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/* MoharIndex2.java
* =========================================================================
* This file is part of the GrInvIn project - http://www.grinvin.org
*
* Copyright (C) 2005-2008 Universiteit Gent
*
* 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.
*
* A copy of the GNU General Public License can be found in the file
* LICENSE.txt provided with the source distribution of this program (see
* the META-INF directory in the source jar). This license can also be
* found on the GNU website at http://www.gnu.org/licenses/gpl.html.
*
* If you did not receive a copy of the GNU General Public License along
* with this program, contact the lead developer, or write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
package org.grinvin.invariants.computers.chemical;
import org.grinvin.graphs.GraphBundleView;
import org.grinvin.invariants.computers.AbstractInvariantComputer;
import org.grinvin.invariants.values.RealValue;
import org.grinvin.util.Tridiagonal;
/**
* Invariant computer which returns the second Mohar index.
*/
public class MoharIndex2 extends AbstractInvariantComputer {
public RealValue compute (GraphBundleView bundle) {
int[][] adjList = bundle.adjacencyList();
int n = adjList.length;
if(n<=1)
return RealValue.undefinedValue(this);
boolean[][] adjMatrix = bundle.booleanAdjacencyMatrix();
double[][] laplacianMatrix = new double[n][n];
for(int i=0; i<n; i++)
for(int j=0; j<n; j++)
if(i==j)
laplacianMatrix[i][j]=adjList[i].length;
else
laplacianMatrix[i][j]=adjMatrix[i][j] ? -1 : 0;
Tridiagonal decomp = new Tridiagonal(laplacianMatrix);
double[] eigenValues;
try {
eigenValues = decomp.eigenvalues();
} catch(RuntimeException ex){
eigenValues = new double[0];
}
//sort
for(int i=0; i < eigenValues.length; i++)
for(int j=eigenValues.length-1; j>i; j--)
if(eigenValues[j] > eigenValues[j-1]){
double tmp = eigenValues[j];
eigenValues[j] = eigenValues[j-1];
eigenValues[j-1] = tmp;
}
if(eigenValues.length == 0)
return RealValue.undefinedValue(this);
else if (eigenValues[eigenValues.length - 2] == 0)
return RealValue.positiveInfinity(this);
else
return new RealValue (4.0/(n*eigenValues[eigenValues.length - 2]), this);
}
public String getInvariantId () {
return "org.grinvin.invariants.MoharIndex2";
}
}
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