source: trunk/EventBenchCore/src/de/ugoe/cs/eventbench/models/TrieBasedModel.java @ 93

package de.ugoe.cs.eventbench.models;

import java.security.InvalidParameterException;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Random;
import java.util.Set;

import de.ugoe.cs.eventbench.data.Event;
import de.ugoe.cs.eventbench.models.Trie.Edge;
import de.ugoe.cs.eventbench.models.Trie.TrieVertex;
import edu.uci.ics.jung.graph.Tree;

public abstract class TrieBasedModel implements IStochasticProcess {

        /**
         * Id for object serialization.
         */
        private static final long serialVersionUID = 1L;

        protected int trieOrder;

        protected Trie<Event<?>> trie;
        protected final Random r;

        
        public TrieBasedModel(int markovOrder, Random r) {
                super();
                this.trieOrder = markovOrder+1;
                this.r = r;
        }

        public void train(List<List<Event<?>>> sequences) {
                trie = new Trie<Event<?>>();
                
                for(List<Event<?>> sequence : sequences) {
                        List<Event<?>> currentSequence = new LinkedList<Event<?>>(sequence); // defensive copy
                        currentSequence.add(0, Event.STARTEVENT);
                        currentSequence.add(Event.ENDEVENT);
                        
                        trie.train(currentSequence, trieOrder);
                }
        }

        /* (non-Javadoc)
         * @see de.ugoe.cs.eventbench.models.IStochasticProcess#randomSequence()
         */
        @Override
        public List<? extends Event<?>> randomSequence() {
                List<Event<?>> sequence = new LinkedList<Event<?>>();
                
                IncompleteMemory<Event<?>> context = new IncompleteMemory<Event<?>>(trieOrder-1);
                context.add(Event.STARTEVENT);
                
                Event<?> currentState = Event.STARTEVENT;
                
                boolean endFound = false;
                
                while(!endFound) {
                        double randVal = r.nextDouble();
                        double probSum = 0.0;
                        List<Event<?>> currentContext = context.getLast(trieOrder);
                        for( Event<?> symbol : trie.getKnownSymbols() ) {
                                probSum += getProbability(currentContext, symbol);
                                if( probSum>=randVal ) {
                                        endFound = (symbol==Event.ENDEVENT);
                                        if( !(symbol==Event.STARTEVENT || symbol==Event.ENDEVENT) ) {
                                                // only add the symbol the sequence if it is not START or END
                                                context.add(symbol);
                                                currentState = symbol;
                                                sequence.add(currentState);
                                        }
                                        break;
                                }
                        }
                }
                return sequence;
        }
        
        public String getTrieDotRepresentation() {
                return trie.getDotRepresentation();
        }
        
        public Tree<TrieVertex, Edge> getTrieGraph() {
                return trie.getGraph();
        }

        @Override
        public String toString() {
                return trie.toString();
        }
        
        public int getNumStates() {
                return trie.getNumSymbols();
        }
        
        public String[] getStateStrings() {
                String[] stateStrings = new String[getNumStates()];
                int i=0;
                for( Event<?> symbol : trie.getKnownSymbols() ) {
                        stateStrings[i] = symbol.toString();
                        i++;
                }
                return stateStrings;
        }
        
        public Set<? extends Event<?>> getEvents() {
                return trie.getKnownSymbols();
        }
        
        public Set<List<? extends Event<?>>> generateSequences(int length) {
                Set<List<? extends Event<?>>> sequenceSet = new LinkedHashSet<List<? extends Event<?>>>();;
                if( length<1 ) {
                        throw new InvalidParameterException("Length of generated subsequences must be at least 1.");
                }
                if( length==1 ) {
                        for( Event<?> event : getEvents() ) {
                                List<Event<?>> subSeq = new LinkedList<Event<?>>();
                                subSeq.add(event);
                                sequenceSet.add(subSeq);
                        }
                        return sequenceSet;
                }
                Set<? extends Event<?>> events = getEvents();
                Set<List<? extends Event<?>>> seqsShorter = generateSequences(length-1);
                for( Event<?> event : events ) {
                        for( List<? extends Event<?>> seqShorter : seqsShorter ) {
                                Event<?> lastEvent = event;
                                if( getProbability(seqShorter, lastEvent)>0.0 ) {
                                        List<Event<?>> subSeq = new ArrayList<Event<?>>(seqShorter);
                                        subSeq.add(lastEvent);
                                        sequenceSet.add(subSeq);
                                }
                        }
                }
                return sequenceSet;
        }

}