SparseParametricDtmcSimplifier.cpp

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#include "storm-pars/transformer/SparseParametricDtmcSimplifier.h"
 
#include <optional>
 
#include "storm/adapters/RationalFunctionAdapter.h"
#include "storm/exceptions/NotSupportedException.h"
#include "storm/exceptions/UnexpectedException.h"
#include "storm/logic/CloneVisitor.h"
#include "storm/modelchecker/propositional/SparsePropositionalModelChecker.h"
#include "storm/modelchecker/results/ExplicitQualitativeCheckResult.h"
#include "storm/models/sparse/Dtmc.h"
#include "storm/transformer/GoalStateMerger.h"
#include "storm/utility/graph.h"
 
namespace storm {
namespace transformer {
 
template<typename SparseModelType>
SparseParametricDtmcSimplifier<SparseModelType>::SparseParametricDtmcSimplifier(SparseModelType const& model)
    : SparseParametricModelSimplifier<SparseModelType>(model) {
    // intentionally left empty
}
 
template<typename SparseModelType>
bool SparseParametricDtmcSimplifier<SparseModelType>::simplifyForUntilProbabilities(storm::logic::ProbabilityOperatorFormula const& formula) {
    // Get the prob0, prob1 and the maybeStates
    storm::modelchecker::SparsePropositionalModelChecker<SparseModelType> propositionalChecker(this->originalModel);
    if (!propositionalChecker.canHandle(formula.getSubformula().asUntilFormula().getLeftSubformula()) ||
        !propositionalChecker.canHandle(formula.getSubformula().asUntilFormula().getRightSubformula())) {
        STORM_LOG_DEBUG("Can not simplify when Until-formula has non-propositional subformula(s). Formula: " << formula);
        return false;
    }
    storm::storage::BitVector phiStates = std::move(propositionalChecker.check(formula.getSubformula().asUntilFormula().getLeftSubformula())
                                                        ->template asExplicitQualitativeCheckResult<typename SparseModelType::ValueType>()
                                                        .getTruthValuesVector());
    storm::storage::BitVector psiStates = std::move(propositionalChecker.check(formula.getSubformula().asUntilFormula().getRightSubformula())
                                                        ->template asExplicitQualitativeCheckResult<typename SparseModelType::ValueType>()
                                                        .getTruthValuesVector());
    std::pair<storm::storage::BitVector, storm::storage::BitVector> statesWithProbability01 =
        storm::utility::graph::performProb01(this->originalModel, phiStates, psiStates);
    // Only consider the maybestates that are reachable from one initial state without hopping over a target (i.e., prob1) state
    storm::storage::BitVector reachableGreater0States = storm::utility::graph::getReachableStates(
        this->originalModel.getTransitionMatrix(), this->originalModel.getInitialStates() & ~statesWithProbability01.first, ~statesWithProbability01.first,
        statesWithProbability01.second);
    storm::storage::BitVector maybeStates = reachableGreater0States & ~statesWithProbability01.second;
 
    // obtain the resulting subsystem
    storm::transformer::GoalStateMerger<SparseModelType> goalStateMerger(this->originalModel);
    typename storm::transformer::GoalStateMerger<SparseModelType>::ReturnType mergerResult =
        goalStateMerger.mergeTargetAndSinkStates(maybeStates, statesWithProbability01.second, statesWithProbability01.first);
    this->simplifiedModel = mergerResult.model;
    statesWithProbability01.second = storm::storage::BitVector(this->simplifiedModel->getNumberOfStates(), false);
    if (mergerResult.targetState) {
        statesWithProbability01.second.set(mergerResult.targetState.get(), true);
    }
    std::string targetLabel = "target";
    while (this->simplifiedModel->hasLabel(targetLabel)) {
        targetLabel = "_" + targetLabel;
    }
    this->simplifiedModel->getStateLabeling().addLabel(targetLabel, std::move(statesWithProbability01.second));
 
