/** Finds shortcuts, does not change the underlying graph. */
void findShortcuts(ShortcutHandler sch) {
long tmpDegreeCounter = 0;
EdgeIterator incomingEdges = vehicleInExplorer.setBaseNode(sch.getNode());
// collect outgoing nodes (goal-nodes) only once
while (incomingEdges.next()) {
int u_fromNode = incomingEdges.getAdjNode();
// accept only uncontracted nodes
if (g.getLevel(u_fromNode) != 0) continue;
double v_u_weight = incomingEdges.getDistance();
int skippedEdge1 = incomingEdges.getEdge();
int incomingEdgeOrigCount = getOrigEdgeCount(skippedEdge1);
// collect outgoing nodes (goal-nodes) only once
EdgeIterator outgoingEdges = vehicleOutExplorer.setBaseNode(sch.getNode());
// force fresh maps etc as this cannot be determined by from node alone (e.g. same from node
// but different avoidNode)
algo.clear();
tmpDegreeCounter++;
while (outgoingEdges.next()) {
int w_toNode = outgoingEdges.getAdjNode();
// add only uncontracted nodes
if (g.getLevel(w_toNode) != 0 || u_fromNode == w_toNode) {
continue;
}
// Limit weight as ferries or forbidden edges can increase local search too much.
// If we decrease the correct weight we only explore less and introduce more shortcuts.
// I.e. no change to accuracy is made.
double existingDirectWeight = v_u_weight + outgoingEdges.getDistance();
algo.setLimitWeight(existingDirectWeight)
.setLimitVisitedNodes((int) meanDegree * 100)
.setEdgeFilter(levelEdgeFilter.setAvoidNode(sch.getNode()));
dijkstraSW.start();
dijkstraCount++;
int endNode = algo.findEndNode(u_fromNode, w_toNode);
dijkstraSW.stop();
// compare end node as the limit could force dijkstra to finish earlier
if (endNode == w_toNode && algo.getWeight(endNode) <= existingDirectWeight)
// FOUND witness path, so do not add shortcut
continue;
sch.foundShortcut(
u_fromNode,
w_toNode,
existingDirectWeight,
outgoingEdges,
skippedEdge1,
incomingEdgeOrigCount);
}
}
if (sch instanceof AddShortcutHandler) {
// sliding mean value when using "*2" => slower changes
meanDegree = (meanDegree * 2 + tmpDegreeCounter) / 3;
// meanDegree = (meanDegree + tmpDegreeCounter) / 2;
}
}
/** Introduces the necessary shortcuts for endNode v in the graph. */
int addShortcuts(int v) {
shortcuts.clear();
findShortcuts(addScHandler.setNode(v));
int tmpNewShortcuts = 0;
for (Shortcut sc : shortcuts.keySet()) {
boolean updatedInGraph = false;
// check if we need to update some existing shortcut in the graph
EdgeSkipIterator iter = vehicleOutExplorer.setBaseNode(sc.from);
while (iter.next()) {
if (iter.isShortcut()
&& iter.getAdjNode() == sc.to
&& prepareEncoder.canBeOverwritten(iter.getFlags(), sc.flags)
&& iter.getDistance() > sc.weight) {
iter.setFlags(sc.flags);
iter.setSkippedEdges(sc.skippedEdge1, sc.skippedEdge2);
iter.setDistance(sc.weight);
setOrigEdgeCount(iter.getEdge(), sc.originalEdges);
updatedInGraph = true;
break;
}
}
if (!updatedInGraph) {
EdgeSkipIterState edgeState = g.shortcut(sc.from, sc.to);
edgeState.setDistance(sc.weight).setFlags(sc.flags);
edgeState.setSkippedEdges(sc.skippedEdge1, sc.skippedEdge2);
setOrigEdgeCount(edgeState.getEdge(), sc.originalEdges);
tmpNewShortcuts++;
}
}
return tmpNewShortcuts;
}
/**
* Calculates the priority of endNode v without changing the graph. Warning: the calculated
* priority must NOT depend on priority(v) and therefor findShortcuts should also not depend on
* the priority(v). Otherwise updating the priority before contracting in contractNodes() could
* lead to a slowishor even endless loop.
*/
int calculatePriority(int v) {
// set of shortcuts that would be added if endNode v would be contracted next.
findShortcuts(calcScHandler.setNode(v));
// System.out.println(v + "\t " + tmpShortcuts);
// # huge influence: the bigger the less shortcuts gets created and the faster is the
// preparation
//
// every endNode has an 'original edge' number associated. initially it is r=1
// when a new shortcut is introduced then r of the associated edges is summed up:
// r(u,w)=r(u,v)+r(v,w) now we can define
// originalEdgesCount = σ(v) := sum_{ (u,w) ∈ shortcuts(v) } of r(u, w)
int originalEdgesCount = calcScHandler.originalEdgesCount;
// for (Shortcut sc : tmpShortcuts) {
// originalEdgesCount += sc.originalEdges;
// }
// # lowest influence on preparation speed or shortcut creation count
// (but according to paper should speed up queries)
//
// number of already contracted neighbors of v
int contractedNeighbors = 0;
int degree = 0;
EdgeSkipIterator iter = calcPrioAllExplorer.setBaseNode(v);
while (iter.next()) {
degree++;
if (iter.isShortcut()) contractedNeighbors++;
}
// from shortcuts we can compute the edgeDifference
// # low influence: with it the shortcut creation is slightly faster
//
// |shortcuts(v)| − |{(u, v) | v uncontracted}| − |{(v, w) | v uncontracted}|
// meanDegree is used instead of outDegree+inDegree as if one endNode is in both directions
// only one bucket memory is used. Additionally one shortcut could also stand for two
// directions.
int edgeDifference = calcScHandler.shortcuts - degree;
// according to the paper do a simple linear combination of the properties to get the priority.
