Examples with Formula org.logicng.formulas.Formula used on opensource projects

Example 46 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class ExistentialQuantifierElimination method apply.

@Override
public Formula apply(final Formula formula, final boolean cache) {
    Formula result = formula;
    final FormulaFactory f = formula.factory();
    for (final Variable var : this.elimination) {
        result = f.or(result.restrict(new Assignment(var)), result.restrict(new Assignment(var.negate())));
    }
    return result;
}

Example 47 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class UniversalQuantifierElimination method apply.

@Override
public Formula apply(final Formula formula, final boolean cache) {
    Formula result = formula;
    final FormulaFactory f = formula.factory();
    for (final Variable var : this.elimination) {
        result = f.and(result.restrict(new Assignment(var)), result.restrict(new Assignment(var.negate())));
    }
    return result;
}

Example 48 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class QuineMcCluskeyAlgorithm method chooseSatBased.

/**
 * Choose a minimal set of prime implicants from the final prime implicant table of QMC.  This implementation uses
 * a MaxSAT formulation for this variant of the SET COVER problem which should be more efficient than e.g. Petrick's
 * method for all cases in which this Quine-McCluskey implementation yields a result in reasonable time.
 * @param table the final prime term table
 * @param f     the formula factory
 * @return the list of chosen prime implicants which are minimal wrt. to their number
 */
static List<Term> chooseSatBased(final TermTable table, final FormulaFactory f) {
    final LinkedHashMap<Variable, Term> var2Term = new LinkedHashMap<>();
    final LinkedHashMap<Formula, Variable> formula2VarMapping = new LinkedHashMap<>();
    final SATSolver satSolver = initializeSolver(table, f, var2Term, formula2VarMapping);
    if (satSolver.sat() == Tristate.FALSE) {
        throw new IllegalStateException("Solver must be satisfiable after adding the initial formula.");
    }
    return minimize(satSolver, var2Term, f);
}

Example 49 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class QuineMcCluskeyAlgorithm method minimize.

/**
 * Performs the minimization via incremental cardinality constraints.
 * @param satSolver the SAT solver
 * @param var2Term  a mapping from selector variable to prime implicant
 * @param f         the formula factory
 * @return a minimal set of prime implicants to cover all minterms
 */
static List<Term> minimize(final SATSolver satSolver, final LinkedHashMap<Variable, Term> var2Term, final FormulaFactory f) {
    final Assignment initialModel = satSolver.model();
    List<Variable> currentTermVars = computeCurrentTermVars(initialModel, var2Term.keySet());
    if (currentTermVars.size() == 2) {
        satSolver.add(f.amo(var2Term.keySet()));
        if (satSolver.sat() == Tristate.TRUE) {
            currentTermVars = computeCurrentTermVars(satSolver.model(), var2Term.keySet());
        }
    } else {
        final Formula cc = f.cc(CType.LE, currentTermVars.size() - 1, var2Term.keySet());
        assert cc instanceof CardinalityConstraint;
        final CCIncrementalData incData = satSolver.addIncrementalCC((CardinalityConstraint) cc);
        while (satSolver.sat() == Tristate.TRUE) {
            currentTermVars = computeCurrentTermVars(satSolver.model(), var2Term.keySet());
            incData.newUpperBoundForSolver(currentTermVars.size() - 1);
        }
    }
    return computeTerms(currentTermVars, var2Term);
}

Example 50 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class QuineMcCluskeyAlgorithm method computeFormula.

/**
 * Computes the formula for a given list of chosen terms and a variable order.
 * @param chosenTerms the chosen terms
 * @param varOrder    the variable order
 * @return the formula for this term list and variable ordering
 */
static Formula computeFormula(final List<Term> chosenTerms, final List<Variable> varOrder) {
    final FormulaFactory f = varOrder.get(0).factory();
    final List<Formula> operands = new ArrayList<>(chosenTerms.size());
    for (final Term term : chosenTerms) {
        operands.add(term.translateToFormula(varOrder));
    }
    return f.or(operands);
}