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Commit e9879a2c authored by Yoann Pigné's avatar Yoann Pigné
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Updated Welsh-Powell from outdated API (assuming color attributes can change... 

Updated Welsh-Powell from outdated API (assuming color attributes can change the display). Added documentation
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src/org/graphstream/algorithm/coloring/WelshPowell.java
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......@@ -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;
}
}
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