double BestFirstReachabilitySearch::lookaheadDistance(const PetriNet& net,
const Structures::State* state,
const PQL::Condition* query,
int depth){
double min = -1;
State* ns = (State*)alloca(StateAllocator<>::stateSize(net));
StateAllocator<>::initializeState(ns, net);
for(unsigned int t = 0; t < net.numberOfTransitions(); t++){
if(net.fire(t, state, ns) && !_states->contains(ns)){
PQL::DistanceContext context(net,
_distanceStrategy,
ns->marking(),
ns->intValuation(),
ns->boolValuation(),
_dm);
double d = query->distance(context);
if(d < min || min == -1)
min = d;
if(depth - 1 > 0)
d = lookaheadDistance(net, ns, query, depth-1);
if(d < min || min == -1)
min = d;
}
}
return min;
}
bool StateConstraints::isInMaxTrap(const PetriNet& net,
size_t place,
const BitField& places,
const MarkVal* resultMarking) const{
if(!places.test(place))
return false;
/*
0 if M(p_i) = 1
0 if there is (p_i , t) ∈ F such that x_j = 0
for every p_j ∈ t•
1 otherwise
*/
if(resultMarking[place] > 0)
return false;
for(unsigned int t = 0; t < net.numberOfTransitions(); t++){
if(net.inArc(place, t) > 0){
bool exclude = true;
for(unsigned int j = 0; j < net.numberOfPlaces(); j++){
if(net.outArc(t, j) > 0){
exclude &= !places.test(j);
}
}
if(exclude)
return false;
}
}
return true;
}
ReachabilityResult MonoDFS::reachable(const PetriNet &net,
const MarkVal *m0,
const VarVal *v0,
const BoolVal *b0,
PQL::Condition *query){
//Do we initially satisfy query?
if(query->evaluate(PQL::EvaluationContext(m0, v0, b0)))
return ReachabilityResult(ReachabilityResult::Satisfied,
"A state satisfying the query was found");
//Create StateSet
MonotonicityContext context(&net,query);
context.analyze();
DFSStateSet states(net,&context, ModeNormal);
StateAllocator<1000000> allocator(net);
State* s0 = allocator.createState();
memcpy(s0->marking(), m0, sizeof(MarkVal)*net.numberOfPlaces());
memcpy(s0->intValuation(), v0, sizeof(VarVal)*net.numberOfIntVariables());
memcpy(s0->boolValuation(), b0, sizeof(BoolVal)*net.numberOfBoolVariables());
states.add(s0, 0);
unsigned int max = 0;
int count = 0;
BigInt exploredStates = 0;
BigInt expandedStates = 0;
BigInt transitionFired = 0;
State* ns = allocator.createState();
while(states.waitingSize()){
if(count++ & 1<<18){
if(states.waitingSize() > max)
max = states.waitingSize();
count = 0;
//report progress
reportProgress((double)(max-states.waitingSize())/(double)max);
//check abort
if(abortRequested())
return ReachabilityResult(ReachabilityResult::Unknown,
"Search was aborted.");
}
//Take first step of the stack
Step tstep = states.getNextStep();
State* s = tstep.state;
ns->setParent(s);
bool foundSomething = false;
for(unsigned int t = tstep.t; t < net.numberOfTransitions(); t++){
if(net.fire(t, s->marking(), s->intValuation(),s->boolValuation(), ns->marking(), ns->intValuation(), ns->boolValuation())){
transitionFired++;
if(states.add(ns,t)){
ns->setTransition(t);
if(query->evaluate(PQL::EvaluationContext(ns->marking(), ns->intValuation(), ns->boolValuation())))
return ReachabilityResult(ReachabilityResult::Satisfied,
"A state satisfying the query was found", expandedStates, exploredStates, transitionFired, states.getCountRemove(), ns->pathLength(), ns->trace());
exploredStates++;
foundSomething = true;
ns = allocator.createState();
break;
}
}
}
if(!foundSomething){
states.popWating();
expandedStates++;
}
}
//states.writeStatistics();
return ReachabilityResult(ReachabilityResult::NotSatisfied,
