Examples with Substitution at.ac.tuwien.kr.alpha.api.grounder.Substitution used on opensource projects

Example 26 with Substitution

use of at.ac.tuwien.kr.alpha.api.grounder.Substitution in project Alpha by alpha-asp.

the class LiteralInstantiationStrategyTest method defaultLazyGroundingSubstituteNonGroundLiteralWithUnassignedInstance.

/**
 * Uses {@link DefaultLazyGroundingInstantiationStrategy} to find the ground
 * instance "q(a, b)" for the partially ground positive literal "q(a, X)".
 *
 * In this case, the instantiation strategy has an empty assignment, so we
 * expect the assignment status (i.e. assignment status of the found ground
 * instance) passed back with the substitution to be UNASSIGNED. Since
 * UNASSIGNED and FALSE atoms are (potentially) stale in working memory, we
 * expect the atom "q(a, b)" to be added to the stale set by the instantiation
 * strategy.
 */
@Test
public void defaultLazyGroundingSubstituteNonGroundLiteralWithUnassignedInstance() {
    Predicate q = Predicates.getPredicate("q", 2);
    BasicAtom nonGroundAtom = Atoms.newBasicAtom(q, Terms.newSymbolicConstant("a"), Terms.newVariable("X"));
    WorkingMemory workingMemory = new WorkingMemory();
    workingMemory.initialize(q);
    workingMemory.addInstance(Atoms.newBasicAtom(q, Terms.newSymbolicConstant("a"), Terms.newSymbolicConstant("b")), true);
    AtomStore atomStore = new AtomStoreImpl();
    WritableAssignment assignment = new TrailAssignment(atomStore);
    LinkedHashSet<Atom> staleSet = new LinkedHashSet<>();
    DefaultLazyGroundingInstantiationStrategy strategy = new DefaultLazyGroundingInstantiationStrategy(workingMemory, atomStore, Collections.emptyMap(), false);
    strategy.setStaleWorkingMemoryEntries(staleSet);
    strategy.setCurrentAssignment(assignment);
    List<ImmutablePair<Substitution, AssignmentStatus>> result = strategy.getAcceptedSubstitutions(Literals.fromAtom(nonGroundAtom, true), new BasicSubstitution());
    assertEquals(1, result.size());
    ImmutablePair<Substitution, AssignmentStatus> substitutionInfo = result.get(0);
    Substitution substitution = substitutionInfo.left;
    AssignmentStatus assignmentStatus = substitutionInfo.right;
    assertEquals(AssignmentStatus.UNASSIGNED, assignmentStatus);
    assertTrue(substitution.isVariableSet(Terms.newVariable("X")));
    assertEquals(Terms.newSymbolicConstant("b"), substitution.eval(Terms.newVariable("X")));
    assertEquals(1, staleSet.size());
    assertTrue(staleSet.contains(Atoms.newBasicAtom(q, Terms.newSymbolicConstant("a"), Terms.newSymbolicConstant("b"))));
}

Example 27 with Substitution

use of at.ac.tuwien.kr.alpha.api.grounder.Substitution in project Alpha by alpha-asp.

the class StratifiedEvaluation method evaluateRule.

private void evaluateRule(CompiledRule rule, boolean checkAllStartingLiterals) {
    LOGGER.debug("Evaluating rule {}", rule);
    List<Substitution> satisfyingSubstitutions = calculateSatisfyingSubstitutionsForRule(rule, checkAllStartingLiterals);
    for (Substitution subst : satisfyingSubstitutions) {
        fireRule(rule, subst);
    }
}

Example 28 with Substitution

use of at.ac.tuwien.kr.alpha.api.grounder.Substitution in project Alpha by alpha-asp.

the class StratifiedEvaluation method calculateSatisfyingSubstitutionsForRule.

private List<Substitution> calculateSatisfyingSubstitutionsForRule(CompiledRule rule, boolean checkAllStartingLiterals) {
    LOGGER.debug("Grounding rule {}", rule);
    RuleGroundingInfo groundingOrders = rule.getGroundingInfo();
    // Treat rules with fixed instantiation first.
    LOGGER.debug("Is fixed rule? {}", rule.getGroundingInfo().hasFixedInstantiation());
    if (groundingOrders.hasFixedInstantiation()) {
        RuleGroundingOrder fixedGroundingOrder = groundingOrders.getFixedGroundingOrder();
        return calcSubstitutionsWithGroundingOrder(fixedGroundingOrder, Collections.singletonList(new BasicSubstitution()));
    }
    List<Literal> startingLiterals = groundingOrders.getStartingLiterals();
    // Check only one starting literal if indicated by the parameter.
    if (!checkAllStartingLiterals) {
        // If this is the first evaluation run, it suffices to start from the first starting literal only.
        Literal lit = startingLiterals.get(0);
        return calcSubstitutionsWithGroundingOrder(groundingOrders.orderStartingFrom(lit), substituteFromRecentlyAddedInstances(lit));
    }
    // Ground from all starting literals.
    // Collection of full ground substitutions for the given rule.
    List<Substitution> groundSubstitutions = new ArrayList<>();
    for (Literal lit : startingLiterals) {
        List<Substitution> substitutionsForStartingLiteral = calcSubstitutionsWithGroundingOrder(groundingOrders.orderStartingFrom(lit), substituteFromRecentlyAddedInstances(lit));
        groundSubstitutions.addAll(substitutionsForStartingLiteral);
    }
    return groundSubstitutions;
}

Example 29 with Substitution

use of at.ac.tuwien.kr.alpha.api.grounder.Substitution in project Alpha by alpha-asp.

the class NaiveGrounderTest method testDeadEnd.

