/*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* TopDownConstructor.java
* Copyright (C) 2007 University of Waikato, Hamilton, New Zealand
*/
package weka.core.neighboursearch.balltrees;
import weka.core.EuclideanDistance;
import weka.core.Instance;
import weka.core.Option;
import weka.core.RevisionUtils;
import weka.core.TechnicalInformation;
import weka.core.TechnicalInformationHandler;
import weka.core.Utils;
import weka.core.TechnicalInformation.Field;
import weka.core.TechnicalInformation.Type;
import weka.core.neighboursearch.balltrees.BallNode;
import java.util.Enumeration;
import java.util.Vector;
/**
<!-- globalinfo-start -->
* The class implementing the TopDown construction method of ball trees. It further uses one of a number of different splitting methods to split a ball while constructing the tree top down.<br/>
* <br/>
* For more information see also:<br/>
* <br/>
* Stephen M. Omohundro (1989). Five Balltree Construction Algorithms.
* <p/>
<!-- globalinfo-end -->
*
<!-- technical-bibtex-start -->
* BibTeX:
* <pre>
* @techreport{Omohundro1989,
* author = {Stephen M. Omohundro},
* institution = {International Computer Science Institute},
* month = {December},
* number = {TR-89-063},
* title = {Five Balltree Construction Algorithms},
* year = {1989}
* }
* </pre>
* <p/>
<!-- technical-bibtex-end -->
*
<!-- options-start -->
* Valid options are: <p/>
*
* <pre> -S <classname and options>
* Ball splitting algorithm to use.</pre>
*
<!-- options-end -->
*
* @author Ashraf M. Kibriya (amk14[at-the-rate]cs[dot]waikato[dot]ac[dot]nz)
* @version $Revision: 5953 $
*/
public class TopDownConstructor
extends BallTreeConstructor
implements TechnicalInformationHandler {
/** for serialization. */
private static final long serialVersionUID = -5150140645091889979L;
/**
* The BallSplitter algorithm used by the TopDown BallTree constructor, if it
* is selected.
*/
protected BallSplitter m_Splitter = new PointsClosestToFurthestChildren();
/**
* Creates a new instance of TopDownConstructor.
*/
public TopDownConstructor() {
}
/**
* Returns a string describing this nearest neighbour search algorithm.
*
* @return a description of the algorithm for displaying in the
* explorer/experimenter gui
*/
public String globalInfo() {
return
"The class implementing the TopDown construction method of "
+ "ball trees. It further uses one of a number of different splitting "
+ "methods to split a ball while constructing the tree top down.\n\n"
+ "For more information see also:\n\n"
+ getTechnicalInformation().toString();
}
/**
* Returns an instance of a TechnicalInformation object, containing detailed
* information about the technical background of this class, e.g., paper
* reference or book this class is based on.
*
* @return the technical information about this class
*/
public TechnicalInformation getTechnicalInformation() {
TechnicalInformation result;
result = new TechnicalInformation(Type.TECHREPORT);
result.setValue(Field.AUTHOR, "Stephen M. Omohundro");
result.setValue(Field.YEAR, "1989");
result.setValue(Field.TITLE, "Five Balltree Construction Algorithms");
result.setValue(Field.MONTH, "December");
result.setValue(Field.NUMBER, "TR-89-063");
result.setValue(Field.INSTITUTION, "International Computer Science Institute");
return result;
}
/**
* Builds the ball tree top down.
* @return The root node of the tree.
* @throws Exception If there is problem building
* the tree.
*/
public BallNode buildTree() throws Exception {
BallNode root;
m_NumNodes = m_MaxDepth = 0;
m_NumLeaves = 1;
m_Splitter.setInstances(m_Instances);
m_Splitter.setInstanceList(m_InstList);
m_Splitter.
setEuclideanDistanceFunction((EuclideanDistance)m_DistanceFunction);
root = new BallNode(0, m_InstList.length-1, 0);
root.setPivot(BallNode.calcCentroidPivot(m_InstList, m_Instances));
root.setRadius(BallNode.calcRadius(m_InstList, m_Instances, root.getPivot(), m_DistanceFunction));
splitNodes(root, m_MaxDepth+1, root.m_Radius);
return root;
}
/**
* Recursively splits nodes of a ball tree until
* <=m_MaxInstancesInLeaf instances remain in a node.
* @param node The node to split.
* @param depth The depth of this node in the tree,
* so that m_MaxDepth is correctly updated.
* @param rootRadius The smallest ball enclosing all
* the data points.
* @throws Exception If there is some problem in
* splitting.
*/
protected void splitNodes(BallNode node, int depth, final double rootRadius) throws Exception {
if(node.m_NumInstances <= m_MaxInstancesInLeaf ||
(rootRadius==0 ? true : node.m_Radius/rootRadius < m_MaxRelLeafRadius))
return;
m_NumLeaves--;
m_Splitter.splitNode(node, m_NumNodes);
m_NumNodes += 2;
m_NumLeaves += 2;
if(m_MaxDepth < depth)
m_MaxDepth = depth;
splitNodes(node.m_Left, depth+1, rootRadius);
splitNodes(node.m_Right, depth+1, rootRadius);
if(m_FullyContainChildBalls) {
double radius = BallNode.calcRadius(node.m_Left, node.m_Right,
node.getPivot(), m_DistanceFunction);
Instance pivot = BallNode.calcPivot(node.m_Left, node.m_Right, m_Instances);
// System.err.println("Left Radius: "+node.m_Left.getRadius()+
// " Right Radius: "+node.m_Right.getRadius()+
// " d(p1,p2): "+
// m_DistanceFunction.distance(node.m_Left.getPivot(), node.m_Right.getPivot())+
// " node's old radius: "+node.getRadius()+
// " node's new Radius: "+radius+
// " node;s old pivot: "+node.getPivot()+
// " node's new pivot: "+pivot);
node.setRadius(radius);
}
}
/**
* Adds an instance to the ball tree.