    // obtain the simplified formula for the simplified model
    auto labelFormula = std::make_shared<storm::logic::AtomicLabelFormula const>(targetLabel);
    auto eventuallyFormula = std::make_shared<storm::logic::EventuallyFormula const>(labelFormula, storm::logic::FormulaContext::Probability);
    this->simplifiedFormula = std::make_shared<storm::logic::ProbabilityOperatorFormula const>(eventuallyFormula, formula.getOperatorInformation());
 
    // Eliminate all states for which all outgoing transitions are constant
    storm::storage::BitVector considerForElimination = ~this->simplifiedModel->getInitialStates();
    if (mergerResult.targetState) {
        considerForElimination.set(*mergerResult.targetState, false);
    }
    if (mergerResult.sinkState) {
        considerForElimination.set(*mergerResult.sinkState, false);
    }
    this->simplifiedModel = this->eliminateConstantDeterministicStates(*this->simplifiedModel, considerForElimination);
 
    return true;
}
 
template<typename SparseModelType>
bool SparseParametricDtmcSimplifier<SparseModelType>::simplifyForBoundedUntilProbabilities(storm::logic::ProbabilityOperatorFormula const& formula) {
    STORM_LOG_THROW(!formula.getSubformula().asBoundedUntilFormula().hasLowerBound(), storm::exceptions::NotSupportedException,
                    "Lower step bounds are not supported.");
    STORM_LOG_THROW(formula.getSubformula().asBoundedUntilFormula().hasUpperBound(), storm::exceptions::UnexpectedException,
                    "Expected a bounded until formula with an upper bound.");
    STORM_LOG_THROW(formula.getSubformula().asBoundedUntilFormula().getUpperBound().getBaseExpression().isIntegerLiteralExpression(),
                    storm::exceptions::UnexpectedException, "Expected a bounded until formula with integral bounds.");
 
    uint_fast64_t upperStepBound = formula.getSubformula().asBoundedUntilFormula().getUpperBound().evaluateAsInt();
    if (formula.getSubformula().asBoundedUntilFormula().isUpperBoundStrict()) {
        STORM_LOG_THROW(upperStepBound > 0, storm::exceptions::UnexpectedException, "Expected a strict upper bound that is greater than zero.");
        --upperStepBound;
    }
 
    // Get the prob0, target, and the maybeStates
    storm::modelchecker::SparsePropositionalModelChecker<SparseModelType> propositionalChecker(this->originalModel);
    if (!propositionalChecker.canHandle(formula.getSubformula().asBoundedUntilFormula().getLeftSubformula()) ||
        !propositionalChecker.canHandle(formula.getSubformula().asBoundedUntilFormula().getRightSubformula())) {
        STORM_LOG_DEBUG("Can not simplify when Until-formula has non-propositional subformula(s). Formula: " << formula);
        return false;
    }
    storm::storage::BitVector phiStates = std::move(propositionalChecker.check(formula.getSubformula().asBoundedUntilFormula().getLeftSubformula())
                                                        ->template asExplicitQualitativeCheckResult<typename SparseModelType::ValueType>()
                                                        .getTruthValuesVector());
    storm::storage::BitVector psiStates = std::move(propositionalChecker.check(formula.getSubformula().asBoundedUntilFormula().getRightSubformula())
                                                        ->template asExplicitQualitativeCheckResult<typename SparseModelType::ValueType>()
                                                        .getTruthValuesVector());
    storm::storage::BitVector probGreater0States =
        storm::utility::graph::performProbGreater0(this->originalModel.getBackwardTransitions(), phiStates, psiStates, true, upperStepBound);
 
    // Only consider the maybestates that are reachable from one initial probGreater0 state within the given amount of steps and without hopping over a target
    // state
    storm::storage::BitVector reachableGreater0States =
        storm::utility::graph::getReachableStates(this->originalModel.getTransitionMatrix(), this->originalModel.getInitialStates() & probGreater0States,
                                                  probGreater0States, psiStates, true, upperStepBound);
    storm::storage::BitVector maybeStates = reachableGreater0States & ~psiStates;
    storm::storage::BitVector prob0States = ~reachableGreater0States & ~psiStates;
 
