bitsetclique.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) 2003 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. */
package edu.umass.cs.mallet.grmm;

import edu.umass.cs.mallet.base.types.Alphabet;

import java.util.*;

import gnu.trove.THashSet;

/**
 * A clique that uses very little time and memory based on the flyweight
 *  pattern.  The owner supplies an Alphabet of vertices and a BitSet,
 *  and the clique contains the vertices in the Alphabet, masked by the BitSet.
 *
 * @author Charles Sutton
 * @version $Id: BitSetClique.java,v 1.2 2004/08/13 19:17:37 casutton Exp $ 
 */
public class BitSetClique extends AbstractSet implements Clique {

  private Alphabet vertexMap;
  private BitSet bitset;

  /**
   * Creates a BitSet clique given an alphabet of Variables,
   *  and a bitset that says which variables in the alphabet
   *  to include in the clique.  Neither is copied, but
   *  neither is modified, either.
   *
   * @param vertexMap
   * @param included Bit mask that indicates which variables to include
   */
  BitSetClique (Alphabet vertexMap, BitSet included)
  {
    this.vertexMap = vertexMap;
    this.bitset = included;
  }

  BitSetClique (Alphabet vertexMap, Collection included)
  {
    this.vertexMap = vertexMap;
    this.bitset = new BitSet (vertexMap.size());

    java.util.Iterator it = included.iterator();
    while (it.hasNext()) {
      bitset.set (vertexMap.lookupIndex (it.next()));
    }
  }

  public boolean add (Object o)
  {
    int idx = vertexMap.lookupIndex (o);
    if (idx == -1)
      throw new UnsupportedOperationException();
    bitset.set (idx);
    return true;
  }

  public Variable get(int idx)
  {
    int mapIdx = 0;
    for (int i = 0; i < idx; i++) {
      mapIdx = bitset.nextSetBit (mapIdx);
      if (mapIdx == -1)
        throw new IndexOutOfBoundsException("Index "+idx+" in BitSetClique");
    }
    return (Variable) vertexMap.lookupObject (mapIdx);
  }


  public Set vertices()
  {
    return null;
  }


  public Variable[] toVariableArray()
  {
    return (Variable[]) toArray (new Variable[0]);
  }


// FIXME cache not updated on changes to the clique
	private int cachedWeight = -1;

  public int weight()
  {
		if (cachedWeight == -1) {
			int weight = 1;
			Iterator it = new Iterator();
			while (it.hasNext()) {
				Variable var = (Variable) it.next();
				weight *= var.getNumOutcomes();
			}
			cachedWeight = weight;
		}

    return cachedWeight;
  }


  public AssignmentIterator assignmentIterator()
  {
    return new AssignmentIterator (Arrays.asList(toArray ()));
  }


  public int size()
  {
    return bitset.cardinality();
  }


  public boolean isEmpty()
  {
    return bitset.isEmpty();
  }


  public boolean contains(Object o)
  {
    return bitset.get(vertexMap.lookupIndex(o, false));
  }


  private class Iterator implements java.util.Iterator {

    int nextIdx;

    public Iterator () { nextIdx = bitset.nextSetBit (0); }

    public boolean hasNext()
    {
      return (nextIdx >= 0);
    }

    public Object next()
    {
      int thisIdx = nextIdx;
      nextIdx = bitset.nextSetBit (thisIdx + 1);
      return vertexMap.lookupObject (thisIdx);
    }

    public void remove()
    {
      throw new UnsupportedOperationException("Removal from BitSetClique not permitted");
    }

  }

  public java.util.Iterator iterator()
  {
    return new Iterator();
  }

  public int hashCode ()
  {
    return bitset.hashCode ();
  }

  public boolean containsAll(Collection c)
  {
    if (c instanceof BitSetClique) {
      return containsAll ((BitSetClique) c);
    } else {
      return super.containsAll (c);
    }
  }

  /**
   * Efficient version of containsAll() for BitSetCliques.
   */
  public boolean containsAll (BitSetClique bsc)
  {
		assert vertexMap == bsc.vertexMap;
		for(int i=bsc.bitset.nextSetBit(0); i>=0; i=bsc.bitset.nextSetBit(i+1)) {
			if (!bitset.get (i)) {
				return false;
			}
		}
		return true;
  }

  public Set intersection (Clique c) {
    if (c instanceof BitSetClique) {
      // Efficient implementation
      BitSetClique bsc = (BitSetClique) c;
      BitSet newBitSet = (BitSet) bitset.clone();
      newBitSet.and (bsc.bitset);
      return new BitSetClique (vertexMap, newBitSet);
    } else {
      // Grossly inefficient implementation
      THashSet hset = new THashSet (this);
      hset.retainAll (c);
      return hset;
    }
  }

  int intersectionSize (BitSetClique bsc)
  {
		assert vertexMap == bsc.vertexMap;
		int size = 0;
		for(int i=bsc.bitset.nextSetBit(0); i>=0; i=bsc.bitset.nextSetBit(i+1)) {
			if (bitset.get (i)) {
				size++;
			}
		}
		return size;
  }

  public void clear()
  {
    bitset.clear();
  }


  public boolean hasLabel()
  {
    return true;
  }


  public String getLabel()
  {
    return toString ();
  }

  public String toString ()
  {
    String foo = "(C";
    Iterator it = new Iterator ();
    while (it.hasNext()) {
      Variable var = (Variable) it.next();
      foo = foo + " " + var;
    }
    foo = foo + ")";
    return foo;
  }

  public void setLabel(String s)
  {
    throw new UnsupportedOperationException();
  }

}