    001package net.sf.cpsolver.ifs.example.csp;
    002
    003import java.util.ArrayList;
    004import java.util.List;
    005import java.util.Map;
    006import java.util.Random;
    007
    008import net.sf.cpsolver.ifs.model.Constraint;
    009import net.sf.cpsolver.ifs.model.Model;
    010import net.sf.cpsolver.ifs.util.DataProperties;
    011
    012/**
    013 * Random Binary CSP with kernels. <br>
    014 * <br>
    015 * This class only implements the generation of Structured CSP problem.<br>
    016 * In Structured CSP, variables are divided into several kernels (some variables
    017 * may remain ouside kernels). Different constraints (in density and tightnes)
    018 * are generated according to whether variables are from the same kernel or not. <br>
    019 * <br>
    020 * Model parameters: <br>
    021 * <table border='1'>
    022 * <tr>
    023 * <th>Parameter</th>
    024 * <th>Type</th>
    025 * <th>Comment</th>
    026 * </tr>
    027 * <tr>
    028 * <td>CSP.NrVariables</td>
    029 * <td>{@link Integer}</td>
    030 * <td>Number of variables</td>
    031 * </tr>
    032 * <tr>
    033 * <td>CSP.DomainSize</td>
    034 * <td>{@link Integer}</td>
    035 * <td>Number of values for each variable</td>
    036 * </tr>
    037 * <tr>
    038 * <td>CSP.NrKernels</td>
    039 * <td>{@link Integer}</td>
    040 * <td>Number of kernels</td>
    041 * </tr>
    042 * <tr>
    043 * <td>CSP.KernelSize</td>
    044 * <td>{@link Integer}</td>
    045 * <td>Number of variables in each kernel</td>
    046 * </tr>
    047 * <tr>
    048 * <td>CSP.Tightness</td>
    049 * <td>{@link Double}</td>
    050 * <td>Tightness of constraints outside kernels</td>
    051 * </tr>
    052 * <tr>
    053 * <td>CSP.KernelTightness</td>
    054 * <td>{@link Double}</td>
    055 * <td>Tightness of constraints inside a kernel</td>
    056 * </tr>
    057 * <tr>
    058 * <td>CSP.Density</td>
    059 * <td>{@link Double}</td>
    060 * <td>Density of constraints outside kernels</td>
    061 * </tr>
    062 * <tr>
    063 * <td>CSP.KernelDensity</td>
    064 * <td>{@link Double}</td>
    065 * <td>Density of constraints inside a kernel</td>
    066 * </tr>
    067 * <tr>
    068 * <td>General.MPP</td>
    069 * <td>{@link String}</td>
    070 * <td>Minimal perturbation problem --> generate initial assignment</td>
    071 * </tr>
    072 * </table>
    073 * <br>
    074 *
    075 * @version IFS 1.2 (Iterative Forward Search)<br>
    076 *          Copyright (C) 2006 - 2010 Tomáš Müller<br>
    077 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    078 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    079 * <br>
    080 *          This library is free software; you can redistribute it and/or modify
    081 *          it under the terms of the GNU Lesser General Public License as
    082 *          published by the Free Software Foundation; either version 3 of the
    083 *          License, or (at your option) any later version. <br>
    084 * <br>
    085 *          This library is distributed in the hope that it will be useful, but
    086 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    087 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    088 *          Lesser General Public License for more details. <br>
    089 * <br>
    090 *          You should have received a copy of the GNU Lesser General Public
    091 *          License along with this library; if not see
    092 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    093 */
    094public class StructuredCSPModel extends Model<CSPVariable, CSPValue> {
    095    private static org.apache.log4j.Logger sLogger = org.apache.log4j.Logger.getLogger(StructuredCSPModel.class);
    096    private DataProperties iProperties = null;
    097
    098    /** Constructor */
    099    public StructuredCSPModel(DataProperties properties, long seed) {