    // obtain the resulting subsystem
    storm::transformer::GoalStateMerger<SparseModelType> goalStateMerger(this->originalModel);
    typename storm::transformer::GoalStateMerger<SparseModelType>::ReturnType mergerResult =
        goalStateMerger.mergeTargetAndSinkStates(maybeStates, psiStates, prob0States);
    this->simplifiedModel = mergerResult.model;
    psiStates = storm::storage::BitVector(this->simplifiedModel->getNumberOfStates(), false);
    if (mergerResult.targetState) {
        psiStates.set(mergerResult.targetState.get(), true);
    }
    std::string targetLabel = "target";
    while (this->simplifiedModel->hasLabel(targetLabel)) {
        targetLabel = "_" + targetLabel;
    }
    this->simplifiedModel->getStateLabeling().addLabel(targetLabel, std::move(psiStates));
 
    // obtain the simplified formula for the simplified model
    auto labelFormula = std::make_shared<storm::logic::AtomicLabelFormula const>(targetLabel);
    auto boundedUntilFormula =
        std::make_shared<storm::logic::BoundedUntilFormula const>(storm::logic::Formula::getTrueFormula(), labelFormula, std::nullopt,
                                                                  storm::logic::TimeBound(formula.getSubformula().asBoundedUntilFormula().isUpperBoundStrict(),
                                                                                          formula.getSubformula().asBoundedUntilFormula().getUpperBound()),
                                                                  storm::logic::TimeBoundReference(storm::logic::TimeBoundType::Steps));
    this->simplifiedFormula = std::make_shared<storm::logic::ProbabilityOperatorFormula const>(boundedUntilFormula, formula.getOperatorInformation());
 
    return true;
}
 
template<typename SparseModelType>
bool SparseParametricDtmcSimplifier<SparseModelType>::simplifyForReachabilityRewards(storm::logic::RewardOperatorFormula const& formula) {
    typename SparseModelType::RewardModelType const& originalRewardModel =
        formula.hasRewardModelName() ? this->originalModel.getRewardModel(formula.getRewardModelName()) : this->originalModel.getUniqueRewardModel();
 
    // Get the prob1 and the maybeStates
    storm::modelchecker::SparsePropositionalModelChecker<SparseModelType> propositionalChecker(this->originalModel);
    if (!propositionalChecker.canHandle(formula.getSubformula().asEventuallyFormula().getSubformula())) {
        STORM_LOG_DEBUG("Can not simplify when reachability reward formula has non-propositional subformula(s). Formula: " << formula);
        return false;
    }
    storm::storage::BitVector targetStates = std::move(propositionalChecker.check(formula.getSubformula().asEventuallyFormula().getSubformula())
                                                           ->template asExplicitQualitativeCheckResult<typename SparseModelType::ValueType>()
                                                           .getTruthValuesVector());
    // The set of target states can be extended by the states that reach target with probability 1 without collecting any reward
    targetStates = storm::utility::graph::performProb1(this->originalModel.getBackwardTransitions(),
                                                       originalRewardModel.getStatesWithZeroReward(this->originalModel.getTransitionMatrix()), targetStates);
    storm::storage::BitVector statesWithProb1 = storm::utility::graph::performProb1(
        this->originalModel.getBackwardTransitions(), storm::storage::BitVector(this->originalModel.getNumberOfStates(), true), targetStates);
    storm::storage::BitVector infinityStates = ~statesWithProb1;
    // Only consider the states that are reachable from an initial state without hopping over a target state
    storm::storage::BitVector reachableStates = storm::utility::graph::getReachableStates(
        this->originalModel.getTransitionMatrix(), this->originalModel.getInitialStates() & statesWithProb1, statesWithProb1, targetStates);
    storm::storage::BitVector maybeStates = reachableStates & ~targetStates;
 