"No state satisfying the query exists.", expandedStates, exploredStates, transitionFired, states.getCountRemove());
}
ReachabilityResult BestFirstReachabilitySearch::reachable(const PetriNet &net,
const MarkVal *m0,
const VarVal *v0,
const BoolVal *ba,
PQL::Condition *query){
StateAllocator<> allocator(net);
State* s0 = allocator.createState();
memcpy(s0->marking(), m0, sizeof(MarkVal) * net.numberOfPlaces());
memcpy(s0->intValuation(), v0, sizeof(VarVal) * net.numberOfIntVariables());
memcpy(s0->boolValuation(), ba, sizeof(BoolVal) * net.numberOfBoolVariables());
if(query->evaluate(*s0))
return ReachabilityResult(ReachabilityResult::Satisfied, "Satisfied initially", 0, 0);
//Initialize subclasses
initialize(query, net);
StateSet states(net);
_states = &states;
states.add(s0);
//PriorityQueue<State*> queue;
EnhancedPriorityQueue<State*> queue;
queue.push(0, s0);
//Allocate new state
State* ns = allocator.createState();
State* ns2 = allocator.createState();
State* ns3 = allocator.createState();
int count = 0;
BigInt expandedStates = 0;
BigInt exploredStates = 0;
BigInt transitionFired = 0;
size_t max = 1;
while(!queue.empty()){
if(count++ & 1<<17){
count = 0;
if(queue.size() > max)
max = queue.size();
this->reportProgress((double)(max - queue.size()) / ((double)(max)));
if(this->abortRequested())
return ReachabilityResult(ReachabilityResult::Unknown,
"Query aborted!");
}
//Take something out of the queue
State* s = queue.pop(depthFirst);
expandedStates++;
// Attempt to fire each transition
for(unsigned int t = 0; t < net.numberOfTransitions(); t++){
if(net.fire(t, s->marking(), s->intValuation(), s->boolValuation(), ns->marking(), ns->intValuation(), ns->boolValuation())){
//If it's new
transitionFired++;
if(states.add(ns)){
exploredStates++;
//Set parent and transition for the state
ns->setParent(s);
ns->setTransition(t);
//Test query
if(query->evaluate(*ns)){
//ns->dumpTrace(net);
return ReachabilityResult(ReachabilityResult::Satisfied,
"Query was satified!", expandedStates, exploredStates, transitionFired,0 , ns->pathLength(), ns->trace());
}
// Insert in queue, with given priority
double bestp = priority(ns, query, net);
queue.push(bestp, ns);
if(fireUntillNoBetter && net.fire(t, ns, ns2)){
if(query->evaluate(*ns2)){
ns2->setTransition(t);
ns2->setParent(ns);
return ReachabilityResult(ReachabilityResult::Satisfied,
"Query was satified!", expandedStates, exploredStates, transitionFired,0, ns2->pathLength(), ns2->trace());
}
double p = priority(ns2, query, net);
if(p <= bestp){
bestp = p;
while(net.fire(t, ns2, ns3) && (p = priority(ns3, query, net)) <= bestp){
ns3->setTransition(t);
ns3->setParent(ns2);
bestp = p;
State* tmp = ns2; //SWAP ns2 and ns3
ns2 = ns3;
ns3 = tmp;
exploredStates++;
if(query->evaluate(*ns2)){
return ReachabilityResult(ReachabilityResult::Satisfied,
"Query was satisfied!", expandedStates, exploredStates, transitionFired, 0, ns2->pathLength(), ns2->trace());
}
}
if(states.add(ns2)){
queue.push(priority(ns2, query, net), ns2);
ns2 = allocator.createState();
}
}
}
//Allocate new stake, as states take ownership
ns = allocator.createState();
}
}
}
}
return ReachabilityResult(ReachabilityResult::NotSatisfied,
"Query cannot be satisfied!", expandedStates, exploredStates, transitionFired,0);
}
ReachabilityResult HeuristicDFS::reachable(const PetriNet& net,
const MarkVal* m0,
const VarVal* v0,
const BoolVal *ba,
PQL::Condition* query){
//Do we initially satisfy query?
