com.sri.ai.grinder.sgdpllt.theory.differencearithmetic.SatisfiabilityOfSingleVariableDifferenceArithmeticConstraintStepSolver Maven / Gradle / Ivy
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* Copyright (c) 2013, SRI International
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* Licensed under the The BSD 3-Clause License;
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package com.sri.ai.grinder.sgdpllt.theory.differencearithmetic;
import static com.sri.ai.expresso.helper.Expressions.FALSE;
import static com.sri.ai.expresso.helper.Expressions.TRUE;
import static com.sri.ai.expresso.helper.Expressions.ZERO;
import static com.sri.ai.expresso.helper.Expressions.apply;
import static com.sri.ai.grinder.sgdpllt.library.FunctorConstants.GREATER_THAN;
import static com.sri.ai.grinder.sgdpllt.theory.base.ExpressionConditionedOnLiteralSolutionStep.stepDependingOnLiteral;
import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.grinder.sgdpllt.api.Context;
import com.sri.ai.grinder.sgdpllt.api.ExpressionLiteralSplitterStepSolver;
import com.sri.ai.grinder.sgdpllt.core.solver.AbstractBooleanWithPropagatedLiteralsRequiringPropagatedLiteralsAndCNFToBeSatisfiedStepSolver;
/**
* A {@link AbstractBooleanWithPropagatedLiteralsRequiringPropagatedLiteralsAndCNFToBeSatisfiedStepSolver} for a {@link SingleVariableLinearRealArithmeticConstraint}.
*
* The solution is guaranteed to be either a boolean constant or a difference arithmetic expression with 0 on the right-hand side.
*
* @author braz
*
*/
@Beta
public class SatisfiabilityOfSingleVariableDifferenceArithmeticConstraintStepSolver implements ExpressionLiteralSplitterStepSolver {
private SingleVariableDifferenceArithmeticConstraint constraint;
private ExpressionLiteralSplitterStepSolver modelCounting;
public SatisfiabilityOfSingleVariableDifferenceArithmeticConstraintStepSolver(SingleVariableDifferenceArithmeticConstraint constraint) {
this.constraint = constraint;
this.modelCounting = new ModelCountingOfSingleVariableDifferenceArithmeticConstraintStepSolver(constraint);
}
public SingleVariableDifferenceArithmeticConstraint getConstraint() {
return constraint;
}
@Override
public SatisfiabilityOfSingleVariableDifferenceArithmeticConstraintStepSolver clone() {
SatisfiabilityOfSingleVariableDifferenceArithmeticConstraintStepSolver result = null;
try {
result = (SatisfiabilityOfSingleVariableDifferenceArithmeticConstraintStepSolver) super.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return result;
}
@Override
public Step step(Context context) {
Step modelCountingStep = modelCounting.step(context);
if (modelCountingStep == null) {
return null;
}
else if (modelCountingStep.itDepends()) {
// satisfiability depends on the same expression, but sub-step solvers must be satisfiability step solvers.
SatisfiabilityOfSingleVariableDifferenceArithmeticConstraintStepSolver ifTrue = clone();
ifTrue.modelCounting = modelCountingStep.getStepSolverForWhenSplitterIsTrue();
SatisfiabilityOfSingleVariableDifferenceArithmeticConstraintStepSolver ifFalse = clone();
ifFalse.modelCounting = modelCountingStep.getStepSolverForWhenSplitterIsFalse();
return new ItDependsOn(modelCountingStep.getSplitterLiteral(), modelCountingStep.getContextSplittingWhenSplitterIsLiteral(), ifTrue, ifFalse);
}
Step result;
Expression satisfiable;
satisfiable = apply(GREATER_THAN, modelCountingStep.getValue(), ZERO);
Expression simplifiedSatisfiable = constraint.getTheory().simplify(satisfiable, context);
// result = new Solution(simplifiedSatisfiable); // used to be like this; not good, for if simplifiedSatisfiable is inconsistent with context, it is not equal to 'false', becoming incomplete even if the context is complete.
result = stepDependingOnLiteral(simplifiedSatisfiable, TRUE, FALSE, context);
return result;
}
}