Merge branch 'dft-approximation' of https://sselab.de/lab9/private/git/storm into dft-approximation

Former-commit-id: 595c5e7891

src/builder/DftExplorationHeuristic.cpp

@@ -3,85 +3,73 @@
 #include "src/utility/macros.h"
 #include "src/utility/constants.h"
 #include "src/exceptions/NotImplementedException.h"
-#include "src/storage/dft/DFTState.h"
-
-#include <limits>
 
 namespace storm {
     namespace builder {
 
         template<typename ValueType>
-        DFTExplorationHeuristic<ValueType>::DFTExplorationHeuristic() : skip(true), depth(std::numeric_limits<std::size_t>::max()), rate(storm::utility::zero<ValueType>()), exitRate(storm::utility::zero<ValueType>()) {
+        DFTExplorationHeuristic<ValueType>::DFTExplorationHeuristic(size_t id) : id(id), expand(true), lowerBound(storm::utility::zero<ValueType>()), upperBound(storm::utility::infinity<ValueType>()), depth(0), probability(storm::utility::one<ValueType>()) {
             // Intentionally left empty
         }
 
         template<typename ValueType>
-        bool DFTExplorationHeuristic<ValueType>::isSkip(double approximationThreshold, ApproximationHeuristic heuristic) const {
-            if (!skip) {
-                return false;
-            }
-            switch (heuristic) {
-                case ApproximationHeuristic::NONE:
-                    return false;
-                case ApproximationHeuristic::DEPTH:
-                    return depth > approximationThreshold;
-                case ApproximationHeuristic::RATERATIO:
-                    // TODO Matthias: implement
-                    STORM_LOG_THROW(false, storm::exceptions::NotImplementedException, "Heuristic rate ration does not work.");
-            }
+        DFTExplorationHeuristic<ValueType>::DFTExplorationHeuristic(size_t id, DFTExplorationHeuristic const& predecessor, ValueType rate, ValueType exitRate) : id(id), expand(false), lowerBound(storm::utility::zero<ValueType>()), upperBound(storm::utility::zero<ValueType>()), depth(predecessor.depth + 1) {
+            STORM_LOG_ASSERT(storm::utility::zero<ValueType>() < exitRate, "Exit rate is 0");
+            probability = predecessor.probability * rate/exitRate;
         }
 
         template<typename ValueType>
-        void DFTExplorationHeuristic<ValueType>::setNotSkip() {
-            skip = false;
+        void DFTExplorationHeuristic<ValueType>::setBounds(ValueType lowerBound, ValueType upperBound) {
+            this->lowerBound = lowerBound;
+            this->upperBound = upperBound;
         }
 
-
-        template<typename ValueType>
-        size_t DFTExplorationHeuristic<ValueType>::getDepth() const {
-            return depth;
+        template<>
+        bool DFTExplorationHeuristicProbability<double>::updateHeuristicValues(DFTExplorationHeuristic<double> const& predecessor, double rate, double exitRate) {
+            STORM_LOG_ASSERT(exitRate > 0, "Exit rate is 0");
+            probability += predecessor.getProbability() * rate/exitRate;
+            return true;
         }
 
-        template<typename ValueType>
-        void DFTExplorationHeuristic<ValueType>::setHeuristicValues(size_t depth, ValueType rate, ValueType exitRate) {
-            this->depth = depth;
-            this->rate = rate;
-            this->exitRate = exitRate;
+        template<>
+        bool DFTExplorationHeuristicProbability<storm::RationalFunction>::updateHeuristicValues(DFTExplorationHeuristic<storm::RationalFunction> const& predecessor, storm::RationalFunction rate, storm::RationalFunction exitRate) {
+            STORM_LOG_THROW(false, storm::exceptions::NotImplementedException, "Heuristic rate ration does not work for rational functions.");
+            return false;
         }
 
-        template<typename ValueType>
-        double DFTExplorationHeuristic<ValueType>::getPriority() const {
-            STORM_LOG_THROW(false, storm::exceptions::NotImplementedException, "Approximation works only for double.");
+        template<>
+        double DFTExplorationHeuristicProbability<double>::getPriority() const {
+            return probability;
         }
 
         template<>
-        double DFTExplorationHeuristic<double>::getPriority() const {
-            // TODO Matthias: change according to heuristic
-            //return rate/exitRate;
-            return depth;
+        double DFTExplorationHeuristicProbability<storm::RationalFunction>::getPriority() const {
+            STORM_LOG_THROW(false, storm::exceptions::NotImplementedException, "Heuristic rate ration does not work for rational functions.");
         }
 
         template<>
-        double DFTExplorationHeuristic<storm::RationalFunction>::getPriority() const {
-            STORM_LOG_THROW(false, storm::exceptions::NotImplementedException, "Approximation works only for double.");
-            /*std::cout << (rate / exitRate) << " < " << threshold << ": " << (number < threshold) << std::endl;
-             std::map<storm::Variable, storm::RationalNumber> mapping;
-             storm::RationalFunction eval(number.evaluate(mapping));
-             std::cout << "Evaluated: " << eval << std::endl;
-             return eval < threshold;*/
+        double DFTExplorationHeuristicBoundDifference<double>::getPriority() const {
+            return upperBound / lowerBound;
         }
 
-        template<typename ValueType>
-        bool compareDepth(std::shared_ptr<storm::storage::DFTState<ValueType>> stateA, std::shared_ptr<storm::storage::DFTState<ValueType>> stateB) {
-            return stateA->getPriority() > stateB->getPriority();
+        template<>
+        double DFTExplorationHeuristicBoundDifference<storm::RationalFunction>::getPriority() const {
+            STORM_LOG_THROW(false, storm::exceptions::NotImplementedException, "Heuristic bound difference does not work for rational functions.");
         }
 
+        // Instantiate templates.
         template class DFTExplorationHeuristic<double>;
-        template bool compareDepth(std::shared_ptr<storm::storage::DFTState<double>>, std::shared_ptr<storm::storage::DFTState<double>>);
+        template class DFTExplorationHeuristicNone<double>;
+        template class DFTExplorationHeuristicDepth<double>;
+        template class DFTExplorationHeuristicProbability<double>;
+        template class DFTExplorationHeuristicBoundDifference<double>;
 
 #ifdef STORM_HAVE_CARL
         template class DFTExplorationHeuristic<storm::RationalFunction>;
-        template bool compareDepth(std::shared_ptr<storm::storage::DFTState<storm::RationalFunction>>, std::shared_ptr<storm::storage::DFTState<storm::RationalFunction>>);
+        template class DFTExplorationHeuristicNone<storm::RationalFunction>;
+        template class DFTExplorationHeuristicDepth<storm::RationalFunction>;
+        template class DFTExplorationHeuristicProbability<storm::RationalFunction>;
+        template class DFTExplorationHeuristicBoundDifference<storm::RationalFunction>;
 #endif
     }
 }

src/builder/DftExplorationHeuristic.h

@@ -2,50 +2,189 @@
 #define STORM_BUILDER_DFTEXPLORATIONHEURISTIC_H_
 
 #include <memory>
-#include <algorithm>
 
 namespace storm {
 
-    // Forward declaration
-    namespace storage {
-        template<typename ValueType>
-        class DFTState;
-    }
-
     namespace builder {
 
         /*!
          * Enum representing the heuristic used for deciding which states to expand.
          */
-        enum class ApproximationHeuristic { NONE, DEPTH, RATERATIO };
+        enum class ApproximationHeuristic { NONE, DEPTH, PROBABILITY };
 
+
+        /*!
+         * General super class for appoximation heuristics.
+         */
         template<typename ValueType>
         class DFTExplorationHeuristic {
 
         public:
-            DFTExplorationHeuristic();
+            DFTExplorationHeuristic(size_t id);
 
-            void setHeuristicValues(size_t depth, ValueType rate, ValueType exitRate);
+            DFTExplorationHeuristic(size_t id, DFTExplorationHeuristic const& predecessor, ValueType rate, ValueType exitRate);
 
-            bool isSkip(double approximationThreshold, ApproximationHeuristic heuristic) const;
+            void setBounds(ValueType lowerBound, ValueType upperBound);
 
-            void setNotSkip();
+            virtual bool updateHeuristicValues(DFTExplorationHeuristic const& predecessor, ValueType rate, ValueType exitRate) = 0;
 
-            size_t getDepth() const;
+            virtual double getPriority() const = 0;
 
-            double getPriority() const;
+            virtual bool isSkip(double approximationThreshold) const = 0;
 
-        private:
+            void markExpand() {
+                expand = true;
+            }
+
+            size_t getId() const {
+                return id;
+            }
+
+            bool isExpand() {
+                return expand;
+            }
+
+            size_t getDepth() const {
+                return depth;
+            }
+
+            ValueType getProbability() const {
+                return probability;
+            }
+
+            ValueType getLowerBound() const {
+                return lowerBound;
+            }
 
-            bool skip;
+            ValueType getUpperBound() const {
+                return upperBound;
+            }
+
+        protected:
+            size_t id;
+            bool expand;
+            ValueType lowerBound;
+            ValueType upperBound;
             size_t depth;
-            ValueType rate;
-            ValueType exitRate;
+            ValueType probability;
+        };
+
+        template<typename ValueType>
+        class DFTExplorationHeuristicNone : public DFTExplorationHeuristic<ValueType> {
+        public:
+            DFTExplorationHeuristicNone(size_t id) : DFTExplorationHeuristic<ValueType>(id) {
+                // Intentionally left empty
+            }
+
+            DFTExplorationHeuristicNone(size_t id, DFTExplorationHeuristicNone<ValueType> const& predecessor, ValueType rate, ValueType exitRate) : DFTExplorationHeuristic<ValueType>(id, predecessor, rate, exitRate) {
+                // Intentionally left empty
+            }
 
+            bool updateHeuristicValues(DFTExplorationHeuristic<ValueType> const& predecessor, ValueType rate, ValueType exitRate) override {
+                return false;
+            }
+
+            double getPriority() const override {
+                return 0;
+            }
+
+            bool isSkip(double approximationThreshold) const override {
+                return false;
+            }
+
+            bool operator<(DFTExplorationHeuristicNone<ValueType> const& other) const {
+                return this->id > other.id;
+            }
         };
 
         template<typename ValueType>
-        bool compareDepth(std::shared_ptr<storm::storage::DFTState<ValueType>> stateA, std::shared_ptr<storm::storage::DFTState<ValueType>> stateB);
+        class DFTExplorationHeuristicDepth : public DFTExplorationHeuristic<ValueType> {
+        public:
+            DFTExplorationHeuristicDepth(size_t id) : DFTExplorationHeuristic<ValueType>(id) {
+                // Intentionally left empty
+            }
+
+            DFTExplorationHeuristicDepth(size_t id, DFTExplorationHeuristicDepth<ValueType> const& predecessor, ValueType rate, ValueType exitRate) : DFTExplorationHeuristic<ValueType>(id, predecessor, rate, exitRate) {
+                // Intentionally left empty
+            }
+
+            bool updateHeuristicValues(DFTExplorationHeuristic<ValueType> const& predecessor, ValueType rate, ValueType exitRate) override {
+                if (predecessor.getDepth() < this->depth) {
+                    this->depth = predecessor.getDepth();
+                    return true;
+                }
+                return false;
+            }
+
+
+            double getPriority() const override {
+                return this->depth;
+            }
+
+            bool isSkip(double approximationThreshold) const override {
+                return !this->expand && this->depth > approximationThreshold;
+            }
+
+            bool operator<(DFTExplorationHeuristicDepth<ValueType> const& other) const {
+                return this->depth > other.depth;
+            }
+        };
+
+        template<typename ValueType>
+        class DFTExplorationHeuristicProbability : public DFTExplorationHeuristic<ValueType> {
+        public:
+            DFTExplorationHeuristicProbability(size_t id) : DFTExplorationHeuristic<ValueType>(id) {
+                // Intentionally left empty
+            }
+
+            DFTExplorationHeuristicProbability(size_t id, DFTExplorationHeuristicProbability<ValueType> const& predecessor, ValueType rate, ValueType exitRate) : DFTExplorationHeuristic<ValueType>(id, predecessor, rate, exitRate) {
+                // Intentionally left empty
+            }
+
+            bool updateHeuristicValues(DFTExplorationHeuristic<ValueType> const& predecessor, ValueType rate, ValueType exitRate) override;
+
+            double getPriority() const override;
+
+            bool isSkip(double approximationThreshold) const override {
+                return !this->expand && this->getPriority() < approximationThreshold;
+            }
+
+            bool operator<(DFTExplorationHeuristicProbability<ValueType> const& other) const {
+                return this->getPriority() < other.getPriority();
+            }
+        };
+
+        template<typename ValueType>
+        class DFTExplorationHeuristicBoundDifference : public DFTExplorationHeuristic<ValueType> {
+        public:
+            DFTExplorationHeuristicBoundDifference(size_t id) : DFTExplorationHeuristic<ValueType>(id) {
+                // Intentionally left empty
+            }
+
+            DFTExplorationHeuristicBoundDifference(size_t id, DFTExplorationHeuristicBoundDifference<ValueType> const& predecessor, ValueType rate, ValueType exitRate) : DFTExplorationHeuristic<ValueType>(id, predecessor, rate, exitRate) {
+                // Intentionally left empty
+            }
+
+            bool updateHeuristicValues(DFTExplorationHeuristic<ValueType> const& predecessor, ValueType rate, ValueType exitRate) override {
+                return false;
+            }
+
+            double getPriority() const override;
+
+            bool isSkip(double approximationThreshold) const override {
+                return !this->expand && this->getPriority() < approximationThreshold;
+            }
+
+            bool operator<(DFTExplorationHeuristicBoundDifference<ValueType> const& other) const {
+                return this->getPriority() < other.getPriority();
+            }
+
+        private:
+            ValueType lowerBound;
+            ValueType upperBound;
+        };
+
+
     }
 }
 

