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Universal Algebra and Hardness Results for Constraint Satisfaction Problems

  • Benoît Larose
  • Pascal Tesson
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4596)

Abstract

We present algebraic conditions on constraint languages Γ that ensure the hardness of the constraint satisfaction problem CSP (Γ) for complexity classes L, NL, P, NP and Mod p L. These criteria also give non-expressibility results for various restrictions of Datalog. Furthermore, we show that if CSP(Γ) is not first-order definable then it is L-hard. Our proofs rely on tame congruence theory and on a fine-grain analysis of the complexity of reductions used in the algebraic study of CSPs. The results pave the way for a refinement of the dichotomy conjecture stating that each CSP(Γ) lies in P or is NP-complete and they match the recent classification of [1] for Boolean CSP. We also infer a partial classification theorem for the complexity of CSP(Γ) when the associated algebra of Γ is the idempotent reduct of a preprimal algebra.

Keywords

Constraint Satisfaction Problem Simple Algebra Unary Type Universal Algebra Hardness Result 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2007

Authors and Affiliations

  • Benoît Larose
    • 1
  • Pascal Tesson
    • 2
  1. 1.Department of Mathematics and Statistics, Concordia University 
  2. 2.Département d’Informatique et de Génie Logiciel, Université Laval 

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