Variable Elimination in Binary CSP via Forbidden Patterns
نویسندگان
چکیده
A variable elimination rule allows the polynomialtime identification of certain variables whose elimination does not affect the satisfiability of an instance. Variable elimination in the constraint satisfaction problem (CSP) can be used in preprocessing or during search to reduce search space size. We show that there are essentially just four variable elimination rules defined by forbidding generic sub-instances, known as irreducible patterns, in arc-consistent CSP instances. One of these rules is the Broken Triangle Property, whereas the other three are novel. keywords: constraint satisfaction, tractability, arc consistency, forbidden pattern.
منابع مشابه
Variable and value elimination in binary constraint satisfaction via forbidden patterns
Variable or value elimination in a constraint satisfaction problem (CSP) can be used in preprocessing or during search to reduce search space size. A variable elimination rule (value elimination rule) allows the polynomial-time identification of certain variables (domain elements) whose elimination, without the introduction of extra compensatory constraints, does not affect the satisfiability o...
متن کاملBinary Constraint Satisfaction Problems Defined by Excluded Topological Minors
The binary Constraint Satisfaction Problem (CSP) is to decide whether there exists an assignment to a set of variables which satisfies specified constraints between pairs of variables. A binary CSP instance can be presented as a labelled graph encoding both the forms of the constraints and where they are imposed. We consider subproblems defined by restricting the allowed form of this graph. One...
متن کاملThe tractability of CSP classes defined by forbidden patterns
The constraint satisfaction problem (CSP) is a general problem central to computer science and artificial intelligence. Although the CSP is NP-hard in general, considerable effort has been spent on identifying tractable subclasses. The main two approaches consider structural properties (restrictions on the hypergraph of constraint scopes) and relational properties (restrictions on the language ...
متن کاملDynamic Combination of Search and Variable Elimination in CSP and Max-CSP
Variable elimination is the basic step of Adaptive Consis-tency8]. It transforms the problem into an equivalent one, having one less variable. Unfortunately, there are many classes of problems for which it is infeasible, due to its exponential space and time complexity. However , by restricting variable elimination so that only low arity constraints are processed and recorded, it can be eeectiv...
متن کاملCharacterising the complexity of constraint satisfaction problems defined by 2-constraint forbidden patterns
Although the CSP (constraint satisfaction problem) is NP-complete, even in the case when all constraints are binary, certain classes of instances are tractable. We study classes of binary CSP instances defined by excluding subproblems. This approach has recently led to the discovery of novel tractable classes. The complete characterisation of all tractable classes defined by forbidding patterns...
متن کامل