edgehistfeatures.java

来自「这是一个CRF(条件随机域)算法的实现,希望能对从事算法的有些帮助.」· Java 代码 · 共 59 行

package iitb.Model;
import iitb.CRF.*;
import iitb.Utils.*;
/**
 *
 * @author Sunita Sarawagi
 *
 * Suppose if history size is H and number of labels in the model
 * graph is m, this will generate m^(H+1) features 
 */ 

public class EdgeHistFeatures extends FeatureTypes {
    String fname;
    String labelNames[];
    int histsize;
    Counters ctr;
    boolean allDone;
    int histArr[];
    public EdgeHistFeatures(FeatureGenImpl m,String name, String labels[], int histsize) {
	super(m);
	fname=name;
	labelNames=labels;
	ctr = new Counters(histsize+1, m.numStates());
	this.histsize = histsize;
	histArr = new int[histsize];
    }
    public boolean startScanFeaturesAt(DataSequence data, int prevPos, int pos) {
	ctr.clear();
	allDone = false;
	if (pos < histsize)
	    allDone = true;
	return allDone;
    }
    public boolean hasNext() {
	return (histsize > 1) && !allDone;
    }	
    public void next(FeatureImpl f) {
	f.ystart = ctr.value(1,1);
	f.yend = ctr.value(0,0);
	ctr.arrayCopy(histsize-1,1,histArr);
	f.historyArray = histArr;
	f.val = 1;
	allDone = !ctr.advance();
	
	String name="";
	for (int i = 0; i < histArr.length; i++) {
	    if (histArr[i] != -1) {
		if (labelNames == null) {
		    name += ctr.value(histsize-1,1);
		} else {
		    int index = i + 1;
		    name += fname+"."+index+"."+labelNames[model.label(f.ystart)];
		}
	    }
	}
	setFeatureIdentifier(ctr.value(histsize-1,0), model.label(f.yend),name,f);
    }
};