src/builder/DftSmtBuilder.cpp

@@ -1,4 +1,4 @@
-#include "src/builder/DFTSMTBuilder.h"
+#include "src/builder/DftSmtBuilder.h"
 #include "src/exceptions/NotImplementedException.h"
 
 namespace storm {

src/builder/ExplicitDFTModelBuilder.cpp

@@ -58,6 +58,7 @@ namespace storm {
                     STORM_LOG_ASSERT(mStates.getValue(pseudoStatePair.second) >= OFFSET_PSEUDO_STATE, "State is no pseudo state.");
                     STORM_LOG_TRACE("Create pseudo state from bit vector " << pseudoStatePair.second);
                     DFTStatePointer pseudoState = std::make_shared<storm::storage::DFTState<ValueType>>(pseudoStatePair.second, mDft, *mStateGenerationInfo, newIndex);
+                    pseudoState->construct();
                     STORM_LOG_ASSERT(pseudoStatePair.second == pseudoState->status(), "Pseudo states do not coincide.");
                     STORM_LOG_TRACE("Explore pseudo state " << mDft.getStateString(pseudoState) << " with id " << pseudoState->getId());
                     auto exploreResult = exploreStates(pseudoState, rowOffset, transitionMatrixBuilder, tmpMarkovianStates, modelComponents.exitRates);

src/builder/ExplicitDFTModelBuilderApprox.cpp

@@ -3,6 +3,7 @@
 #include <src/models/sparse/Ctmc.h>
 #include <src/utility/constants.h>
 #include <src/utility/vector.h>
+#include "src/utility/bitoperations.h"
 #include <src/exceptions/UnexpectedException.h>
 #include "src/settings/modules/DFTSettings.h"
 #include "src/settings/SettingsManager.h"
@@ -31,18 +32,75 @@ namespace storm {
                 generator(dft, *stateGenerationInfo, enableDC, mergeFailedStates),
                 matrixBuilder(!generator.isDeterministicModel()),
                 stateStorage(((dft.stateVectorSize() / 64) + 1) * 64),
-                explorationQueue([this](StateType idA, StateType idB) {
-                        return isPriorityGreater(idA, idB);
-                    })
+                // TODO Matthias: make choosable
+                //explorationQueue(dft.nrElements()+1, 0, 1)
+                explorationQueue(200, 0, 0.9)
         {
             // Intentionally left empty.
+            // TODO Matthias: remove again
+            heuristic = storm::builder::ApproximationHeuristic::PROBABILITY;
+
+            // Compute independent subtrees
+            if (dft.topLevelType() == storm::storage::DFTElementType::OR) {
+                // We only support this for approximation with top level element OR
+                for (auto const& child : dft.getGate(dft.getTopLevelIndex())->children()) {
+                    // Consider all children of the top level gate
+                    std::vector<size_t> isubdft;
+                    if (child->nrParents() > 1 || child->hasOutgoingDependencies()) {
+                        STORM_LOG_TRACE("child " << child->name() << "does not allow modularisation.");
+                        isubdft.clear();
+                    } else if (dft.isGate(child->id())) {
+                        isubdft = dft.getGate(child->id())->independentSubDft(false);
+                    } else {
+                        STORM_LOG_ASSERT(dft.isBasicElement(child->id()), "Child is no BE.");
+                        if(dft.getBasicElement(child->id())->hasIngoingDependencies()) {
+                            STORM_LOG_TRACE("child " << child->name() << "does not allow modularisation.");
+                            isubdft.clear();
+                        } else {
+                            isubdft = {child->id()};
+                        }
+                    }
+                    if(isubdft.empty()) {
+                        subtreeBEs.clear();
+                        break;
+                    } else {
+                        // Add new independent subtree
+                        std::vector<size_t> subtree;
+                        for (size_t id : isubdft) {
+                            if (dft.isBasicElement(id)) {
+                                subtree.push_back(id);
+                            }
+                        }
+                        subtreeBEs.push_back(subtree);
+                    }
+                }
+            }
+            if (subtreeBEs.empty()) {
+                // Consider complete tree
+                std::vector<size_t> subtree;
+                for (size_t id = 0; id < dft.nrElements(); ++id) {
+                    if (dft.isBasicElement(id)) {
+                        subtree.push_back(id);
+                    }
+                }
+                subtreeBEs.push_back(subtree);
+            }
+
+            for (auto tree : subtreeBEs) {
+                std::stringstream stream;
+                stream << "Subtree: ";
+                for (size_t id : tree) {
+                    stream << id << ", ";
+                }
+                STORM_LOG_TRACE(stream.str());
+            }
         }
 
         template<typename ValueType, typename StateType>
-        void ExplicitDFTModelBuilderApprox<ValueType, StateType>::buildModel(LabelOptions const& labelOpts, bool firstTime, double approximationThreshold) {
+        void ExplicitDFTModelBuilderApprox<ValueType, StateType>::buildModel(LabelOptions const& labelOpts, size_t iteration, double approximationThreshold) {
             STORM_LOG_TRACE("Generating DFT state space");
 
-            if (firstTime) {
+            if (iteration < 1) {
                 // Initialize
                 modelComponents.markovianStates = storm::storage::BitVector(INITIAL_BITVECTOR_SIZE);
 
@@ -75,11 +133,28 @@ namespace storm {
                 STORM_LOG_ASSERT(stateStorage.initialStateIndices.size() == 1, "Only one initial state assumed.");
                 initialStateIndex = stateStorage.initialStateIndices[0];
                 STORM_LOG_TRACE("Initial state: " << initialStateIndex);
-
+                // Initialize heuristic values for inital state
+                STORM_LOG_ASSERT(!statesNotExplored.at(initialStateIndex).second, "Heuristic for initial state is already initialized");
+                ExplorationHeuristicPointer heuristic = std::make_shared<ExplorationHeuristic>(initialStateIndex);
+                heuristic->markExpand();
+                statesNotExplored[initialStateIndex].second = heuristic;
+                explorationQueue.push(heuristic);
             } else {
                 initializeNextIteration();
             }
 
+            switch (heuristic) {
+                case storm::builder::ApproximationHeuristic::NONE:
+                    // Do not change anything
+                    approximationThreshold = dft.nrElements()+10;
+                    break;
+                case storm::builder::ApproximationHeuristic::DEPTH:
+                    approximationThreshold = iteration;
+                    break;
+                case storm::builder::ApproximationHeuristic::PROBABILITY:
+                    approximationThreshold = 10 * std::pow(2, iteration);
+                    break;
+            }
             exploreStateSpace(approximationThreshold);
 
             size_t stateSize = stateStorage.getNumberOfStates() + (mergeFailedStates ? 1 : 0);
@@ -94,8 +169,7 @@ namespace storm {
 
             STORM_LOG_TRACE("State remapping: " << matrixBuilder.stateRemapping);
             STORM_LOG_TRACE("Markovian states: " << modelComponents.markovianStates);
-            STORM_LOG_DEBUG("Generated " << stateSize << " states");
-            STORM_LOG_DEBUG("Skipped " << skippedStates.size() << " states");
+            STORM_LOG_DEBUG("Model has " << stateSize << " states");
             STORM_LOG_DEBUG("Model is " << (generator.isDeterministicModel() ? "deterministic" : "non-deterministic"));
 
             // Build transition matrix
@@ -117,8 +191,8 @@ namespace storm {
             // Push skipped states to explore queue
             // TODO Matthias: remove
             for (auto const& skippedState : skippedStates) {
-                statesNotExplored[skippedState.second->getId()] = skippedState.second;
-                explorationQueue.push(skippedState.second->getId());
+                statesNotExplored[skippedState.second.first->getId()] = skippedState.second;
+                explorationQueue.push(skippedState.second.second);
             }
 
             // Initialize matrix builder again
@@ -134,7 +208,8 @@ namespace storm {
             auto iterSkipped = skippedStates.begin();
             size_t skippedBefore = 0;
             for (size_t i = 0; i < indexRemapping.size(); ++i) {
-                while (iterSkipped->first <= i) {
+                while (iterSkipped != skippedStates.end() && iterSkipped->first <= i) {
+                    STORM_LOG_ASSERT(iterSkipped->first < indexRemapping.size(), "Skipped is too high.");
                     ++skippedBefore;
                     ++iterSkipped;
                 }
@@ -146,7 +221,7 @@ namespace storm {
             matrixBuilder.mappingOffset = nrStates;
             STORM_LOG_TRACE("# expanded states: " << nrExpandedStates);
             StateType skippedIndex = nrExpandedStates;
-            std::map<StateType, DFTStatePointer> skippedStatesNew;
+            std::map<StateType, std::pair<DFTStatePointer, ExplorationHeuristicPointer>> skippedStatesNew;
             for (size_t id = 0; id < matrixBuilder.stateRemapping.size(); ++id) {
                 StateType index = matrixBuilder.stateRemapping[id];
                 auto itFind = skippedStates.find(index);
@@ -193,7 +268,7 @@ namespace storm {
                             auto itFind = skippedStates.find(itEntry->getColumn());
                             if (itFind != skippedStates.end()) {
                                 // Set id for skipped states as we remap it later
-                                matrixBuilder.addTransition(matrixBuilder.mappingOffset + itFind->second->getId(), itEntry->getValue());
+                                matrixBuilder.addTransition(matrixBuilder.mappingOffset + itFind->second.first->getId(), itEntry->getValue());
                             } else {
                                 // Set newly remapped index for expanded states
                                 matrixBuilder.addTransition(indexRemapping[itEntry->getColumn()], itEntry->getValue());
@@ -212,13 +287,17 @@ namespace storm {
 
         template<typename ValueType, typename StateType>
         void ExplicitDFTModelBuilderApprox<ValueType, StateType>::exploreStateSpace(double approximationThreshold) {
+            size_t nrExpandedStates = 0;
+            size_t nrSkippedStates = 0;
             // TODO Matthias: do not empty queue every time but break before
             while (!explorationQueue.empty()) {
                 // Get the first state in the queue
-                StateType currentId = explorationQueue.popTop();
+                ExplorationHeuristicPointer currentExplorationHeuristic = explorationQueue.popTop();
+                StateType currentId = currentExplorationHeuristic->getId();
                 auto itFind = statesNotExplored.find(currentId);
                 STORM_LOG_ASSERT(itFind != statesNotExplored.end(), "Id " << currentId << " not found");
-                DFTStatePointer currentState = itFind->second;
+                DFTStatePointer currentState = itFind->second.first;
+                STORM_LOG_ASSERT(currentExplorationHeuristic == itFind->second.second, "Exploration heuristics do not match");
                 STORM_LOG_ASSERT(currentState->getId() == currentId, "Ids do not match");
                 // Remove it from the list of not explored states
                 statesNotExplored.erase(itFind);
@@ -240,18 +319,21 @@ namespace storm {
                 // Try to explore the next state
                 generator.load(currentState);
 
