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

Example 51 with Formula

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

the class AdvancedSimplifier method apply.

@Override
public Formula apply(final Formula formula, final boolean cache) {
    start(this.handler);
    final FormulaFactory f = formula.factory();
    final Backbone backbone = BackboneGeneration.compute(Collections.singletonList(formula), formula.variables(), BackboneType.POSITIVE_AND_NEGATIVE, satHandler(this.handler));
    if (backbone == null || aborted(this.handler)) {
        return null;
    }
    if (!backbone.isSat()) {
        return f.falsum();
    }
    final SortedSet<Literal> backboneLiterals = backbone.getCompleteBackbone();
    final Formula restrictedFormula = formula.restrict(new Assignment(backboneLiterals));
    final PrimeResult primeResult = PrimeCompiler.getWithMinimization().compute(restrictedFormula, PrimeResult.CoverageType.IMPLICANTS_COMPLETE, this.handler);
    if (primeResult == null || aborted(this.handler)) {
        return null;
    }
    final List<SortedSet<Literal>> primeImplicants = primeResult.getPrimeImplicants();
    final List<Formula> minimizedPIs = SmusComputation.computeSmusForFormulas(negateAllLiterals(primeImplicants, f), Collections.singletonList(restrictedFormula), f, this.handler);
    if (minimizedPIs == null || aborted(this.handler)) {
        return null;
    }
    final Formula minDnf = f.or(negateAllLiteralsInFormulas(minimizedPIs, f).stream().map(f::and).collect(Collectors.toList()));
    final Formula fullFactor = minDnf.transform(new FactorOutSimplifier(this.ratingFunction));
    return f.and(f.and(backboneLiterals), fullFactor).transform(new NegationSimplifier());
}

Example 52 with Formula

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

the class BackboneSimplifier method apply.

@Override
public Formula apply(final Formula formula, final boolean cache) {
    final SATSolver solver = MiniSat.miniSat(formula.factory());
    solver.add(formula);
    final Backbone backbone = solver.execute(BackboneFunction.builder().variables(formula.variables()).type(BackboneType.POSITIVE_AND_NEGATIVE).build());
    if (!backbone.isSat()) {
        return formula.factory().falsum();
    }
    if (!backbone.getNegativeBackbone().isEmpty() || !backbone.getPositiveBackbone().isEmpty()) {
        final Formula backboneFormula = backbone.toFormula(formula.factory());
        final Assignment assignment = new Assignment(backbone.getCompleteBackbone());
        final Formula restrictedFormula = formula.restrict(assignment);
        return formula.factory().and(backboneFormula, restrictedFormula);
    } else {
        return formula;
    }
}

Example 53 with Formula

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

the class PlaistedGreenbaumTransformationSolver method handleNary.

