/** 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;
}
@Test
public void testExpandMultipleSkippedNodes() {
LevelGraphStorage g = (LevelGraphStorage) createGraph(20);
EdgeSkipIterator iter = g.edge(0, 1, 10, true); // 1
g.edge(1, 2, 10, true); // 2
g.edge(2, 3, 10, true); // 3
g.edge(3, 4, 10, true); // 4
g.setLevel(1, -1);
g.setLevel(2, -1);
g.edge(0, 3, 30, CarStreetType.flagsDefault(true)).skippedEdge(iter.edge()); // 5
Path4Shortcuts path = new Path4Shortcuts(g, ShortestCarCalc.DEFAULT);
path.edgeEntry = new EdgeEntry(5, 3, 30);
path.edgeEntry.parent = new EdgeEntry(-1, 0, 0);
path.edgeTo = new EdgeEntry(4, 3, 10);
path.edgeTo.parent = new EdgeEntry(EdgeIterator.NO_EDGE, 4, 0);
Path p = path.extract();
assertEquals(Helper.createTList(0, 1, 2, 3, 4), p.calcNodes());
}
void initUnpackingGraph(LevelGraphStorage g, WeightCalculation w) {
double dist = 1;
int flags = carEncoder.flags(30, false);
g.edge(10, 0, w.getWeight(dist, flags), flags);
EdgeSkipIterator iter1 = g.edge(0, 1, w.getWeight(dist, flags), flags);
EdgeSkipIterator iter2 = g.edge(1, 2, w.getWeight(dist, flags), flags);
EdgeSkipIterator iter3 = g.edge(2, 3, w.getWeight(dist, flags), flags);
EdgeSkipIterator iter4 = g.edge(3, 4, w.getWeight(dist, flags), flags);
EdgeSkipIterator iter5 = g.edge(4, 5, w.getWeight(dist, flags), flags);
EdgeSkipIterator iter6 = g.edge(5, 6, w.getWeight(dist, flags), flags);
int oneDirFlags = new PrepareContractionHierarchies().scOneDir();
int tmp = iter1.edge();
iter1 = g.edge(0, 2, 2, oneDirFlags);
iter1.skippedEdges(tmp, iter2.edge());
tmp = iter1.edge();
iter1 = g.edge(0, 3, 3, oneDirFlags);
iter1.skippedEdges(tmp, iter3.edge());
tmp = iter1.edge();
iter1 = g.edge(0, 4, 4, oneDirFlags);
iter1.skippedEdges(tmp, iter4.edge());
tmp = iter1.edge();
iter1 = g.edge(0, 5, 5, oneDirFlags);
iter1.skippedEdges(tmp, iter5.edge());
tmp = iter1.edge();
iter1 = g.edge(0, 6, 6, oneDirFlags);
iter1.skippedEdges(tmp, iter6.edge());
g.setLevel(0, 10);
g.setLevel(6, 9);
g.setLevel(5, 8);
g.setLevel(4, 7);
g.setLevel(3, 6);
g.setLevel(2, 5);
g.setLevel(1, 4);
g.setLevel(10, 3);
}
@Test
public void testFindShortcuts_Roundabout() {
LevelGraphStorage g = (LevelGraphStorage) createGraph();
EdgeSkipIterator iter1_1 = g.edge(1, 3, 1, true);
EdgeSkipIterator iter1_2 = g.edge(3, 4, 1, true);
EdgeSkipIterator iter2_1 = g.edge(4, 5, 1, false);
EdgeSkipIterator iter2_2 = g.edge(5, 6, 1, false);
EdgeSkipIterator iter3_1 = g.edge(6, 7, 1, true);
EdgeSkipIterator iter3_2 = g.edge(6, 8, 2, false);
g.edge(8, 4, 1, false);
g.setLevel(3, 3);
g.setLevel(5, 5);
g.setLevel(7, 7);
g.setLevel(8, 8);
PrepareContractionHierarchies prepare = new PrepareContractionHierarchies().graph(g);
g.edge(1, 4, 2, prepare.scBothDir()).skippedEdges(iter1_1.edge(), iter1_2.edge());
int f = prepare.scOneDir();
g.edge(4, 6, 2, f).skippedEdges(iter2_1.edge(), iter2_2.edge());
g.edge(6, 4, 3, f).skippedEdges(iter3_1.edge(), iter3_2.edge());
prepare.initFromGraph();
// there should be two different shortcuts for both directions!
Collection<Shortcut> sc = prepare.testFindShortcuts(4);
assertEquals(2, sc.size());
}
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);
}