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/**
*
*/
package rinde.sim.core.graph;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
import javax.annotation.Nullable;
import org.apache.commons.math3.random.RandomGenerator;
import com.google.common.base.Function;
/**
* Utility class containing many methods for working with graphs.
* @author Rinde van Lon
* @author Bartosz Michalik - change in the
* graphs model
*/
public final class Graphs {
private Graphs() {}
/**
* Create a path of connections on the specified {@link Graph} using the
* specified {@link Point}s. If the points A, B, C are specified,
* the two connections: A -> B and B -> C will be
* added to the graph.
* @param graph The graph to which the connections will be added.
* @param path Points that will be treated as a path.
* @param The type of connection data.
*/
public static void addPath(Graph graph,
Point... path) {
for (int i = 1; i < path.length; i++) {
graph.addConnection(path[i - 1], path[i]);
}
}
/**
* Create a path of bi-directional connections on the specified {@link Graph}
* using the specified {@link Point}s. If the points A, B, C are
* specified, the four connections: A -> B, B -> A,
* B -> C and C -> B will be added to the graph.
* @param graph The graph to which the connections will be added.
* @param path Points that will be treated as a path.
* @param The type of connection data.
*/
public static void addBiPath(Graph graph,
Point... path) {
addPath(graph, path);
final List list = Arrays.asList(path);
Collections.reverse(list);
addPath(graph, list.toArray(new Point[path.length]));
}
/**
* Returns an unmodifiable view on the specified {@link Graph}.
* @param graph A graph.
* @param The type of connection data.
* @return An unmodifiable view on the graph.
*/
public static Graph unmodifiableGraph(
Graph graph) {
return new UnmodifiableGraph(graph);
}
/**
* Returns an unmodifiable view on the specified {@link Connection}.
* @param conn A connection.
* @param The type of connection data.
* @return An unmodifiable view on the connection.
*/
public static Connection unmodifiableConnection(
Connection conn) {
return new UnmodifiableConnection(conn);
}
/**
* Returns an unmodifiable view on the specified {@link ConnectionData}.
* @param connData Connection data.
* @param The type of connection data.
* @return An unmodifiable view on the connection data.
*/
@SuppressWarnings("unchecked")
@Nullable
public static E unmodifiableConnectionData(
@Nullable E connData) {
if (connData instanceof MultiAttributeData) {
return (E) new UnmodifiableMultiAttributeEdgeData(
(MultiAttributeData) connData);
}
return connData;
}
/**
* Basic equals method.
* @param g1 A graph.
* @param g2 Another graph.
* @param The type of connection data.
* @return true if the provided graphs are equal,
* false otherwise.
*/
@SuppressWarnings("null")
public static boolean equals(
Graph g1, Graph g2) {
if (g1.getNumberOfNodes() != g2.getNumberOfNodes()) {
return false;
}
if (g1.getNumberOfConnections() != g2.getNumberOfConnections()) {
return false;
}
for (final Connection g1conn : g1.getConnections()) {
if (!g2.hasConnection(g1conn.from, g1conn.to)) {
return false;
}
final E g2connEdgeData = g2.connectionData(g1conn.from, g1conn.to);
final boolean null1 = g1conn.getData() == null;
final boolean null2 = g2connEdgeData == null;
final int nullCount = (null1 ? 1 : 0) + (null2 ? 1 : 0);
if ((nullCount == 0 && !g1conn.getData().equals(g2connEdgeData))
|| nullCount == 1) {
return false;
}
}
return true;
}
/**
* Computes the shortest path based on the Euclidean distance.
* @param graph The {@link Graph} on which the shortest path is searched.
* @param from The start point of the path.
* @param to The destination of the path.
* @param The type of connection data.
* @return The shortest path that exists between from and
* to.
*/
public static List shortestPathEuclideanDistance(
Graph graph, final Point from, final Point to) {
return Graphs.shortestPath(graph, from, to, new Graphs.EuclidianDistance());
}
/**
* A standard implementation of the A* algorithm.
*
* @param graph The {@link Graph} which contains from and
* to.
* @param from The start position
* @param to The end position
* @param h The {@link Heuristic} used in the A* implementation.
* @param The type of connection data.
* @return The shortest path from from to to if it
* exists, otherwise a {@link PathNotFoundException} is thrown.
* @throws PathNotFoundException if a path does not exist between
* from and to.