private LNGIntVector handleNary(final Formula formula, final boolean polarity, final Proposition proposition, final boolean topLevel) {
    final boolean skipPg = topLevel || formula.type() == FType.AND && !polarity || formula.type() == FType.OR && polarity;
    final Pair<Boolean, Integer> pgVarResult = skipPg ? new Pair<>(false, null) : getPgVar(formula, polarity);
    if (pgVarResult.first()) {
        return polarity ? vector(pgVarResult.second()) : vector(pgVarResult.second() ^ 1);
    }
    final int pgVar = skipPg ? -1 : pgVarResult.second();
    switch(formula.type()) {
        case AND:
            {
                if (polarity) {
                    // pg => (v1 & ... & vk) = (~pg | v1) & ... & (~pg | vk)
                    for (final Formula op : formula) {
                        final LNGIntVector opPgVars = computeTransformation(op, true, proposition, topLevel);
                        if (topLevel) {
                            if (opPgVars != null) {
                                this.solver.addClause(opPgVars, proposition);
                            }
                        } else {
                            this.solver.addClause(vector(pgVar ^ 1, opPgVars), proposition);
                        }
                    }
                    if (topLevel) {
                        return null;
                    }
                } else {
                    // (v1 & ... & vk) => pg = ~v1 | ... | ~vk | pg
                    // Speed-Up: Skip pg var
                    final LNGIntVector singleClause = new LNGIntVector();
                    for (final Formula op : formula) {
                        final LNGIntVector opPgVars = computeTransformation(op, false, proposition, false);
                        for (int i = 0; i < opPgVars.size(); i++) {
                            singleClause.push(opPgVars.get(i));
                        }
                    }
                    return singleClause;
                }
                break;
            }
        case OR:
            {
                if (polarity) {
                    // pg => (v1 | ... | vk) = ~pg | v1 | ... | vk
                    // Speed-Up: Skip pg var
                    final LNGIntVector singleClause = new LNGIntVector();
                    for (final Formula op : formula) {
                        final LNGIntVector opPgVars = computeTransformation(op, true, proposition, false);
                        for (int i = 0; i < opPgVars.size(); i++) {
                            singleClause.push(opPgVars.get(i));
                        }
                    }
                    return singleClause;
                } else {
                    // (v1 | ... | vk) => pg = (~v1 | pg) & ... & (~vk | pg)
                    for (final Formula op : formula) {
                        final LNGIntVector opPgVars = computeTransformation(op, false, proposition, topLevel);
                        if (topLevel) {
                            if (opPgVars != null) {
                                this.solver.addClause(opPgVars, proposition);
                            }
                        } else {
                            this.solver.addClause(vector(pgVar, opPgVars), proposition);
                        }
                    }
                    if (topLevel) {
                        return null;
                    }
                }
                break;
            }
        default:
            throw new IllegalArgumentException("Unexpected type: " + formula.type());
    }
    return polarity ? vector(pgVar) : vector(pgVar ^ 1);
}

Example 54 with Formula

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

the class DNFFactorization method distribute.

/**
 * Computes the distribution (factorization) of two formulas.
 * @param f1 the first formula
 * @param f2 the second formula
 * @return the distribution of the two formulas
 */
private Formula distribute(final Formula f1, final Formula f2) {
    if (this.handler != null) {
        this.proceed = this.handler.performedDistribution();
    }
    if (this.proceed) {
        final FormulaFactory f = f1.factory();
        if (f1.type() == FType.OR || f2.type() == FType.OR) {
            final LinkedHashSet<Formula> nops = new LinkedHashSet<>();
            for (final Formula op : f1.type() == FType.OR ? f1 : f2) {
                final Formula distribute = this.distribute(op, f1.type() == FType.OR ? f2 : f1);
                if (!this.proceed) {
                    return null;
                }
                nops.add(distribute);
            }
            return f.or(nops);
        }
        final Formula clause = f.and(f1, f2);
        if (this.handler != null) {
            this.proceed = this.handler.createdClause(clause);
        }
        return clause;
    }
    return null;
}

Example 55 with Formula

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

the class CNFEncoder method singleAdvancedEncoding.

protected Formula singleAdvancedEncoding(final Formula formula) {
    Formula result = formula.transform(this.advancedFactorization);
    if (result == null) {
        switch(this.config().fallbackAlgorithmForAdvancedEncoding) {
            case TSEITIN:
                if (this.tseitin == null || this.currentAtomBoundary != this.config().atomBoundary) {
                    this.currentAtomBoundary = this.config().atomBoundary;
                    this.tseitin = new TseitinTransformation(this.config().atomBoundary);
                }
                result = formula.transform(this.tseitin);
                break;
            case PLAISTED_GREENBAUM:
                if (this.plaistedGreenbaum == null || this.currentAtomBoundary != this.config().atomBoundary) {
                    this.currentAtomBoundary = this.config().atomBoundary;
                    this.plaistedGreenbaum = new PlaistedGreenbaumTransformation(this.config().atomBoundary);
                }
                result = formula.transform(this.plaistedGreenbaum);
                break;
            default:
                throw new IllegalStateException("Invalid fallback CNF encoding algorithm: " + this.config().fallbackAlgorithmForAdvancedEncoding);
        }
    }
    return result;
}