1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.math3.optimization.direct;
19
20 import org.apache.commons.math3.analysis.MultivariateFunction;
21 import org.apache.commons.math3.analysis.UnivariateFunction;
22 import org.apache.commons.math3.analysis.function.Logit;
23 import org.apache.commons.math3.analysis.function.Sigmoid;
24 import org.apache.commons.math3.exception.DimensionMismatchException;
25 import org.apache.commons.math3.exception.NumberIsTooSmallException;
26 import org.apache.commons.math3.util.FastMath;
27 import org.apache.commons.math3.util.MathUtils;
28
29 /**
30 * <p>Adapter for mapping bounded {@link MultivariateFunction} to unbounded ones.</p>
31 *
32 * <p>
33 * This adapter can be used to wrap functions subject to simple bounds on
34 * parameters so they can be used by optimizers that do <em>not</em> directly
35 * support simple bounds.
36 * </p>
37 * <p>
38 * The principle is that the user function that will be wrapped will see its
39 * parameters bounded as required, i.e when its {@code value} method is called
40 * with argument array {@code point}, the elements array will fulfill requirement
41 * {@code lower[i] <= point[i] <= upper[i]} for all i. Some of the components
42 * may be unbounded or bounded only on one side if the corresponding bound is
43 * set to an infinite value. The optimizer will not manage the user function by
44 * itself, but it will handle this adapter and it is this adapter that will take
45 * care the bounds are fulfilled. The adapter {@link #value(double[])} method will
46 * be called by the optimizer with unbound parameters, and the adapter will map
47 * the unbounded value to the bounded range using appropriate functions like
48 * {@link Sigmoid} for double bounded elements for example.
49 * </p>
50 * <p>
51 * As the optimizer sees only unbounded parameters, it should be noted that the
52 * start point or simplex expected by the optimizer should be unbounded, so the
53 * user is responsible for converting his bounded point to unbounded by calling
54 * {@link #boundedToUnbounded(double[])} before providing them to the optimizer.
55 * For the same reason, the point returned by the {@link
56 * org.apache.commons.math3.optimization.BaseMultivariateOptimizer#optimize(int,
57 * MultivariateFunction, org.apache.commons.math3.optimization.GoalType, double[])}
58 * method is unbounded. So to convert this point to bounded, users must call
59 * {@link #unboundedToBounded(double[])} by themselves!</p>
60 * <p>
61 * This adapter is only a poor man solution to simple bounds optimization constraints
62 * that can be used with simple optimizers like {@link SimplexOptimizer} with {@link
63 * NelderMeadSimplex} or {@link MultiDirectionalSimplex}. A better solution is to use
64 * an optimizer that directly supports simple bounds like {@link CMAESOptimizer} or
65 * {@link BOBYQAOptimizer}. One caveat of this poor man solution is that behavior near
66 * the bounds may be numerically unstable as bounds are mapped from infinite values.
67 * Another caveat is that convergence values are evaluated by the optimizer with respect
68 * to unbounded variables, so there will be scales differences when converted to bounded
69 * variables.
70 * </p>
71 *
72 * @see MultivariateFunctionPenaltyAdapter
73 *
74 * @version $Id: MultivariateFunctionMappingAdapter.java 1422230 2012-12-15 12:11:13Z erans $
75 * @deprecated As of 3.1 (to be removed in 4.0).
76 * @since 3.0
77 */
78
79 @Deprecated
80 public class MultivariateFunctionMappingAdapter implements MultivariateFunction {
81
82 /** Underlying bounded function. */
83 private final MultivariateFunction bounded;
84
85 /** Mapping functions. */
86 private final Mapper[] mappers;
87
88 /** Simple constructor.
89 * @param bounded bounded function
90 * @param lower lower bounds for each element of the input parameters array
91 * (some elements may be set to {@code Double.NEGATIVE_INFINITY} for
92 * unbounded values)
93 * @param upper upper bounds for each element of the input parameters array
94 * (some elements may be set to {@code Double.POSITIVE_INFINITY} for
95 * unbounded values)
96 * @exception DimensionMismatchException if lower and upper bounds are not
97 * consistent, either according to dimension or to values
98 */
99 public MultivariateFunctionMappingAdapter(final MultivariateFunction bounded,
100 final double[] lower, final double[] upper) {
101
102 // safety checks
103 MathUtils.checkNotNull(lower);
104 MathUtils.checkNotNull(upper);
105 if (lower.length != upper.length) {
106 throw new DimensionMismatchException(lower.length, upper.length);
107 }
108 for (int i = 0; i < lower.length; ++i) {
109 // note the following test is written in such a way it also fails for NaN
110 if (!(upper[i] >= lower[i])) {
111 throw new NumberIsTooSmallException(upper[i], lower[i], true);
112 }
113 }
114
115 this.bounded = bounded;
116 this.mappers = new Mapper[lower.length];
117 for (int i = 0; i < mappers.length; ++i) {
118 if (Double.isInfinite(lower[i])) {
119 if (Double.isInfinite(upper[i])) {
120 // element is unbounded, no transformation is needed
121 mappers[i] = new NoBoundsMapper();
122 } else {
123 // element is simple-bounded on the upper side
124 mappers[i] = new UpperBoundMapper(upper[i]);
125 }
126 } else {
127 if (Double.isInfinite(upper[i])) {
128 // element is simple-bounded on the lower side
129 mappers[i] = new LowerBoundMapper(lower[i]);
130 } else {
131 // element is double-bounded
132 mappers[i] = new LowerUpperBoundMapper(lower[i], upper[i]);
133 }
134 }
135 }
136
137 }
138
139 /** Map an array from unbounded to bounded.
