source: src/main/java/negotiator/boaframework/omstrategy/OfferBestN.java@ 209

package negotiator.boaframework.omstrategy;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.Set;

import genius.core.Bid;
import genius.core.bidding.BidDetails;
import genius.core.bidding.BidDetailsSorterUtility;
import genius.core.boaframework.BOAparameter;
import genius.core.boaframework.NegotiationSession;
import genius.core.boaframework.OMStrategy;
import genius.core.boaframework.OpponentModel;

/**
 * This class uses an opponent model to determine the next bid for the opponent,
 * while taking the opponent's preferences into account. The opponent model is
 * used to select the N best bids. Following, a random bid is selected from this
 * subset. Setting N > 1 is rational, as opponent models cannot be assumed to be
 * perfect.
 * 
 * Due to performance reasons, it is recommended to use BestBid if N = 1.
 * 
 * @author Mark Hendrikx
 */
public class OfferBestN extends OMStrategy {

        private Random rand;
        /** parameter which determines which n best bids should be considered */
        private int bestN;
        /** used to sort the opponent's bid with regard to utility */
        private BidDetailsSorterUtility comp = new BidDetailsSorterUtility();
        /** when to stop updating */
        double updateThreshold = 1.1;

        /**
         * Initializes the agent by storing the size of the domain, and checking if
         * the domain is large.
         * 
         * @param negotiationSession
         *            state of the negotiation.
         * @param model
         *            opponent model used in conjunction with this opponent modeling
         *            strategy.
         * @param parameters
         *            set of parameters for this opponent model strategy.
         */
        @Override
        public void init(NegotiationSession negotiationSession, OpponentModel model, Map<String, Double> parameters) {
                super.init(negotiationSession, model, parameters);
                this.negotiationSession = negotiationSession;
                this.model = model;
                if (parameters.get("n") != null) {
                        int n = parameters.get("n").intValue();
                        if (n == 1) {
                                throw new IllegalArgumentException("For \"n\"=1 use BestBid instead.");
                        }
                        initializeAgent(negotiationSession, model, n);
                } else {
                        throw new IllegalArgumentException("Constant \"n\" for amount of best bids was not set.");
                }
                if (parameters.get("t") != null) {
                        updateThreshold = parameters.get("t").doubleValue();
                } else {
                        System.out.println("OMStrategy assumed t = 1.1");
                }
        }

        private void initializeAgent(NegotiationSession negotiationSession, OpponentModel model, int n) {
                try {
                        super.init(negotiationSession, model, new HashMap<String, Double>());
                } catch (Exception e) {
                        e.printStackTrace();
                }
                this.rand = new Random();
                this.bestN = n;
        }

        /**
         * First this method determines the N best bids given the array of similarly
         * preferred bids. Next, a random bid is offered from this set.
         * 
         * @param allBids
         *            list of similarly preferred bids.
         * @return random bid from the subset of N best bids in the given set.
         */
        @Override
        public BidDetails getBid(List<BidDetails> allBids) {
                // 1. Determine the utility for the opponent for each of the bids
                ArrayList<BidDetails> oppBids = new ArrayList<BidDetails>(allBids.size());
                for (BidDetails bidDetail : allBids) {
                        Bid bid = bidDetail.getBid();
                        BidDetails newBid = new BidDetails(bid, model.getBidEvaluation(bid), negotiationSession.getTime());
                        oppBids.add(newBid);
                }

                // 2. Sort the bids on the utility for the opponent
                Collections.sort(oppBids, comp);

                // 3. Select a random bid from the N best bids and offer this bid
                int entry = rand.nextInt(Math.min(bestN, oppBids.size()));
                Bid opponentBestBid = oppBids.get(entry).getBid();
                BidDetails nextBid = null;
                try {
                        nextBid = new BidDetails(opponentBestBid, negotiationSession.getUtilitySpace().getUtility(opponentBestBid),
                                        negotiationSession.getTime());
                } catch (Exception e) {
                        e.printStackTrace();
                }
                return nextBid;
        }

        /**
         * Specifies that the opponent model may be updated when the current time is
         * smaller than the deadline.
         * 
         * @return true if the model may be updated
         */
        @Override
        public boolean canUpdateOM() {
                return negotiationSession.getTime() < updateThreshold;
        }

        @Override
        public Set<BOAparameter> getParameterSpec() {
                Set<BOAparameter> set = new HashSet<BOAparameter>();
                set.add(new BOAparameter("n", 3.0, "A random bid is selected from the best n bids"));
                set.add(new BOAparameter("t", 1.1, "Time after which the OM should not be updated"));
                return set;
        }

        @Override
        public String getName() {
                return "Offer Best N";
        }
}