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Started work on including reachability encoding in SAT-based counterexample generator. 

Former-commit-id: 739b8850f0
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dehnert 12 years ago
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1 changed files with 124 additions and 4 deletions
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  1. 128
      src/counterexamples/SMTMinimalCommandSetGenerator.h

128
src/counterexamples/SMTMinimalCommandSetGenerator.h
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@ -67,6 +67,24 @@ namespace storm {
// A vector of variables that can be used to constrain the number of variables that are set to true.
std::vector<z3::expr> adderVariables;
// A flag whether or not there are variables reserved for encoding reachability of a target state.
bool hasReachabilityVariables;
// Starting from here, all structures hold information only if hasReachabilityVariables is true;
// A mapping from each pair of adjacent relevant states to their index in the corresponding variable vector.
std::map<std::pair<uint_fast64_t, uint_fast64_t>, uint_fast64_t> statePairToIndexMap;
// A vector of variables associated with each pair of relevant states (s, s') such that s' is
// a successor of s.
std::vector<z3::expr> statePairVariables;
// A mapping from relevant states to the index with the corresponding order variable in the state order variable vector.
std::map<uint_fast64_t, uint_fast64_t> relevantStatesToOrderVariableIndexMap;
// A vector of variables that holds all state order variables.
std::vector<z3::expr> stateOrderVariables;
};
/*!
@ -141,13 +159,14 @@ namespace storm {
* @param relevantCommands A set of relevant labels for which to create the expressions.
* @return A mapping from relevant labels to their corresponding expressions.
*/
static VariableInformation createExpressionsForRelevantLabels(z3::context& context, storm::storage::VectorSet<uint_fast64_t> const& relevantLabels) {
static VariableInformation createVariables(z3::context& context, storm::models::Mdp<T> const& labeledMdp, storm::storage::BitVector const& psiStates, RelevancyInformation const& relevancyInformation, bool createReachabilityVariables) {
VariableInformation variableInformation;
// Create stringstream to build expression names.
std::stringstream variableName;
for (auto label : relevantLabels) {
// Create the variables for the relevant labels.
for (auto label : relevancyInformation.relevantLabels) {
variableInformation.labelToIndexMap[label] = variableInformation.labelVariables.size();
// Clear contents of the stream to construct new expression name.
@ -165,6 +184,68 @@ namespace storm {
variableInformation.originalAuxiliaryVariables.push_back(context.bool_const(variableName.str().c_str()));
}
// A mapping from each pair of adjacent relevant states to their index in the corresponding variable vector.
std::map<std::pair<uint_fast64_t, uint_fast64_t>, uint_fast64_t> statePairToIndexMap;
// A vector of variables associated with each pair of relevant states (s, s') such that s' is
// a successor of s.
std::vector<z3::expr> statePairVariables;
// Create variables needed for encoding reachability of a target state if requested.
if (createReachabilityVariables) {
variableInformation.hasReachabilityVariables = true;
storm::storage::SparseMatrix<T> const& transitionMatrix = labeledMdp.getTransitionMatrix();
std::vector<uint_fast64_t> const& nondeterministicChoiceIndices = labeledMdp.getNondeterministicChoiceIndices();
for (auto state : relevancyInformation.relevantStates) {
variableInformation.relevantStatesToOrderVariableIndexMap[state] = variableInformation.stateOrderVariables.size();
// Clear contents of the stream to construct new expression name.
variableName.clear();
variableName.str("");
variableName << "o" << state;
variableInformation.stateOrderVariables.push_back(context.real_const(variableName.str().c_str()));
for (auto const& relevantChoices : relevancyInformation.relevantChoicesForRelevantStates.at(state)) {
for (typename storm::storage::SparseMatrix<T>::ConstIndexIterator successorIt = transitionMatrix.constColumnIteratorBegin(relevantChoices); successorIt != transitionMatrix.constColumnIteratorEnd(relevantChoices); ++successorIt) {
// If the successor state is neither the state itself nor an irrelevant state, we need to add a variable for the transition.
if (state != *successorIt && (relevancyInformation.relevantStates.get(*successorIt) || psiStates.get(*successorIt))) {
// Make sure that there is not already one variable for the state pair. This may happen because of several nondeterministic choices
// targeting the same state.
if (variableInformation.statePairToIndexMap.find(std::make_pair(state, *successorIt)) != variableInformation.statePairToIndexMap.end()) {
continue;
}
// At this point we know that the state-pair does not have an associated variable.
variableInformation.statePairToIndexMap[std::make_pair(state, *successorIt)] = variableInformation.statePairVariables.size();
// Clear contents of the stream to construct new expression name.
