Near Unanimity Constraints Have Bounded Pathwidth Duality

—We show that if a finite relational structure has a near unanimity polymorphism, then the constraint satisfaction problem with that structure as its fixed template has bounded pathwidth duality (equivalently, the complement of the problem is definable in linear Datalog). As a consequence, the problem is in the complexity class NL. This generalizes the analogous result of Dalmau and Krokhin for majority polymorphisms and lends further support to a conjecture suggested by Larose and Tesson.

• Type: Journal
• Year: 2012
• Where: LICS
• Authors: Libor Barto, Marcin Kozik, Ross Willard
• Keywords: Automated Reasoning, Complexity Class, Constraint Satisfaction Problem, LICS 2012, Relational Structure