4,273 research outputs found
Boolean Satisfiability in Electronic Design Automation
Boolean Satisfiability (SAT) is often used as the underlying model for a significant and increasing number of applications in Electronic Design Automation (EDA) as well as in many other fields of Computer Science and Engineering. In recent years, new and efficient algorithms for SAT have been developed, allowing much larger problem instances to be solved. SAT “packages” are currently expected to have an impact on EDA applications similar to that of BDD packages since their introduction more than a decade ago. This tutorial paper is aimed at introducing the EDA professional to the Boolean satisfiability problem. Specifically, we highlight the use of SAT models to formulate a number of EDA problems in such diverse areas as test pattern generation, circuit delay computation, logic optimization, combinational equivalence checking, bounded model checking and functional test vector generation, among others. In addition, we provide an overview of the algorithmic techniques commonly used for solving SAT, including those that have seen widespread use in specific EDA applications. We categorize these algorithmic techniques, indicating which have been shown to be best suited for which tasks
ON EQUIVALENCY REASONING FOR CONFLICT DRIVEN CLAUSE LEARNING SATISFIABILITY SOLVERS
Satisfiability problem or SAT is the problem of deciding whether a Boolean function evaluates
to true for at least one of the assignments in its domain. The satisfiability problem
is the first problem to be proved NP-complete. Therefore, the problems in NP can be encoded
into SAT instances. Many hard real world problems can be solved when encoded
efficiently into SAT instances. These facts give SAT an important place in both theoretical
and practical computer science.
In this thesis we address the problem of integrating a special class of equivalency reasoning
techniques, the strongly connected components or SCC based reasoning, into the
class of conflict driven clause learning or CDCL SAT solvers. Because of the complications
that arise from integrating the equivalency reasoning in CDCL SAT solvers, to our knowledge,
there has been no CDCL solver which has applied SCC based equivalency reasoning
dynamically during the search. We propose a method to overcome these complications.
The method is integrated into a prominent satisfiability solver: MiniSat. The equivalency
enhanced MiniSat, Eq-MiniSat, is used to explore the advantages and disadvantages of the
equivalency reasoning in conflict clause learning satisfiability solvers. Different implementation
approaches for Eq-MiniSat are discussed. The experimental results on 16 families
of instances shows that equivalency reasoning does not have noticeable effects for the instances
in one family. The equivalency reasoning enables Eq-MiniSat to outperform MiniSat
on eight classes of instances. For the remaining seven families, MiniSat outperforms Eq-
MiniSat. The experimental results for random instances demonstrate that almost in all
cases the number of branchings for Eq-Minisat is smaller than Minisat
Investigations into Satisfiability Search
In this dissertation we investigate theoretical aspects of some practical approaches used in solving and understanding search problems. We concentrate on the Satisfiability problem, which is a strong representative from search problem domains. The work develops general theoretical foundations to investigate some practical aspects of satisfiability search. This results in a better understanding of the fundamental mechanics for search algorithm construction and behaviour. A theory of choice or branching heuristics is presented, accompanied by results showing a correspondence of both parameterisations and performance when the method is compared to previous empirically motivated branching techniques. The logical foundations of the backtracking mechanism are explored alongside formulations for reasoning in relevant logics which results in the development of a malleable backtracking mechanism that subsumes other intelligent backtracking proof construction techniques and allows the incorporation of proof rearrangement strategies. Moreover, empirical tests show that relevant backtracking outperforms all other forms of intelligent backtracking search tree construction methods. An investigation into modelling and generating world problem instances justifies a modularised problem model proposal which is used experimentally to highlight the practicability of search algorithms for the proposed model and related domains
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