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Identifying and breaking the symmetries of CNF for-mulae has been shown to lead to significant reductions
 

Summary: Abstract
Identifying and breaking the symmetries of CNF for-
mulae has been shown to lead to significant reductions
in search times. In this paper we describe a more sys-
tematic and efficient construction of symmetry-break-
ing predicates (SBPs). In particular, we use the cycle
structure of symmetry generators, which typically
involve very few variables, to drastically reduce the
size of SBPs. Furthermore, our new SBP construction
grows linearly with the number of relevant variables as
opposed to the previous quadratic constructions. Our
empirical data suggest that these improvements reduce
search run times by one to two orders of magnitude on
a wide variety of benchmarks with symmetries.
1 Introduction
Modern Boolean satisfiability (SAT) solvers, based on back-
track search, are now capable of attacking instances with
thousands of variables and millions of clauses [Velev and
Bryant, 2001] and are being routinely deployed in a wide
range of industrial applications [Biere et al., 1999], [Nam et

  

Source: Aloul, Fadi - Department of Computer Engineering, American University of Sharjah

 

Collections: Engineering