منابع مشابه
Backdoor Trees
The surprisingly good performance of modern satisfiability (SAT) solvers is usually explained by the existence of a certain “hidden structure” in real-world instances. We introduce the notion of backdoor trees as an indicator for the presence of a hidden structure. Backdoor trees refine the notion of strong backdoor sets, taking into account the relationship between backdoor variables. We prese...
متن کاملBackdoor Branching
We present an exact Mixed Integer Programming (MIP) solution scheme where a set covering model is used to find a small set of first-choice branching variables. In a preliminary “sampling” phase, our method quickly collects a number of relevant lowcost fractional solutions that qualify as obstacles for the Linear Programming (LP) relaxation bound improvement. Then a set covering model is solved ...
متن کاملFrom Horn Strong Backdoor Sets to Ordered Strong Backdoor Sets
Identifying and exploiting hidden problem structures is recognized as a fundamental way to deal with the intractability of combinatorial problems. Recently, a particular structure called (strong) backdoor has been identified in the context of the satisfiability problem. Connections has been established between backdoors and problem hardness leading to a better approximation of the worst case ti...
متن کاملA generalized backdoor criterion
We generalize Pearl’s back-door criterion for directed acyclic graphs (DAGs) to more general types of graphs that describe Markov equivalence classes of DAGs and/or allow for arbitrarily many hidden variables. We also give easily checkable necessary and sufficient graphical criteria for the existence of a set of variables that satisfies our generalized back-door criterion, when considering a si...
متن کاملBackdoor Treewidth for SAT
A strong backdoor in a CNF formula is a set of variables such that each possible instantiation of these variables moves the formula into a tractable class. The algorithmic problem of finding a strong backdoor has been the subject of intensive study, mostly within the parameterized complexity framework. Results to date focused primarily on backdoors of small size. In this paper we propose a new ...
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ژورنال
عنوان ژورنال: BMJ
سال: 1999
ISSN: 0959-8138,1468-5833
DOI: 10.1136/bmj.318.7195.1415