Abstract
This paper gives an algorithm for determining the setU 0(Θ) of all maximal independent subsets of a finite poset Θ=(A, O), based on a (complex) Θ-induced arrangement ofU 0(Θ) as a rooted tree. By this procedure, all essential data manipulations can be restricted to certain bipartite graphs, thereby leading to a computation complexity not exceedingO(|A|·|\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{O} \)) per maximal independent subset obtained (where\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{O} \) denotes the immediate ordering relations). In fact, an intensive study of examples (with |A| ranging from 10–200) even showed almost total independence of external parameters such as |A|, |O| or |\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{O} \)| and at the same time led to considerably low computation times. Thus, in particular, the application of standard graph-theoretical methods to the associated comparability graph of Θ would no longer seem a reasonable approach to the considered problem.
Zusammenfassung
Es wird ein Algorithmus entwickelt, welcher das SystemU 0(Θ) aller unabhängigen Mengen einer endlichen Ordnung Θ=(A, O) generiert, und zwar aufbauend auf einer (komplizierten) Darstellung vonU 0(Θ) als Wurzelbaum. Hierbei können alle wesentlichen Datenmanipulationen innerhalb zugehöriger bipartiter Graphen durchgeführt werden, woraus eine Komplexität von höchstensO(|A|·|\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{O} \)) pro gefundener maximal unabhängiger Menge resultiert (\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{O} \) bezeichnet die unmittelbaren Ordnungs-relationen). Tatsächlich zeigte eine intensive Untersuchung von Beispielen mit Trägermengen der Kardinalität 10 bis 200 nahezu überhaupt keine Abhängigkeit der durchschnittlichen Rechenzeit von externen Parametern (wie |A|, |O| und |\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{O} \)|). Zudem ergaben sich erstaunlich niedrige Rechenzeiten. Insgesamt erweist sich somit der Algorithmus als empfehlenswerte Alternative gegenüber der Anwendung der bekannten graphentheoretischen Verfahren auf den zu Θ gehörenden Vergleichbarkeitsgraphen.
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This paper was supported by the Minister für Wissenschaft und Forschung des Landes NRW, Federal Republic of Germany.
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Bartusch, M. An algorithm for generating all maximal independent subsets of posets. Computing 26, 343–354 (1981). https://doi.org/10.1007/BF02237953
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DOI: https://doi.org/10.1007/BF02237953