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Networks engine for netroles library
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/*
* This file is part of netroles.
*
* netroles is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* netroles is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with netroles. If not, see componentsToNodeLists(final ConstMapping.OfInt components) {
Objects.requireNonNull(components);
final ArrayList lists = new ArrayList<>();
for (int i = 0; i < components.size(); i++) {
final int c = components.getInt(i);
while (lists.size() <= c) {
lists.add(Mappings.newIntList());
}
lists.get(c).add(i);
}
return lists;
}
@Override
public Mapping.OfInt components(final UndirectedGraph graph) {
Objects.requireNonNull(graph);
final Mapping.OfInt comp = Mappings.newIntList(-1, graph.countVertices());
TRAVERSAL.dfs(graph.countVertices(), graph::getNeighbors, graph.getVertices(),
new ConnectednessImpl.Label(comp));
return comp;
}
@Override
public Mapping.OfInt components(final UndirectedGraph graph, final IntPredicate filter) {
Objects.requireNonNull(graph);
final Mapping.OfInt comp = Mappings.newIntList(-1, graph.countVertices());
TRAVERSAL.dfs(graph.countVertices(), vertex -> {
if (!filter.test(vertex)) {
return Iterators.emptyInt();
}
return Iterators.filter(graph.getNeighbors(vertex), filter);
}, graph.getVertices(), new ConnectednessImpl.Label(comp));
return comp;
}
@Override
public Mapping.OfInt strongComponents(final DirectedGraph graph) {
Objects.requireNonNull(graph);
final int n = graph.countVertices();
final Mapping.OfInt comp = Mappings.newIntList(-1, n);
final Mapping.OfInt dfsns = Mappings.newIntList(-1, n);
TRAVERSAL.dfs(graph::getOutNeighbors, graph.getVertices(), dfsns,
new ConnectednessImpl.LabelStrongComponents(n, comp, dfsns));
return comp;
}
@Override
public Mapping.OfInt twoEdgeComponents(final UndirectedGraph graph) {
Objects.requireNonNull(graph);
final int n = graph.countVertices();
final Mapping.OfInt comp = Mappings.newIntList(-1, n);
final Mapping.OfInt dfsns = Mappings.newIntList(-1, n);
TRAVERSAL.edgeDfs(graph.countEdges(), graph::getEdges, graph.getVertices(), dfsns,
new ConnectednessImpl.LabelStrongComponents(n, comp, dfsns));
return comp;
}
@Override
public Mapping.OfInt biconnectedComponents(UndirectedGraph graph) {
Objects.requireNonNull(graph);
final int n = graph.countVertices();
final int m = graph.countEdges();
final Mapping.OfInt comp = Mappings.newIntList(-1, m);
final Mapping.OfInt dfsns = Mappings.newIntList(-1, n);
TRAVERSAL.edgeDfs(graph.countEdges(), graph::getEdges, graph.getVertices(), dfsns,
new ConnectednessImpl.LabelBiconnectedComponents(n, m, comp, dfsns));
return comp;
}
@Override
public Mapping.OfInt weakComponents(final DirectedGraph graph) {
Objects.requireNonNull(graph);
return weakComponents(graph.countVertices(), graph::getNeighbors);
}
@Override
public Mapping.OfInt weakComponents(final int numVertices,
final IntFunction neighbors) {
final Mapping.OfInt comp = Mappings.newIntList(-1, numVertices);
TRAVERSAL.dfs(numVertices, neighbors, Mappings.intRange(0, numVertices),
new ConnectednessImpl.Label(comp));
return comp;
}
private static class Label implements TraversalImpl.Visitor {
final Mapping.OfInt comp;
int compn;
Label(final Mapping.OfInt comp) {
this.comp = comp;
}
@Override
public void startSearch(final int node) {
}
@Override
public void endSearch() {
++compn;
}
@Override
public void visitEdge(final int source, final int target, int idx) {
}
@Override
public void visitVertex(final int node) {
comp.setInt(node, compn);
}
@Override
public void backtrackVertex(int node) {
