source: boa/src/main/java/geniusweb/boa/biddingstrategy/ExtendedUtilSpace.java

package geniusweb.boa.biddingstrategy;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Collections;
import java.util.LinkedList;

import geniusweb.bidspace.BidsWithUtility;
import geniusweb.bidspace.Interval;
import geniusweb.bidspace.IssueInfo;
import geniusweb.issuevalue.Bid;
import geniusweb.issuevalue.Value;
import geniusweb.profile.utilityspace.LinearAdditive;
import tudelft.utilities.immutablelist.ImmutableList;

/**
 * Inner class for TimeDependentParty, made public for testing purposes. This
 * class may change in the future, use at your own risk. Copy of
 * geniusweb.exampleparties.timedependentparty
 *
 */
public class ExtendedUtilSpace {
        private LinearAdditive utilspace;
        private BigDecimal tolerance; // utility tolerance for a bid.
        private BidsWithUtility bidutils;
        // min and max achievable utility
        private BigDecimal minUtil;
        private BigDecimal maxUtil;

        public ExtendedUtilSpace(LinearAdditive space) {
                this.utilspace = space;
                bidutils = new BidsWithUtility(utilspace);
                computeMinMax();
                this.tolerance = computeTolerance();

        }

        /**
         * Computes the fields minutil and maxUtil.
         * <p>
         * TODO this is simplistic, very expensive method and may cause us to run
         * out of time on large domains.
         * <p>
         * Assumes that utilspace and bidutils have been set properly.
         */
        private void computeMinMax() {
                Interval range = bidutils.getRange();
                this.minUtil = range.getMin();
                this.maxUtil = range.getMax();

                Bid rvbid = utilspace.getReservationBid();
                if (rvbid != null) {
                        BigDecimal rv = utilspace.getUtility(rvbid);
                        if (rv.compareTo(minUtil) > 0)
                                minUtil = rv;
                }
        }

        /**
         * Tolerance is the Interval we need when searching bids. When we are close
         * to the maximum utility, this value has to be the distance between the
         * best and one-but-best utility.
         * 
         * @return the minimum tolerance required, which is the minimum difference
         *         between the weighted utility of the best and one-but-best issue
         *         value.
         */
        protected BigDecimal computeTolerance() {
                BigDecimal tolerance = BigDecimal.ONE;
                for (IssueInfo iss : bidutils.getInfo()) {
                        if (iss.getValues().size().compareTo(BigInteger.ONE) > 0) {
                                // we have at least 2 values.
                                LinkedList<BigDecimal> values = new LinkedList<BigDecimal>();
                                for (Value val : iss.getValues()) {
                                        values.add(iss.getWeightedUtil(val));
                                }
                                Collections.sort(values);
                                Collections.reverse(values);
                                tolerance = tolerance
                                                .min(values.get(0).subtract(values.get(1)));
                        }
                }
                return tolerance;
        }

        public BigDecimal getMin() {
                return minUtil;
        }

        public BigDecimal getMax() {
                return maxUtil;
        }

        /**
         * @param utilityGoal the intended utilty
         * @return bids with utility inside [utilitygoal-tolerance, utilitygoal]
         */
        public ImmutableList<Bid> getBids(BigDecimal utilityGoal) {
                return bidutils.getBids(
                                new Interval(utilityGoal.subtract(tolerance), utilityGoal));
        }

}