Examples with Backbone org.logicng.backbones.Backbone used on opensource projects

Example 1 with Backbone

use of org.logicng.backbones.Backbone in project LogicNG by logic-ng.

the class MiniSatStyleSolver method computeBackbone.

/**
 * Computes the backbone of the given variables with respect to the formulas added to the solver.
 * @param variables variables to test
 * @param type      backbone type
 * @param handler   the handler
 * @return the backbone projected to the relevant variables or {@code null} if the computation was aborted by the handler
 */
public Backbone computeBackbone(final Collection<Variable> variables, final BackboneType type, final SATHandler handler) {
    final boolean sat = solve(handler) == Tristate.TRUE;
    if (aborted(handler)) {
        return null;
    }
    if (sat) {
        this.computingBackbone = true;
        final List<Integer> relevantVarIndices = getRelevantVarIndices(variables);
        initBackboneDS(relevantVarIndices);
        computeBackbone(relevantVarIndices, type, handler);
        if (aborted(handler)) {
            return null;
        }
        final Backbone backbone = buildBackbone(variables, type);
        this.computingBackbone = false;
        return backbone;
    } else {
        return Backbone.unsatBackbone();
    }
}

Example 2 with Backbone

use of org.logicng.backbones.Backbone in project LogicNG by logic-ng.

the class BackboneFunction method apply.

@Override
public Backbone apply(final MiniSat solver, final Consumer<Tristate> resultSetter) {
    start(handler);
    SolverState stateBeforeBackbone = null;
    if (solver.getStyle() == MiniSat.SolverStyle.MINISAT && solver.isIncremental()) {
        stateBeforeBackbone = solver.saveState();
    }
    final Backbone backbone = solver.underlyingSolver().computeBackbone(this.variables, this.type, handler);
    if (solver.getStyle() == MiniSat.SolverStyle.MINISAT && solver.isIncremental()) {
        solver.loadState(stateBeforeBackbone);
    }
    return backbone;
}

Example 3 with Backbone

use of org.logicng.backbones.Backbone 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 4 with Backbone

use of org.logicng.backbones.Backbone 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 5 with Backbone

use of org.logicng.backbones.Backbone in project LogicNG by logic-ng.

the class BackboneFunctionTest method testSimpleFormulas.

@ParameterizedTest
@MethodSource("solvers")
public void testSimpleFormulas(final MiniSat solver) throws ParserException {
    solver.reset();
    solver.add(f.parse("(a => c | d) & (b => d | ~e) & (a | b)"));
    Backbone backbone = solver.backbone(v("a b c d e f"));
    assertThat(backbone.isSat()).isTrue();
    assertThat(backbone.getCompleteBackbone()).isEmpty();
    solver.add(f.parse("a => b"));
    solver.add(f.parse("b => a"));
    solver.add(f.parse("~d"));
    backbone = solver.backbone(v("a b c d e f g h"));
    assertThat(backbone.isSat()).isTrue();
    assertThat(backbone.getCompleteBackbone()).containsExactly(f.variable("a"), f.variable("b"), f.variable("c"), f.literal("d", false), f.literal("e", false));
}