    100        iProperties = properties;
    101        generate(seed);
    102    }
    103
    104    private void swap(CSPVariable[][] allPairs, int first, int second) {
    105        CSPVariable[] a = allPairs[first];
    106        allPairs[first] = allPairs[second];
    107        allPairs[second] = a;
    108    }
    109
    110    private void buildBinaryConstraintGraph(List<CSPVariable> variables, List<CSPBinaryConstraint> constraints,
    111            Random rnd) {
    112        int numberOfAllPairs = variables.size() * (variables.size() - 1) / 2;
    113        CSPVariable[][] allPairs = new CSPVariable[numberOfAllPairs][];
    114        int idx = 0;
    115        for (CSPVariable v1 : variables) {
    116            for (CSPVariable v2 : variables) {
    117                if (v1.getId() >= v2.getId())
    118                    continue;
    119                allPairs[idx++] = new CSPVariable[] { v1, v2 };
    120            }
    121        }
    122        for (idx = 0; idx < constraints.size(); idx++) {
    123            swap(allPairs, idx, idx + (int) (rnd.nextDouble() * (numberOfAllPairs - idx)));
    124        }
    125        idx = 0;
    126        for (CSPBinaryConstraint c : constraints) {
    127            c.addVariable(allPairs[idx][0]);
    128            c.addVariable(allPairs[idx][1]);
    129            idx++;
    130        }
    131    }
    132
    133    private void buildBinaryConstraintGraph2(List<CSPVariable> variables, int numberOfAllPairs,
    134            List<CSPBinaryConstraint> constraints, Random rnd) {
    135        CSPVariable[][] allPairs = new CSPVariable[numberOfAllPairs][];
    136        int idx = 0;
    137        for (CSPVariable v1 : variables) {
    138            for (CSPVariable v2 : variables) {
    139                if (v1.getId() >= v2.getId())
    140                    continue;
    141                if (v1.getKernelId() >= 0 && v1.getKernelId() == v2.getKernelId())
    142                    continue;
    143                allPairs[idx++] = new CSPVariable[] { v1, v2 };
    144            }
    145        }
    146        for (idx = 0; idx < constraints.size(); idx++) {
    147            swap(allPairs, idx, idx + (int) (rnd.nextDouble() * (numberOfAllPairs - idx)));
    148        }
    149        idx = 0;
    150        for (CSPBinaryConstraint c : constraints) {
    151            c.addVariable(allPairs[idx][0]);
    152            c.addVariable(allPairs[idx][1]);
    153            idx++;
    154        }
    155    }
    156
    157    @SuppressWarnings("unchecked")
    158    private void generate(long seed) {
    159        int nrVariables = iProperties.getPropertyInt("CSP.NrVariables", 60);
    160        int nrValues = iProperties.getPropertyInt("CSP.DomainSize", 15);
    161        int nrKernels = iProperties.getPropertyInt("CSP.NrKernels", 2);
    162        int nrKernelVariables = iProperties.getPropertyInt("CSP.KernelSize", 8);
    163
    164        int nrPairValues = nrValues * nrValues;
    165        float tightnessPerc = iProperties.getPropertyFloat("CSP.Tightness", 0.01f);
    166        float kernelTightnessPerc = iProperties.getPropertyFloat("CSP.KernelTightness", 0.097f);
    167        int nrCompatiblePairs = (int) Math.round((1.0 - tightnessPerc) * nrPairValues);
    168        int kernelNrCompatiblePairs = (int) Math.round((1.0 - kernelTightnessPerc) * nrPairValues);
    169
    170        int nrPairVariables = (nrVariables * (nrVariables - 1)) / 2;
    171        int nrPairKernelVariables = (nrKernelVariables * (nrKernelVariables - 1)) / 2;
    172        nrPairVariables -= nrKernels * nrPairKernelVariables;
    173        float densityPerc = iProperties.getPropertyFloat("CSP.Density", 0.01f);
    174        float densityKernelPerc = iProperties.getPropertyFloat("CSP.KernelDensity", 0.097f);
