source: src/main/java/agents/anac/y2010/Yushu/Utility.java@ 126

package agents.anac.y2010.Yushu;

import java.util.HashMap;
import java.util.List;
import java.util.Random;

import genius.core.Agent;
import genius.core.Bid;
import genius.core.actions.Accept;
import genius.core.actions.Action;
import genius.core.actions.Offer;
import genius.core.issue.Issue;
import genius.core.issue.IssueDiscrete;
import genius.core.issue.IssueInteger;
import genius.core.issue.IssueReal;
import genius.core.issue.Value;
import genius.core.issue.ValueInteger;
import genius.core.issue.ValueReal;
import genius.core.utility.AdditiveUtilitySpace;

public class Utility {
        static double MINIMUM_BID_UTILITY = 0.95;

        /**
         * Wrapper for getRandomBid, for convenience.
         * 
         * @param lastOppBid
         *            the last opponent bid that was received.
         * @return new Action(Bid(..)), with bid utility > MINIMUM_BID_UTIL. If a
         *         problem occurs, it returns an Accept() action.
         */
        public static Action chooseRandomBidAction(Agent agent, Bid lastOppBid) {
                Bid nextBid = null;
                try {
                        nextBid = Utility
                                        .getRandomBid((AdditiveUtilitySpace) agent.utilitySpace);
                } catch (Exception e) {
                        e.printStackTrace();
                }
                if (nextBid == null)
                        return (new Accept(agent.getAgentID(), lastOppBid));
                return (new Offer(agent.getAgentID(), nextBid));
        }

        /**
         * @return a random bid with high enough utility value.
         * @throws Exception
         *             if we can't compute the utility (eg no evaluators have been
         *             set) or when other evaluators than a DiscreteEvaluator are
         *             present in the util space.
         */
        public static Bid getRandomBid(AdditiveUtilitySpace utilityspace)
                        throws Exception {
                HashMap<Integer, Value> values = new HashMap<Integer, Value>(); // pairs
                                                                                                                                                // <issuenumber,chosen
                                                                                                                                                // value
                                                                                                                                                // string>
                List<Issue> issues = utilityspace.getDomain().getIssues();
                Random randomnr = new Random();
                // createFrom a random bid with utility>MINIMUM_BID_UTIL.
                // note that this may never succeed if you set MINIMUM too high!!!
                // in that case we will search for a bid till the time is up (2 minutes)
                // but this is just a simple agent.
                Bid bid = null;
                do {

                        for (Issue lIssue : issues) {
                                switch (lIssue.getType()) {
                                case DISCRETE:
                                        IssueDiscrete lIssueDiscrete = (IssueDiscrete) lIssue;
                                        int optionIndex = randomnr.nextInt(lIssueDiscrete
                                                        .getNumberOfValues());
                                        values.put(lIssue.getNumber(),
                                                        lIssueDiscrete.getValue(optionIndex));
                                        break;
                                case REAL:
                                        IssueReal lIssueReal = (IssueReal) lIssue;
                                        int optionInd = randomnr.nextInt(lIssueReal
                                                        .getNumberOfDiscretizationSteps() - 1);
                                        values.put(
                                                        lIssueReal.getNumber(),
                                                        new ValueReal(lIssueReal.getLowerBound()
                                                                        + (lIssueReal.getUpperBound() - lIssueReal
                                                                                        .getLowerBound())
                                                                        * (double) (optionInd)
                                                                        / (double) (lIssueReal
                                                                                        .getNumberOfDiscretizationSteps())));
                                        break;
                                case INTEGER:
                                        IssueInteger lIssueInteger = (IssueInteger) lIssue;
                                        int optionIndex2 = lIssueInteger.getLowerBound()
                                                        + randomnr.nextInt(lIssueInteger.getUpperBound()
                                                                        - lIssueInteger.getLowerBound());
                                        values.put(lIssueInteger.getNumber(), new ValueInteger(
                                                        optionIndex2));
                                        break;
                                default:
                                        throw new Exception("issue type " + lIssue.getType()
                                                        + " not supported by SimpleAgent2");
                                }
                        }
                        bid = new Bid(utilityspace.getDomain(), values);
                } while (utilityspace.getUtility(bid) < MINIMUM_BID_UTILITY);

                return bid;
        }

        /**
         * This function determines the accept probability for an offer. At t=0 it
         * will prefer high-utility offers. As t gets closer to 1, it will accept
         * lower utility offers with increasing probability. it will never accept
         * offers with utility 0.
         * 
         * @param u
         *            is the utility
         * @param t
         *            is the time as fraction of the total available time (t=0 at
         *            start, and t=1 at end time)
         * @return the probability of an accept at time t
         * @throws Exception
         *             if you use wrong values for u or t.
         * 
         */
        public static double Paccept(double u, double t1) throws Exception {
                double t = t1 * t1 * t1; // steeper increase when deadline approaches.
                if (u < 0 || u > 1.05)
                        throw new Exception("utility " + u + " outside [0,1]");
                // normalization may be slightly off, therefore we have a broad boundary
                // up to 1.05
                if (t < 0 || t > 1)
                        throw new Exception("time " + t + " outside [0,1]");
                if (u > 1.)
                        u = 1;
                if (t == 0.5)
                        return u;
                return (u - 2. * u * t + 2. * (-1. + t + Math.sqrt(sq(-1. + t) + u
                                * (-1. + 2 * t))))
                                / (-1. + 2 * t);
        }

        public static double sq(double x) {
                return x * x;
        }

}