*
* @author Rutger Claes
* @author Rinde van Lon
*/
public static List shortestPath(
Graph graph, final Point from, final Point to, Graphs.Heuristic h) {
if (!graph.containsNode(from)) {
throw new IllegalArgumentException("from should be valid vertex. " + from);
}
// The set of nodes already evaluated.
final Set closedSet = new LinkedHashSet();
// Distance from start along optimal path.
final Map gScore = new LinkedHashMap();
gScore.put(from, 0d);
// heuristic estimates
final Map hScore = new LinkedHashMap();
hScore.put(from, h.estimateCost(Point.distance(from, to)));
// Estimated total distance from start to goal through y
final SortedMap fScore = new TreeMap();
fScore.put(h.estimateCost(Point.distance(from, to)), from);
// The map of navigated nodes.
final Map cameFrom = new LinkedHashMap();
while (!fScore.isEmpty()) {
final Point current = fScore.remove(fScore.firstKey());
if (current.equals(to)) {
final List result = new ArrayList();
result.add(from);
result.addAll(Graphs.reconstructPath(cameFrom, to));
return result;
}
closedSet.add(current);
for (final Point outgoingPoint : graph.getOutgoingConnections(current)) {
if (closedSet.contains(outgoingPoint)) {
continue;
}
// tentative_g_score := g_score[x] + dist_between(x,y)
final double tgScore = gScore.get(current)
+ h.calculateCost(current, outgoingPoint);
boolean tIsBetter = false;
if (!fScore.values().contains(outgoingPoint)) {
hScore.put(outgoingPoint,
h.estimateCost(Point.distance(outgoingPoint, to)));
tIsBetter = true;
} else if (tgScore < gScore.get(outgoingPoint)) {
tIsBetter = true;
}
if (tIsBetter) {
cameFrom.put(outgoingPoint, current);
gScore.put(outgoingPoint, tgScore);
double fScoreValue = gScore.get(outgoingPoint)
+ hScore.get(outgoingPoint);
while (fScore.containsKey(fScoreValue)) {
fScoreValue = Double.longBitsToDouble(Double
.doubleToLongBits(fScoreValue) + 1);
}
fScore.put(fScoreValue, outgoingPoint);
}
}
}
throw new PathNotFoundException("Cannot reach " + to + " from " + from);
}
/**
* A method for finding the closest object to a point. If there is no object
* null is returned instead.
* @param pos The {@link Point} which is used as reference.
* @param objects The {@link Collection} which is searched.
* @param transformation A {@link Function} that transforms an object from
* objects into a {@link Point}, normally this means
* that the position of the object is retrieved.
* @param the type of object.
* @return The closest object in objects to pos or
* null if no object exists.
*/
@Nullable
public static T findClosestObject(Point pos, Collection objects,
Function transformation) {
double dist = Double.MAX_VALUE;
T closest = null;
for (final T obj : objects) {
@Nullable
final Point objPos = transformation.apply(obj);
checkNotNull(objPos);
final double currentDist = Point.distance(pos, objPos);
if (currentDist < dist) {
dist = currentDist;
closest = obj;
}
}
return closest;
}
/**
* Searches the closest n objects to position pos in
* collection objects using transformation.
* @param pos The {@link Point} which is used as a reference point.
* @param objects The list of objects which is searched.
* @param transformation A function that transforms objects from
* objects to a point.
* @param n The maximum number of objects to return where n must be >= 0.
* @param The type of object.
* @return A list of objects that are closest to pos. The list is
* ordered such that the closest object appears first. An empty list
* is returned when objects is empty.
*/
public static List findClosestObjects(Point pos,
Collection objects, Function transformation, int n) {
checkArgument(n > 0, "n must be positive.");
final List> objs = new ArrayList>();
for (final T obj : objects) {
@Nullable
final Point objPos = transformation.apply(obj);
checkNotNull(objPos);
objs.add(new ObjectWithDistance(obj, Point.distance(pos, objPos)));
}
Collections.sort(objs);
final List results = new ArrayList();
for (final ObjectWithDistance o : objs.subList(0,
Math.min(n, objs.size()))) {
results.add(o.obj);
}
return results;
}
/**
* Calculates the length of a path. The length is calculated by simply summing
* the distances of every two neighboring positions.
* @param path A list of {@link Point}s forming a path.
* @return The total length of the path.
*/
public static double pathLength(List path) {
double dist = 0;
for (int i = 1; i < path.size(); i++) {
dist += Point.distance(path.get(i - 1), path.get(i));
}
return dist;
}
static List reconstructPath(final Map cameFrom,
final Point end) {
if (cameFrom.containsKey(end)) {
final List path = reconstructPath(cameFrom, cameFrom.get(end));
path.add(end);
return path;
}
return new LinkedList();
}
/**
* A heuristic can be used to direct the {@link #shortestPath} algorithm, it
* determines the cost of traveling which should be minimized.
* @author Rinde van Lon
*/
public interface Heuristic {
/**
* Can be used to estimate the cost of traveling a distance.
* @param distance A distance.
* @return The estimate of the cost.
*/
double estimateCost(double distance);
/**
* Computes the cost of traveling over the connection as specified by the
* provided points.
* @param from Start point of a connection.
* @param to End point of a connection.
* @return The cost of traveling.