    175        int density = Math.round(densityPerc * nrPairVariables);
    176        int kernelDensity = Math.round(densityKernelPerc * nrPairKernelVariables);
    177
    178        Random rnd = new Random(seed);
    179        List<CSPVariable> generalVariables = new ArrayList<CSPVariable>(nrVariables - (nrKernels * nrKernelVariables));
    180        int varId = 1;
    181        for (int i = 0; i < nrVariables - (nrKernels * nrKernelVariables); i++) {
    182            CSPVariable var = new CSPVariable(varId++, nrValues);
    183            generalVariables.add(var);
    184            addVariable(var);
    185        }
    186        sLogger.debug("Created " + generalVariables.size() + " general variables.");
    187        List<CSPVariable>[] kernelVariables = new ArrayList[nrKernels];
    188        for (int k = 0; k < nrKernels; k++) {
    189            kernelVariables[k] = new ArrayList<CSPVariable>(nrKernelVariables);
    190            for (int i = 0; i < nrKernelVariables; i++) {
    191                CSPVariable var = new CSPVariable(varId++, nrValues, k);
    192                kernelVariables[k].add(var);
    193                addVariable(var);
    194            }
    195            if (k == 0)
    196                sLogger.debug("Created " + kernelVariables[0].size() + " kernel variables (per kernel).");
    197        }
    198        sLogger.debug("Created " + variables().size() + " variables at total.");
    199        int constId = 1;
    200        List<CSPBinaryConstraint> generalConstraints = new ArrayList<CSPBinaryConstraint>(density);
    201        for (int i = 0; i < density; i++) {
    202            CSPBinaryConstraint c = new CSPBinaryConstraint(constId++, nrCompatiblePairs);
    203            generalConstraints.add(c);
    204            addConstraint(c);
    205        }
    206        sLogger.debug("Created " + generalConstraints.size() + " general constraints (tightness=" + tightnessPerc
    207                + ").");
    208        List<CSPBinaryConstraint>[] kernelConstraints = new List[nrKernels];
    209        for (int k = 0; k < nrKernels; k++) {
    210            kernelConstraints[k] = new ArrayList<CSPBinaryConstraint>(kernelDensity);
    211            for (int i = 0; i < kernelDensity; i++) {
    212                CSPBinaryConstraint c = new CSPBinaryConstraint(constId++, kernelNrCompatiblePairs);
    213                kernelConstraints[k].add(c);
    214                addConstraint(c);
    215            }
    216            if (k == 0)
    217                sLogger.debug("Created " + kernelConstraints[0].size() + " kernel constraints (per kernel, tightness="
    218                        + kernelTightnessPerc + ").");
    219        }
    220        sLogger.debug("Created " + constraints().size() + " constraints at total.");
    221
    222        for (int k = 0; k < nrKernels; k++) {
    223            buildBinaryConstraintGraph(kernelVariables[k], kernelConstraints[k], rnd);
    224        }
    225        buildBinaryConstraintGraph2(variables(), nrPairVariables, generalConstraints, rnd);
    226
    227        for (Constraint<CSPVariable, CSPValue> c : constraints()) {
    228            CSPBinaryConstraint constraint = (CSPBinaryConstraint) c;
    229            constraint.init(rnd);
    230        }
    231
    232        if (iProperties.getPropertyBoolean("General.MPP", false)) {
    233            for (CSPVariable variable : variables()) {
    234                variable.generateInitialValue(rnd);
    235            }
    236        }
    237    }
    238
    239    /** Return information table */
    240    @Override
    241    public Map<String, String> getInfo() {
    242        Map<String, String> ret = super.getInfo();
    243        ret.put("Solution value", String.valueOf(getTotalValue()));
    244        return ret;
    245    }
    246}