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Isochrone calculation with GraphHopper
/*
* Licensed to GraphHopper GmbH under one or more contributor
* license agreements. See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*
* GraphHopper GmbH licenses this file to you under the Apache License,
* Version 2.0 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.graphhopper.isochrone.algorithm;
import com.carrotsearch.hppc.IntObjectHashMap;
import com.graphhopper.coll.GHIntObjectHashMap;
import com.graphhopper.routing.AbstractRoutingAlgorithm;
import com.graphhopper.routing.Path;
import com.graphhopper.routing.util.EdgeFilter;
import com.graphhopper.routing.util.TraversalMode;
import com.graphhopper.routing.weighting.Weighting;
import com.graphhopper.storage.Graph;
import com.graphhopper.util.EdgeIterator;
import com.graphhopper.util.GHUtility;
import java.util.PriorityQueue;
import java.util.function.Consumer;
import static com.graphhopper.isochrone.algorithm.ShortestPathTree.ExploreType.*;
import static java.util.Comparator.comparingDouble;
/**
* Computes a shortest path tree by a given weighting. Terminates when all shortest paths up to
* a given travel time or distance have been explored. The catch is that the function for termination
* is different from the function for search. This implementation uses a second queue to keep track of
* the termination criterion.
*
* IMPLEMENTATION NOTE:
* util.PriorityQueue doesn't support efficient removes. We work around this by giving the labels
* a deleted flag, not remove()ing them, and popping deleted elements off both queues.
* Note to self/others: If you think this optimization is not needed, please test it with a scenario
* where updates actually occur a lot, such as using finite, non-zero u-turn costs.
*
* @author Peter Karich
* @author Michael Zilske
*/
public class ShortestPathTree extends AbstractRoutingAlgorithm {
enum ExploreType {TIME, DISTANCE, WEIGHT}
public static class IsoLabel {
IsoLabel(int node, int edge, double weight, long time, double distance, IsoLabel parent) {
this.node = node;
this.edge = edge;
this.weight = weight;
this.time = time;
this.distance = distance;
this.parent = parent;
}
public boolean deleted = false;
public int node;
public int edge;
public double weight;
public long time;
public double distance;
public IsoLabel parent;
@Override
public String toString() {
return "IsoLabel{" +
"node=" + node +
", edge=" + edge +
", weight=" + weight +
", time=" + time +
", distance=" + distance +
'}';
}
}
private IntObjectHashMap fromMap;
private PriorityQueue queueByWeighting;
private int visitedNodes;
private double limit = -1;
private ExploreType exploreType = TIME;
private final boolean reverseFlow;
public ShortestPathTree(Graph g, Weighting weighting, boolean reverseFlow, TraversalMode traversalMode) {
super(g, weighting, traversalMode);
queueByWeighting = new PriorityQueue<>(1000, comparingDouble(l -> l.weight));
fromMap = new GHIntObjectHashMap<>(1000);
this.reverseFlow = reverseFlow;
}
@Override
public Path calcPath(int from, int to) {
throw new IllegalStateException("call search instead");
}
/**
* Time limit in milliseconds
*/
public void setTimeLimit(double limit) {
exploreType = TIME;
this.limit = limit;
}
/**
* Distance limit in meter
*/
public void setDistanceLimit(double limit) {
exploreType = DISTANCE;
this.limit = limit;
}
public void setWeightLimit(double limit) {
exploreType = WEIGHT;
this.limit = limit;
}
public void search(int from, final Consumer consumer) {
checkAlreadyRun();
IsoLabel currentLabel = new IsoLabel(from, -1, 0, 0, 0, null);
queueByWeighting.add(currentLabel);
if (traversalMode == TraversalMode.NODE_BASED) {
fromMap.put(from, currentLabel);
}
EdgeFilter filter = reverseFlow ? inEdgeFilter : outEdgeFilter;
while (!finished()) {
currentLabel = queueByWeighting.poll();
if (currentLabel.deleted)
continue;
consumer.accept(currentLabel);
currentLabel.deleted = true;
visitedNodes++;
EdgeIterator iter = edgeExplorer.setBaseNode(currentLabel.node);
while (iter.next()) {
if (!accept(iter, currentLabel.edge)) {
continue;
}
// todo: for #1835 move the access check into weighting
double nextWeight = !filter.accept(iter)
? Double.POSITIVE_INFINITY
: (GHUtility.calcWeightWithTurnWeight(weighting, iter, reverseFlow, currentLabel.edge) + currentLabel.weight);
if (Double.isInfinite(nextWeight))
continue;
double nextDistance = iter.getDistance() + currentLabel.distance;
long nextTime = GHUtility.calcMillisWithTurnMillis(weighting, iter, reverseFlow, currentLabel.edge) + currentLabel.time;
int nextTraversalId = traversalMode.createTraversalId(iter, reverseFlow);
IsoLabel label = fromMap.get(nextTraversalId);
if (label == null) {
label = new IsoLabel(iter.getAdjNode(), iter.getEdge(), nextWeight, nextTime, nextDistance, currentLabel);
if (getExploreValue(label) <= limit) {
fromMap.put(nextTraversalId, label);
queueByWeighting.add(label);
}
} else if (label.weight > nextWeight) {
label.deleted = true;
label = new IsoLabel(iter.getAdjNode(), iter.getEdge(), nextWeight, nextTime, nextDistance, currentLabel);
if (getExploreValue(label) <= limit) {
fromMap.put(nextTraversalId, label);
queueByWeighting.add(label);
}
}
}
}
}
private double getExploreValue(IsoLabel label) {
if (exploreType == TIME)
return label.time;
if (exploreType == WEIGHT)
return label.weight;
return label.distance;
}
@Override
protected boolean finished() {
return queueByWeighting.isEmpty();
}
@Override
protected Path extractPath() {
throw new UnsupportedOperationException();
}
@Override
public String getName() {
return "reachability";
}
@Override
public int getVisitedNodes() {
return visitedNodes;
}
}