--- /dev/null
+/*
+ * Created on Jul 15, 2007
+ *
+ * Copyright (c) 2007, the JUNG Project and the Regents of the University
+ * of California
+ * All rights reserved.
+ *
+ * This software is open-source under the BSD license; see either
+ * "license.txt" or
+ * http://jung.sourceforge.net/license.txt for a description.
+ */
+package edu.uci.ics.jung.algorithms.scoring;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.commons.collections15.Transformer;
+
+import edu.uci.ics.jung.algorithms.scoring.util.UniformDegreeWeight;
+import edu.uci.ics.jung.graph.Hypergraph;
+
+/**
+ * Assigns scores to vertices according to their 'voltage' in an approximate
+ * solution to the Kirchoff equations. This is accomplished by tying "source"
+ * vertices to specified positive voltages, "sink" vertices to 0 V, and
+ * iteratively updating the voltage of each other vertex to the (weighted)
+ * average of the voltages of its neighbors.
+ *
+ * <p>The resultant voltages will all be in the range <code>[0, max]</code>
+ * where <code>max</code> is the largest voltage of any source vertex (in the
+ * absence of negative source voltages; see below).
+ *
+ * <p>A few notes about this algorithm's interpretation of the graph data:
+ * <ul>
+ * <li/>Higher edge weights are interpreted as indicative of greater
+ * influence/effect than lower edge weights.
+ * <li/>Negative edge weights (and negative "source" voltages) invalidate
+ * the interpretation of the resultant values as voltages. However, this
+ * algorithm will not reject graphs with negative edge weights or source voltages.
+ * <li/>Parallel edges are equivalent to a single edge whose weight is the
+ * sum of the weights on the parallel edges.
+ * <li/>Current flows along undirected edges in both directions,
+ * but only flows along directed edges in the direction of the edge.
+ * </ul>
+ * </p>
+ */
+public class VoltageScorer<V, E> extends AbstractIterativeScorer<V, E, Double>
+ implements VertexScorer<V, Double>
+{
+ protected Map<V, ? extends Number> source_voltages;
+ protected Collection<V> sinks;
+
+ /**
+ * Creates an instance with the specified graph, edge weights, source voltages,
+ * and sinks.
+ * @param g the input graph
+ * @param edge_weights the edge weights, representing conductivity
+ * @param source_voltages the (fixed) voltage for each source
+ * @param sinks the vertices whose voltages are tied to 0
+ */
+ public VoltageScorer(Hypergraph<V, E> g, Transformer<E, ? extends Number> edge_weights,
+ Map<V, ? extends Number> source_voltages, Collection<V> sinks)
+ {
+ super(g, edge_weights);
+ this.source_voltages = source_voltages;
+ this.sinks = sinks;
+ initialize();
+ }
+
+ /**
+ * Creates an instance with the specified graph, edge weights, source vertices
+ * (each of whose 'voltages' are tied to 1), and sinks.
+ * @param g the input graph
+ * @param edge_weights the edge weights, representing conductivity
+ * @param sources the vertices whose voltages are tied to 1
+ * @param sinks the vertices whose voltages are tied to 0
+ */
+ public VoltageScorer(Hypergraph<V, E> g, Transformer<E, ? extends Number> edge_weights,
+ Collection<V> sources, Collection<V> sinks)
+ {
+ super(g, edge_weights);
+
+ Map<V, Double> unit_voltages = new HashMap<V, Double>();
+ for(V v : sources)
+ unit_voltages.put(v, new Double(1.0));
+ this.source_voltages = unit_voltages;
+ this.sinks = sinks;
+ initialize();
+ }
+
+ /**
+ * Creates an instance with the specified graph, source vertices
+ * (each of whose 'voltages' are tied to 1), and sinks.
+ * The outgoing edges for each vertex are assigned
+ * weights that sum to 1.
+ * @param g the input graph
+ * @param sources the vertices whose voltages are tied to 1
+ * @param sinks the vertices whose voltages are tied to 0
+ */
+ public VoltageScorer(Hypergraph<V, E> g, Collection<V> sources, Collection<V> sinks)
+ {
+ super(g);
+
+ Map<V, Double> unit_voltages = new HashMap<V, Double>();
+ for(V v : sources)
+ unit_voltages.put(v, new Double(1.0));
+ this.source_voltages = unit_voltages;
+ this.sinks = sinks;
+ initialize();
+ }
+
+ /**
+ * Creates an instance with the specified graph, source voltages,
+ * and sinks. The outgoing edges for each vertex are assigned
+ * weights that sum to 1.