*/
double calculateCost(Point from, Point to);
}
static class ObjectWithDistance implements
Comparable> {
final double dist;
final T obj;
ObjectWithDistance(T pObj, double pDist) {
obj = pObj;
dist = pDist;
}
@Override
public int compareTo(ObjectWithDistance o) {
return Double.compare(dist, o.dist);
}
@SuppressWarnings("unchecked")
@Override
public boolean equals(@Nullable Object o) {
if (o == null) {
return false;
}
if (o.getClass() == ObjectWithDistance.class) {
return compareTo((ObjectWithDistance) o) == 0;
}
return false;
}
}
private static class UnmodifiableMultiAttributeEdgeData extends
MultiAttributeData {
private final MultiAttributeData original;
UnmodifiableMultiAttributeEdgeData(MultiAttributeData pOriginal) {
super(-1);
original = pOriginal;
}
@Override
public double getLength() {
return original.getLength();
}
@Override
public double getMaxSpeed() {
return original.getMaxSpeed();
}
@Override
public Map getAttributes() {
return original.getAttributes();
}
@Nullable
@Override
public E get(String key, Class type) {
return original.get(key, type);
}
@Override
public double setMaxSpeed(double maxSpeed) {
throw new UnsupportedOperationException();
}
@Override
public void put(String key, E value) {
throw new UnsupportedOperationException();
}
@Override
public boolean equals(@Nullable Object obj) {
return original.equals(obj);
}
@Override
public int hashCode() {
return original.hashCode();
}
}
private static final class UnmodifiableConnection
extends Connection {
private final Connection original;
UnmodifiableConnection(Connection c) {
super(c.from, c.to, null);
original = c;
}
@Override
public void setData(E data) {
throw new UnsupportedOperationException();
}
@Override
@Nullable
public E getData() {
final E d = original.getData();
if (d == null) {
return null;
}
return Graphs.unmodifiableConnectionData(d);
}
@Override
public boolean equals(@Nullable Object obj) {
return original.equals(obj);
}
@Override
public int hashCode() {
return original.hashCode();
}
@Override
public String toString() {
return original.toString();
}
}
private static class UnmodifiableGraph implements
Graph {
final Graph delegate;
UnmodifiableGraph(Graph pDelegate) {
delegate = pDelegate;
}
@Override
public boolean containsNode(Point node) {
return delegate.containsNode(node);
}
@Override
public Collection getOutgoingConnections(Point node) {
return Collections.unmodifiableCollection(delegate
.getOutgoingConnections(node));
}
@Override
public Collection getIncomingConnections(Point node) {
return Collections.unmodifiableCollection(delegate
.getIncomingConnections(node));
}
@Override
public boolean hasConnection(Point from, Point to) {
return delegate.hasConnection(from, to);
}
@Override
public int getNumberOfConnections() {
return delegate.getNumberOfConnections();
}
@Override
public List> getConnections() {
final List> conn = delegate.getConnections();
final List> unmodConn = new ArrayList>();
for (final Connection c : conn) {
unmodConn.add(unmodifiableConnection(c));
}
return Collections.unmodifiableList(unmodConn);
}
@Override
public int getNumberOfNodes() {
return delegate.getNumberOfNodes();
}
@Override
public Set getNodes() {
return Collections.unmodifiableSet(delegate.getNodes());
}
@Override
public double connectionLength(Point from, Point to) {
return delegate.connectionLength(from, to);
}
@Override
public boolean isEmpty() {
return delegate.isEmpty();
}
@Override
public void addConnection(Point from, Point to) {
throw new UnsupportedOperationException();
}
@Override
public void merge(Graph other) {
throw new UnsupportedOperationException();
}
@Override
public void addConnections(Collection> connections) {
throw new UnsupportedOperationException();
}
@Override
public void removeNode(Point node) {
throw new UnsupportedOperationException();
}
@Override
public void removeConnection(Point from, Point to) {
throw new UnsupportedOperationException();
}
@SuppressWarnings({ "unchecked" })
@Override
public boolean equals(@Nullable Object other) {
return other instanceof Graph ? Graphs.equals(this, (Graph) other)
: false;
}
@Override
public int hashCode() {
return delegate.hashCode();
}
@Nullable
@Override
public E connectionData(Point from, Point to) {
return unmodifiableConnectionData(delegate.connectionData(from, to));
}
@Override
public void addConnection(Point from, Point to, E edgeData) {
throw new UnsupportedOperationException();
}
@Override
public void addConnection(Connection connection) {
throw new UnsupportedOperationException();
}
@Override
public E setConnectionData(Point from, Point to, E edgeData) {
throw new UnsupportedOperationException();
}
@Override
public Point getRandomNode(RandomGenerator generator) {
return delegate.getRandomNode(generator);
}
@Override
public Connection getConnection(Point from, Point to) {
return unmodifiableConnection(delegate.getConnection(from, to));
}
}
static class EuclidianDistance implements Graphs.Heuristic {
@Override
public double calculateCost(final Point from, Point to) {
return Point.distance(from, to);
}
@Override
public double estimateCost(final double distance) {
return distance;
}
}
}
