gapt.provers.maxsat.MaxSat4j.scala Maven / Gradle / Ivy

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package gapt.provers.maxsat

import java.math.BigInteger
import gapt.formats.dimacs.DIMACS
import gapt.provers.sat.Sat4j
import org.sat4j.maxsat.WeightedMaxSatDecorator
import org.sat4j.specs.ContradictionException

object MaxSat4j extends MaxSat4j
class MaxSat4j extends MaxSATSolver {
  import Sat4j._

  override def solve(hard: DIMACS.CNF, soft: Seq[(DIMACS.Clause, Int)]): Option[DIMACS.Model] = {
    val threshold = soft.map(_._2).sum + 1

    val solver = org.sat4j.pb.SolverFactory.newDefaultOptimizer()
    val decorator = new WeightedMaxSatDecorator(solver)

    decorator.newVar(DIMACS maxAtom (hard ++ soft.map(_._1)))
    decorator.setTopWeight(BigInteger.valueOf(threshold))

    try {
      hard foreach { decorator.addHardClause(_) }
      soft foreach { case (clause, weight) => decorator.addSoftClause(weight, clause) }

      if (solver.isSatisfiable) {
        Some(solver.model().toIndexedSeq)
      } else {
        None
      }
    } catch {
      case _: ContradictionException => None
    }
  }
}