/*
* This file is part of Caliph & Emir.
*
* Caliph & Emir 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.
*
* Caliph & Emir 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 Caliph & Emir; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Copyright statement:
* --------------------
* (c) 2002-2005 by Mathias Lux (mathias@juggle.at)
* http://www.juggle.at, http://caliph-emir.sourceforge.net
*/
package at.lux.retrieval.fdp;
import at.lux.retrieval.calculations.DistanceMatrix;
/**
* Date: 02.02.2005
* Time: 22:42:51
*
* @author Mathias Lux, mathias@juggle.at
*/
public class FDP {
private float[][] points;
private DistanceMatrix fastmapDistanceMatrix;
private FDPParameters parameters = new FDPParameters();
private float currentMovement = -1;
public FDP(DistanceMatrix fastmapDistanceMatrix, float[][] points) {
this.fastmapDistanceMatrix = fastmapDistanceMatrix;
this.points = points;
// setting the gravitation related to the number of points.
parameters.setGravitation(3d/Math.sqrt(points.length));
}
public FDP(DistanceMatrix fastmapDistanceMatrix, FDPParameters parameters, float[][] points) {
this.fastmapDistanceMatrix = fastmapDistanceMatrix;
this.parameters = parameters;
this.points = points;
}
public void step() {
currentMovement = 0;
for (int i = 0; i < points.length; i++) {
float[] point = points[i];
double[] moveVector = new double[point.length];
for (int j = 0; j < points.length; j++) {
if (i!=j) {
// I take for granted that the distance is normalized:
double oSimilarity = 1 - fastmapDistanceMatrix.getDistance(i,j);
double pDist = 0f;
for (int k = 0; k < point.length; k++) {
double l1 = point[k] - points[j][k];
pDist += l1*l1;
}
pDist = Math.sqrt(pDist);
if (pDist <= Double.MIN_VALUE) pDist = parameters.minimumDistance;
double currentForce = Math.pow(oSimilarity, parameters.d) - parameters.w/(Math.pow(pDist, parameters.r)) + parameters.gravitation;
for (int k = 0; k < moveVector.length; k++) {
moveVector[k] += currentForce * points[j][k] + (1 - currentForce) * point[k];
}
}
}
float fraction = 1f/((float) points.length);
for (int j = 0; j < point.length; j++) {
float moveInComponent = fraction * (float) moveVector[j];
point[j] = moveInComponent;
currentMovement += Math.abs(moveInComponent);
}
}
}
/**
* Returns movement of the last step - used to check if
* equilibrium is reached.
* @return the sum of absolute movements or -1 if no step was taken
*/
public float getCurrentMovement() {
return currentMovement;
}
}