Affiliations: Dipartimento di Ingegneria dell'Informazione, Università degli Studi di Brescia, Via Branze 38, I-25123 Brescia, Italy. {gerevini,saetti}@ing.unibs.it | Free University of Bozen – Bolzano, Viale Ratisbona 16, I-39042 Bressanone, Italy. [email protected]
Note: [] Address for correspondence: Dipartimento di Ingegneria dell'Informazione, Università degli Studi di Brescia, Via Branze 38, I-25123 Brescia, Italy
Abstract: Planning through local search and action graphs is a powerful approach to fully-automated planning which is implemented in the well-known LPG planner. The approach is based on a stochastic local search procedure exploring a space of partial plans and several heuristic features with different possible options. In this paper, we experimentally analyze the most important of them, with the goal of understanding and evaluating their impact on the performance of LPG, and of identifying default settings that work well on a large class of problems. In particular, we analyze several heuristic techniques for (a) evaluating the search neighborhood, (b) defining/restricting the search neighborhood, (c) selecting the next plan flaw to handle, (d) setting the “noise” parameter randomizing the search, and (e) computing reachability information that can be exploited by the heuristic functions used to evaluate the neighborhood elements. Some of these techniques were introduced in previous work on LPG, while others are new. Additional experimental results indicate that the current version of LPG using the identified best heuristic techniques as the default settings is competitive with the winner of the last (2008) International Planning Competition.