+ * @param g the input graph
+ * @param source_voltages the (fixed) voltage for each source
+ * @param sinks the vertices whose voltages are tied to 0
+ */
+ public VoltageScorer(Hypergraph<V, E> g, Map<V, ? extends Number> source_voltages,
+ Collection<V> sinks)
+ {
+ super(g);
+ this.source_voltages = source_voltages;
+ this.sinks = sinks;
+ this.edge_weights = new UniformDegreeWeight<V,E>(g);
+ initialize();
+ }
+
+ /**
+ * Creates an instance with the specified graph, edge weights, source, and
+ * sink. The source vertex voltage is tied to 1.
+ * @param g the input graph
+ * @param edge_weights the edge weights, representing conductivity
+ * @param source the vertex whose voltage is tied to 1
+ * @param sink the vertex whose voltage is tied to 0
+ */
+ public VoltageScorer(Hypergraph<V,E> g, Transformer<E, ? extends Number> edge_weights,
+ V source, V sink)
+ {
+ this(g, edge_weights, Collections.singletonMap(source, 1.0), Collections.singletonList(sink));
+ initialize();
+ }
+
+ /**
+ * Creates an instance with the specified graph, edge weights, source, and
+ * sink. The source vertex voltage is tied to 1.
+ * The outgoing edges for each vertex are assigned
+ * weights that sum to 1.
+ * @param g the input graph
+ * @param source the vertex whose voltage is tied to 1
+ * @param sink the vertex whose voltage is tied to 0
+ */
+ public VoltageScorer(Hypergraph<V,E> g, V source, V sink)
+ {
+ this(g, Collections.singletonMap(source, 1.0), Collections.singletonList(sink));
+ initialize();
+ }
+
+
+ /**
+ * Initializes the state of this instance.
+ */
+ @Override
+ public void initialize()
+ {
+ super.initialize();
+
+ // sanity check
+ if (source_voltages.isEmpty() || sinks.isEmpty())
+ throw new IllegalArgumentException("Both sources and sinks (grounds) must be defined");
+
+ if (source_voltages.size() + sinks.size() > graph.getVertexCount())
+ throw new IllegalArgumentException("Source/sink sets overlap, or contain vertices not in graph");
+
+ for (Map.Entry<V, ? extends Number> entry : source_voltages.entrySet())
+ {
+ V v = entry.getKey();
+ if (sinks.contains(v))
+ throw new IllegalArgumentException("Vertex " + v + " is incorrectly specified as both source and sink");
+ double value = entry.getValue().doubleValue();
+ if (value <= 0)
+ throw new IllegalArgumentException("Source vertex " + v + " has negative voltage");
+ }
+
+ // set up initial voltages
+ for (V v : graph.getVertices())
+ {
+ if (source_voltages.containsKey(v))
+ setOutputValue(v, source_voltages.get(v).doubleValue());
+ else
+ setOutputValue(v, 0.0);
+ }
+ }
+
+ /**
+ * @see edu.uci.ics.jung.algorithms.scoring.AbstractIterativeScorer#update(Object)
+ */
+ @Override
+ public double update(V v)
+ {
+ // if it's a voltage source or sink, we're done
+ Number source_volts = source_voltages.get(v);
+ if (source_volts != null)
+ {
+ setOutputValue(v, source_volts.doubleValue());
+ return 0.0;
+ }
+ if (sinks.contains(v))
+ {
+ setOutputValue(v, 0.0);
+ return 0.0;
+ }
+
+ Collection<E> edges = graph.getInEdges(v);
+ double voltage_sum = 0;
+ double weight_sum = 0;
+ for (E e: edges)
+ {
+ int incident_count = getAdjustedIncidentCount(e);
+ for (V w : graph.getIncidentVertices(e))
+ {
+ if (!w.equals(v) || hyperedges_are_self_loops)
+ {
+ double weight = getEdgeWeight(w,e).doubleValue() / incident_count;
+ voltage_sum += getCurrentValue(w).doubleValue() * weight;
+ weight_sum += weight;
+ }
+ }
+// V w = graph.getOpposite(v, e);
+// double weight = getEdgeWeight(w,e).doubleValue();
+// voltage_sum += getCurrentValue(w).doubleValue() * weight;
+// weight_sum += weight;
+ }
+
+ // if either is 0, new value is 0
+ if (voltage_sum == 0 || weight_sum == 0)
+ {
+ setOutputValue(v, 0.0);
+ return getCurrentValue(v).doubleValue();
+ }
+
+ setOutputValue(v, voltage_sum / weight_sum);
+ return Math.abs(getCurrentValue(v).doubleValue() - voltage_sum / weight_sum);
+ }
+
+}
+
Code Review / controller.git / blobdiff