub-evaluators) entries for removal.
pareto(evals, pref_only=false, state_uniform_selection=false)
evals (list of ScalarEvaluator): scalar evaluators
pref_only (bool): insert only nodes generated by preferred operators
state_uniform_selection (bool): When removing an entry, we select a non-dominated bucket and return its oldest entry. If this option is false, we select uniformly from the non-dominated buckets; if the option is true, we weight the buckets with the number of entries.
Standard open list
Standard open list that uses a single evaluator
single(eval, pref_only=false)
eval (ScalarEvaluator): scalar evaluator
pref_only (bool): insert only nodes generated by preferred operators
Bucket-based open list
Bucket-based open list implementation that uses a single evaluator
single_buckets(eval, pref_only=false)
eval (ScalarEvaluator): scalar evaluator
pref_only (bool): insert only nodes generated by preferred operators
Tie-breaking open list
tiebreaking(evals, pref_only=false, unsafe_pruning=true)
evals (list of ScalarEvaluator): scalar evaluators
pref_only (bool): insert only nodes generated by preferred operators
unsafe_pruning (bool): allow unsafe pruning when the main evaluator regards a state a dead end