class TransformToCnf extends CnfBuilder
Plaisted transformation: used for conversion of a propositional formula into conjunctive normal form (CNF) (input format for SAT solver). A simple conversion into CNF via Shannon expansion would also be possible but it's worst-case complexity is exponential (in the number of variables) and thus even simple problems could become untractable. The Plaisted transformation results in an _equisatisfiable_ CNF-formula (it generates auxiliary variables) but runs with linear complexity. The common known Tseitin transformation uses bi-implication, whereas the Plaisted transformation uses implication only, thus the resulting CNF formula has (on average) only half of the clauses of a Tseitin transformation. The Plaisted transformation uses the polarities of sub-expressions to figure out which part of the bi-implication can be omitted. However, if all sub-expressions have positive polarity (e.g., after transformation into negation normal form) then the conversion is rather simple and the pseudo-normalization via NNF increases chances only one side of the bi-implication is needed.
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- new TransformToCnf(symbolMapping: SymbolMapping)
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final
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!=(arg0: Any): Boolean
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def
addClauseProcessed(clause: Clause): Unit
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- def apply(p: CNF.Prop): Solvable
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asInstanceOf[T0]: T0
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def
buildCnf: Array[Clause]
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def
constFalse: Lit
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lazy val
constTrue: Lit
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- def convertSym(sym: CNF.Sym): Lit
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literalCount: Int
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- TransformToCnf → CnfBuilder
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ne(arg0: AnyRef): Boolean
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def
newLiteral(): Lit
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new Tseitin variable
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