-                if (currentState->isSkip(approximationThreshold, heuristic)) {
+                if (nrExpandedStates > approximationThreshold && !currentExplorationHeuristic->isExpand()) {
+                //if (currentExplorationHeuristic->isSkip(approximationThreshold)) {
                     // Skip the current state
+                    ++nrSkippedStates;
                     STORM_LOG_TRACE("Skip expansion of state: " << dft.getStateString(currentState));
                     setMarkovian(true);
                     // Add transition to target state with temporary value 0
                     // TODO Matthias: what to do when there is no unique target state?
                     matrixBuilder.addTransition(failedStateId, storm::utility::zero<ValueType>());
                     // Remember skipped state
-                    skippedStates[matrixBuilder.getCurrentRowGroup() - 1] = currentState;
+                    skippedStates[matrixBuilder.getCurrentRowGroup() - 1] = std::make_pair(currentState, currentExplorationHeuristic);
                     matrixBuilder.finishRow();
                 } else {
                     // Explore the current state
+                    ++nrExpandedStates;
                     storm::generator::StateBehavior<ValueType, StateType> behavior = generator.expand(std::bind(&ExplicitDFTModelBuilderApprox::getOrAddStateIndex, this, std::placeholders::_1));
                     STORM_LOG_ASSERT(!behavior.empty(), "Behavior is empty.");
                     setMarkovian(behavior.begin()->isMarkovian());
@@ -260,18 +342,40 @@ namespace storm {
                     for (auto const& choice : behavior) {
                         // Add the probabilistic behavior to the matrix.
                         for (auto const& stateProbabilityPair : choice) {
+                            STORM_LOG_ASSERT(!storm::utility::isZero(stateProbabilityPair.second), "Probability zero.");
                             // Set transition to state id + offset. This helps in only remapping all previously skipped states.
                             matrixBuilder.addTransition(matrixBuilder.mappingOffset + stateProbabilityPair.first, stateProbabilityPair.second);
-                            // TODO Matthias: set heuristic values here
+                            // Set heuristic values for reached states
+                            auto iter = statesNotExplored.find(stateProbabilityPair.first);
+                            if (iter != statesNotExplored.end()) {
+                                // Update heuristic values
+                                DFTStatePointer state = iter->second.first;
+                                if (!iter->second.second) {
+                                    // Initialize heuristic values
+                                    ExplorationHeuristicPointer heuristic = std::make_shared<ExplorationHeuristic>(stateProbabilityPair.first, *currentExplorationHeuristic, stateProbabilityPair.second, choice.getTotalMass());
+                                    iter->second.second = heuristic;
+                                    if (state->hasFailed(dft.getTopLevelIndex()) || state->isFailsafe(dft.getTopLevelIndex()) || state->nrFailableDependencies() > 0 || (state->nrFailableDependencies() == 0 && state->nrFailableBEs() == 0)) {
+                                        // Do not skip absorbing state or if reached by dependencies
+                                        iter->second.second->markExpand();
+                                    }
+                                    explorationQueue.push(heuristic);
+                                } else if (!iter->second.second->isExpand()) {
+                                    double oldPriority = iter->second.second->getPriority();
+                                    if (iter->second.second->updateHeuristicValues(*currentExplorationHeuristic, stateProbabilityPair.second, choice.getTotalMass())) {
+                                        // Update priority queue
+                                        explorationQueue.update(iter->second.second, oldPriority);
+                                    }
+                                }
+                            }
                         }
                         matrixBuilder.finishRow();
                     }
                 }
-
-                // Update priority queue
-                // TODO Matthias: only when necessary
-                explorationQueue.fix();
             } // end exploration
+
+            STORM_LOG_INFO("Expanded " << nrExpandedStates << " states");
+            STORM_LOG_INFO("Skipped " << nrSkippedStates << " states");
+            STORM_LOG_ASSERT(nrSkippedStates == skippedStates.size(), "Nr skipped states is wrong");
         }
 
         template<typename ValueType, typename StateType>
@@ -328,11 +432,7 @@ namespace storm {
         template<typename ValueType, typename StateType>
         std::shared_ptr<storm::models::sparse::Model<ValueType>> ExplicitDFTModelBuilderApprox<ValueType, StateType>::getModelApproximation(bool lowerBound) {
             // TODO Matthias: handle case with no skipped states
-            if (lowerBound) {
-                changeMatrixLowerBound(modelComponents.transitionMatrix);
-            } else {
-                changeMatrixUpperBound(modelComponents.transitionMatrix);
-            }
+            changeMatrixBound(modelComponents.transitionMatrix, lowerBound);
             return createModel(true);
         }
 
@@ -388,42 +488,148 @@ namespace storm {
         }
 
         template<typename ValueType, typename StateType>
-        void ExplicitDFTModelBuilderApprox<ValueType, StateType>::changeMatrixLowerBound(storm::storage::SparseMatrix<ValueType> & matrix) const {
+        void ExplicitDFTModelBuilderApprox<ValueType, StateType>::changeMatrixBound(storm::storage::SparseMatrix<ValueType> & matrix, bool lowerBound) const {
             // Set lower bound for skipped states
             for (auto it = skippedStates.begin(); it != skippedStates.end(); ++it) {
                 auto matrixEntry = matrix.getRow(it->first, 0).begin();
                 STORM_LOG_ASSERT(matrixEntry->getColumn() == failedStateId, "Transition has wrong target state.");
-                // Get the lower bound by considering the failure of all possible BEs
-                ValueType newRate = storm::utility::zero<ValueType>();
-                for (size_t index = 0; index < it->second->nrFailableBEs(); ++index) {
-                    newRate += it->second->getFailableBERate(index);
+                STORM_LOG_ASSERT(!it->second.first->isPseudoState(), "State is still pseudo state.");
+
+                ExplorationHeuristicPointer heuristic = it->second.second;
+                if (storm::utility::isZero(heuristic->getUpperBound())) {
+                    // Initialize bounds
+                    ValueType lowerBound = getLowerBound(it->second.first);
+                    ValueType upperBound = getUpperBound(it->second.first);
+                    heuristic->setBounds(lowerBound, upperBound);
                 }
-                for (size_t index = 0; index < it->second->nrNotFailableBEs(); ++index) {
-                    newRate += it->second->getNotFailableBERate(index);
+
+                // Change bound
+                if (lowerBound) {
+                    matrixEntry->setValue(it->second.second->getLowerBound());
+                } else {
+                    matrixEntry->setValue(it->second.second->getUpperBound());
                 }
-                matrixEntry->setValue(newRate);
             }
         }
 
         template<typename ValueType, typename StateType>
-        void ExplicitDFTModelBuilderApprox<ValueType, StateType>::changeMatrixUpperBound(storm::storage::SparseMatrix<ValueType> & matrix) const {
-            // Set uppper bound for skipped states
-            for (auto it = skippedStates.begin(); it != skippedStates.end(); ++it) {
-                auto matrixEntry = matrix.getRow(it->first, 0).begin();
-                STORM_LOG_ASSERT(matrixEntry->getColumn() == failedStateId, "Transition has wrong target state.");
-                // Get the upper bound by considering the failure of all BEs
-                // The used formula for the rate is 1/( 1/a + 1/b + ...)
-                // TODO Matthias: improve by using closed formula for AND of all BEs
-                ValueType newRate = storm::utility::zero<ValueType>();
-                for (size_t index = 0; index < it->second->nrFailableBEs(); ++index) {
-                    newRate += storm::utility::one<ValueType>() / it->second->getFailableBERate(index);
+        ValueType ExplicitDFTModelBuilderApprox<ValueType, StateType>::getLowerBound(DFTStatePointer const& state) const {
+            // Get the lower bound by considering the failure of all possible BEs
+            ValueType lowerBound = storm::utility::zero<ValueType>();
+            for (size_t index = 0; index < state->nrFailableBEs(); ++index) {
+                lowerBound += state->getFailableBERate(index);
+            }
+            return lowerBound;
+        }
+
+        template<typename ValueType, typename StateType>
+        ValueType ExplicitDFTModelBuilderApprox<ValueType, StateType>::getUpperBound(DFTStatePointer const& state) const {
+            // Get the upper bound by considering the failure of all BEs
+            ValueType upperBound = storm::utility::one<ValueType>();
+            ValueType rateSum = storm::utility::zero<ValueType>();
+
+            // Compute for each independent subtree
+            for (std::vector<size_t> const& subtree : subtreeBEs) {
+                // Get all possible rates
+                std::vector<ValueType> rates;
+                storm::storage::BitVector coldBEs(subtree.size(), false);
+                for (size_t i = 0; i < subtree.size(); ++i) {
+                    size_t id = subtree[i];
+                    if (state->isOperational(id)) {
+                        // Get BE rate
+                        ValueType rate = state->getBERate(id);
+                        if (storm::utility::isZero<ValueType>(rate)) {
+                            // Get active failure rate for cold BE
+                            rate = dft.getBasicElement(id)->activeFailureRate();
+                            // Mark BE as cold
+                            coldBEs.set(i, true);
+                        }
+                        rates.push_back(rate);
+                        rateSum += rate;
+                    }
+                }
+
+                STORM_LOG_ASSERT(rates.size() > 0, "No rates failable");
+
+                // Sort rates
+                std::sort(rates.begin(), rates.end());
+                std::vector<size_t> rateCount(rates.size(), 0);
+                size_t lastIndex = 0;
+                for (size_t i = 0; i < rates.size(); ++i) {
+                    if (rates[lastIndex] != rates[i]) {
+                        lastIndex = i;
+                    }
+                    ++rateCount[lastIndex];
                 }
-                for (size_t index = 0; index < it->second->nrNotFailableBEs(); ++index) {
-                    newRate += storm::utility::one<ValueType>() / it->second->getNotFailableBERate(index);
+
+                for (size_t i = 0; i < rates.size(); ++i) {
+                    // Cold BEs cannot fail in the first step
+                    if (!coldBEs.get(i) && rateCount[i] > 0) {
+                        // Compute AND MTTF of subtree without current rate and scale with current rate
+                        upperBound += rates.back() * rateCount[i] * computeMTTFAnd(rates, rates.size() - 1);
+                        // Swap here to avoid swapping back
+                        std::iter_swap(rates.begin() + i, rates.end() - 1);
+                    }
                 }
-                newRate = storm::utility::one<ValueType>() / newRate;
-                matrixEntry->setValue(newRate);
             }
+
+            STORM_LOG_TRACE("Upper bound is " << (rateSum / upperBound) << " for state " << state->getId());
+            STORM_LOG_ASSERT(!storm::utility::isZero(upperBound), "Upper bound is 0");
+            STORM_LOG_ASSERT(!storm::utility::isZero(rateSum), "State is absorbing");
+            return rateSum / upperBound;
+        }
+
+        template<typename ValueType, typename StateType>
+        ValueType ExplicitDFTModelBuilderApprox<ValueType, StateType>::computeMTTFAnd(std::vector<ValueType> const& rates, size_t size) const {
+            ValueType result = storm::utility::zero<ValueType>();
+            if (size == 0) {
+                return result;
+            }
+
+            // TODO Matthias: works only for <64 BEs!
+            // WARNING: this code produces wrong results for more than 32 BEs
+            /*for (size_t i = 1; i < 4 && i <= rates.size(); ++i) {
+                size_t permutation = smallestIntWithNBitsSet(static_cast<size_t>(i));
+                ValueType sum = storm::utility::zero<ValueType>();
+                do {
+                    ValueType permResult = storm::utility::zero<ValueType>();
+                    for(size_t j = 0; j < rates.size(); ++j) {
+                        if(permutation & static_cast<size_t>(1 << static_cast<size_t>(j))) {
+                            // WARNING: if the first bit is set, it also recognizes the 32nd bit as set
+                            // TODO: fix
+                            permResult += rates[j];
+                        }
+                    }
+                    permutation = nextBitPermutation(permutation);
+                    STORM_LOG_ASSERT(!storm::utility::isZero(permResult), "PermResult is 0");
+                    sum += storm::utility::one<ValueType>() / permResult;
+                } while(permutation < (static_cast<size_t>(1) << rates.size()) && permutation != 0);
+                if (i % 2 == 0) {
+                    result -= sum;
+                } else {
+                    result += sum;
+                }
+            }*/
+
+            // Compute result with permutations of size <= 3
+            ValueType one = storm::utility::one<ValueType>();
+            for (size_t i1 = 0; i1 < size; ++i1) {
+                // + 1/a
+                ValueType sum = rates[i1];
+                result += one / sum;
+                for (size_t i2 = 0; i2 < i1; ++i2) {
+                    // - 1/(a+b)
+                    ValueType sum2 = sum + rates[i2];
+                    result -= one / sum2;
+                    for (size_t i3 = 0; i3 < i2; ++i3) {
+                        // + 1/(a+b+c)
+                        result += one / (sum2 + rates[i3]);
+                    }
+                }
+            }
+
+            STORM_LOG_ASSERT(!storm::utility::isZero(result), "UpperBound is 0");
+            return result;
         }
 