variableName.clear();
variableName.str("");
variableName << "t" << state << "_" << *successorIt;
variableInformation.statePairVariables.push_back(context.bool_const(variableName.str().c_str()));
}
}
}
}
for (auto psiState : psiStates) {
variableInformation.relevantStatesToOrderVariableIndexMap[psiState] = variableInformation.stateOrderVariables.size();
// Clear contents of the stream to construct new expression name.
variableName.clear();
variableName.str("");
variableName << "o" << psiState;
variableInformation.stateOrderVariables.push_back(context.real_const(variableName.str().c_str()));
}
}
return variableInformation;
}
@ -808,6 +889,41 @@ namespace storm {
}
}
}
/*!
* Asserts constraints necessary to encode the reachability of at least one target state from the initial states.
*/
static void assertReachabilityCuts(storm::models::Mdp<T> const& labeledMdp, storm::storage::BitVector const& psiStates, VariableInformation const& variableInformation, RelevancyInformation const& relevancyInformation, z3::context& context, z3::solver& solver) {
// Get some data from the MDP for convenient access.
storm::storage::SparseMatrix<T> const& transitionMatrix = labeledMdp.getTransitionMatrix();
std::vector<storm::storage::VectorSet<uint_fast64_t>> const& choiceLabeling = labeledMdp.getChoiceLabeling();
storm::storage::SparseMatrix<bool> backwardTransitions = labeledMdp.getBackwardTransitions();
for (auto relevantState : relevancyInformation.relevantStates) {
// Only consider the state if it's not an initial state.
if (!labeledMdp.getInitialStates().get(relevantState)) {
storm::storage::VectorSet<uint_fast64_t> relevantPredecessors;
for (typename storm::storage::SparseMatrix<T>::ConstIndexIterator predecessorIt = backwardTransitions.constColumnIteratorBegin(relevantState), predecessorIte = backwardTransitions.constColumnIteratorEnd(relevantState); predecessorIt != predecessorIte; ++predecessorIt) {
if (relevantState != *predecessorIt && relevancyInformation.relevantStates.get(*predecessorIt)) {
relevantPredecessors.insert(*predecessorIt);
}
}
storm::storage::VectorSet<uint_fast64_t> relevantSuccessors;
for (auto const& relevantChoices : relevancyInformation.relevantChoicesForRelevantStates.at(relevantState)) {
for (typename storm::storage::SparseMatrix<T>::ConstIndexIterator successorIt = transitionMatrix.constColumnIteratorBegin(relevantChoices); successorIt != transitionMatrix.constColumnIteratorEnd(relevantChoices); ++successorIt) {
if (relevantState != *successorIt && (relevancyInformation.relevantStates.get(*successorIt) || psiStates.get(*successorIt))) {
relevantSuccessors.insert(*successorIt);
}
}
}
// TODO: build the constraints
}
}
}
/*!
* Asserts that the disjunction of the given formulae holds. If the content of the disjunction is empty,
@ -1425,7 +1541,7 @@ namespace storm {
* @param checkThresholdFeasible If set, it is verified that the model can actually achieve/exceed the given probability value. If this check
* is made and fails, an exception is thrown.
*/
static storm::storage::VectorSet<uint_fast64_t> getMinimalCommandSet(storm::ir::Program program, std::string const& constantDefinitionString, storm::models::Mdp<T> const& labeledMdp, storm::storage::BitVector const& phiStates, storm::storage::BitVector const& psiStates, double probabilityThreshold, bool strictBound, bool checkThresholdFeasible = false) {
static storm::storage::VectorSet<uint_fast64_t> getMinimalCommandSet(storm::ir::Program program, std::string const& constantDefinitionString, storm::models::Mdp<T> const& labeledMdp, storm::storage::BitVector const& phiStates, storm::storage::BitVector const& psiStates, double probabilityThreshold, bool strictBound, bool checkThresholdFeasible = false, bool includeReachabilityEncoding = false) {
#ifdef STORM_HAVE_Z3
// Set up all clocks used for time measurement.
auto totalClock = std::chrono::high_resolution_clock::now();
@ -1469,7 +1585,7 @@ namespace storm {
z3::context context;
// (4) Create the variables for the relevant commands.
VariableInformation variableInformation = createExpressionsForRelevantLabels(context, relevancyInformation.relevantLabels);
VariableInformation variableInformation = createVariables(context, labeledMdp, psiStates, relevancyInformation, includeReachabilityEncoding);
LOG4CPLUS_DEBUG(logger, "Created variables.");
// (5) After all variables have been created, create a solver for that context.
@ -1487,6 +1603,10 @@ namespace storm {
LOG4CPLUS_DEBUG(logger, "Asserted explicit cuts.");
assertSymbolicCuts(program, labeledMdp, variableInformation, relevancyInformation, context, solver);
LOG4CPLUS_DEBUG(logger, "Asserted symbolic cuts.");
if (includeReachabilityEncoding) {
assertReachabilityCuts(labeledMdp, psiStates, variableInformation, relevancyInformation, context, solver);
LOG4CPLUS_DEBUG(logger, "Asserted reachability cuts.");
}
// As we are done with the setup at this point, stop the clock for the setup time.
totalSetupTime = std::chrono::high_resolution_clock::now() - setupTimeClock;

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