if(query->evaluate(PQL::EvaluationContext(m0, v0, ba)))
return ReachabilityResult(ReachabilityResult::Satisfied,
"A state satisfying the query was found");
StateSet states(net);
StateAllocator<> allocator(net);
std::list<State*> stack;
State* s0 = allocator.createState();
memcpy(s0->marking(), m0, sizeof(MarkVal)*net.numberOfPlaces());
memcpy(s0->intValuation(), v0, sizeof(VarVal)*net.numberOfIntVariables());
memcpy(s0->boolValuation(), ba, sizeof(BoolVal)*net.numberOfBoolVariables());
stack.push_back(s0);
states.add(s0);
Structures::DistanceMatrix distanceMatrix(net);
State* ns = allocator.createState();
unsigned int max = 0;
int count = 0;
BigInt expandedStates = 0;
BigInt exploredStates = 0;
BigInt transitionFired = 0;
while(!stack.empty()){
// Progress reporting and abort checking
if(count++ & 1<<16){
if(stack.size() > max)
max = stack.size();
count = 0;
// Report progress
reportProgress((double)(max - stack.size())/(double)max);
// Check abort
if(abortRequested())
return ReachabilityResult(ReachabilityResult::Unknown,
"Search was aborted.");
}
State* s = stack.back();
stack.pop_back();
State* succ[net.numberOfTransitions()];
double distances[net.numberOfTransitions()];
memset(succ, 0, net.numberOfTransitions()*sizeof(State*));
for(unsigned int t = 0; t < net.numberOfTransitions(); t++){
if(net.fire(t, s, ns)){
transitionFired++;
if(states.add(ns)){
exploredStates++;
ns->setParent(s);
ns->setTransition(t);
if(query->evaluate(*ns))
return ReachabilityResult(ReachabilityResult::Satisfied,
"A state satisfying the query was found", expandedStates, exploredStates, transitionFired, 0, ns->pathLength(), ns->trace());
PQL::DistanceContext context(net,
_distanceStrategy,
ns->marking(),
ns->intValuation(),
ns->boolValuation(),
&distanceMatrix);
succ[t] = ns;
distances[t] = query->distance(context);
ns = allocator.createState();
}
}
}
// Pretty bobble sort of the successors
while(true){
bool foundSomething = false;
unsigned int min = 0;
for(unsigned int t = 0; t < net.numberOfTransitions(); t++){
if(succ[t] && (!foundSomething || distances[t] < distances[min])){
min = t;
foundSomething = true;
}
}
if(foundSomething){
stack.push_back(succ[min]);
succ[min] = NULL;
}else
break;
}
expandedStates++;
}
return ReachabilityResult(ReachabilityResult::NotSatisfied,
"No state satisfying the query exists.", expandedStates, exploredStates, transitionFired, 0);
}
int StateConstraints::fireVectorSize(const PetriNet& net,
const MarkVal* m0,
const VarVal*) const{
assert(nPlaces == net.numberOfPlaces());
assert(nVars == net.numberOfVariables());
// Create linary problem
lprec* lp;
lp = make_lp(0, net.numberOfTransitions()); // One variable for each entry in the firing vector
assert(lp);
if(!lp) return false;
// Set verbosity
set_verbose(lp, IMPORTANT);
// Set transition names (not strictly needed)
for(size_t i = 0; i < net.numberOfTransitions(); i++)
set_col_name(lp, i+1, const_cast<char*>(net.transitionNames()[i].c_str()));
// Start adding rows
set_add_rowmode(lp, TRUE);
REAL row[net.numberOfTransitions() + 1];
for(size_t p = 0; p < nPlaces; p++){
// Set row zero
memset(row, 0, sizeof(REAL) * net.numberOfTransitions() + 1);
for(size_t t = 0; t < net.numberOfTransitions(); t++){
int d = net.outArc(t, p) - net.inArc(p, t);
row[1+t] = d;
}
if(pcs[p].min == pcs[p].max &&
pcs[p].max != CONSTRAINT_INFTY){
double target = pcs[p].min - m0[p];
add_constraint(lp, row, EQ, target);
}else{
// There's always a min, even zero is interesting
double target = pcs[p].min - m0[p];
add_constraint(lp, row, GE, target);
if(pcs[p].max != CONSTRAINT_INFTY){
double target = pcs[p].max - m0[p];
add_constraint(lp, row, LE, target);
}
}
}
// Finished adding rows
set_add_rowmode(lp, FALSE);