         template<typename ValueType, typename StateType>
@@ -446,14 +652,14 @@ namespace storm {
                     // Check if state is pseudo state
                     // If state is explored already the possible pseudo state was already constructed
                     auto iter = statesNotExplored.find(stateId);
-                    if (iter != statesNotExplored.end() && iter->second->isPseudoState()) {
+                    if (iter != statesNotExplored.end() && iter->second.first->isPseudoState()) {
                         // Create pseudo state now
-                        STORM_LOG_ASSERT(iter->second->getId() == stateId, "Ids do not match.");
-                        STORM_LOG_ASSERT(iter->second->status() == state->status(), "Pseudo states do not coincide.");
+                        STORM_LOG_ASSERT(iter->second.first->getId() == stateId, "Ids do not match.");
+                        STORM_LOG_ASSERT(iter->second.first->status() == state->status(), "Pseudo states do not coincide.");
                         state->setId(stateId);
                         // Update mapping to map to concrete state now
-                        statesNotExplored[stateId] = state;
-                        // TODO Matthias: copy explorationHeuristic
+                        // TODO Matthias: just change pointer?
+                        statesNotExplored[stateId] = std::make_pair(state, iter->second.second);
                         // We do not push the new state on the exploration queue as the pseudo state was already pushed
                         STORM_LOG_TRACE("Created pseudo state " << dft.getStateString(state));
                     }
@@ -466,8 +672,8 @@ namespace storm {
                 stateId = stateStorage.stateToId.findOrAdd(state->status(), state->getId());
                 STORM_LOG_ASSERT(stateId == state->getId(), "Ids do not match.");
                 // Insert state as not yet explored
-                statesNotExplored[stateId] = state;
-                explorationQueue.push(stateId);
+                ExplorationHeuristicPointer nullHeuristic;
+                statesNotExplored[stateId] = std::make_pair(state, nullHeuristic);
                 // Reserve one slot for the new state in the remapping
                 matrixBuilder.stateRemapping.push_back(0);
                 STORM_LOG_TRACE("New " << (state->isPseudoState() ? "pseudo" : "concrete") << " state: " << dft.getStateString(state));
@@ -485,9 +691,11 @@ namespace storm {
         }
 
         template<typename ValueType, typename StateType>
-        bool ExplicitDFTModelBuilderApprox<ValueType, StateType>::isPriorityGreater(StateType idA, StateType idB) const {
-            // TODO Matthias: compare directly and according to heuristic
-            return storm::builder::compareDepth(statesNotExplored.at(idA), statesNotExplored.at(idB));
+        void ExplicitDFTModelBuilderApprox<ValueType, StateType>::printNotExplored() const {
+            std::cout << "states not explored:" << std::endl;
+            for (auto it : statesNotExplored) {
+                std::cout << it.first << " -> " << dft.getStateString(it.second.first) << std::endl;
+            }
         }
 
 

src/builder/ExplicitDFTModelBuilderApprox.h

@@ -10,7 +10,7 @@
 #include "src/storage/sparse/StateStorage.h"
 #include "src/storage/dft/DFT.h"
 #include "src/storage/dft/SymmetricUnits.h"
-#include "src/storage/DynamicPriorityQueue.h"
+#include "src/storage/BucketPriorityQueue.h"
 #include <boost/container/flat_set.hpp>
 #include <boost/optional/optional.hpp>
 #include <stack>
@@ -26,11 +26,10 @@ namespace storm {
         template<typename ValueType, typename StateType = uint32_t>
         class ExplicitDFTModelBuilderApprox {
 
-            using DFTElementPointer = std::shared_ptr<storm::storage::DFTElement<ValueType>>;
-            using DFTElementCPointer = std::shared_ptr<storm::storage::DFTElement<ValueType> const>;
-            using DFTGatePointer = std::shared_ptr<storm::storage::DFTGate<ValueType>>;
             using DFTStatePointer = std::shared_ptr<storm::storage::DFTState<ValueType>>;
-            using DFTRestrictionPointer = std::shared_ptr<storm::storage::DFTRestriction<ValueType>>;
+            // TODO Matthias: make choosable
+            using ExplorationHeuristic = DFTExplorationHeuristicProbability<ValueType>;
+            using ExplorationHeuristicPointer = std::shared_ptr<ExplorationHeuristic>;
 
 
             // A structure holding the individual components of a model.
@@ -159,10 +158,10 @@ namespace storm {
              * Build model from DFT.
              *
              * @param labelOpts              Options for labeling.
-             * @param firstTime              Flag indicating if the model is built for the first time or rebuilt.
+             * @param iteration              Current number of iteration.
              * @param approximationThreshold Threshold determining when to skip exploring states.
              */
-            void buildModel(LabelOptions const& labelOpts, bool firstTime, double approximationThreshold = 0.0);
+            void buildModel(LabelOptions const& labelOpts, size_t iteration, double approximationThreshold = 0.0);
 
             /*!
              * Get the built model.
@@ -218,18 +217,36 @@ namespace storm {
             void setMarkovian(bool markovian);
 
             /**
-             * Change matrix to reflect the lower approximation bound.
+             * Change matrix to reflect the lower or upper approximation bound.
              *
-             * @param matrix Matrix to change. The change are reflected here.
+             * @param matrix     Matrix to change. The change are reflected here.
+             * @param lowerBound Flag indicating if the lower bound should be used. Otherwise the upper bound is used.
              */
-            void changeMatrixLowerBound(storm::storage::SparseMatrix<ValueType> & matrix) const;
+            void changeMatrixBound(storm::storage::SparseMatrix<ValueType> & matrix, bool lowerBound) const;
 
             /*!
-             * Change matrix to reflect the upper approximation bound.
+             * Get lower bound approximation for state.
              *
-             * @param matrix Matrix to change. The change are reflected here.
+             * @return Lower bound approximation.
              */
-            void changeMatrixUpperBound(storm::storage::SparseMatrix<ValueType> & matrix) const;
+            ValueType getLowerBound(DFTStatePointer const& state) const;
+
+            /*!
+             * Get upper bound approximation for state.
+             *
+             * @return Upper bound approximation.
+             */
+            ValueType getUpperBound(DFTStatePointer const& state) const;
+
+            /*!
+             * Compute the MTTF of an AND gate via a closed formula.
+             * The used formula is 1/( 1/a + 1/b + 1/c + ... - 1/(a+b) - 1/(a+c) - ... + 1/(a+b+c) + ... - ...)
+             *
+             * @param rates List of rates of children of AND.
+             * @param size  Only indices < size are considered in the vector.
+             * @return MTTF.
+             */
+            ValueType computeMTTFAnd(std::vector<ValueType> const& rates, size_t size) const;
 
             /*!
              * Compares the priority of two states.
@@ -241,6 +258,8 @@ namespace storm {
              */
             bool isPriorityGreater(StateType idA, StateType idB) const;
 
+            void printNotExplored() const;
+
             /*!
              * Create the model model from the model components.
              *
@@ -294,16 +313,20 @@ namespace storm {
             storm::storage::sparse::StateStorage<StateType> stateStorage;
 
             // A priority queue of states that still need to be explored.
-            storm::storage::DynamicPriorityQueue<StateType, std::vector<StateType>, std::function<bool(StateType, StateType)>> explorationQueue;
+            storm::storage::BucketPriorityQueue<ValueType> explorationQueue;
+            //storm::storage::DynamicPriorityQueue<ExplorationHeuristicPointer, std::vector<ExplorationHeuristicPointer>, std::function<bool(ExplorationHeuristicPointer, ExplorationHeuristicPointer)>> explorationQueue;
 
-            // A mapping of not yet explored states from the id to the state object.
-            std::map<StateType, DFTStatePointer> statesNotExplored;
+            // A mapping of not yet explored states from the id to the tuple (state object, heuristic values).
+            std::map<StateType, std::pair<DFTStatePointer, ExplorationHeuristicPointer>> statesNotExplored;
 
             // Holds all skipped states which were not yet expanded. More concretely it is a mapping from matrix indices
             // to the corresponding skipped states.
             // Notice that we need an ordered map here to easily iterate in increasing order over state ids.
             // TODO remove again
-            std::map<StateType, DFTStatePointer> skippedStates;
+            std::map<StateType, std::pair<DFTStatePointer, ExplorationHeuristicPointer>> skippedStates;
+
+            // List of independent subtrees and the BEs contained in them.
+            std::vector<std::vector<size_t>> subtreeBEs;
         };
 
     }

src/generator/DftNextStateGenerator.cpp

@@ -20,7 +20,6 @@ namespace storm {
         template<typename ValueType, typename StateType>
         std::vector<StateType> DftNextStateGenerator<ValueType, StateType>::getInitialStates(StateToIdCallback const& stateToIdCallback) {
             DFTStatePointer initialState = std::make_shared<storm::storage::DFTState<ValueType>>(mDft, mStateGenerationInfo, 0);
-            initialState->setHeuristicValues(0, storm::utility::zero<ValueType>(), storm::utility::zero<ValueType>());
 
             // Register initial state
             StateType id = stateToIdCallback(initialState);
@@ -158,10 +157,8 @@ namespace storm {
                         ValueType remainingProbability = storm::utility::one<ValueType>() - probability;
                         choice.addProbability(unsuccessfulStateId, remainingProbability);
                         STORM_LOG_TRACE("Added transition to " << unsuccessfulStateId << " with remaining probability " << remainingProbability);
-                        unsuccessfulState->setHeuristicValues(state, remainingProbability, storm::utility::one<ValueType>());
                     }
                     result.addChoice(std::move(choice));
-                    newState->setHeuristicValues(state, probability, storm::utility::one<ValueType>());
                 } else {
                     // Failure is due to "normal" BE failure
                     // Set failure rate according to activation
@@ -174,7 +171,6 @@ namespace storm {
                     STORM_LOG_ASSERT(!storm::utility::isZero(rate), "Rate is 0.");
                     choice.addProbability(newStateId, rate);
                     STORM_LOG_TRACE("Added transition to " << newStateId << " with " << (isActive ? "active" : "passive") << " failure rate " << rate);
-                    newState->setHeuristicValues(state, rate, choice.getTotalMass());
                 }
 
                 ++currentFailable;

src/modelchecker/dft/DFTModelChecker.cpp

@@ -17,13 +17,13 @@ namespace storm {
         template<typename ValueType>
         void DFTModelChecker<ValueType>::check(storm::storage::DFT<ValueType> const& origDft, std::shared_ptr<const storm::logic::Formula> const& formula, bool symred, bool allowModularisation, bool enableDC, double approximationError) {
             // Initialize
-            this->buildingTime = std::chrono::duration<double>::zero();
             this->explorationTime = std::chrono::duration<double>::zero();
+            this->buildingTime = std::chrono::duration<double>::zero();
             this->bisimulationTime = std::chrono::duration<double>::zero();
             this->modelCheckingTime = std::chrono::duration<double>::zero();
             this->totalTime = std::chrono::duration<double>::zero();
             this->approximationError = approximationError;
-            std::chrono::high_resolution_clock::time_point totalStart = std::chrono::high_resolution_clock::now();
+            totalStart = std::chrono::high_resolution_clock::now();
 
             // Optimizing DFT
             storm::storage::DFT<ValueType> dft = origDft.optimize();
@@ -100,6 +100,8 @@ namespace storm {
                     ValueType result = storm::utility::zero<ValueType>();
                     int limK = invResults ? -1 : nrM+1;
                     int chK = invResults ? -1 : 1;
+                    // WARNING: there is a bug for computing permutations with more than 32 elements
+                    STORM_LOG_ASSERT(res.size() < 32, "Permutations work only for < 32 elements");
                     for(int cK = nrK; cK != limK; cK += chK ) {
                         STORM_LOG_ASSERT(cK >= 0, "ck negative.");
                         size_t permutation = smallestIntWithNBitsSet(static_cast<size_t>(cK));
@@ -132,7 +134,7 @@ namespace storm {
 
         template<typename ValueType>
         typename DFTModelChecker<ValueType>::dft_result DFTModelChecker<ValueType>::checkDFT(storm::storage::DFT<ValueType> const& dft, std::shared_ptr<const storm::logic::Formula> const& formula, bool symred, bool enableDC, double approximationError) {
-            std::chrono::high_resolution_clock::time_point buildingStart = std::chrono::high_resolution_clock::now();
+            std::chrono::high_resolution_clock::time_point checkingStart = std::chrono::high_resolution_clock::now();
 
             // Find symmetries
             std::map<size_t, std::vector<std::vector<size_t>>> emptySymmetry;
@@ -143,35 +145,38 @@ namespace storm {
                 STORM_LOG_INFO("Found " << symmetries.groups.size() << " symmetries.");
                 STORM_LOG_TRACE("Symmetries: " << std::endl << symmetries);
             }
-            std::chrono::high_resolution_clock::time_point buildingEnd = std::chrono::high_resolution_clock::now();
-            buildingTime += buildingEnd - buildingStart;
 
             if (approximationError > 0.0) {
                 // Comparator for checking the error of the approximation
                 storm::utility::ConstantsComparator<ValueType> comparator;
                 // Build approximate Markov Automata for lower and upper bound
-                double currentApproximationError = approximationError;
                 approximation_result approxResult = std::make_pair(storm::utility::zero<ValueType>(), storm::utility::zero<ValueType>());
-                std::chrono::high_resolution_clock::time_point explorationStart;
                 std::shared_ptr<storm::models::sparse::Model<ValueType>> model;
                 storm::builder::ExplicitDFTModelBuilderApprox<ValueType> builder(dft, symmetries, enableDC);
                 typename storm::builder::ExplicitDFTModelBuilderApprox<ValueType>::LabelOptions labeloptions; // TODO initialize this with the formula
 
+                bool probabilityFormula = formula->isProbabilityOperatorFormula();
+                STORM_LOG_ASSERT((formula->isTimeOperatorFormula() && !probabilityFormula) || (!formula->isTimeOperatorFormula() && probabilityFormula), "Probability formula not initialized correctly");
                 size_t iteration = 0;
                 do {
                     // Iteratively build finer models
-                    explorationStart = std::chrono::high_resolution_clock::now();
+                    std::chrono::high_resolution_clock::time_point explorationStart = std::chrono::high_resolution_clock::now();
                     STORM_LOG_INFO("Building model...");
                     // TODO Matthias refine model using existing model and MC results
-                    currentApproximationError = pow(0.1, iteration) * approximationError;
-                    builder.buildModel(labeloptions, iteration < 1, iteration);
+                    builder.buildModel(labeloptions, iteration, approximationError);
+                    std::chrono::high_resolution_clock::time_point explorationEnd = std::chrono::high_resolution_clock::now();
+                    explorationTime = explorationEnd - explorationStart;
 
                     // TODO Matthias: possible to do bisimulation on approximated model and not on concrete one?
 
