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}