140 * @param point unbounded value
141 * @return bounded value
142 */
143 public double[] unboundedToBounded(double[] point) {
144
145 // map unbounded input point to bounded point
146 final double[] mapped = new double[mappers.length];
147 for (int i = 0; i < mappers.length; ++i) {
148 mapped[i] = mappers[i].unboundedToBounded(point[i]);
149 }
150
151 return mapped;
152
153 }
154
155 /** Map an array from bounded to unbounded.
156 * @param point bounded value
157 * @return unbounded value
158 */
159 public double[] boundedToUnbounded(double[] point) {
160
161 // map bounded input point to unbounded point
162 final double[] mapped = new double[mappers.length];
163 for (int i = 0; i < mappers.length; ++i) {
164 mapped[i] = mappers[i].boundedToUnbounded(point[i]);
165 }
166
167 return mapped;
168
169 }
170
171 /** Compute the underlying function value from an unbounded point.
172 * <p>
173 * This method simply bounds the unbounded point using the mappings
174 * set up at construction and calls the underlying function using
175 * the bounded point.
176 * </p>
177 * @param point unbounded value
178 * @return underlying function value
179 * @see #unboundedToBounded(double[])
180 */
181 public double value(double[] point) {
182 return bounded.value(unboundedToBounded(point));
183 }
184
185 /** Mapping interface. */
186 private interface Mapper {
187
188 /** Map a value from unbounded to bounded.
189 * @param y unbounded value
190 * @return bounded value
191 */
192 double unboundedToBounded(double y);
193
194 /** Map a value from bounded to unbounded.
195 * @param x bounded value
196 * @return unbounded value
197 */
198 double boundedToUnbounded(double x);
199
200 }
201
202 /** Local class for no bounds mapping. */
203 private static class NoBoundsMapper implements Mapper {
204
205 /** Simple constructor.
206 */
207 public NoBoundsMapper() {
208 }
209
210 /** {@inheritDoc} */
211 public double unboundedToBounded(final double y) {
212 return y;
213 }
214
215 /** {@inheritDoc} */
216 public double boundedToUnbounded(final double x) {
217 return x;
218 }
219
220 }
221
222 /** Local class for lower bounds mapping. */
223 private static class LowerBoundMapper implements Mapper {
224
225 /** Low bound. */
226 private final double lower;
227
228 /** Simple constructor.
229 * @param lower lower bound
230 */
231 public LowerBoundMapper(final double lower) {
232 this.lower = lower;
233 }
234
235 /** {@inheritDoc} */
236 public double unboundedToBounded(final double y) {
237 return lower + FastMath.exp(y);
238 }
239
240 /** {@inheritDoc} */
241 public double boundedToUnbounded(final double x) {
242 return FastMath.log(x - lower);
243 }
244
245 }
246
247 /** Local class for upper bounds mapping. */
248 private static class UpperBoundMapper implements Mapper {
249
250 /** Upper bound. */
251 private final double upper;
252
253 /** Simple constructor.
254 * @param upper upper bound
255 */
256 public UpperBoundMapper(final double upper) {
257 this.upper = upper;
258 }
259
260 /** {@inheritDoc} */
261 public double unboundedToBounded(final double y) {
262 return upper - FastMath.exp(-y);
263 }
264
265 /** {@inheritDoc} */
266 public double boundedToUnbounded(final double x) {
267 return -FastMath.log(upper - x);
268 }
269
270 }
271
272 /** Local class for lower and bounds mapping. */
273 private static class LowerUpperBoundMapper implements Mapper {
274
275 /** Function from unbounded to bounded. */
276 private final UnivariateFunction boundingFunction;
277
278 /** Function from bounded to unbounded. */
279 private final UnivariateFunction unboundingFunction;
280
281 /** Simple constructor.
282 * @param lower lower bound
283 * @param upper upper bound
284 */
285 public LowerUpperBoundMapper(final double lower, final double upper) {
286 boundingFunction = new Sigmoid(lower, upper);
287 unboundingFunction = new Logit(lower, upper);
288 }
289
290 /** {@inheritDoc} */
291 public double unboundedToBounded(final double y) {
292 return boundingFunction.value(y);
293 }
294
295 /** {@inheritDoc} */
296 public double boundedToUnbounded(final double x) {
297 return unboundingFunction.value(x);
298 }
299
300 }
301
302 }