Examples with LiteralStepSolver com.sri.ai.grinder.theory.base.LiteralStepSolver used on opensource projects

Example 1 with LiteralStepSolver

use of com.sri.ai.grinder.theory.base.LiteralStepSolver in project aic-expresso by aic-sri-international.

the class AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver method solutionIfPropagatedLiteralsAndSplittersCNFAreSatisfied.

@Override
protected Step solutionIfPropagatedLiteralsAndSplittersCNFAreSatisfied(Context context) {
    Expression solutionExpression;
    // sequelBase keeps track of updates to non-splitting sub-step solvers so far.
    // When a splitting sub-step solver is found, it is used as a basis
    // for the sequel step solvers.
    // The reason we keep this clone, that is itself cloned later,
    // as opposed to updating and cloning "this" every time,
    // is that step solvers must not be modified by their method "step",
    // unless they are caching context-independent information.
    // sequelBase serves as a blackboard for all the updates learned while executing this method,
    // which then don't need to be kept by "this".
    // These updates are then cloned into the sequel step solvers.
    AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver sequelBase = clone();
    if (getConstraint().getPropagateAllLiteralsWhenVariableIsBound() && !getEquals().isEmpty()) {
        solutionExpression = getSolutionExpressionForBoundVariable();
    } else {
        ExpressionLiteralSplitterStepSolver maximumLowerBoundStepSolver;
        if (initialMaximumLowerBoundStepSolver == null) {
            maximumLowerBoundStepSolver = new MaximumExpressionStepSolver(getLowerBoundsIncludingImplicitOnes(context), // use total order <
            LESS_THAN_SYMBOL, MINUS_INFINITY, // at first, I placed the type minimum and maximum strict lower bounds here. This is incorrect because if the type maximum is, say, 4, and I have "X > 3 and X > I" (3 is the maximum strict lower bounds for values in the type), the step solver short-circuits and returns 3, without ever even looking at I. Looking at I is needed because if I is greater than 3 than this constraint is unsatisfiable.
            INFINITY);
        } else {
            maximumLowerBoundStepSolver = initialMaximumLowerBoundStepSolver;
        }
        ExpressionLiteralSplitterStepSolver.Step maximumLowerBoundStep = maximumLowerBoundStepSolver.step(context);
        if (maximumLowerBoundStep.itDepends()) {
            AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver ifTrue = makeSequelStepSolver(sequelBase);
            ifTrue.initialMaximumLowerBoundStepSolver = maximumLowerBoundStep.getStepSolverForWhenSplitterIsTrue();
            AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver ifFalse = makeSequelStepSolver(sequelBase);
            ifFalse.initialMaximumLowerBoundStepSolver = maximumLowerBoundStep.getStepSolverForWhenSplitterIsFalse();
            ItDependsOn result = new ItDependsOn(maximumLowerBoundStep.getSplitterLiteral(), maximumLowerBoundStep.getContextSplittingWhenSplitterIsLiteral(), ifTrue, ifFalse);
            return result;
        }
        Expression maximumLowerBound = maximumLowerBoundStep.getValue();
        sequelBase.initialMaximumLowerBoundStepSolver = new ConstantExpressionStepSolver(maximumLowerBound);
        ExpressionLiteralSplitterStepSolver minimumUpperBoundStepSolver;
        if (initialMinimumUpperBoundStepSolver == null) {
            minimumUpperBoundStepSolver = new MaximumExpressionStepSolver(getUpperBoundsIncludingImplicitOnes(context), // use total order > since "minimum" is maximum under it
            GREATER_THAN_SYMBOL, // "minimum" is maximum value because we are operating on the inverse order
            INFINITY, // "maximum" is minimum value because we are operating on the inverse order
            MINUS_INFINITY);
        } else {
            minimumUpperBoundStepSolver = initialMinimumUpperBoundStepSolver;
        }
        ExpressionLiteralSplitterStepSolver.Step minimumUpperBoundStep = minimumUpperBoundStepSolver.step(context);
        if (minimumUpperBoundStep.itDepends()) {
            AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver ifTrue = makeSequelStepSolver(sequelBase);
            ifTrue.initialMinimumUpperBoundStepSolver = minimumUpperBoundStep.getStepSolverForWhenSplitterIsTrue();
            AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver ifFalse = makeSequelStepSolver(sequelBase);
            ifFalse.initialMinimumUpperBoundStepSolver = minimumUpperBoundStep.getStepSolverForWhenSplitterIsFalse();
            ItDependsOn result = new ItDependsOn(minimumUpperBoundStep.getSplitterLiteral(), minimumUpperBoundStep.getContextSplittingWhenSplitterIsLiteral(), ifTrue, ifFalse);
            return result;
        }
        Expression minimumUpperBound = minimumUpperBoundStep.getValue();
        sequelBase.initialMinimumUpperBoundStepSolver = new ConstantExpressionStepSolver(minimumUpperBound);
        if (unboundedVariableProducesShortCircuitSolution() && (maximumLowerBound.equals(MINUS_INFINITY) || minimumUpperBound.equals(INFINITY))) {
            solutionExpression = getSolutionExpressionForUnboundedVariables();
        } else {
            StepSolver<Boolean> boundedSpaceIsNotEmptyStepSolver;
            if (initialBoundedSpaceIsNotEmptyStepSolver == null) {
                Expression boundedSpaceIsNotEmpty = makeLiteralCheckingWhetherThereAreAnyValuesWithinBounds(maximumLowerBound, minimumUpperBound, context);
                boundedSpaceIsNotEmptyStepSolver = new LiteralStepSolver(boundedSpaceIsNotEmpty);
            } else {
                boundedSpaceIsNotEmptyStepSolver = initialBoundedSpaceIsNotEmptyStepSolver;
            }
            StepSolver.Step<Boolean> lowerBoundIsLessThanUpperBoundStep = boundedSpaceIsNotEmptyStepSolver.step(context);
            if (lowerBoundIsLessThanUpperBoundStep.itDepends()) {
                AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver ifTrue = makeSequelStepSolver(sequelBase);
                ifTrue.initialBoundedSpaceIsNotEmptyStepSolver = lowerBoundIsLessThanUpperBoundStep.getStepSolverForWhenSplitterIsTrue();
                AbstractSingleVariableNumericConstraintFeasibilityRegionStepSolver ifFalse = makeSequelStepSolver(sequelBase);
                ifFalse.initialBoundedSpaceIsNotEmptyStepSolver = lowerBoundIsLessThanUpperBoundStep.getStepSolverForWhenSplitterIsFalse();
                ItDependsOn result = new ItDependsOn(lowerBoundIsLessThanUpperBoundStep.getSplitter(), lowerBoundIsLessThanUpperBoundStep.getContextSplittingWhenSplitterIsLiteral(), ifTrue, ifFalse);
                return result;
            }
            if (!lowerBoundIsLessThanUpperBoundStep.getValue()) {
                return new Solution(getSolutionExpressionGivenContradiction());
            }
            // else, bounds difference is positive and we can move on
            sequelBase.initialBoundedSpaceIsNotEmptyStepSolver = new ConstantStepSolver<Boolean>(true);
            Step result = getSolutionStepAfterBoundsAreCheckedForFeasibility(maximumLowerBound, minimumUpperBound, sequelBase, context);
            return result;
        }
    }
    return new Solution(solutionExpression);
}