source: src/main/java/bargainingchips/players/TimeDependentNegotiationAgent.java@ 325

package bargainingchips.players;

import static java.lang.Math.pow;

import java.util.concurrent.BlockingQueue;

import bargainingchips.Bundle;
import bargainingchips.NegotiationContext;
import bargainingchips.OutcomeSpace;
import bargainingchips.actions.Accept;
import bargainingchips.actions.Bid;
import bargainingchips.actions.Offer;
import bargainingchips.actions.OfferBy;
import bargainingchips.utilityfunctions.UtilityFunction;
import genius.core.protocol.MultilateralProtocol;

/**
 * Boulware/Conceder tactics, by Tim Baarslag, adapted from [1].
 *
 * [1] S. Shaheen Fatima Michael Wooldridge Nicholas R. Jennings Optimal
 * Negotiation Strategies for Agents with Incomplete Information
 * http://eprints.ecs.soton.ac.uk/6151/1/atal01.pdf
 */
public abstract class TimeDependentNegotiationAgent extends Agent 
{
        private Offer lastReceivedOffer = null;
        
        public TimeDependentNegotiationAgent(String name, UtilityFunction u, NegotiationContext nc,
                        BlockingQueue<Offer> in,
                        BlockingQueue<OfferBy> out,
                        BlockingQueue<CoordinationMessage> cin,
                        BlockingQueue<StatusMessage> cout) {
                super(name, u, nc, in, out, cin, cout);
        }

        /**
         * When this class is called, it is expected that the Party chooses one of
         * the actions from the possible action list and returns an instance of the
         * chosen action. This class is only called if this
         * {@link genius.core.parties.NegotiationParty} is in the
         * {@link MultilateralProtocol#getRoundStructure(java.util.List, negotiator.session.Session)}
         * .
         *
         * @param possibleActions
         *            List of all actions possible.
         * @return The chosen action
         */
        @Override
        protected Offer sendOffer()
        {
                // Nothing received yet
                if (lastReceivedOffer == null)
                        return new Bid(getNextBid());
                
                // Our last bid got accepted. We are also accepting (and we should notify the coordinator).
                if (lastReceivedOffer.isAccept())                       
                        return new Accept(lastReceivedOffer);
                
                Bundle lastReceivedBid = lastReceivedOffer.getBundle();
                Bundle nextBid = getNextBid();
                
                double lastUtil = lastReceivedBid != null ? u.getUtility(lastReceivedBid) : 0;
                double nextUtil = nextBid != null ? u.getUtility(nextBid) : 0;

                // Accept
                if (nextUtil <= lastUtil)
                        return new Accept(lastReceivedOffer);
                // Counter offer based actions
                else 
                        return new Bid(nextBid);
        }

        /**
         * Get the next bid we should do
         */
        protected Bundle getNextBid() 
        {
                OutcomeSpace outcomeSpace = negotiationContext.getOutcomeSpace();
                return outcomeSpace.getBidNearUtility(getTargetUtility(), u, this);
        }

        @Override
        protected void receiveOffer(Offer o) 
        {
                lastReceivedOffer = o;
        }

        /**
         * Gets the target utility for the next bid
         *
         * @return The target utility for the given time
         */
        private double getTargetUtility() 
        {
                // timeline runs from 0.0 to 1.0
                int totalrounds = NegotiationContext.DEADLINE;
                double time = (double) k / totalrounds;
                double target = 1d - f(time);
//              System.out.println(this + ": t = " + time + ". Target util: " + target);
                return target;
        }

        /**
         * From [1]:
         *
         * A wide range of time dependent functions can be defined by varying the
         * way in which f(t) is computed. However, functions must ensure that 0 <=
         * f(t) <= 1, f(0) = k, and f(1) = 1.
         *
         * That is, the offer will always be between the value range, at the
         * beginning it will give the initial constant and when the deadline is
         * reached, it will offer the reservation value.
         *
         * For e = 0 (special case), it will behave as a Hardliner.
         */
        private double f(double t) {
                if (getE() == 0) {
                        return 0;
                }
                return pow(t, 1 / getE());
        }

        /**
         * Depending on the value of e, extreme sets show clearly different patterns
         * of behaviour [1]:
         *
         * 1. Boulware: For this strategy e < 1 and the initial offer is maintained
         * till time is almost exhausted, when the agent concedes up to its
         * reservation value.
         *
         * 2. Conceder: For this strategy e > 1 and the agent goes to its
         * reservation value very quickly.
         *
         * 3. When e = 1, the price is increased linearly.
         *
         * 4. When e = 0, the agent plays hardball.
         */
        public abstract double getE();
        
        @Override
        protected Offer sendOpeningOffer() 
        {
                return sendOffer();
        }

        /**
         * Messaging with the coordinator can happen below
         */
        
        @Override
        protected void receiveCoordinationMessage(CoordinationMessage cpoll) 
        {
                // Update the utility function
                u = cpoll.getUtilityFunction();
        }
        
        @Override
        protected StatusMessage sendStatusMessage() 
        {
                return null;
        }
}