From e9879a2cb18f69db3cefb300137167b3c20dbdcb Mon Sep 17 00:00:00 2001
From: pigne <yoann.pigne@gmail.com>
Date: Sun, 15 May 2011 15:15:36 +0200
Subject: [PATCH] Updated Welsh-Powell from outdated API (assuming color
attributes can change the display). Added documentation
---
.../algorithm/coloring/WelshPowell.java | 197 ++++++++++++------
1 file changed, 132 insertions(+), 65 deletions(-)
diff --git a/src/org/graphstream/algorithm/coloring/WelshPowell.java b/src/org/graphstream/algorithm/coloring/WelshPowell.java
index 823971a..2ed1f5b 100644
--- a/src/org/graphstream/algorithm/coloring/WelshPowell.java
+++ b/src/org/graphstream/algorithm/coloring/WelshPowell.java
@@ -37,12 +37,12 @@ import org.graphstream.algorithm.*;
import org.graphstream.graph.*;
/**
- * Welsh Powell static colorating algorithm.
+ * Welsh Powell static graph coloring algorithm.
*
* <p>
- * This class is intended to give some algorithm for computing the well-known
- * coloring problem. It provides the Welsh and Powell greedy algorithm that may
- * used as a static method.
+ * This class is intended to implement the Welsh-Powell algorithm for the
+ * problem of graph coloring. It provides a greedy algorithm that runs on a
+ * static graph.
* </p>
*
* <p>
@@ -63,39 +63,134 @@ import org.graphstream.graph.*;
* <p>
*
* <p>
- * This algorithm is known to use at most d(G)+1 colors where d(G) represents
- * the largest value of the degree in the graph G.
+ * Note that the given colors are not real colors. Instead they are positive
+ * integers starting 0. So, for instance, if a colored graph's chromatic number
+ * is 3, then nodes will be "colored" with one of 0, 1 or 2.
* </p>
*
+ *
* <p>
- * After computation (using {@link #compute()}, the algorithm returns its result
- * using the {@link #getLastComputedResult()} method. If you passed "true" to
- * the <tt>modify</tt> parameter, the colors are stored in the graph as
- * attributes. By default the attribute name is "color", so that the viewer
- * displays them accordingly, but you can optionnaly choose the attribute name.
+ * After computation (using {@link #compute()}, the algorithm result for the
+ * computation, the chromatic number, is accessible with the
+ * {@link #getLastComputedResult()} method. Colors (of "Integer" type) are stored in the graph as attributes (one for each node).
+ * By default the attribute name is "WelshPowell.color", but you can optional choose the
+ * attribute name.
* </p>
*
+ *
+ *
+ * <h2>Example</h2>
+ * import java.io.IOException;
+ * import java.io.StringReader;
+ *
+ * import org.graphstream.algorithm.coloring.WelshPowell;
+ * import org.graphstream.graph.ElementNotFoundException;
+ * import org.graphstream.graph.Graph;
+ * import org.graphstream.graph.Node;
+ * import org.graphstream.graph.implementations.DefaultGraph;
+ * import org.graphstream.stream.GraphParseException;
+ * import org.graphstream.stream.file.FileSourceDGS;
+ *
+ * public class WelshPowellTest {
+ * // B-(1)-C
+ * // / \
+ * // (1) (10)
+ * // / \
+ * // A F
+ * // \ /
+ * // (1) (1)
+ * // \ /
+ * // D-(1)-E
+ * static String my_graph =
+ * "DGS004\n"
+ * + "my 0 0\n"
+ * + "an A \n"
+ * + "an B \n"
+ * + "an C \n"
+ * + "an D \n"
+ * + "an E \n"
+ * + "an F \n"
+ * + "ae AB A B weight:1 \n"
+ * + "ae AD A D weight:1 \n"
+ * + "ae BC B C weight:1 \n"
+ * + "ae CF C F weight:10 \n"
+ * + "ae DE D E weight:1 \n"
+ * + "ae EF E F weight:1 \n"
+ * ;
+ * public static void main(String[] args) throws IOException, ElementNotFoundException, GraphParseException {
+ * Graph graph = new DefaultGraph("Welsh Powell Test");
+ * StringReader reader = new StringReader(my_graph);
+ *
+ * FileSourceDGS source = new FileSourceDGS();
+ * source.addSink(graph);
+ * source.readAll(reader);
+ *
+ * WelshPowell wp = new WelshPowell("color");
+ * wp.init(graph);
+ * wp.compute();
+ *
+ * System.out.println("The chromatic number of this graph is : "+wp.getChromaticNumber());
+ * for(Node n : graph){
+ * System.out.println("Node "+n.getId()+ " : color " +n.getAttribute("color"));
+ * }
+ * }
+ * }
+ * </pre>
+ *
+ * This shall return:
+ * <pre>
+ * The chromatic number of this graph is : 3
+ * Node D : color 0
+ * Node E : color 2
+ * Node F : color 1
+ * Node A : color 2
+ * Node B : color 1
+ * Node C : color 0
+ * </pre>
+ *
+ *
+ * <h2>Extra Feature</h2>
+ *
* <p>
- * This algorithm uses the <i>std-algo-1.0</i> algorithm's standard.
