@misc{Clausecker, author = {Clausecker, Robert}, title = {The Quality of Heuristic Functions for IDA*}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-78489}, abstract = {The aim of this thesis is to deepen our understand of how IDA* heuristics influence the number of nodes expanded during search. To this end, we develop Korf's formula for the number of expanded nodes into a heuristic quality η which expresses the quality of a heuristic function as a constant factor on the number of expanded nodes, independent of a particular problem instance. We proceed to show how to compute η for some common kinds of heuristics and how to estimate η by means of a random sample for arbitrary heuristics. Using the value of η for some concrete examples, we then inspect for which parts of the search space the values of h(v) are particularly critical to the performance of the heuristic, allowing us to build better heuristics for future problems. This report originally appeared as a master thesis at Humboldt University of Berlin.}, language = {en} } @misc{Clausecker, author = {Clausecker, Robert}, title = {Notes on the Construction of Pattern Databases}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-65586}, abstract = {This report aims to explain and extend pattern databases as a tool in finding optimal solutions to combination puzzles. Using sliding tile puzzles as an example, an overview over techniques to construct and use pattern databases is given, analysed, and extended. As novel results, zero aware additive pattern databases and PDB catalogues are introduced. This report originally appeared as a bachelor thesis at Humboldt University of Berlin under the title Notes on the Construction of Tablebases.}, language = {en} }