                     // Build model for lower bound
                     STORM_LOG_INFO("Getting model for lower bound...");
-                    model = builder.getModelApproximation(true);
-                    explorationTime += std::chrono::high_resolution_clock::now() - explorationStart;
+                    model = builder.getModelApproximation(probabilityFormula ? false : true);
+                    // We only output the info from the lower bound as the info for the upper bound is the same
+                    STORM_LOG_INFO("No. states: " << model->getNumberOfStates());
+                    STORM_LOG_INFO("No. transitions: " << model->getNumberOfTransitions());
+                    buildingTime += std::chrono::high_resolution_clock::now() - explorationEnd;
+
                     // Check lower bound
                     std::unique_ptr<storm::modelchecker::CheckResult> result = checkModel(model, formula);
                     result->filter(storm::modelchecker::ExplicitQualitativeCheckResult(model->getInitialStates()));
@@ -181,9 +186,9 @@ namespace storm {
 
                     // Build model for upper bound
                     STORM_LOG_INFO("Getting model for upper bound...");
-                    explorationStart = std::chrono::high_resolution_clock::now();
-                    model = builder.getModelApproximation(false);
-                    explorationTime += std::chrono::high_resolution_clock::now() - explorationStart;
+                    explorationEnd = std::chrono::high_resolution_clock::now();
+                    model = builder.getModelApproximation(probabilityFormula ? true : false);
+                    buildingTime += std::chrono::high_resolution_clock::now() - explorationEnd;
                     // Check upper bound
                     result = checkModel(model, formula);
                     result->filter(storm::modelchecker::ExplicitQualitativeCheckResult(model->getInitialStates()));
@@ -193,8 +198,10 @@ namespace storm {
 
                     ++iteration;
                     STORM_LOG_INFO("Result after iteration " << iteration << ": (" << std::setprecision(10) << approxResult.first << ", " << approxResult.second << ")");
+                    totalTime = std::chrono::high_resolution_clock::now() - totalStart;
+                    printTimings();
                     STORM_LOG_THROW(!storm::utility::isInfinity<ValueType>(approxResult.first) && !storm::utility::isInfinity<ValueType>(approxResult.second), storm::exceptions::NotSupportedException, "Approximation does not work if result might be infinity.");
-                } while (!isApproximationSufficient(approxResult.first, approxResult.second, approximationError));
+                } while (!isApproximationSufficient(approxResult.first, approxResult.second, approximationError, probabilityFormula));
 
                 STORM_LOG_INFO("Finished approximation after " << iteration << " iteration" << (iteration > 1 ? "s." : "."));
                 return approxResult;
@@ -203,10 +210,10 @@ namespace storm {
                 STORM_LOG_INFO("Building Model...");
                 std::shared_ptr<storm::models::sparse::Model<ValueType>> model;
                 // TODO Matthias: use only one builder if everything works again
-                if (approximationError >= 0.0) {
+                if (storm::settings::getModule<storm::settings::modules::DFTSettings>().isApproximationErrorSet()) {
                     storm::builder::ExplicitDFTModelBuilderApprox<ValueType> builder(dft, symmetries, enableDC);
                     typename storm::builder::ExplicitDFTModelBuilderApprox<ValueType>::LabelOptions labeloptions; // TODO initialize this with the formula
-                    builder.buildModel(labeloptions, true);
+                    builder.buildModel(labeloptions, 0);
                     model = builder.getModel();
                 } else {
                     storm::builder::ExplicitDFTModelBuilder<ValueType> builder(dft, symmetries, enableDC);
@@ -216,7 +223,7 @@ namespace storm {
                 //model->printModelInformationToStream(std::cout);
                 STORM_LOG_INFO("No. states (Explored): " << model->getNumberOfStates());
                 STORM_LOG_INFO("No. transitions (Explored): " << model->getNumberOfTransitions());
-                explorationTime += std::chrono::high_resolution_clock::now() - buildingEnd;
+                explorationTime += std::chrono::high_resolution_clock::now() - checkingStart;
 
                 // Model checking
                 std::unique_ptr<storm::modelchecker::CheckResult> result = checkModel(model, formula);
@@ -248,20 +255,25 @@ namespace storm {
         }
 
         template<typename ValueType>
-        bool DFTModelChecker<ValueType>::isApproximationSufficient(ValueType lowerBound, ValueType upperBound, double approximationError) {
+        bool DFTModelChecker<ValueType>::isApproximationSufficient(ValueType lowerBound, ValueType upperBound, double approximationError, bool relative) {
             STORM_LOG_THROW(false, storm::exceptions::NotImplementedException, "Approximation works only for double.");
         }
 
         template<>
-        bool DFTModelChecker<double>::isApproximationSufficient(double lowerBound, double upperBound, double approximationError) {
-            return upperBound - lowerBound <= approximationError * (lowerBound + upperBound) / 2;
+        bool DFTModelChecker<double>::isApproximationSufficient(double lowerBound, double upperBound, double approximationError, bool relative) {
+            STORM_LOG_THROW(!std::isnan(lowerBound) && !std::isnan(upperBound), storm::exceptions::NotSupportedException, "Approximation does not work if result is NaN.");
+            if (relative) {
+                return upperBound - lowerBound <= approximationError;
+            } else {
+                return upperBound - lowerBound <= approximationError * (lowerBound + upperBound) / 2;
+            }
         }
 
         template<typename ValueType>
         void DFTModelChecker<ValueType>::printTimings(std::ostream& os) {
             os << "Times:" << std::endl;
-            os << "Building:\t" << buildingTime.count() << std::endl;
             os << "Exploration:\t" << explorationTime.count() << std::endl;
+            os << "Building:\t" << buildingTime.count() << std::endl;
             os << "Bisimulation:\t" << bisimulationTime.count() << std::endl;
             os << "Modelchecking:\t" << modelCheckingTime.count() << std::endl;
             os << "Total:\t\t" << totalTime.count() << std::endl;

src/modelchecker/dft/DFTModelChecker.h

@@ -61,6 +61,7 @@ namespace storm {
             std::chrono::duration<double> bisimulationTime = std::chrono::duration<double>::zero();
             std::chrono::duration<double> modelCheckingTime = std::chrono::duration<double>::zero();
             std::chrono::duration<double> totalTime = std::chrono::duration<double>::zero();
+            std::chrono::high_resolution_clock::time_point totalStart;
 
             // Model checking result
             dft_result checkResult;
@@ -107,15 +108,17 @@ namespace storm {
 
             /*!
              * Checks if the computed approximation is sufficient, i.e.
-             * upperBound - lowerBound <= approximationError * mean(upperBound, lowerBound).
+             * upperBound - lowerBound <= approximationError * mean(lowerBound, upperBound).
              *
              * @param lowerBound         The lower bound on the result.
              * @param upperBound         The upper bound on the result.
              * @param approximationError The allowed error for approximating.
+             * @param relative           Flag indicating if the error should be relative to 1 or
+                                         to the mean of lower and upper bound.
              *
              * @return True, if the approximation is sufficient.
              */
-            bool isApproximationSufficient(ValueType lowerBound, ValueType upperBound, double approximationError);
+            bool isApproximationSufficient(ValueType lowerBound, ValueType upperBound, double approximationError, bool relative);
 
         };
     }

src/settings/modules/DFTSettings.cpp

@@ -40,7 +40,7 @@ namespace storm {
                 this->addOption(storm::settings::OptionBuilder(moduleName, modularisationOptionName, false, "Use modularisation (not applicable for expected time).").build());
                 this->addOption(storm::settings::OptionBuilder(moduleName, disableDCOptionName, false, "Disable Dont Care propagation.").build());
                 this->addOption(storm::settings::OptionBuilder(moduleName, approximationErrorOptionName, false, "Approximation error allowed.").setShortName(approximationErrorOptionShortName).addArgument(storm::settings::ArgumentBuilder::createDoubleArgument("error", "The relative approximation error to use.").addValidationFunctionDouble(storm::settings::ArgumentValidators::doubleGreaterValidatorIncluding(0.0)).build()).build());
-                this->addOption(storm::settings::OptionBuilder(moduleName, approximationHeuristicOptionName, false, "Set the heuristic used for approximation.").addArgument(storm::settings::ArgumentBuilder::createStringArgument("heuristic", "Sets which heuristic is used for approximation. Must be in {depth, rateratio}. Default is").setDefaultValueString("depth").addValidationFunctionString(storm::settings::ArgumentValidators::stringInListValidator({"depth", "rateratio"})).build()).build());
+                this->addOption(storm::settings::OptionBuilder(moduleName, approximationHeuristicOptionName, false, "Set the heuristic used for approximation.").addArgument(storm::settings::ArgumentBuilder::createStringArgument("heuristic", "Sets which heuristic is used for approximation. Must be in {depth, probability}. Default is").setDefaultValueString("depth").addValidationFunctionString(storm::settings::ArgumentValidators::stringInListValidator({"depth", "rateratio"})).build()).build());
                 this->addOption(storm::settings::OptionBuilder(moduleName, propExpectedTimeOptionName, false, "Compute expected time of system failure.").setShortName(propExpectedTimeOptionShortName).build());
                 this->addOption(storm::settings::OptionBuilder(moduleName, propProbabilityOptionName, false, "Compute probability of system failure.").build());
                 this->addOption(storm::settings::OptionBuilder(moduleName, propTimeBoundOptionName, false, "Compute probability of system failure up to given timebound.").addArgument(storm::settings::ArgumentBuilder::createDoubleArgument("time", "The timebound to use.").addValidationFunctionDouble(storm::settings::ArgumentValidators::doubleGreaterValidatorExcluding(0.0)).build()).build());
@@ -87,8 +87,8 @@ namespace storm {
                 std::string heuristicAsString = this->getOption(approximationHeuristicOptionName).getArgumentByName("heuristic").getValueAsString();
                 if (heuristicAsString == "depth") {
                     return storm::builder::ApproximationHeuristic::DEPTH;
-                } else if (heuristicAsString == "rateratio") {
-                    return storm::builder::ApproximationHeuristic::RATERATIO;
+                } else if (heuristicAsString == "probability") {
+                    return storm::builder::ApproximationHeuristic::PROBABILITY;
                 }
                 STORM_LOG_THROW(false, storm::exceptions::IllegalArgumentValueException, "Illegal value '" << heuristicAsString << "' set as heuristic for approximation.");
             }

