Title
On good algorithms for determining unsatisfiability of propositional formulas
Abstract
This paper is concerned with an algorithm that provides short certificates of unsatisfiability with high probability when an input I is a random instance of 3-SAT. Rather than build a refutation DAG, the algorithm finds bounds on nI(true), the number of variables that must be set to true, and nI(false), the number that must be set to false, if all clauses of I are to be satisfied. If the sum nI(true) + nI(false) is greater than the number of variables in I then I must be unsatisfiable. Bounds on nI(true) and nI(false) may be found by throwing out all clauses except those having only negative or only positive literals and finding nI+(true) for the remaining positive clause set I+ and nI-(false) for the remaining negative clause set I-. These questions can alternatively be stated as 3-hitting set problems on I+ and I- separately. It is shown that a good enough approximation algorithm for 3-hitting set can determine useful bounds on nI(true) and nI(false) (high probability of success for large enough constant ratio of clauses to variables). Although a good enough algorithm seems evasive, one that comes fairly close is proposed and analyzed.
Year
DOI
Venue
2003
10.1016/S0166-218X(02)00401-8
Discrete Applied Mathematics
Keywords
Field
DocType
set theory,mathematical models,theorem proving,random variables,algorithms,satisfiability,resolution
Set theory,Discrete mathematics,Approximation algorithm,Combinatorics,Random variable,Satisfiability,Automated theorem proving,Boolean satisfiability problem,Algorithm,Conjunctive normal form,Mathematics,Propositional formula
Journal
Volume
Issue
ISSN
130
2
0166-218X
Citations 
PageRank 
References 
1
0.37
15
Authors
2
Name
Order
Citations
PageRank
John Franco1383116.78
R. P. Swaminathan2685.91