* @param node The root node of the tree.
* @param inst The instance to add to the tree.
* @return The new master index array after adding the
* instance.
* @throws Exception If there is some problem adding the
* given instance to the tree.
*/
public int[] addInstance(BallNode node, Instance inst) throws Exception {
double leftDist, rightDist;
if (node.m_Left!=null && node.m_Right!=null) { //if node is not a leaf
// go further down the tree to look for the leaf the instance should be in
leftDist = m_DistanceFunction.distance(inst, node.m_Left.getPivot(),
Double.POSITIVE_INFINITY); //instance.value(m_SplitDim);
rightDist = m_DistanceFunction.distance(inst, node.m_Right.getPivot(),
Double.POSITIVE_INFINITY);
if (leftDist < rightDist) {
addInstance(node.m_Left, inst);
// go into right branch to correct instance list boundaries
processNodesAfterAddInstance(node.m_Right);
}
else {
addInstance(node.m_Right, inst);
}
// correct end index of instance list of this node
node.m_End++;
}
else if(node.m_Left!=null || node.m_Right!=null) {
throw new Exception("Error: Only one leaf of the built ball tree is " +
"assigned. Please check code.");
}
else { // found the leaf to insert instance
int index = m_Instances.numInstances() - 1;
int instList[] = new int[m_Instances.numInstances()];
System.arraycopy(m_InstList, 0, instList, 0, node.m_End+1);
if(node.m_End < m_InstList.length-1)
System.arraycopy(m_InstList, node.m_End+2, instList, node.m_End+2, m_InstList.length-node.m_End-1);
instList[node.m_End+1] = index;
node.m_End++;
node.m_NumInstances++;
m_InstList = instList;
m_Splitter.setInstanceList(m_InstList);
if(node.m_NumInstances > m_MaxInstancesInLeaf) {
m_Splitter.splitNode(node, m_NumNodes);
m_NumNodes += 2;
}
}
return m_InstList;
}
/**
* Post process method to correct the start and end
* indices of BallNodes on the right of the
* node where the instance was added.
* @param node The node whose m_Start and m_End
* need to be updated.
*/
protected void processNodesAfterAddInstance(BallNode node) {
//updating start and end indices for the node
node.m_Start++;
node.m_End++;
//processing child nodes
if(node.m_Left!=null && node.m_Right!=null) {
processNodesAfterAddInstance(node.m_Left);
processNodesAfterAddInstance(node.m_Right);
}
}
/**
* Returns the tip text for this property.
*
* @return tip text for this property suitable for
* displaying in the explorer/experimenter gui
*/
public String ballSplitterTipText() {
return
"The BallSplitter algorithm set that would be used by the TopDown "
+ "BallTree constructor.";
}
/**
* Returns the BallSplitter algorithm set that would be
* used by the TopDown BallTree constructor.
* @return The BallSplitter currently in use.
*/
public BallSplitter getBallSplitter() {
return m_Splitter;
}
/**
* Sets the ball splitting algorithm to be used by the
* TopDown constructor.
* @param splitter The BallSplitter to use.
*/
public void setBallSplitter(BallSplitter splitter) {
m_Splitter = splitter;
}
/**
* Returns an enumeration describing the available options.
*
* @return an enumeration of all the available options.
*/
public Enumeration listOptions() {
Vector<Option> newVector = new Vector<Option>();
newVector.addElement(new Option(
"\tBall splitting algorithm to use.",
"S", 1, "-S <classname and options>"));
return newVector.elements();
}
/**
* Parses a given list of options.
*
<!-- options-start -->
* Valid options are: <p/>
*
* <pre> -S <classname and options>
* Ball splitting algorithm to use.</pre>
*
<!-- options-end -->
*
* @param options the list of options as an array of strings
* @throws Exception if an option is not supported
*/
public void setOptions(String[] options)
throws Exception {
super.setOptions(options);
String optionString = Utils.getOption('S', options);
if(optionString.length() != 0) {
String nnSearchClassSpec[] = Utils.splitOptions(optionString);
if(nnSearchClassSpec.length == 0) {
throw new Exception("Invalid BallSplitter specification string.");
}
String className = nnSearchClassSpec[0];
nnSearchClassSpec[0] = "";
setBallSplitter( (BallSplitter)
Utils.forName( BallSplitter.class,
className, nnSearchClassSpec) );
}
else {
setBallSplitter(new PointsClosestToFurthestChildren());
}
}
/**
* Gets the current settings of KDtree.
*
* @return an array of strings suitable for passing to setOptions
*/
public String[] getOptions() {
Vector<String> result;
String[] options;
int i;
result = new Vector<String>();
options = super.getOptions();
for (i = 0; i < options.length; i++)
result.add(options[i]);
result.add("-S");
result.add(m_Splitter.getClass().getName());
return result.toArray(new String[result.size()]);
}
/**
* Returns the revision string.
*
* @return the revision
*/
public String getRevision() {
return RevisionUtils.extract("$Revision: 5953 $");
}
}