source: src/main/java/negotiator/parties/AbstractTimeDependentNegotiationParty.java@ 48

package negotiator.parties;

import static java.lang.Math.pow;

import java.util.List;

import genius.core.AgentID;
import genius.core.Bid;
import genius.core.actions.Accept;
import genius.core.actions.Action;
import genius.core.actions.NoAction;
import genius.core.actions.Offer;
import genius.core.actions.OfferForVoting;
import genius.core.actions.Reject;
import genius.core.boaframework.SortedOutcomeSpace;
import genius.core.parties.AbstractNegotiationParty;
import genius.core.parties.NegotiationInfo;
import genius.core.protocol.MultilateralProtocol;
import genius.core.timeline.DiscreteTimeline;

/**
 * Boulware/Conceder tactics, by Tim Baarslag, adapted from [1]. Adapted by Mark
 * Hendrikx to use the SortedOutcomeSpace instead of BidHistory. Adapted by
 * David Festen for multilateral case.
 *
 * [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
 *
 * @author David Festen, Tim Baarslag, Mark Hendrikx
 */
public abstract class AbstractTimeDependentNegotiationParty extends AbstractNegotiationParty {
        SortedOutcomeSpace outcomeSpace;
        Bid lastBid = null; // last RECEIVED bid

        @Override
        public void init(NegotiationInfo info) 
        {
                super.init(info);
                outcomeSpace = new SortedOutcomeSpace(getUtilitySpace());
        }

        /**
         * 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
        public Action chooseAction(List<Class<? extends Action>> possibleActions) {
                Bid nextBid = getNextBid();
                double lastUtil = lastBid != null ? utilitySpace.getUtilityWithDiscount(lastBid, timeline) : 0;
                double nextUtil = nextBid != null ? utilitySpace.getUtilityWithDiscount(nextBid, timeline) : 0;

                // Accept is for both voting and counter offer protocols
                if (possibleActions.contains(Accept.class) && nextUtil < lastUtil)
                        return new Accept(getPartyId(), lastBid);

                // Counter offer based actions
                else if (possibleActions.contains(Offer.class))
                        return new Offer(getPartyId(), nextBid);

                // Voting based actions
                else if (possibleActions.contains(OfferForVoting.class))
                        return new OfferForVoting(getPartyId(), nextBid);
                else if (possibleActions.contains(Reject.class))
                        return new Reject(getPartyId(), lastBid); // Accept is higher up the
                                                                                                                // chain

                // default action
                else
                        return new NoAction(getPartyId());
        }

        /**
         * Get the next bid we should do
         */
        protected Bid getNextBid() {
                return outcomeSpace.getBidNearUtility(getTargetUtility()).getBid();
        }

        /**
         * This method is called when an observable action is performed. Observable
         * actions are defined in
         * {@link MultilateralProtocol#getActionListeners(java.util.List)}
         *
         * @param sender
         *            The initiator of the action
         * @param arguments
         *            The action performed
         */
        @Override
        public void receiveMessage(AgentID sender, Action arguments) {
                if (arguments instanceof Offer)
                        lastBid = ((Offer) arguments).getBid();
        }

        /**
         * Gets the target utility for the next bid
         *
         * @return The target utility for the given time
         */
        public double getTargetUtility() {

                // timeline runs from 0.0 to 1.0

                // we have a slight offset because discrete timeline is 1-based, this
                // needs to be addressed
                double offset = timeline instanceof DiscreteTimeline ? 1d / ((DiscreteTimeline) timeline).getTotalRounds() : 0d;
                return 1d - f(timeline.getTime() - offset);
        }

        /**
         * 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.
         */
        public 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();
}