// this is the current optimum for unterfranken:
return 10 * edgeDifference + originalEdgesCount + contractedNeighbors;
}
void contractNodes() {
meanDegree = g.getAllEdges().getMaxId() / g.getNodes();
int level = 1;
counter = 0;
int initSize = sortedNodes.getSize();
int logSize =
(int) Math.round(Math.max(10, sortedNodes.getSize() / 100 * logMessagesPercentage));
if (logMessagesPercentage == 0) logSize = Integer.MAX_VALUE;
// preparation takes longer but queries are slightly faster with preparation
// => enable it but call not so often
boolean periodicUpdate = true;
StopWatch periodSW = new StopWatch();
int updateCounter = 0;
int periodicUpdatesCount =
Math.max(10, sortedNodes.getSize() / 100 * periodicUpdatesPercentage);
if (periodicUpdatesPercentage == 0) periodicUpdate = false;
// disable as preparation is slower and query time does not benefit
int lastNodesLazyUpdates =
lastNodesLazyUpdatePercentage == 0
? 0
: sortedNodes.getSize() / 100 * lastNodesLazyUpdatePercentage;
StopWatch lazySW = new StopWatch();
// Recompute priority of uncontracted neighbors.
// Without neighborupdates preparation is faster but we need them
// to slightly improve query time. Also if not applied too often it decreases the shortcut
// number.
boolean neighborUpdate = true;
if (neighborUpdatePercentage == 0) neighborUpdate = false;
StopWatch neighborSW = new StopWatch();
LevelGraphStorage lg = ((LevelGraphStorage) g);
while (!sortedNodes.isEmpty()) {
// periodically update priorities of ALL nodes
if (periodicUpdate && counter > 0 && counter % periodicUpdatesCount == 0) {
periodSW.start();
sortedNodes.clear();
int len = g.getNodes();
for (int node = 0; node < len; node++) {
if (g.getLevel(node) != 0) continue;
int priority = oldPriorities[node] = calculatePriority(node);
sortedNodes.insert(node, priority);
}
periodSW.stop();
updateCounter++;
}
if (counter % logSize == 0) {
// TODO necessary?
System.gc();
logger.info(
Helper.nf(counter)
+ ", updates:"
+ updateCounter
+ ", nodes: "
+ Helper.nf(sortedNodes.getSize())
+ ", shortcuts:"
+ Helper.nf(newShortcuts)
+ ", dijkstras:"
+ Helper.nf(dijkstraCount)
+ ", t(dijk):"
+ (int) dijkstraSW.getSeconds()
+ ", t(period):"
+ (int) periodSW.getSeconds()
+ ", t(lazy):"
+ (int) lazySW.getSeconds()
+ ", t(neighbor):"
+ (int) neighborSW.getSeconds()
+ ", meanDegree:"
+ (long) meanDegree
+ ", algo:"
+ algo.getMemoryUsageAsString()
+ ", "
+ Helper.getMemInfo());
dijkstraSW = new StopWatch();
periodSW = new StopWatch();
lazySW = new StopWatch();
neighborSW = new StopWatch();
}
counter++;
int polledNode = sortedNodes.pollKey();
if (sortedNodes.getSize() < lastNodesLazyUpdates) {
lazySW.start();
int priority = oldPriorities[polledNode] = calculatePriority(polledNode);
if (!sortedNodes.isEmpty() && priority > sortedNodes.peekValue()) {
// current node got more important => insert as new value and contract it later
sortedNodes.insert(polledNode, priority);
lazySW.stop();
continue;
}
lazySW.stop();
}
// contract!
newShortcuts += addShortcuts(polledNode);
g.setLevel(polledNode, level);
level++;
EdgeSkipIterator iter = vehicleAllExplorer.setBaseNode(polledNode);
while (iter.next()) {
int nn = iter.getAdjNode();
if (g.getLevel(nn) != 0)
// already contracted no update necessary
continue;
if (neighborUpdate && rand.nextInt(100) < neighborUpdatePercentage) {
neighborSW.start();
int oldPrio = oldPriorities[nn];
int priority = oldPriorities[nn] = calculatePriority(nn);
if (priority != oldPrio) sortedNodes.update(nn, oldPrio, priority);
neighborSW.stop();
}
if (removesHigher2LowerEdges) lg.disconnect(vehicleAllTmpExplorer, iter);
}
}
// Preparation works only once so we can release temporary data.
// The preparation object itself has to be intact to create the algorithm.
close();
logger.info(
"took:"
+ (int) allSW.stop().getSeconds()
+ ", new shortcuts: "
+ newShortcuts
+ ", "
+ prepareWeighting
+ ", "
+ prepareEncoder
+ ", removeHigher2LowerEdges:"
+ removesHigher2LowerEdges
+ ", dijkstras:"
+ dijkstraCount
+ ", t(dijk):"
+ (int) dijkstraSW.getSeconds()
+ ", t(period):"
+ (int) periodSW.getSeconds()
+ ", t(lazy):"
+ (int) lazySW.getSeconds()
+ ", t(neighbor):"
+ (int) neighborSW.getSeconds()
+ ", meanDegree:"
+ (long) meanDegree
+ ", initSize:"
+ initSize
+ ", periodic:"
+ periodicUpdatesPercentage
+ ", lazy:"
+ lastNodesLazyUpdatePercentage
+ ", neighbor:"
+ neighborUpdatePercentage);
}