    // obtain the resulting subsystem
    std::vector<std::string> rewardModelNameAsVector(
        1, formula.hasRewardModelName() ? formula.getRewardModelName() : this->originalModel.getRewardModels().begin()->first);
    storm::transformer::GoalStateMerger<SparseModelType> goalStateMerger(this->originalModel);
    typename storm::transformer::GoalStateMerger<SparseModelType>::ReturnType mergerResult =
        goalStateMerger.mergeTargetAndSinkStates(maybeStates, targetStates, infinityStates, rewardModelNameAsVector);
    this->simplifiedModel = mergerResult.model;
    targetStates = storm::storage::BitVector(this->simplifiedModel->getNumberOfStates(), false);
    if (mergerResult.targetState) {
        targetStates.set(mergerResult.targetState.get(), true);
    }
    std::string targetLabel = "target";
    while (this->simplifiedModel->hasLabel(targetLabel)) {
        targetLabel = "_" + targetLabel;
    }
    this->simplifiedModel->getStateLabeling().addLabel(targetLabel, std::move(targetStates));
 
    // obtain the simplified formula for the simplified model
    auto labelFormula = std::make_shared<storm::logic::AtomicLabelFormula const>(targetLabel);
    auto eventuallyFormula = std::make_shared<storm::logic::EventuallyFormula const>(labelFormula, storm::logic::FormulaContext::Reward);
    this->simplifiedFormula =
        std::make_shared<storm::logic::RewardOperatorFormula const>(eventuallyFormula, rewardModelNameAsVector.front(), formula.getOperatorInformation());
 
    // Eliminate all states for which all outgoing transitions are constant
    storm::storage::BitVector considerForElimination = ~this->simplifiedModel->getInitialStates();
    if (mergerResult.targetState) {
        considerForElimination.set(*mergerResult.targetState, false);
    }
    if (mergerResult.sinkState) {
        considerForElimination.set(*mergerResult.sinkState, false);
    }
    this->simplifiedModel = this->eliminateConstantDeterministicStates(*this->simplifiedModel, considerForElimination, rewardModelNameAsVector.front());
 
    return true;
}
 
template<typename SparseModelType>
bool SparseParametricDtmcSimplifier<SparseModelType>::simplifyForCumulativeRewards(storm::logic::RewardOperatorFormula const& formula) {
    STORM_LOG_THROW(formula.getSubformula().asCumulativeRewardFormula().getBound().getBaseExpression().isIntegerLiteralExpression(),
                    storm::exceptions::UnexpectedException, "Expected a cumulative reward formula with integral bound.");
 
    typename SparseModelType::RewardModelType const& originalRewardModel =
        formula.hasRewardModelName() ? this->originalModel.getRewardModel(formula.getRewardModelName()) : this->originalModel.getUniqueRewardModel();
 
    uint_fast64_t stepBound = formula.getSubformula().asCumulativeRewardFormula().getBound().evaluateAsInt();
    if (formula.getSubformula().asCumulativeRewardFormula().isBoundStrict()) {
        STORM_LOG_THROW(stepBound > 0, storm::exceptions::UnexpectedException, "Expected a strict upper bound that is greater than zero.");
        --stepBound;
    }
 
    // Get the states with non-zero reward
    storm::storage::BitVector maybeStates = storm::utility::graph::performProbGreater0(
        this->originalModel.getBackwardTransitions(), storm::storage::BitVector(this->originalModel.getNumberOfStates(), true),
        ~originalRewardModel.getStatesWithZeroReward(this->originalModel.getTransitionMatrix()), true, stepBound);
    storm::storage::BitVector zeroRewardStates = ~maybeStates;
    storm::storage::BitVector noStates(this->originalModel.getNumberOfStates(), false);
 
    // obtain the resulting subsystem
    std::vector<std::string> rewardModelNameAsVector(
        1, formula.hasRewardModelName() ? formula.getRewardModelName() : this->originalModel.getRewardModels().begin()->first);
    storm::transformer::GoalStateMerger<SparseModelType> goalStateMerger(this->originalModel);
    typename storm::transformer::GoalStateMerger<SparseModelType>::ReturnType mergerResult =
        goalStateMerger.mergeTargetAndSinkStates(maybeStates, noStates, zeroRewardStates, rewardModelNameAsVector);
    this->simplifiedModel = mergerResult.model;
 
    // obtain the simplified formula for the simplified model
    this->simplifiedFormula = storm::logic::CloneVisitor().clone(formula);
 
    return true;
}
 
template class SparseParametricDtmcSimplifier<storm::models::sparse::Dtmc<storm::RationalFunction>>;
}  // namespace transformer
}  // namespace storm