// Create objective
memset(row, 0, sizeof(REAL) * net.numberOfTransitions() + 1);
for(size_t t = 0; t < net.numberOfTransitions(); t++)
row[1+t] = 1; // The sum the components in the firing vector
// Set objective
set_obj_fn(lp, row);
// Minimize the objective
set_minim(lp);
// Set variables as integer variables
for(size_t i = 0; i < net.numberOfTransitions(); i++)
set_int(lp, 1+i, TRUE);
// Attempt to solve the problem
int result = solve(lp);
// Limit on traps to test
size_t traplimit = nPlaces * OVER_APPROX_TRAP_FACTOR;
// Try to add a minimal trap constraint
while((result == OPTIMAL) && traplimit-- < 0){
memset(row, 0, sizeof(REAL) * net.numberOfTransitions() + 1);
// Get the firing vector
get_variables(lp, row);
// Compute the resulting marking
MarkVal rMark[net.numberOfPlaces()];
for(size_t p = 0; p < nPlaces; p++){
rMark[p] = m0[p];
for(size_t t = 0; t < net.numberOfTransitions(); t++)
rMark[p] += (net.outArc(t, p) - net.inArc(p, t)) * (int)row[t];
}
// Find an M-trap
BitField trap(minimalTrap(net, m0, rMark));
//Break if there's no trap
if(trap.none()) break;
// Compute the new equation
for(size_t t = 0; t < net.numberOfTransitions(); t++){
row[1+t] = 0;
for(size_t p = 0; p < nPlaces; p++)
if(trap.test(p))
row[1+t] += net.outArc(t, p) - net.inArc(p, t);
}
// Add a new row with target as greater than equal to 1
set_add_rowmode(lp, TRUE);
add_constraint(lp, row, GE, 1);
set_add_rowmode(lp, FALSE);
// Attempt to solve the again
result = solve(lp);
}
int retval = 0;
if(result != INFEASIBLE){
get_variables(lp, row);
for(size_t t = 0; t < net.numberOfTransitions(); t++)
retval += (int)row[t];
}
// Delete the linear problem
delete_lp(lp);
lp = NULL;
// Return true, if it was infeasible
return retval;
}
ReachabilityResult MonoBFS::reachable(const PetriNet &net,
const MarkVal *m0,
const VarVal *v0,
const BoolVal *ba,
PQL::Condition *query){
//Do we initially satisfy query?
if(query->evaluate(PQL::EvaluationContext(m0, v0,ba)))
return ReachabilityResult(ReachabilityResult::Satisfied,
"A state satisfying the query was found");
//Create StateSet
MonotonicityContext context(&net, query);
context.analyze();
BFSOrderableStateSet states(net,&context);
StateAllocator<1000000> allocator(net);
State* s0 = allocator.createState();
memcpy(s0->marking(), m0, sizeof(MarkVal)*net.numberOfPlaces());
memcpy(s0->intValuation(), v0, sizeof(VarVal)*net.numberOfIntVariables());
memcpy(s0->boolValuation(), ba, sizeof(BoolVal)*net.numberOfBoolVariables());
states.add(s0);
unsigned int max = 0;
int count = 0;
BigInt expandedStates = 0;
BigInt exploredStates = 0;
BigInt transitionFired = 0;
State* ns = allocator.createState();
State* s = states.getNextState();
while(s){
// Progress reporting and abort checking
if(count++ & 1<<15){
if(states.waitingSize() > max)
max = states.waitingSize();
count = 0;
// Report progress
reportProgress((double)(max - states.waitingSize())/(double)max);
// Check abort
if(abortRequested())
return ReachabilityResult(ReachabilityResult::Unknown,
"Search was aborted.");
}
for(unsigned int t = 0; t < net.numberOfTransitions(); t++){
if(net.fire(t, s, ns)){
transitionFired++;
if(states.add(ns)){
exploredStates++;
ns->setParent(s);
ns->setTransition(t);
if(query->evaluate(PQL::EvaluationContext(ns->marking(), ns->intValuation(), ns->boolValuation()))){
//ns->dumpTrace(net);
return ReachabilityResult(ReachabilityResult::Satisfied,
"A state satisfying the query was found", expandedStates, exploredStates, transitionFired, states.getCountRemove(), ns->pathLength(), ns->trace());
}
ns = allocator.createState();
}
}
}
s = states.getNextState();
expandedStates++;
}
return ReachabilityResult(ReachabilityResult::NotSatisfied,