/**
 * Tests the method {@link NaiveGrounder#getGroundInstantiations(InternalRule, RuleGroundingOrder, Substitution, Assignment)} on a
 * predefined program:
 * <code>
 *  p1(1). q1(1). <br/>
 * 	x :- p1(X), p2(X), q1(Y), q2(Y). <br/>
 * 	p2(X) :- something(X). <br/>
 * 	q2(X) :- something(X). <br/>
 * </code>
 * Given one grounding order {@code groundingOrder} for the first rule in this program which starts with
 * the literal whose predicate name is {@code predicateNameOfStartingLiteral} and a substitution substituting
 * the variable in this literal by 1 it is attempted to ground the rule.
 * It is then asserted that ground instantiations are produced if and only if {@code expectNoGoods} is true.
 *
 * @param predicateNameOfStartingLiteral the predicate name of the starting literal, either "p1" or "q1".
 * @param groundingOrder                 a grounding order for the first rule in the predefined program that starts with the literal
 *                                       whose predicate name is {@code predicateNameOfStartingLiteral}.
 * @param expectNoGoods                  {@code true} iff ground instantiations are expected to be produced under the conditions
 *                                       described above.
 */
private void testDeadEnd(String predicateNameOfStartingLiteral, RuleGroundingOrderImpl groundingOrder, boolean expectNoGoods) {
    String aspStr = "p1(1). q1(1). " + "x :- p1(X), p2(X), q1(Y), q2(Y). " + "p2(X) :- something(X). " + "q2(X) :- something(X). ";
    CompiledProgram program = InternalProgram.fromNormalProgram(NORMALIZE_TRANSFORM.apply(PROGRAM_PARSER.parse(aspStr)));
    AtomStore atomStore = new AtomStoreImpl();
    NaiveGrounder grounder = (NaiveGrounder) GrounderFactory.getInstance("naive", program, atomStore, p -> true, GrounderHeuristicsConfiguration.permissive(), true);
    CompiledRule nonGroundRule = grounder.getNonGroundRule(0);
    String strLiteral = "p1".equals(predicateNameOfStartingLiteral) ? "p1(X)" : "p1(Y)";
    final Literal startingLiteral = PROGRAM_PART_PARSER.parseLiteral(strLiteral);
    ((RuleGroundingInfoImpl) nonGroundRule.getGroundingInfo()).groundingOrders.put(startingLiteral, groundingOrder);
    grounder.bootstrap();
    TrailAssignment currentAssignment = new TrailAssignment(atomStore);
    final Substitution subst1 = BasicSubstitution.specializeSubstitution(startingLiteral, new Instance(Terms.newConstant(1)), BasicSubstitution.EMPTY_SUBSTITUTION);
    final BindingResult bindingResult = grounder.getGroundInstantiations(nonGroundRule, groundingOrder, subst1, currentAssignment);
    assertEquals(expectNoGoods, bindingResult.size() > 0);
}

Example 30 with Substitution

use of at.ac.tuwien.kr.alpha.api.grounder.Substitution in project Alpha by alpha-asp.

the class NaiveGrounderTest method testIfGrounderGroundsRule.

/**
 * Tests if {@link NaiveGrounder#getGroundInstantiations(InternalRule, RuleGroundingOrder, Substitution, Assignment)}
 * produces ground instantiations for the rule with ID {@code ruleID} in {@code program} when {@code startingLiteral}
 * unified with the numeric instance {@code startingInstance} is used as starting literal and {@code b(1)} is assigned
 * {@code bTruth}.
 * It is asserted that ground instantiations are produced if and only if {@code expectNoGoods} is true.
 */
private void testIfGrounderGroundsRule(ASPCore2Program program, int ruleID, Literal startingLiteral, int startingInstance, ThriceTruth bTruth, boolean expectNoGoods) {
    CompiledProgram internalPrg = InternalProgram.fromNormalProgram(NORMALIZE_TRANSFORM.apply(program));
    AtomStore atomStore = new AtomStoreImpl();
    TrailAssignment currentAssignment = new TrailAssignment(atomStore);
    NaiveGrounder grounder = (NaiveGrounder) GrounderFactory.getInstance("naive", internalPrg, atomStore, p -> true, GrounderHeuristicsConfiguration.permissive(), true);
    int b = atomStore.putIfAbsent(atom("b", 1));
    currentAssignment.growForMaxAtomId();
    currentAssignment.assign(b, bTruth);
    grounder.bootstrap();
    final CompiledRule nonGroundRule = grounder.getNonGroundRule(ruleID);
    final Substitution substStartingLiteral = BasicSubstitution.specializeSubstitution(startingLiteral, new Instance(Terms.newConstant(startingInstance)), BasicSubstitution.EMPTY_SUBSTITUTION);
    final BindingResult bindingResult = grounder.getGroundInstantiations(nonGroundRule, nonGroundRule.getGroundingInfo().orderStartingFrom(startingLiteral), substStartingLiteral, currentAssignment);
    assertEquals(expectNoGoods, bindingResult.size() > 0);
}