rankedfeaturevector.java

这是一个matlab的java实现。里面有许多内容。请大家慢慢捉摸。

/* Copyright (C) 2002 Univ. of Massachusetts Amherst, Computer Science Dept.
   This file is part of "MALLET" (MAchine Learning for LanguagE Toolkit).
   http://www.cs.umass.edu/~mccallum/mallet
   This software is provided under the terms of the Common Public License,
   version 1.0, as published by http://www.opensource.org.  For further
   information, see the file `LICENSE' included with this distribution. */




/**
	 A FeatureVector for which you can efficiently get the feature with
	 highest value, and other ranks.

   @author Andrew McCallum <a href="mailto:[e-mail]">[e-mail]</a>
 */

package edu.umass.cs.mallet.base.types;

import edu.umass.cs.mallet.base.types.Label;
import edu.umass.cs.mallet.base.types.FeatureVector;

public class RankedFeatureVector extends FeatureVector
{
	int[] rankOrder;
	private static final int SORTINIT = -1;
	int sortedTo = SORTINIT; /* Extent of latest sort */
	
	public RankedFeatureVector (Alphabet dict,
														 int[] indices,
														 double[] values)
	{
		super (dict, indices, values);
	}

	public RankedFeatureVector (Alphabet dict, double[] values)
	{
		super (dict, values);
	}

	public RankedFeatureVector (Alphabet dict, DenseVector v)
	{
		this (dict, v.values);
	}

	public RankedFeatureVector (Alphabet dict, AugmentableFeatureVector v)
	{
		super (dict, v.indices, v.values, v.size, v.size,
					 true, true, true);
	}

	public RankedFeatureVector (Alphabet dict, SparseVector v)
	{
		super (dict, v.indices, v.values);
	}
	
	// xxx This bubble sort is a major inefficiency.
	// Implement a O(n log(n)) method!
	// No longer used!
	protected void setRankOrder ()
	{
		this.rankOrder = new int[values.length];
		for (int i = 0; i < rankOrder.length; i++) {
			rankOrder[i] = i;
			assert (!Double.isNaN(values[i]));
		}
		// BubbleSort from back
		for (int i = rankOrder.length-1; i >= 0; i--) {
			//if (i % 1000 == 0)
			//System.out.println ("RankedFeatureVector.setRankOrder i="+i);
			boolean swapped = false;
			for (int j = 0; j < i; j++)
				if (values[rankOrder[j]] < values[rankOrder[j+1]]) {
					// swap
					int r = rankOrder[j];
					rankOrder[j] = rankOrder[j+1];
					rankOrder[j+1] = r;
				}
		}
	}

	protected void setRankOrder (int extent, boolean reset)
	{
		int sortExtent;
		// Set the number of cells to sort, making sure we don't go past the max.
		// Since we are using insertion sort, sorting n-1 sorts the whole array.
		sortExtent = (extent >= values.length) ? values.length - 1: extent;
		if (sortedTo == SORTINIT || reset) { // reinitialize and sort
			this.rankOrder = new int[values.length];
			for (int i = 0; i < rankOrder.length; i++) {
				rankOrder[i] = i;
				assert (!Double.isNaN(values[i]));
			}
		}
		// Selection sort
		for (int i = sortedTo+1; i <= sortExtent; i++) {
			double max = values[rankOrder[i]];
			int maxIndex = i;
			for(int j = i+1; j < rankOrder.length; j++) {
				if (values[rankOrder[j]] > max) {
					max = values[rankOrder[j]];
					maxIndex = j;
				}
			}
			//swap
			int r = rankOrder[maxIndex];
			rankOrder[maxIndex] = rankOrder[i];
			rankOrder[i] = r;
			sortedTo = i;
		}
	}

	protected void setRankOrder (int extent) {
		setRankOrder(extent, false);
	}
	
	public int getMaxValuedIndex ()
	{
		if (rankOrder == null)
			setRankOrder (0);
		return rankOrder[0];
	}

	public Object getMaxValuedObject ()
	{
		return dictionary.lookupObject (getMaxValuedIndex());
	}

	public int getMaxValuedIndexIn (FeatureSelection fs)
	{
		if (fs == null)
			return getMaxValuedIndex();
		assert (fs.getAlphabet() == dictionary);
		// xxx Make this more efficient!  I'm pretty sure that Java BitSet's can do this more efficiently
		int i = 0;
		while (!fs.contains(rankOrder[i])) {
			setRankOrder (i);
			i++;
		}
		//System.out.println ("RankedFeatureVector.getMaxValuedIndexIn feature="
		//+dictionary.lookupObject(rankOrder[i]));
		return rankOrder[i];
	}

	public Object getMaxValuedObjectIn (FeatureSelection fs)
	{
		return dictionary.lookupObject (getMaxValuedIndexIn(fs));
	}

	public double getMaxValue ()
	{
		if (rankOrder == null)
			setRankOrder (0);
		return values[rankOrder[0]];
	}

	public double getMaxValueIn (FeatureSelection fs)
	{
		if (fs == null)
			return getMaxValue();
		int i = 0;
		while (!fs.contains(i)) {
			setRankOrder (i);
			i++;
		}
		return values[rankOrder[i]];
	}
	
	public int getIndexAtRank (int rank)
	{
		setRankOrder (rank);
		return rankOrder[rank];
	}

	public Object getObjectAtRank (int rank)
	{
		setRankOrder (rank);
		return dictionary.lookupObject (rankOrder[rank]);
	}

	public double getValueAtRank (int rank)
	{
		if (values == null)
			return 1.0;
		setRankOrder (rank);
		if (rank >= rankOrder.length) {
			rank = rankOrder.length -1;
			System.err.println("rank larger than rankOrder.length. rank = " + rank + "rankOrder.length = " + rankOrder.length);
		}
		if (rankOrder[rank] >= values.length) {
			System.err.println("rankOrder[rank] out of range.");
			return 1.0;
		}
		return values[rankOrder[rank]];
	}

	public int getRank (Object o)
	{
		throw new UnsupportedOperationException ("Not yet implemented");
	}

	public int getRank (int index)
	{
		throw new UnsupportedOperationException ("Not yet implemented");
	}

	
	public void set (int i, double v)
	{
		throw new UnsupportedOperationException (RankedFeatureVector.class.getName() + " is immutable");
	}


	public interface Factory
	{
		public RankedFeatureVector newRankedFeatureVector (InstanceList ilist);
	}

	public interface PerLabelFactory
	{
		public RankedFeatureVector[] newRankedFeatureVectors (InstanceList ilist);
	}
	
}