"No state satisfying the query exists.", expandedStates, exploredStates, transitionFired, states.getCountRemove());
}
bool KarpMillerL1SearchStrategy::reachable(const PetriNet &net,
const MarkVal *initialMarking,
const VarVal*,
PQL::Condition *query){
assert(net.numberOfVariables() == 0);
if(net.numberOfVariables() > 0){
//TODO: Return unknown, or could not be found
return false;
}
const unsigned int nTransitions = net.numberOfTransitions(),
nPlaces = net.numberOfPlaces();
MarkVal old_m[nPlaces];
MarkVal new_m[nPlaces];
memcpy(old_m, initialMarking, nPlaces * sizeof(MarkVal));
size_t depth = 1;
uint8_t* stack = new uint8_t[MAX_DEPTH];
stack[0] = 0;
uint8_t t = 0;
while(true){
// Invariant:
// old_m is the current marking
// stack[depth] is where the next transtion goes
// t is the next transition to fire
while(!fire(net, t, old_m, new_m)){
while(++t == nTransitions){
if(--depth == 0) //Pop the stack
return false; //Terminate algorithm, we're done now
// Reverse transition on the stack
t = stack[depth];
for(size_t i = 0; i < nPlaces; i++)
old_m[i] -= net.transitionVector(t)[i];
}
}
//Test if query is satisfied
if(query->evaluate(PQL::EvaluationContext(new_m, NULL)))
return true;
//Check if it's seen
bool seen = false;
size_t d = depth;
while(--d > 0){
seen = true;
const MarkVal* tv = net.transitionVector(stack[d]);
for(size_t i = 0; i < nPlaces; i++){
old_m[i] -= tv[i];
seen &= old_m[i] == new_m[i];
if(!seen) break;
}
if(seen) break;
}
if(seen)
printf("|");
else
printf("%i", (int)t);
fflush(stdout);
memcpy(old_m, new_m, nPlaces * sizeof(MarkVal));
if(!seen){
stack[depth++] = t;
t = 0;
}else{
for(size_t i = 0; i < nPlaces; i++)
old_m[i] -= net.transitionVector(t)[i];
//Pop if needed as long as needed
while(++t == nTransitions){
if(--depth == 0) //Pop the stack
return false; //Terminate algorithm, we're done now
// Reverse transition on the stack
t = stack[depth];
for(size_t i = 0; i < nPlaces; i++)
old_m[i] -= net.transitionVector(t)[i];
}
}
}
}
ReachabilityResult IndexedBestFS::reachable(const PetriNet &net,
const MarkVal *m0,
const VarVal *v0,
const BoolVal *ba,
PQL::Condition *query){
StateAllocator<> allocator(net);
State* s0 = allocator.createState();
memcpy(s0->marking(), m0, sizeof(MarkVal) * net.numberOfPlaces());
memcpy(s0->intValuation(), v0, sizeof(VarVal) * net.numberOfIntVariables());
memcpy(s0->boolValuation(), ba, sizeof(BoolVal) * net.numberOfBoolVariables());
if(query->evaluate(*s0))
return ReachabilityResult(ReachabilityResult::Satisfied, "Satisfied initially", 0, 0);
//Initialize subclasses
MonotonicityContext context(&net, query);
context.analyze();
//Initialise StateSet
IndexedBestFSStateSet states(net, &context, _distanceStrategy, query, _varianceFirst);
states.add(s0);
//Allocate new state
State* ns = allocator.createState();
int count = 0;
BigInt expandedStates = 0;
BigInt exploredStates = 0;
BigInt transitionFired = 0;
size_t max = 1;
State* s = states.getNextState();
while(s){
if(count++ & 1<<16){
count = 0;
if(states.waitingSize() > max)
max = states.waitingSize();
this->reportProgress((double)(max - states.waitingSize()) / ((double)(max)));
if(this->abortRequested())
return ReachabilityResult(ReachabilityResult::Unknown,
"Query aborted!");
}
// Attempt to fire each transition
for(unsigned int t = 0; t < net.numberOfTransitions(); t++){
if(net.fire(t, s, ns)){
//If it's new
transitionFired++;
if(states.add(ns)){
exploredStates++;
//Set parent and transition for the state
ns->setParent(s);
ns->setTransition(t);
//Test query
if(query->evaluate(*ns)){
//ns->dumpTrace(net);
return ReachabilityResult(ReachabilityResult::Satisfied,
"Query was satified!", expandedStates, exploredStates, transitionFired, states.getCountRemove(), ns->pathLength(), ns->trace());