}
}
private static class LabelStrongComponents implements Traversal.Visitor {
// path-based strongly connected component algorithm
// based on the implementation suggested in
// the lectures notes of the lecture "Network Analysis"
private ConstMapping.OfInt dfsns;
private PrimitiveList.OfInt vertexStack = Mappings.newIntList();
private PrimitiveList.OfInt componentsStack = Mappings.newIntList();
private boolean[] onVertexStack;
final Mapping.OfInt comp;
int compn = 0;
public LabelStrongComponents(int numVertices, Mapping.OfInt comp, ConstMapping.OfInt dfsns) {
this.dfsns = dfsns;
onVertexStack = new boolean[numVertices];
this.comp = comp;
}
@Override
public void startSearch(int node) {
}
@Override
public void endSearch() {
}
@Override
public void visitEdge(int source, int target, int idx) {
if (dfsns.getInt(target) < 0) {
// (future) tree or forward edge
// nothing to do, it seems
} else {
int dfsTarget = dfsns.getInt(target);
// it's either a cross, a forward or a back edge
// we have to process cross or back edges
if (dfsTarget <= dfsns.getInt(source) && source != target && onVertexStack[target]) {
while (dfsns.getInt(componentsStack.getInt(componentsStack.size() - 1)) > dfsTarget) {
componentsStack.removeIndex(componentsStack.size() - 1);
}
}
}
}
@Override
public void visitVertex(int node) {
vertexStack.add(node);
componentsStack.add(node);
onVertexStack[node] = true;
}
@Override
public void backtrackVertex(int node) {
// when backtracking from the representative of the component
// then assign each node in the component the component number
if (componentsStack.getInt(componentsStack.size() - 1) == node) {
componentsStack.removeIndex(componentsStack.size() - 1);
int u;
do {
u = vertexStack.removeInt(vertexStack.size() - 1);
comp.setInt(u, compn);
onVertexStack[u] = false;
} while (u != node);
++compn;
}
}
}
private static class LabelBiconnectedComponents implements Traversal.Visitor {
private ConstMapping.OfInt dfsns;
private PrimitiveList.OfInt edgeStack = Mappings.newIntList();
private PrimitiveList.OfInt componentsEdgeStack = Mappings.newIntList();
private PrimitiveList.OfInt componentsDfsStack = Mappings.newIntList();
final Mapping.OfInt comp;
int compn = 0;
Mapping.OfInt incoming;
public LabelBiconnectedComponents(int numVertices, int numEdges, Mapping.OfInt comp,
ConstMapping.OfInt dfsns) {
this.dfsns = dfsns;
this.comp = comp;
incoming = Mappings.newIntList(-1, numEdges);
}
@Override
public void startSearch(int node) {
}
@Override
public void endSearch() {
}
@Override
public void visitEdge(int source, int target, int idx) {
if (source == target) {
// it's a loop
comp.setInt(idx, compn);
++compn;
return;
}
edgeStack.addInt(idx);
if (dfsns.getInt(target) < 0) { // tree edge
incoming.setInt(target, idx);
componentsEdgeStack.addInt(idx);
componentsDfsStack.addInt(dfsns.getInt(source));
} else { // back edge
int dfsTarget = dfsns.getInt(target);
while (componentsDfsStack.getInt(componentsDfsStack.size() - 1) > dfsTarget) {
componentsDfsStack.removeIndex(componentsDfsStack.size() - 1);
}
componentsEdgeStack.removeRange(componentsDfsStack.size(), componentsEdgeStack.size());
}
}
@Override
public void visitVertex(int node) {
}
@Override
public void backtrackVertex(int node) {
int idx = incoming.getInt(node);
if (!componentsEdgeStack.isEmpty()
&& componentsEdgeStack.getInt(componentsEdgeStack.size() - 1) == idx) {
componentsEdgeStack.removeIndex(componentsEdgeStack.size() - 1);
componentsDfsStack.removeIndex(componentsDfsStack.size() - 1);
int u;
do {
u = edgeStack.removeInt(edgeStack.size() - 1);
comp.setInt(u, compn);
} while (u != idx);
++compn;
}
}
}
}