src/storage/BucketPriorityQueue.cpp

@@ -0,0 +1,203 @@
+#include "src/storage/BucketPriorityQueue.h"
+#include "src/utility/macros.h"
+#include "src/adapters/CarlAdapter.h"
+
+#include <cmath>
+
+namespace storm {
+    namespace storage {
+
+        template<typename ValueType>
+        BucketPriorityQueue<ValueType>::BucketPriorityQueue(size_t nrBuckets, double lowerValue, double ratio) : lowerValue(lowerValue), logBase(std::log(ratio)), nrBuckets(nrBuckets), nrUnsortedItems(0), buckets(nrBuckets), currentBucket(nrBuckets) {
+            compare = ([this](HeuristicPointer a, HeuristicPointer b) {
+                return *a < *b;
+            });
+        }
+
+        template<typename ValueType>
+        void BucketPriorityQueue<ValueType>::fix() {
+            if (currentBucket < nrBuckets && nrUnsortedItems > buckets[currentBucket].size() / 10) {
+                // Fix current bucket
+                std::make_heap(buckets[currentBucket].begin(), buckets[currentBucket].end(), compare);
+                nrUnsortedItems = 0;
+            }
+        }
+
+        template<typename ValueType>
+        bool BucketPriorityQueue<ValueType>::empty() const {
+            return currentBucket == nrBuckets && immediateBucket.empty();
+        }
+
+        template<typename ValueType>
+        std::size_t BucketPriorityQueue<ValueType>::size() const {
+            size_t size = immediateBucket.size();
+            for (size_t i = currentBucket; currentBucket < nrBuckets; ++i) {
+                size += buckets[i].size();
+            }
+            return size;
+        }
+
+        template<typename ValueType>
+        typename BucketPriorityQueue<ValueType>::HeuristicPointer const& BucketPriorityQueue<ValueType>::top() const {
+            if (!immediateBucket.empty()) {
+                return immediateBucket.back();
+            }
+            STORM_LOG_ASSERT(!empty(), "BucketPriorityQueue is empty");
+            return buckets[currentBucket].front();
+        }
+
+        template<typename ValueType>
+        void BucketPriorityQueue<ValueType>::push(HeuristicPointer const& item) {
+            if (item->isExpand()) {
+                immediateBucket.push_back(item);
+                return;
+            }
+            size_t bucket = getBucket(item->getPriority());
+            if (bucket < currentBucket) {
+                currentBucket = bucket;
+                nrUnsortedItems = 0;
+            }
+            buckets[bucket].push_back(item);
+            if (bucket == currentBucket) {
+                // Insert in first bucket
+                if (AUTOSORT) {
+                    std::push_heap(buckets[currentBucket].begin(), buckets[currentBucket].end(), compare);
+                } else {
+                    ++nrUnsortedItems;
+                }
+            }
+        }
+
+        template<typename ValueType>
+        void BucketPriorityQueue<ValueType>::update(HeuristicPointer const& item, double oldPriority) {
+            STORM_LOG_ASSERT(!item->isExpand(), "Item is marked for expansion");
+            size_t newBucket = getBucket(item->getPriority());
+            size_t oldBucket = getBucket(oldPriority);
+
+            if (oldBucket == newBucket) {
+                if (currentBucket < newBucket) {
+                    // No change as the bucket is not sorted yet
+                } else {
+                    if (AUTOSORT) {
+                        // Sort first bucket
+                        fix();
+                    } else {
+                        ++nrUnsortedItems;
+                    }
+                }
+            } else {
+                // Move to new bucket
+                STORM_LOG_ASSERT(newBucket < oldBucket, "Will update to higher bucket");
+                if (newBucket < currentBucket) {
+                    currentBucket = newBucket;
+                    nrUnsortedItems = 0;
+                }
+                // Remove old entry by swap-and-pop
+                if (buckets[oldBucket].size() >= 2) {
+                    // Find old index by linear search
+                    // Notice: using a map to rememeber index was not efficient
+                    size_t oldIndex = 0;
+                    for ( ; oldIndex < buckets[oldBucket].size(); ++oldIndex) {
+                        if (buckets[oldBucket][oldIndex]->getId() == item->getId()) {
+                            break;
+                        }
+                    }
+                    STORM_LOG_ASSERT(oldIndex < buckets[oldBucket].size(), "Id " << item->getId() << " not found");
+                    std::iter_swap(buckets[oldBucket].begin() + oldIndex, buckets[oldBucket].end() - 1);
+                }
+                buckets[oldBucket].pop_back();
+                // Insert new element
+                buckets[newBucket].push_back(item);
+                if (newBucket == currentBucket) {
+                    if (AUTOSORT) {
+                        // Sort in first bucket
+                        std::push_heap(buckets[currentBucket].begin(), buckets[currentBucket].end(), compare);
+                    } else {
+                        ++nrUnsortedItems;
+                    }
+                }
+            }
+        }
+
+
+        template<typename ValueType>
+        void BucketPriorityQueue<ValueType>::pop() {
+            if (!immediateBucket.empty()) {
+                immediateBucket.pop_back();
+                return;
+            }
+            STORM_LOG_ASSERT(!empty(), "BucketPriorityQueue is empty");
+            std::pop_heap(buckets[currentBucket].begin(), buckets[currentBucket].end(), compare);
+            buckets[currentBucket].pop_back();
+            if (buckets[currentBucket].empty()) {
+                // Find next bucket with elements
+                for ( ; currentBucket < nrBuckets; ++currentBucket) {
+                    if (!buckets[currentBucket].empty()) {
+                        nrUnsortedItems = buckets[currentBucket].size();
+                        if (AUTOSORT) {
+                            fix();
+                        }
+                        break;
+                    }
+                }
+            }
+        }
+
+        template<typename ValueType>
+        typename BucketPriorityQueue<ValueType>::HeuristicPointer BucketPriorityQueue<ValueType>::popTop() {
+            HeuristicPointer item = top();
+            pop();
+            return item;
+        }
+
+        template<typename ValueType>
+        size_t BucketPriorityQueue<ValueType>::getBucket(double priority) const {
+            STORM_LOG_ASSERT(priority >= lowerValue, "Priority " << priority << " is too low");
+            size_t newBucket = std::log(priority - lowerValue) / logBase;
+            if (newBucket >= nrBuckets) {
+                newBucket = nrBuckets - 1;
+            }
+            if (!HIGHER) {
+                newBucket = nrBuckets-1 - newBucket;
+            }
+            //std::cout << "get Bucket: " << priority << ", " << newBucket << std::endl;
+            STORM_LOG_ASSERT(newBucket < nrBuckets, "Priority " << priority << " is too high");
+            return newBucket;
+        }
+
+        template<typename ValueType>
+        void BucketPriorityQueue<ValueType>::print(std::ostream& out) const {
+            out << "Bucket priority queue with size " << buckets.size() << ", lower value: " << lowerValue << " and logBase: " << logBase << std::endl;
+            out << "Immediate bucket: ";
+            for (HeuristicPointer heuristic : immediateBucket) {
+                out << heuristic->getId() << ", ";
+            }
+            out << std::endl;
+            out << "Current bucket (" << currentBucket << ") has " << nrUnsortedItems  << " unsorted items" << std::endl;
+            for (size_t bucket = 0; bucket < buckets.size(); ++bucket) {
+                if (!buckets[bucket].empty()) {
+                    out << "Bucket " << bucket << ":" << std::endl;
+                    for (HeuristicPointer heuristic : buckets[bucket]) {
+                        out << "\t" << heuristic->getId() << ": " << heuristic->getPriority() << std::endl;
+                    }
+                }
+            }
+        }
+
+        template<typename ValueType>
+        void BucketPriorityQueue<ValueType>::printSizes(std::ostream& out) const {
+            out << "Bucket sizes: " << immediateBucket.size() << " | ";
+            for (size_t bucket = 0; bucket < buckets.size(); ++bucket) {
+                out << buckets[bucket].size() << " ";
+            }
+            std::cout << std::endl;
+        }
+
+        // Template instantiations
+        template class BucketPriorityQueue<double>;
+
+#ifdef STORM_HAVE_CARL
+        template class BucketPriorityQueue<storm::RationalFunction>;
+#endif
+    }
+}

src/storage/BucketPriorityQueue.h

@@ -0,0 +1,73 @@
+#ifndef STORM_STORAGE_BUCKETPRIORITYQUEUE_H_
+#define STORM_STORAGE_BUCKETPRIORITYQUEUE_H_
+
+#include "src/builder/DftExplorationHeuristic.h"
+#include <algorithm>
+#include <functional>
+#include <unordered_map>
+#include <vector>
+
+namespace storm {
+    namespace storage {
+
+        template<typename ValueType>
+        class BucketPriorityQueue {
+
+            using HeuristicPointer = std::shared_ptr<storm::builder::DFTExplorationHeuristicProbability<ValueType>>;
+
+        public:
+            explicit BucketPriorityQueue(size_t nrBuckets, double lowerValue, double ratio);
+
+            void fix();
+
+            bool empty() const;
+
+            std::size_t size() const;
+
+            HeuristicPointer const& top() const;
+
+            void push(HeuristicPointer const& item);
+
+            void update(HeuristicPointer const& item, double oldPriority);
+
+            void pop();
+
+            HeuristicPointer popTop();
+
+            void print(std::ostream& out) const;
+
+            void printSizes(std::ostream& out) const;
+
+        private:
+
+            size_t getBucket(double priority) const;
+
+            const double lowerValue;
+
+            const bool HIGHER = true;
+
+            const bool AUTOSORT = false;
+
+            const double logBase;
+
+            const size_t nrBuckets;
+
+            size_t nrUnsortedItems;
+
+            // List of buckets
+            std::vector<std::vector<HeuristicPointer>> buckets;
+
+            // Bucket containing all items which should be considered immediately
+            std::vector<HeuristicPointer> immediateBucket;
+
+            // Index of first bucket which contains items
+            size_t currentBucket;
+
+            std::function<bool(HeuristicPointer, HeuristicPointer)> compare;
+
+        };
+
+    }
+}
+
+#endif // STORM_STORAGE_BUCKETPRIORITYQUEUE_H_

src/storage/bisimulation/BisimulationDecomposition.cpp

@@ -230,25 +230,25 @@ namespace storm {
         
         template<typename ModelType, typename BlockDataType>
         void BisimulationDecomposition<ModelType, BlockDataType>::performPartitionRefinement() {
-            // Insert all blocks into the splitter queue as a (potential) splitter.
-            std::deque<Block<BlockDataType>*> splitterQueue;
-            std::for_each(partition.getBlocks().begin(), partition.getBlocks().end(), [&] (std::unique_ptr<Block<BlockDataType>> const& block) { block->data().setSplitter(); splitterQueue.push_back(block.get()); } );
+            // Insert all blocks into the splitter vector as a (potential) splitter.
+            std::vector<Block<BlockDataType>*> splitterVector;
+            std::for_each(partition.getBlocks().begin(), partition.getBlocks().end(), [&] (std::unique_ptr<Block<BlockDataType>> const& block) { block->data().setSplitter(); splitterVector.push_back(block.get()); } );
             
             // Then perform the actual splitting until there are no more splitters.
             uint_fast64_t iterations = 0;
-            while (!splitterQueue.empty()) {
+            while (!splitterVector.empty()) {
                 ++iterations;
 
                 // Get and prepare the next splitter.
                 // Sort the splitters according to their sizes to prefer small splitters. That is just a heuristic, but
                 // tends to work well.
-                std::sort(splitterQueue.begin(), splitterQueue.end(), [] (Block<BlockDataType> const* b1, Block<BlockDataType> const* b2) { return b1->getNumberOfStates() < b2->getNumberOfStates(); } );
-                Block<BlockDataType>* splitter = splitterQueue.front();
-                splitterQueue.pop_front();
+                std::sort(splitterVector.begin(), splitterVector.end(), [] (Block<BlockDataType> const* b1, Block<BlockDataType> const* b2) { return b1->getNumberOfStates() > b2->getNumberOfStates(); } );
+                Block<BlockDataType>* splitter = splitterVector.back();
+                splitterVector.pop_back();
                 splitter->data().setSplitter(false);
                 
                 // Now refine the partition using the current splitter.
-                refinePartitionBasedOnSplitter(*splitter, splitterQueue);
+                refinePartitionBasedOnSplitter(*splitter, splitterVector);
             }
         }
         

src/storage/bisimulation/BisimulationDecomposition.h

@@ -1,7 +1,7 @@
 #ifndef STORM_STORAGE_BISIMULATIONDECOMPOSITION_H_
 #define STORM_STORAGE_BISIMULATIONDECOMPOSITION_H_
 
-#include <deque>
+#include <vector>
 
 #include "src/settings/SettingsManager.h"
 #include "src/settings/modules/BisimulationSettings.h"
@@ -219,12 +219,12 @@ namespace storm {
             
             /*!
              * Refines the partition by considering the given splitter. All blocks that become potential splitters
-             * because of this refinement, are marked as splitters and inserted into the splitter queue.
+             * because of this refinement, are marked as splitters and inserted into the splitter vector.
              *
              * @param splitter The splitter to use.
-             * @param splitterQueue The queue into which to insert the newly discovered potential splitters.
+             * @param splitterVector The vector into which to insert the newly discovered potential splitters.
              */
-            virtual void refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue) = 0;
+            virtual void refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector) = 0;
             
             /*!
              * Builds the quotient model based on the previously computed equivalence classes (stored in the blocks

src/storage/bisimulation/DeterministicModelBisimulationDecomposition.cpp

@@ -157,7 +157,7 @@ namespace storm {
         }
         
         template<typename ModelType>
-        void DeterministicModelBisimulationDecomposition<ModelType>::refinePredecessorBlocksOfSplitterStrong(std::list<Block<BlockDataType>*> const& predecessorBlocks, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue) {
+        void DeterministicModelBisimulationDecomposition<ModelType>::refinePredecessorBlocksOfSplitterStrong(std::list<Block<BlockDataType>*> const& predecessorBlocks, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector) {
             for (auto block : predecessorBlocks) {
                 STORM_LOG_TRACE("Refining predecessor " << block->getId() << " of splitter");
 