}
//Allocate new state, as states take ownership
ns = allocator.createState();
}
}
}
//Take something out of the queue
expandedStates++;
s = states.getNextState();
}
return ReachabilityResult(ReachabilityResult::NotSatisfied,
"Query cannot be satisfied!", expandedStates, exploredStates, transitionFired, states.getCountRemove());
}
ReachabilityResult MagicSearch::reachable(const PetriNet &net,
const MarkVal *m0,
const VarVal *v0,
PQL::Condition *query){
SmartStateAllocator<MEMORY_BOUND> allocator(net);
SmartStateSet states(net);
EnhancedPriorityQueue<Step> queue;
_dm = new Structures::DistanceMatrix(net);
{ //Compute constraints
ConstraintAnalysisContext context(net);
query->findConstraints(context);
if(context.canAnalyze)
contraints = context.retval;
}
//Create s0
SmartState* s0 = allocator.createStoredState();
memcpy(s0->marking(), m0, sizeof(MarkVal) * net.numberOfPlaces());
memcpy(s0->valuation(), v0, sizeof(VarVal) * net.numberOfVariables());
states.add(s0, s0->marking(), s0->valuation());
Step step0;
step0.depth = 0;
step0.lastApprox = INT_MAX;
step0.lastStored = 0;
step0.state = s0;
queue.push(0, step0);
//Temporary marking and valuation to work with
MarkVal tmpM[net.numberOfPlaces()];
VarVal tmpV[net.numberOfVariables()];
SmartState* ns = allocator.createStoredState();
SmartState* ls = allocator.createState();
//Statistics
int lastReport = 0;
BigInt expanded = 0, explored = 0;
size_t max = 1;
//Main loop
while(!queue.empty()){
// Report progress if needed
if(lastReport++ & 1<<17){
lastReport = 0;
if(queue.size() > max)
max = queue.size();
this->reportProgress((double)(max - queue.size()) / ((double)(max)));
if(this->abortRequested())
return ReachabilityResult(ReachabilityResult::Unknown,
"Query aborted!");
}
//Pop stuff of the queue
Step step = queue.pop(depthFirst);
expanded++; //Cound expanded states
// Get current state
const MarkVal* m;
const VarVal* v;
if(step.state->stored()){
m = step.state->marking();
v = step.state->valuation();
}else{
step.state->getState(net, tmpM, tmpV);
m = tmpM;
v = tmpV;
}
//Attempt to exclude by over-approx
if(step.lastApprox >= approxScale(step.depth)){
if(canExcludeByOverApprox(net, m, v))
continue;
step.lastApprox = 0;
}
for(unsigned int t = 0; t < net.numberOfTransitions(); t++){
//Fire the transition
if(net.fire(t, m, v, ns->marking(), ns->valuation())){
//Determine whether or not to store the entire state
bool storeCurrentState = step.lastStored >= storeScale(allocator.percentMemoryUsed());// storeScale(allocator.percentMemoryUsed());
SmartState* storeState;
if(storeCurrentState)
storeState = ns;
else
storeState = ls;
storeState->setParent(step.state);
storeState->setTransition(t);
//Add it to the state set
if(states.add(storeState, ns->marking(), ns->valuation())){
explored++; //Count explored states
//Test the query
if(query->evaluate(EvaluationContext(ns->marking(), ns->valuation()))){
printf("\nmemory usage: %f\n",allocator.percentMemoryUsed());
return ReachabilityResult(ReachabilityResult::Satisfied,
"Query was satified!",
expanded,
explored,
storeState->pathLength(),
storeState->trace());
}
//Make the next step
Step nextstep;
nextstep.depth = step.depth + 1;
nextstep.lastApprox = step.lastApprox + 1;
if(storeState == ns)
nextstep.lastStored = 0;
else
nextstep.lastStored = step.lastStored + 1;
nextstep.state = storeState;
//Push step on the queue
double p = priority(ns->marking(), ns->valuation(), query, net);
queue.push(p, nextstep);
//Allocate new memory, depending on what was stored
if(storeState == ns)
ns = allocator.createStoredState();
else
ls = allocator.createState();
}
}
}
}
return ReachabilityResult(ReachabilityResult::NotSatisfied,
"Query cannot be satisfied!",
expanded,
explored);
}