int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "Usage: benchmark GRAPH\n");
return 0;
}
PrunedHighwayLabeling phl;
phl.ConstructLabel(argv[1]);
phl.Statistics();
int V = phl.NumVertices();
vector <int> v(NumQueries);
vector <int> w(NumQueries);
for (int i = 0; i < NumQueries; i++) {
v[i] = rand() % V;
w[i] = rand() % V;
}
double start_time = GetTime();
for (int i = 0; i < NumQueries; i++) phl.Query(v[i], w[i]);
double end_time = GetTime();
printf("Query Time : %lf usec\n", (end_time - start_time) * 1e6 / NumQueries);
return 0;
}
void IER::getKNNsByPHLTravelTimes(StaticRtree& rtree, unsigned int k, NodeID queryNodeID, std::vector<NodeID>& kNNs,
std::vector<EdgeWeight>& kNNDistances, Graph& graph, PrunedHighwayLabeling& phl)
{
// Retrieve kNN by euclidean distance
std::vector<NodeID> euclideanKNNs;
std::vector<EuclideanDistanceSqrd> euclideanKNNDistances;
Coordinate queryNodeX, queryNodeY;
graph.getCoordinates(queryNodeID,queryNodeX,queryNodeY);
BinaryMinHeap<EuclideanDistanceSqrd,RtreeDataTuple> heap = rtree.getKNNs(k,queryNodeX,queryNodeY,euclideanKNNs,euclideanKNNDistances);
// Note: We keep heap so that we incrementally retrieve further euclidean NNs
// We compute the network distances to each of these
BinaryMaxHeap<EdgeWeight,NodeID> knnCandidates;
EdgeWeight spDist, Dk, minTimeByEuclid;
for (std::size_t i = 0; i < euclideanKNNs.size(); ++i) {
spDist = phl.Query(queryNodeID,euclideanKNNs[i]);
knnCandidates.insert(euclideanKNNs[i],spDist);
}
// While the euclidean distance to the next euclidean nearest neigbour
// is smaller than than network distance to the current kth neighbour
// we can potentially find a closer nearest neighbour. Keep searching
// until this lower bound exceed the kth neighbour network distance.
Dk = knnCandidates.getMaxKey();
NodeID nextEuclidNN;
EuclideanDistanceSqrd currEuclidDistSqrd;
while (true) {
if (rtree.getNextNearestNeighbour(heap,queryNodeX,queryNodeY,nextEuclidNN,currEuclidDistSqrd)) {
// Note: If there were less than k objects to begin with then getNextNearestNeighbour
// would return false (as the heap is empty) and we not reach here
minTimeByEuclid = std::ceil(std::sqrt(currEuclidDistSqrd)/graph.getMaxGraphSpeedByEdge()); // Floor as it's a lowerbound
if (minTimeByEuclid < Dk) {
spDist = phl.Query(queryNodeID,nextEuclidNN);
if (spDist < Dk) {
// Only insert if it is a better kNN candidate
knnCandidates.insert(nextEuclidNN,spDist);
knnCandidates.extractMaxElement();
Dk = knnCandidates.getMaxKey();
}
} else {
break;
}
} else {
// This mean no nearest neighbours were found (we have reported
// all objects) so we can stop the search
break;
}
}
knnCandidates.populateKNNs(kNNs,kNNDistances);
}