@@ -176,15 +176,15 @@ namespace storm {
                                                     [this] (storm::storage::sparse::state_type state1, storm::storage::sparse::state_type state2) {
                                                         return this->comparator.isLess(getProbabilityToSplitter(state1), getProbabilityToSplitter(state2));
                                                     },
-                                                    [&splitterQueue] (Block<BlockDataType>& block) {
-                                                        splitterQueue.emplace_back(&block); block.data().setSplitter();
+                                                    [&splitterVector] (Block<BlockDataType>& block) {
+                                                        splitterVector.emplace_back(&block); block.data().setSplitter();
                                                     });
                 
                 
-                // If the predecessor block was split, we need to insert it into the splitter queue if it is not already
+                // If the predecessor block was split, we need to insert it into the splitter vector if it is not already
                 // marked as a splitter.
                 if (split && !blockToRefineProbabilistically->data().splitter()) {
-                    splitterQueue.emplace_back(blockToRefineProbabilistically);
+                    splitterVector.emplace_back(blockToRefineProbabilistically);
                     blockToRefineProbabilistically->data().setSplitter();
                 }
                 
@@ -378,7 +378,7 @@ namespace storm {
         }
         
         template<typename ModelType>
-        void DeterministicModelBisimulationDecomposition<ModelType>::refinePredecessorBlockOfSplitterWeak(bisimulation::Block<BlockDataType>& block, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue) {
+        void DeterministicModelBisimulationDecomposition<ModelType>::refinePredecessorBlockOfSplitterWeak(bisimulation::Block<BlockDataType>& block, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector) {
             // First, we need to turn the one-step probabilities to go to the splitter to the conditional probabilities
             // for all non-silent states.
             computeConditionalProbabilitiesForNonSilentStates(block);
@@ -395,12 +395,12 @@ namespace storm {
                                                      [&weakStateLabels,&block,originalBlockIndex,this] (storm::storage::sparse::state_type state1, storm::storage::sparse::state_type state2) {
                                                          return weakStateLabels[this->partition.getPosition(state1) - originalBlockIndex] < weakStateLabels[this->partition.getPosition(state2) - originalBlockIndex];
                                                      },
-                                                     [this, &splitterQueue] (bisimulation::Block<BlockDataType>& block) {
+                                                     [this, &splitterVector] (bisimulation::Block<BlockDataType>& block) {
                                                          updateSilentProbabilitiesBasedOnTransitions(block);
                                                          
                                                          // Insert the new block as a splitter.
                                                          block.data().setSplitter();
-                                                         splitterQueue.emplace_back(&block);
+                                                         splitterVector.emplace_back(&block);
                                                      });
             
             // If the block was split, we also update the silent probabilities.
@@ -410,16 +410,16 @@ namespace storm {
                 if (!block.data().splitter()) {
                     // Insert the new block as a splitter.
                     block.data().setSplitter();
-                    splitterQueue.emplace_back(&block);
+                    splitterVector.emplace_back(&block);
                 }
             }
         }
         
         template<typename ModelType>
-        void DeterministicModelBisimulationDecomposition<ModelType>::refinePredecessorBlocksOfSplitterWeak(bisimulation::Block<BlockDataType>& splitter, std::list<bisimulation::Block<BlockDataType>*> const& predecessorBlocks, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue) {
+        void DeterministicModelBisimulationDecomposition<ModelType>::refinePredecessorBlocksOfSplitterWeak(bisimulation::Block<BlockDataType>& splitter, std::list<bisimulation::Block<BlockDataType>*> const& predecessorBlocks, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector) {
             for (auto block : predecessorBlocks) {
                 if (*block != splitter) {
-                    refinePredecessorBlockOfSplitterWeak(*block, splitterQueue);
+                    refinePredecessorBlockOfSplitterWeak(*block, splitterVector);
                 } else {
                     // If the block to split is the splitter itself, we must not do any splitting here.
                 }
@@ -439,7 +439,7 @@ namespace storm {
         }
         
         template<typename ModelType>
-        void DeterministicModelBisimulationDecomposition<ModelType>::refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue) {
+        void DeterministicModelBisimulationDecomposition<ModelType>::refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector) {
             STORM_LOG_TRACE("Refining partition based on splitter " << splitter.getId());
 
             // The outline of the refinement is as follows.
@@ -513,7 +513,7 @@ namespace storm {
             if (this->options.getType() == BisimulationType::Strong || this->model.getType() == storm::models::ModelType::Ctmc) {
                 // In the case of CTMCs and weak bisimulation, we still call the "splitStrong" method, but we already have
                 // taken care of not adding the splitter to the predecessor blocks, so this is safe.
-                refinePredecessorBlocksOfSplitterStrong(predecessorBlocks, splitterQueue);
+                refinePredecessorBlocksOfSplitterStrong(predecessorBlocks, splitterVector);
             } else {
                 // If the splitter is a predecessor of we can use the computed probabilities to update the silent
                 // probabilities.
@@ -521,7 +521,7 @@ namespace storm {
                     updateSilentProbabilitiesBasedOnProbabilitiesToSplitter(splitter);
                 }
                 
-                refinePredecessorBlocksOfSplitterWeak(splitter, predecessorBlocks, splitterQueue);
+                refinePredecessorBlocksOfSplitterWeak(splitter, predecessorBlocks, splitterVector);
             }
         }
         

src/storage/bisimulation/DeterministicModelBisimulationDecomposition.h

@@ -39,11 +39,11 @@ namespace storm {
             
             virtual void buildQuotient() override;
             
-            virtual void refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue) override;
+            virtual void refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector) override;
 
         private:
             // Refines the predecessor blocks wrt. strong bisimulation.
-            void refinePredecessorBlocksOfSplitterStrong(std::list<bisimulation::Block<BlockDataType>*> const& predecessorBlocks, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue);
+            void refinePredecessorBlocksOfSplitterStrong(std::list<bisimulation::Block<BlockDataType>*> const& predecessorBlocks, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector);
 
             /*!
              * Performs the necessary steps to compute a weak bisimulation on a DTMC.
@@ -99,10 +99,10 @@ namespace storm {
             void updateSilentProbabilitiesBasedOnTransitions(bisimulation::Block<BlockDataType>& block);
             
             // Refines the predecessor blocks of the splitter wrt. weak bisimulation in DTMCs.
-            void refinePredecessorBlocksOfSplitterWeak(bisimulation::Block<BlockDataType>& splitter, std::list<bisimulation::Block<BlockDataType>*> const& predecessorBlocks, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue);
+            void refinePredecessorBlocksOfSplitterWeak(bisimulation::Block<BlockDataType>& splitter, std::list<bisimulation::Block<BlockDataType>*> const& predecessorBlocks, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector);
             
             // Refines the given block wrt to weak bisimulation in DTMCs.
-            void refinePredecessorBlockOfSplitterWeak(bisimulation::Block<BlockDataType>& block, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue);
+            void refinePredecessorBlockOfSplitterWeak(bisimulation::Block<BlockDataType>& block, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector);
             
             // Converts the one-step probabilities of going into the splitter into the conditional probabilities needed
             // for weak bisimulation (on DTMCs).

src/storage/bisimulation/NondeterministicModelBisimulationDecomposition.cpp

@@ -198,7 +198,7 @@ namespace storm {
         }
         
         template<typename ModelType>
-        void NondeterministicModelBisimulationDecomposition<ModelType>::updateQuotientDistributionsOfPredecessors(Block<BlockDataType> const& newBlock, Block<BlockDataType> const& oldBlock, std::deque<Block<BlockDataType>*>& splitterQueue) {
+        void NondeterministicModelBisimulationDecomposition<ModelType>::updateQuotientDistributionsOfPredecessors(Block<BlockDataType> const& newBlock, Block<BlockDataType> const& oldBlock, std::vector<Block<BlockDataType>*>& splitterVector) {
             uint_fast64_t lastState = 0;
             bool lastStateInitialized = false;
             
@@ -220,7 +220,7 @@ namespace storm {
                     // If the predecessor block is not marked as to-refined, we do so now.
                     if (!predecessorBlock.data().splitter()) {
                         predecessorBlock.data().setSplitter();
-                        splitterQueue.push_back(&predecessorBlock);
+                        splitterVector.push_back(&predecessorBlock);
                     }
                     
                     if (lastStateInitialized) {
@@ -332,7 +332,7 @@ namespace storm {
         }
         
         template<typename ModelType>
-        bool NondeterministicModelBisimulationDecomposition<ModelType>::splitBlockAccordingToCurrentQuotientDistributions(Block<BlockDataType>& block, std::deque<Block<BlockDataType>*>& splitterQueue) {
+        bool NondeterministicModelBisimulationDecomposition<ModelType>::splitBlockAccordingToCurrentQuotientDistributions(Block<BlockDataType>& block, std::vector<Block<BlockDataType>*>& splitterVector) {
             std::list<Block<BlockDataType>*> newBlocks;
             bool split = this->partition.splitBlock(block,
                                                     [this] (storm::storage::sparse::state_type state1, storm::storage::sparse::state_type state2) {
@@ -340,7 +340,7 @@ namespace storm {
 //                                                        std::cout << state1 << " is " << (!result ? "not" : "") << " smaller than " << state2 << std::endl;
                                                         return result;
                                                     },
-                                                    [this, &block, &splitterQueue, &newBlocks] (Block<BlockDataType>& newBlock) {
+                                                    [this, &block, &splitterVector, &newBlocks] (Block<BlockDataType>& newBlock) {
                                                         newBlocks.push_back(&newBlock);
                                                         
 //                                                        this->checkBlockStable(newBlock);
@@ -357,7 +357,7 @@ namespace storm {
             // defer updating the quotient distributions until *after* all splits, because
             // it otherwise influences the subsequent splits!
             for (auto el : newBlocks) {
-                this->updateQuotientDistributionsOfPredecessors(*el, block, splitterQueue);
+                this->updateQuotientDistributionsOfPredecessors(*el, block, splitterVector);
             }
             
 //            this->checkQuotientDistributions();
@@ -405,14 +405,14 @@ namespace storm {
         }
         
         template<typename ModelType>
-        void NondeterministicModelBisimulationDecomposition<ModelType>::refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue) {
+        void NondeterministicModelBisimulationDecomposition<ModelType>::refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector) {
             if (!possiblyNeedsRefinement(splitter)) {
                 return;
             }
             
             STORM_LOG_TRACE("Refining block " << splitter.getId());
             
-            splitBlockAccordingToCurrentQuotientDistributions(splitter, splitterQueue);
+            splitBlockAccordingToCurrentQuotientDistributions(splitter, splitterVector);
         }
         
         template class NondeterministicModelBisimulationDecomposition<storm::models::sparse::Mdp<double>>;

src/storage/bisimulation/NondeterministicModelBisimulationDecomposition.h

@@ -37,7 +37,7 @@ namespace storm {
             
             virtual void buildQuotient() override;
             
-            virtual void refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue) override;
+            virtual void refinePartitionBasedOnSplitter(bisimulation::Block<BlockDataType>& splitter, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector) override;
             
             virtual void initialize() override;
             
@@ -52,7 +52,7 @@ namespace storm {
             bool possiblyNeedsRefinement(bisimulation::Block<BlockDataType> const& block) const;
             
             // Splits the given block according to the current quotient distributions.
-            bool splitBlockAccordingToCurrentQuotientDistributions(bisimulation::Block<BlockDataType>& block, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue);
+            bool splitBlockAccordingToCurrentQuotientDistributions(bisimulation::Block<BlockDataType>& block, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector);
             
             // Retrieves whether the quotient distributions of state 1 are considered to be less than the ones of state 2.
             bool quotientDistributionsLess(storm::storage::sparse::state_type state1, storm::storage::sparse::state_type state2) const;
@@ -62,7 +62,7 @@ namespace storm {
             
             // Updates the quotient distributions of the predecessors of the new block by taking the probability mass
             // away from the old block.
-            void updateQuotientDistributionsOfPredecessors(bisimulation::Block<BlockDataType> const& newBlock, bisimulation::Block<BlockDataType> const& oldBlock, std::deque<bisimulation::Block<BlockDataType>*>& splitterQueue);
+            void updateQuotientDistributionsOfPredecessors(bisimulation::Block<BlockDataType> const& newBlock, bisimulation::Block<BlockDataType> const& oldBlock, std::vector<bisimulation::Block<BlockDataType>*>& splitterVector);
             
             bool checkQuotientDistributions() const;
             bool checkBlockStable(bisimulation::Block<BlockDataType> const& newBlock) const;

src/storage/dft/DFTState.cpp

@@ -6,7 +6,7 @@ namespace storm {
     namespace storage {
 
         template<typename ValueType>
-        DFTState<ValueType>::DFTState(DFT<ValueType> const& dft, DFTStateGenerationInfo const& stateGenerationInfo, size_t id) : mStatus(dft.stateVectorSize()), mId(id), mPseudoState(false), mDft(dft), mStateGenerationInfo(stateGenerationInfo), exploreHeuristic()  {
+        DFTState<ValueType>::DFTState(DFT<ValueType> const& dft, DFTStateGenerationInfo const& stateGenerationInfo, size_t id) : mStatus(dft.stateVectorSize()), mId(id), mPseudoState(false), mDft(dft), mStateGenerationInfo(stateGenerationInfo) {
             // TODO Matthias: use construct()
             
