The CSP Dichotomy Holds for Digraphs with No Sources and No Sinks (A Positive Answer to a Conjecture of Bang-Jensen and Hell)
نویسندگان
چکیده
Bang-Jensen and Hell conjectured in 1990 (using the language of graph homomorphisms) a CSP dichotomy for digraphs with no sources or sinks. The conjecture states that the constraint satisfaction problem for such a digraph is tractable if each component of its core is a circle and is NP-complete otherwise. In this paper we prove this conjecture, and, as a consequence, a conjecture of Bang-Jensen, Hell and MacGillivray from 1995 classifying hereditarily hard digraphs. Further, we show that the CSP dichotomy for digraphs with no sources or sinks agrees with the algebraic characterization conjectured by Bulatov, Jeavons and Krokhin in 2005.
منابع مشابه
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ورودعنوان ژورنال:
- SIAM J. Comput.
دوره 38 شماره
صفحات -
تاریخ انتشار 2009