source: trunk/EventBenchCore/src/de/ugoe/cs/eventbench/markov/SimpleState.java @ 1

package de.ugoe.cs.eventbench.markov;

import java.util.ArrayList;
import java.util.List;

import de.ugoe.cs.eventbench.data.Event;


/**
 * This class implements a simple first-order markov state. 
 * Transitions are unlabled.
 * @author Steffen Herbold
 */
public class SimpleState extends State implements DotPrinter {
        
        List<Double> transitionProbs;
        List<State> toStates;
        
        // members for learning
        private int transitionsObserved;
        
        private String idShort = null;
        
        public SimpleState(String id, Event<?> action) {
                super(id, action);
                transitionsObserved = 0;
                toStates = new ArrayList<State>();
                transitionProbs = new ArrayList<Double>();
        }
        
        public SimpleState(String id, Event<?> action, String idShort) {
                this(id, action);
                this.idShort = idShort;
        }
        
        @Override
        public State getNextState() {
                double randVal = rand.nextDouble();
                double probSum = 0;
                int index = 0;
                while( index<transitionProbs.size() && probSum+transitionProbs.get(index) < randVal ) {
                        probSum += transitionProbs.get(index);
                        index++;
                }
                return toStates.get(index);
        }
        
        public void incTransTo(State state) {
                int index = toStates.indexOf(state);
                if( index==-1 ) {
                        toStates.add(state);
                        transitionProbs.add(0.0);
                        index = toStates.size()-1;
                }
                // update trans probs
                for( int i=0 ; i<toStates.size() ; i++ ) {
                        double currentProb = transitionProbs.get(i);
                        double newProb = 0.0;
                        if( i!=index ) {
                                newProb = (currentProb*transitionsObserved)/(transitionsObserved+1);
                        } else {
                                newProb = ((currentProb*transitionsObserved)+1)/(transitionsObserved+1);
                        }
                        transitionProbs.set(i, newProb);
                }
                transitionsObserved++;
        }
        
        // get the transition probability to the given state
        public double getProb(State state) {
                double prob = 0.0;
                int index = toStates.indexOf(state);
                if( index>=0 ) {
                        prob = transitionProbs.get(index);
                }
                return prob;
        }
        
        public String getShortId() {
                String shortId;
                if( idShort!=null ) {
                        shortId = idShort;
                } else {
                        shortId = getId();
                }
                return shortId;
        }

        @Override
        public void printDot() {
                final String thisSaneId = getShortId().replace("\"", "\\\"").replaceAll("[\r\n]","");
                System.out.println(" " + hashCode() + " [label=\""+thisSaneId+"\"];");
                for(int i=0 ; i<toStates.size() ; i++ ) {
                        System.out.print(" "+hashCode()+" -> " + toStates.get(i).hashCode() + " ");
                        System.out.println("[label=\"" + transitionProbs.get(i) + "\"];");
                }
                
        }
        
}