com.google.common.graph.StandardNetwork Maven / Gradle / Ivy
/*
* Copyright (C) 2016 The Guava Authors
*
* Licensed 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.google.common.graph;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.graph.GraphConstants.DEFAULT_EDGE_COUNT;
import static com.google.common.graph.GraphConstants.DEFAULT_NODE_COUNT;
import static com.google.common.graph.GraphConstants.EDGE_NOT_IN_GRAPH;
import static com.google.common.graph.GraphConstants.NODE_NOT_IN_GRAPH;
import static java.util.Objects.requireNonNull;
import com.google.common.collect.ImmutableSet;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
/**
* Standard implementation of {@link Network} that supports the options supplied by {@link
* NetworkBuilder}.
*
* This class maintains a map of nodes to {@link NetworkConnections}. This class also maintains a
* map of edges to reference nodes. The reference node is defined to be the edge's source node on
* directed graphs, and an arbitrary endpoint of the edge on undirected graphs.
*
*
Collection-returning accessors return unmodifiable views: the view returned will reflect
* changes to the graph (if the graph is mutable) but may not be modified by the user.
*
*
The time complexity of all collection-returning accessors is O(1), since views are returned.
*
* @author James Sexton
* @author Joshua O'Madadhain
* @author Omar Darwish
* @param Node parameter type
* @param Edge parameter type
*/
@ElementTypesAreNonnullByDefault
class StandardNetwork extends AbstractNetwork {
private final boolean isDirected;
private final boolean allowsParallelEdges;
private final boolean allowsSelfLoops;
private final ElementOrder nodeOrder;
private final ElementOrder edgeOrder;
final MapIteratorCache> nodeConnections;
// We could make this a Map>. It would make incidentNodes(edge) slightly
// faster, but also make Networks consume 5 to 20+% (increasing with average degree) more memory.
final MapIteratorCache edgeToReferenceNode; // referenceNode == source if directed
/** Constructs a graph with the properties specified in {@code builder}. */
StandardNetwork(NetworkBuilder builder) {
this(
builder,
builder.nodeOrder.>createMap(
builder.expectedNodeCount.or(DEFAULT_NODE_COUNT)),
builder.edgeOrder.createMap(builder.expectedEdgeCount.or(DEFAULT_EDGE_COUNT)));
}
/**
* Constructs a graph with the properties specified in {@code builder}, initialized with the given
* node and edge maps.
*/
StandardNetwork(
NetworkBuilder builder,
Map> nodeConnections,
Map edgeToReferenceNode) {
this.isDirected = builder.directed;
this.allowsParallelEdges = builder.allowsParallelEdges;
this.allowsSelfLoops = builder.allowsSelfLoops;
this.nodeOrder = builder.nodeOrder.cast();
this.edgeOrder = builder.edgeOrder.cast();
// Prefer the heavier "MapRetrievalCache" for nodes if lookup is expensive. This optimizes
// methods that access the same node(s) repeatedly, such as Graphs.removeEdgesConnecting().
this.nodeConnections =
(nodeConnections instanceof TreeMap)
? new MapRetrievalCache>(nodeConnections)
: new MapIteratorCache>(nodeConnections);
this.edgeToReferenceNode = new MapIteratorCache<>(edgeToReferenceNode);
}
@Override
public Set nodes() {
return nodeConnections.unmodifiableKeySet();
}
@Override
public Set edges() {
return edgeToReferenceNode.unmodifiableKeySet();
}
@Override
public boolean isDirected() {
return isDirected;
}
@Override
public boolean allowsParallelEdges() {
return allowsParallelEdges;
}
@Override
public boolean allowsSelfLoops() {
return allowsSelfLoops;
}
@Override
public ElementOrder nodeOrder() {
return nodeOrder;
}
@Override
public ElementOrder edgeOrder() {
return edgeOrder;
}
@Override
public Set incidentEdges(N node) {
return checkedConnections(node).incidentEdges();
}
@Override
public EndpointPair incidentNodes(E edge) {
N nodeU = checkedReferenceNode(edge);
// requireNonNull is safe because checkedReferenceNode made sure the edge is in the network.
N nodeV = requireNonNull(nodeConnections.get(nodeU)).adjacentNode(edge);
return EndpointPair.of(this, nodeU, nodeV);
}
@Override
public Set adjacentNodes(N node) {
return checkedConnections(node).adjacentNodes();
}
@Override
public Set edgesConnecting(N nodeU, N nodeV) {
NetworkConnections connectionsU = checkedConnections(nodeU);
if (!allowsSelfLoops && nodeU == nodeV) { // just an optimization, only check reference equality
return ImmutableSet.of();
}
checkArgument(containsNode(nodeV), NODE_NOT_IN_GRAPH, nodeV);
return connectionsU.edgesConnecting(nodeV);
}
@Override
public Set inEdges(N node) {
return checkedConnections(node).inEdges();
}
@Override
public Set outEdges(N node) {
return checkedConnections(node).outEdges();
}
@Override
public Set predecessors(N node) {
return checkedConnections(node).predecessors();
}
@Override
public Set successors(N node) {
return checkedConnections(node).successors();
}
final NetworkConnections checkedConnections(N node) {
NetworkConnections connections = nodeConnections.get(node);
if (connections == null) {
checkNotNull(node);
throw new IllegalArgumentException(String.format(NODE_NOT_IN_GRAPH, node));
}
return connections;
}
final N checkedReferenceNode(E edge) {
N referenceNode = edgeToReferenceNode.get(edge);
if (referenceNode == null) {
checkNotNull(edge);
throw new IllegalArgumentException(String.format(EDGE_NOT_IN_GRAPH, edge));
}
return referenceNode;
}
final boolean containsNode(N node) {
return nodeConnections.containsKey(node);
}
final boolean containsEdge(E edge) {
return edgeToReferenceNode.containsKey(edge);
}
}