+ * Consider you what to display the result of they coloring algorithm on a displayed graph,
+ * then adding the following code to the previous example may help you:
* </p>
*
+ * <pre>
+ * Color[] cols = new Color[wp.getChromaticNumber()];
+ * for(int i=0;i< wp.getChromaticNumber();i++){
+ * cols[i]=Color.getHSBColor((float) (Math.random()), 0.8f, 0.9f);
+ * }
+ * for(Node n : graph){
+ * int col = (int) n.getNumber("color");
+ * n.addAttribute("ui.style", "fill-color:rgba("+cols[col].getRed()+","+cols[col].getGreen()+","+cols[col].getBlue()+",200);" );
+ * }
+ *
+ * graph.display();
+ * </pre>
+
+ *
+ *
+ * @complexity
+ * This algorithm is known to use at most d(G)+1 colors where d(G) represents
+ * the largest value of the degree in the graph G.
+ *
+ * @reference
+ * Welsh, D. J. A.; Powell, M. B. (1967),
+ * "An upper bound for the chromatic number of a graph and its application to timetabling problems",
+ * The Computer Journal 10 (1): 85–86, doi:10.1093/comjnl/10.1.85
+ *
* @version 0.1 30/08/2007
* @author Frédéric Guinand
* @author Antoine Dutot
* @author Yoann Pigné
*/
public class WelshPowell implements Algorithm {
- // Attributes
-
- /**
- * Modify the graph ?.
- */
- protected boolean modify = false;
/**
* Name of the attributes added to the graph.
*/
- protected String attrName = "color";
+ protected String attrName = "WelshPowell.color";
/**
* The graph.
@@ -103,40 +198,29 @@ public class WelshPowell implements Algorithm {
protected Graph g;
/**
- * The algorithm result (number of colors).
+ * The algorithm's result : the chromatic number.
*/
- protected int result;
+ protected int chromaticNumber;
// Constructors
/**
* New Welsh and Powell coloring algorithm.
*
- * @param modify
- * A boolean equals to true if the graph has to be modified,
- * false otherwise
* @param attrName
- * If modify is true, then attrName may be indicated as the name
- * of the attribute corresponding to the color allocated by this
- * algorithm. Note that if attrName is "color", then the color of
- * the nodes will be modified accordingly.
+ * name of the attribute corresponding to the color allocated by
+ * this algorithm.
*/
- public WelshPowell(boolean modify, String attrName) {
- this.modify = modify;
+ public WelshPowell(String attrName) {
this.attrName = attrName;
}
/**
- * New Welsh and Powell coloring algorithm, using "color" as the attribute
- * name. If the graph is to be modified, the modification will store colors
- * in it and the viewer should display them accordingly.
+ * New Welsh and Powell coloring algorithm, using "WelshPowell.color" as the attribute
+ * name.
*
- * @param modify
- * A boolean equals to true if the graph has to be modified,
- * false otherwise
*/
- public WelshPowell(boolean modify) {
- this.modify = modify;
+ public WelshPowell() {
}
// Accessors
@@ -147,8 +231,8 @@ public class WelshPowell implements Algorithm {
* @return The number of colors.
* @see #compute()
*/
- public int getLastComputedResult() {
- return result;
+ public int getChromaticNumber() {
+ return chromaticNumber;
}
// Commands
@@ -163,15 +247,6 @@ public class WelshPowell implements Algorithm {
this.attrName = attrName;
}
- /**
- * Modify the graph when computing the algorithm?.
- *
- * @param modify
- * If true, attributes are stored in the graph.
- */
- public void setModify(boolean modify) {
- this.modify = modify;
- }
/*
* (non-Javadoc)
@@ -189,9 +264,9 @@ public class WelshPowell implements Algorithm {
* @see org.graphstream.algorithm.Algorithm#compute()
*/
public void compute() {
- String attributeName = "welshpowell";
+ String attributeName = "WelshPowell.color";
- if (modify && (attrName != null))
+ if (attrName != null)
attributeName = attrName;
// ------- STEP 1 -----------
@@ -230,18 +305,18 @@ public class WelshPowell implements Algorithm {
// ------ STEP 2 --------
// color initialization
- ArrayList<Color> allColors = new ArrayList<Color>();
- Color col;
+ ArrayList<Integer> allColors = new ArrayList<Integer>();
+ Integer col;
int nbColors = 0;
for (int i = 0; i < g.getNodeCount(); i++) {
- col = Color.getHSBColor((float) (Math.random()), 0.8f, 0.9f);
+ col = i;
allColors.add(col);
}
// ------- STEP 3 --------
- Color currentColor = allColors.remove(0);
+ Integer currentColor = allColors.remove(0);
nbColors++;
while (!sortedNodes.isEmpty()) {
@@ -257,7 +332,7 @@ public class WelshPowell implements Algorithm {
Node neighb = neighbors.next();
if (neighb.hasAttribute(attributeName)) {
- if (((Color) (neighb.getAttribute(attributeName)))
+ if (((neighb.getAttribute(attributeName)))
.equals(currentColor)) {
conflict = true;
}
@@ -276,14 +351,6 @@ public class WelshPowell implements Algorithm {
nbColors++;
}
- if (!modify) {
- nodes = g.getNodeIterator();
-
- while (nodes.hasNext()) {
- nodes.next().removeAttribute(attributeName);
- }
- }
-
- result = nbColors;
+ chromaticNumber = nbColors-1;
}
}
\ No newline at end of file
--
GitLab