EigenOnFFT.java

package GeDBIT.index.algorithms;

import java.util.List;

import GeDBIT.dist.Metric;
import GeDBIT.type.IndexObject;

@SuppressWarnings("serial")
public class EigenOnFFT implements PivotSelectionMethod, java.io.Serializable {
    // private static final long serialVersionUID = 6928847050089693231L;
    @SuppressWarnings("unused")
    private final int FFTScale;

    public EigenOnFFT(int scale) {
	this.FFTScale = scale;
    }

    public int[] selectPivots(Metric metric, List<? extends IndexObject> data,
	    int numPivots) {
	final int dataSize = data.size();

	if (numPivots >= dataSize) {
	    int[] pivots = new int[dataSize];
	    for (int i = 0; i < dataSize; i++)
		pivots[i] = i;

	    return IncrementalSelection.removeDuplicate(metric, data, pivots);
	}

	/*
	 * // run fft to get a candidate set int[] fftResult =
	 * PivotSelectionMethods.FFT.selectPivots(metric, data, numPivots *
	 * FFTScale);
	 * 
	 * // compute the distance matrix if (fftResult.length <=
	 * Math.min(dataSize, numPivots)) return fftResult;
	 */

	// DoubleMatrix2D matrix =
	// LargeDenseDoubleMatrix2D.createDoubleMatrix2D(dataSize,
	// fftResult.length);
	double matrix[][] = new double[dataSize][dataSize];
	for (int col = 0; col < dataSize; col++)
	    for (int row = 0; row < dataSize; row++)
		// matrix.set(row, col, metric.getDistance(data.get(row),
		// data.get(fftResult[col])));
		matrix[row][col] = metric.getDistance(data.get(row),
			data.get(col));

	// compute eigen value

	Eigen eigen = new Eigen(matrix);

	eigen.calEigen();
	int[] result = eigen.getEigen();
	// eigen.printEigenDouble();
	// eigen.printEigenFloat();
	// eigen.printEigenFloatPositive();
	eigen.printBiggestEigen(dataSize);

	return result;
    }

    /*
     * (non-Javadoc)
     * 
     * @see
     * GeDBIT.index.algorithms.PivotSelectionMethod#selectPivots(GeDBIT.dist
     * .Metric, java.util.List, int, int, int)
     */
    public int[] selectPivots(Metric metric, List<? extends IndexObject> data,
	    int first, int dataSize, int numPivots) {
	int[] result = selectPivots(metric, data.subList(first, dataSize),
		numPivots);
	for (int i = 0; i < result.length; i++)
	    result[i] += first;

	return result;
    }

}