source: src/main/java/negotiator/parties/Annealer.java@ 126

package negotiator.parties;

import static java.lang.Math.E;
import static java.lang.Math.max;
import static java.lang.Math.pow;

import java.util.List;

import genius.core.AgentID;
import genius.core.DeadlineType;
import genius.core.Vote;
import genius.core.actions.Action;
import genius.core.actions.InformVotingResult;
import genius.core.actions.OfferForVoting;
import genius.core.actions.VoteForOfferAcceptance;
import genius.core.parties.AbstractNegotiationParty;
import genius.core.parties.NegotiationInfo;
import genius.core.parties.NegotiationParty;
import genius.core.protocol.MultilateralProtocol;

/**
 * Implementation of a party that uses simulated annealing strategy to get to an
 * agreement.
 * <p/>
 * This party should be run with {@link genius.core.protocol.MediatorProtocol}
 *
 * @author David Festen
 * @author Reyhan
 */
public class Annealer extends AbstractNegotiationParty {

        /**
         * Holds the utility value for the most recently accepted offer.
         */
        private double lastAcceptedBidUtility;

        /**
         * Holds the utility value for the most recently received offer.
         */
        private double lastReceivedBidUtility;

        /**
         * Holds the vote that will be done when asked for voting.
         */
        private Vote currentVote;

        /**
         * Holds the current round number (used for cooling down the annealing).
         */
        private int currentRound;

        @Override
        public void init(NegotiationInfo info) {
                super.init(info);
                lastAcceptedBidUtility = 0;
                lastReceivedBidUtility = 0;
                currentVote = Vote.REJECT;
                currentRound = 0;
        }

        /**
         * 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 NegotiationParty}
         * is in the
         * {@link negotiator.protocol .DefaultProtocol#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) {
                return new VoteForOfferAcceptance(getPartyId(), currentVote);
        }

        /**
         * 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 OfferForVoting) {
                        lastReceivedBidUtility = getUtility(((OfferForVoting) arguments).getBid());
                        if (lastReceivedBidUtility >= lastAcceptedBidUtility) {
                                currentVote = Vote.ACCEPT;
                        } else {
                                double temperature = getNormalizedRoundOrTimeValue();

                                double probability = pow(E, ((lastReceivedBidUtility - lastAcceptedBidUtility) / temperature));
                                currentVote = probability > rand.nextDouble() ? Vote.ACCEPT : Vote.REJECT;
                        }
                } else if (arguments instanceof InformVotingResult) {
                        if (((InformVotingResult) arguments).getVotingResult() == Vote.ACCEPT) {
                                lastAcceptedBidUtility = lastReceivedBidUtility;
                        }
                        currentRound++;
                }
        }

        /**
         * returns the highest of normalized time and round values
         *
         * @return a value between 0.0 and 1.0
         */
        private double getNormalizedRoundOrTimeValue() {
                // return the most urgent value
                return max(getNormalizedRoundValue(), getNormalizedTimeValue());
        }

        /**
         * Gets the normalized current round between 0.0 and 1.0
         *
         * @return A value between 0.0 and 1.0 or 0.0 if no round deadline given
         */
        private double getNormalizedRoundValue() {
                if (getDeadlines().getType() == DeadlineType.ROUND) {
                        return ((double) currentRound / (double) getDeadlines().getValue());
                } else {
                        return 0d;
                }
        }

        /**
         * Gets the normalized current time, which runs from 0.0 to 1.0
         *
         * @return A value between 0.0 and 1.0 which defaults to 0.0 if no time
         *         deadline set
         */
        private double getNormalizedTimeValue() {
                return timeline == null ? 0d : timeline.getTime();
        }

        @Override
        public String getDescription() {
                return "Annealer Party";
        }

}