             // Initialize uses
@@ -17,27 +17,15 @@ namespace storm {
                 this->setUses(spareId, elem->children()[0]->id());
             }
 
-            for (auto elem : mDft.getBasicElements()) {
-                mCurrentlyNotFailableBE.push_back(elem->id());
-            }
-
             // Initialize activation
             propagateActivation(mDft.getTopLevelIndex());
 
             std::vector<size_t> alwaysActiveBEs = mDft.nonColdBEs();
             mCurrentlyFailableBE.insert(mCurrentlyFailableBE.end(), alwaysActiveBEs.begin(), alwaysActiveBEs.end());
-            // Remove always active BEs from currently not failable BEs
-            for (size_t id : alwaysActiveBEs) {
-                auto it = std::find(mCurrentlyNotFailableBE.begin(), mCurrentlyNotFailableBE.end(), id);
-                STORM_LOG_ASSERT(it != mCurrentlyNotFailableBE.end(), "Id not found.");
-                mCurrentlyNotFailableBE.erase(it);
-            }
-
-            sortFailableBEs();
         }
 
         template<typename ValueType>
-        DFTState<ValueType>::DFTState(storm::storage::BitVector const& status, DFT<ValueType> const& dft, DFTStateGenerationInfo const& stateGenerationInfo, size_t id) : mStatus(status), mId(id), mPseudoState(true), mDft(dft), mStateGenerationInfo(stateGenerationInfo), exploreHeuristic() {
+        DFTState<ValueType>::DFTState(storm::storage::BitVector const& status, DFT<ValueType> const& dft, DFTStateGenerationInfo const& stateGenerationInfo, size_t id) : mStatus(status), mId(id), mPseudoState(true), mDft(dft), mStateGenerationInfo(stateGenerationInfo) {
             // Intentionally left empty
         }
         
@@ -46,7 +34,6 @@ namespace storm {
             STORM_LOG_TRACE("Construct concrete state from pseudo state " << mDft.getStateString(mStatus, mStateGenerationInfo, mId));
             // Clear information from pseudo state
             mCurrentlyFailableBE.clear();
-            mCurrentlyNotFailableBE.clear();
             mFailableDependencies.clear();
             mUsedRepresentants.clear();
             STORM_LOG_ASSERT(mPseudoState, "Only pseudo states can be constructed.");
@@ -57,10 +44,6 @@ namespace storm {
                     if ((!be->isColdBasicElement() && be->canFail()) || !mDft.hasRepresentant(index) || isActive(mDft.getRepresentant(index))) {
                         mCurrentlyFailableBE.push_back(index);
                         STORM_LOG_TRACE("Currently failable: " << mDft.getBasicElement(index)->toString());
-                    } else {
-                        // BE currently is not failable
-                        mCurrentlyNotFailableBE.push_back(index);
-                        STORM_LOG_TRACE("Currently not failable: " << mDft.getBasicElement(index)->toString());
                     }
                 } else if (mDft.getElement(index)->isSpareGate()) {
                     // Initialize used representants
@@ -69,7 +52,6 @@ namespace storm {
                     STORM_LOG_TRACE("Spare " << index << " uses " << useId);
                 }
             }
-            sortFailableBEs();
 
             // Initialize failable dependencies
             for (size_t dependencyId : mDft.getDependencies()) {
@@ -85,9 +67,7 @@ namespace storm {
 
         template<typename ValueType>
         std::shared_ptr<DFTState<ValueType>> DFTState<ValueType>::copy() const {
-            std::shared_ptr<DFTState<ValueType>> stateCopy = std::make_shared<storm::storage::DFTState<ValueType>>(*this);
-            stateCopy->exploreHeuristic = storm::builder::DFTExplorationHeuristic<ValueType>();
-            return stateCopy;
+            return std::make_shared<storm::storage::DFTState<ValueType>>(*this);
         }
 
         template<typename ValueType>
@@ -205,7 +185,7 @@ namespace storm {
         template<typename ValueType>
         void DFTState<ValueType>::beNoLongerFailable(size_t id) {
             auto it = std::find(mCurrentlyFailableBE.begin(), mCurrentlyFailableBE.end(), id);
-            if(it != mCurrentlyFailableBE.end()) {
+            if (it != mCurrentlyFailableBE.end()) {
                 mCurrentlyFailableBE.erase(it);
             }
         }
@@ -239,11 +219,14 @@ namespace storm {
         }
 
         template<typename ValueType>
-        ValueType DFTState<ValueType>::getBERate(size_t id, bool considerPassive) const {
+        ValueType DFTState<ValueType>::getBERate(size_t id) const {
             STORM_LOG_ASSERT(mDft.isBasicElement(id), "Element is no BE.");
-            if (considerPassive && mDft.hasRepresentant(id) && !isActive(mDft.getRepresentant(id))) {
+
+            if (mDft.hasRepresentant(id) && !isActive(mDft.getRepresentant(id))) {
+                // Return passive failure rate
                 return mDft.getBasicElement(id)->passiveFailureRate();
             } else {
+                // Return active failure rate
                 return mDft.getBasicElement(id)->activeFailureRate();
             }
         }
@@ -251,16 +234,7 @@ namespace storm {
         template<typename ValueType>
         ValueType DFTState<ValueType>::getFailableBERate(size_t index) const {
             STORM_LOG_ASSERT(index < nrFailableBEs(), "Index invalid.");
-            return getBERate(mCurrentlyFailableBE[index], true);
-        }
-
-        template<typename ValueType>
-        ValueType DFTState<ValueType>::getNotFailableBERate(size_t index) const {
-            STORM_LOG_ASSERT(index < nrNotFailableBEs(), "Index invalid.");
-            STORM_LOG_ASSERT(storm::utility::isZero<ValueType>(mDft.getBasicElement(mCurrentlyNotFailableBE[index])->activeFailureRate()) ||
-                             (mDft.hasRepresentant(mCurrentlyNotFailableBE[index]) && !isActive(mDft.getRepresentant(mCurrentlyNotFailableBE[index]))), "BE " << mCurrentlyNotFailableBE[index] << " can fail");
-            // Use active failure rate as passive failure rate is 0.
-            return getBERate(mCurrentlyNotFailableBE[index], false);
+            return getBERate(mCurrentlyFailableBE[index]);
         }
 
         template<typename ValueType>
@@ -317,16 +291,11 @@ namespace storm {
                     if (be->isColdBasicElement() && be->canFail()) {
                         // Add to failable BEs
                         mCurrentlyFailableBE.push_back(elem);
-                        // Remove from not failable BEs
-                        auto it = std::find(mCurrentlyNotFailableBE.begin(), mCurrentlyNotFailableBE.end(), elem);
-                        STORM_LOG_ASSERT(it != mCurrentlyNotFailableBE.end(), "Element " << mDft.getElement(elem)->name() << " not found.");
-                        mCurrentlyNotFailableBE.erase(it);
                     }
                 } else if (mDft.getElement(elem)->isSpareGate() && !isActive(uses(elem))) {
                     propagateActivation(uses(elem));
                 }
             }
-            sortFailableBEs();
         }
 
         template<typename ValueType>
@@ -425,14 +394,6 @@ namespace storm {
             return changed;
         }
 
-        template<typename ValueType>
-        void DFTState<ValueType>::sortFailableBEs() {
-            std::sort(mCurrentlyFailableBE.begin( ), mCurrentlyFailableBE.end( ), [&](size_t const& lhs, size_t const& rhs) {
-                // Sort decreasing
-                return getBERate(rhs, true) < getBERate(lhs, true);
-            });
-        }
-
 
         // Explicitly instantiate the class.
         template class DFTState<double>;

src/storage/dft/DFTState.h

@@ -27,14 +27,12 @@ namespace storm {
             storm::storage::BitVector mStatus;
             size_t mId;
             std::vector<size_t> mCurrentlyFailableBE;
-            std::vector<size_t> mCurrentlyNotFailableBE;
             std::vector<size_t> mFailableDependencies;
             std::vector<size_t> mUsedRepresentants;
             bool mPseudoState;
             bool mValid = true;
             const DFT<ValueType>& mDft;
             const DFTStateGenerationInfo& mStateGenerationInfo;
-            storm::builder::DFTExplorationHeuristic<ValueType> exploreHeuristic;
 
         public:
             /**
@@ -123,26 +121,6 @@ namespace storm {
                 return mPseudoState;
             }
 
-            void setHeuristicValues(size_t depth, ValueType rate, ValueType exitRate) {
-                exploreHeuristic.setHeuristicValues(depth, rate, exitRate);
-            }
-
-            void setHeuristicValues(std::shared_ptr<storm::storage::DFTState<ValueType>> oldState, ValueType rate, ValueType exitRate) {
-                if (hasFailed(mDft.getTopLevelIndex()) || isFailsafe(mDft.getTopLevelIndex()) || nrFailableDependencies() > 0 || (nrFailableDependencies() == 0 && nrFailableBEs() == 0)) {
-                    // Do not skip absorbing state or if reached by dependencies
-                    exploreHeuristic.setNotSkip();
-                }
-                exploreHeuristic.setHeuristicValues(oldState->exploreHeuristic.getDepth() + 1, rate, exitRate);
-            }
-
-            bool isSkip(double approximationThreshold, storm::builder::ApproximationHeuristic heuristic) {
-                return exploreHeuristic.isSkip(approximationThreshold, heuristic);
-            }
-
-            double getPriority() const {
-                return exploreHeuristic.getPriority();
-            }
-            
             storm::storage::BitVector const& status() const {
                 return mStatus;
             }
@@ -202,15 +180,6 @@ namespace storm {
                 return mCurrentlyFailableBE.size();
             }
 
-            /**
-             * Get number of currently not failable BEs. These are cold BE which can fail in the future.
-             *
-             * @return Number of not failable BEs.
-             */
-            size_t nrNotFailableBEs() const {
-                return mCurrentlyNotFailableBE.size();
-            }
-
             /**
              * Get the failure rate of the currently failable BE on the given index.
              *
@@ -221,13 +190,13 @@ namespace storm {
             ValueType getFailableBERate(size_t index) const;
 
             /**
-             * Get the failure rate of the currently not failable BE on the given index.
+             * Get the current failure rate of the given BE.
              *
-             * @param index Index of BE in list of currently not failable BEs.
+             * @param id        Id of BE.
              *
              * @return Failure rate of the BE.
              */
-            ValueType getNotFailableBERate(size_t index) const;
+            ValueType getBERate(size_t id) const;
 
             /** Get number of currently failable dependencies.
              *
@@ -323,22 +292,6 @@ namespace storm {
         private:
             void propagateActivation(size_t representativeId);
 
-            /**
-             * Get the failure rate of the given BE.
-             *
-             * @param id              Id of BE.
-             * @param considerPassive Flag indicating if the passive failure rate should be returned if
-             *                        the BE currently is passive.
-             *
-             * @return Failure rate of the BE.
-             */
-            ValueType getBERate(size_t id, bool considerPassive) const;
-
-            /*!
-             * Sort failable BEs in decreasing order of their active failure rate.
-             */
-            void sortFailableBEs();
-
         };
 
     }

src/storm-dyftee.cpp

@@ -120,6 +120,7 @@ int main(const int argc, const char** argv) {
         parametric = generalSettings.isParametricSet();
 #endif
         
+#ifdef STORM_HAVE_Z3
         if (dftSettings.solveWithSMT()) {
             // Solve with SMT
             if (parametric) {
@@ -130,6 +131,7 @@ int main(const int argc, const char** argv) {
             storm::utility::cleanUp();
             return 0;
         }
+#endif
         
         // Set min or max
         bool minimal = true;

src/utility/bitoperations.h

@@ -10,6 +10,6 @@ inline size_t smallestIntWithNBitsSet(size_t n) {
 inline size_t nextBitPermutation(size_t v) {
     if (v==0) return static_cast<size_t>(0);
     // From https://graphics.stanford.edu/~seander/bithacks.html#NextBitPermutation
-    unsigned int t = (v | (v - 1)) + 1;  
+    size_t t = (v | (v - 1)) + 1;
     return t | ((((t & -t) / (v & -v)) >> 1) - 1);  
 }