001 /*
002 * Java Genetic Algorithm Library (jenetics-4.3.0).
003 * Copyright (c) 2007-2018 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 * Author:
018 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
019 */
020 package io.jenetics.prog;
021
022 import static java.lang.String.format;
023 import static java.util.Objects.requireNonNull;
024
025 import java.util.Random;
026 import java.util.function.Function;
027
028 import io.jenetics.Gene;
029 import io.jenetics.util.ISeq;
030 import io.jenetics.util.RandomRegistry;
031
032 import io.jenetics.ext.AbstractTreeGene;
033
034 import io.jenetics.prog.op.Op;
035 import io.jenetics.prog.op.Program;
036
037 /**
038 * This gene represents a program, build upon an AST of {@link Op} functions.
039 * Because of the tight coupling with the {@link ProgramChromosome}, a
040 * {@code ProgramGene} can't be created directly. This reduces the the possible
041 * <em>error space</em>. Since the {@code ProgramGene} also is a {@code Tree},
042 * it can be easily used as result.
043 *
044 * <pre>{@code
045 * final ProgramGene<Double> program = engine.stream()
046 * .limit(300)
047 * .collect(EvolutionResult.toBestGenotype())
048 * .getGene();
049 *
050 * final double result = program.eval(3.4);
051 * }</pre>
052 *
053 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
054 * @version 3.9
055 * @since 3.9
056 */
057 public final class ProgramGene<A>
058 extends AbstractTreeGene<Op<A>, ProgramGene<A>>
059 implements Gene<Op<A>, ProgramGene<A>>, Function<A[], A>
060 {
061
062 private static final long serialVersionUID = 1L;
063
064 private final ISeq<? extends Op<A>> _operations;
065 private final ISeq<? extends Op<A>> _terminals;
066
067 ProgramGene(
068 final Op<A> op,
069 final int childOffset,
070 final ISeq<? extends Op<A>> operations,
071 final ISeq<? extends Op<A>> terminals
072 ) {
073 super(requireNonNull(get(op)), childOffset, op.arity());
074 _operations = requireNonNull(operations);
075 _terminals = requireNonNull(terminals);
076 }
077
078 private static <A> Op<A> get(final Op<A> op) {
079 final Op<A> instance = op.get();
080 if (instance != op && instance.arity() != op.arity()) {
081 throw new IllegalArgumentException(format(
082 "Original op and created op have different arity: %d != %d,",
083 instance.arity(), op.arity()
084 ));
085 }
086 return instance;
087 }
088
089 /**
090 * Evaluates this program gene (recursively) with the given variable values.
091 *
092 * @see ProgramGene#eval(Object[])
093 * @see ProgramChromosome#eval(Object[])
094 *
095 * @param args the input variables
096 * @return the evaluated value
097 * @throws NullPointerException if the given variable array is {@code null}
098 */
099 @Override
100 public A apply(final A[] args) {
101 checkTreeState();
102 return Program.eval(this, args);
103 }
104
105 /**
106 * Convenient method, which lets you apply the program function without
107 * explicitly create a wrapper array.
108 *
109 * @see ProgramGene#apply(Object[])
110 * @see ProgramChromosome#eval(Object[])
111 *
112 * @param args the function arguments
113 * @return the evaluated value
114 * @throws NullPointerException if the given variable array is {@code null}
115 */
116 @SafeVarargs
117 public final A eval(final A... args) {
118 return apply(args);
119 }
120
121 /**
122 * Return the allowed operations.
123 *
124 * @return the allowed operations
125 */
126 public ISeq<? extends Op<A>> getOperations() {
127 return _operations;
128 }
129
130 /**
131 * Return the allowed terminal operations.
132 *
133 * @return the allowed terminal operations
134 */
135 public ISeq<? extends Op<A>> getTerminals() {
136 return _terminals;
137 }
138
139 @Override
140 public ProgramGene<A> newInstance() {
141 final Random random = RandomRegistry.getRandom();
142
143 Op<A> operation = getValue();
144 if (isLeaf()) {
145 operation = _terminals.get(random.nextInt(_terminals.length()));
146 } else {
147 final ISeq<Op<A>> operations = _operations.stream()
148 .filter(op -> op.arity() == getValue().arity())
149 .map(op -> (Op<A>)op)
150 .collect(ISeq.toISeq());
151
152 if (operations.length() > 1) {
153 operation = operations.get(random.nextInt(operations.length()));
154 }
155 }
156
157 return newInstance(operation);
158 }
159
160 /**
161 * Create a new program gene with the given operation.
162 *
163 * @param op the operation of the new program gene
164 * @return a new program gene with the given operation
165 * @throws NullPointerException if the given {@code op} is {@code null}
166 * @throws IllegalArgumentException if the arity of the given operation is
167 * different from the arity of current operation. This restriction
168 * ensures that only valid program genes are created by this method.
169 */
170 @Override
171 public ProgramGene<A> newInstance(final Op<A> op) {
172 if (getValue().arity() != op.arity()) {
173 throw new IllegalArgumentException(format(
174 "New operation must have same arity: %s[%d] != %s[%d]",
175 getValue().name(), getValue().arity(), op.name(), op.arity()
176 ));
177 }
178 return new ProgramGene<>(op, childOffset(), _operations, _terminals);
179 }
180
181 /**
182 * Return a new program gene with the given operation and the <em>local</em>
183 * tree structure.
184 *
185 * @param op the new operation
186 * @param childOffset the offset of the first node child within the
187 * chromosome
188 * @param childCount the number of children of the new tree gene
189 * @return a new tree gene with the given parameters
190 * @throws IllegalArgumentException if the {@code childCount} is smaller
191 * than zero
192 * @throws IllegalArgumentException if the operation arity is different from
193 * the {@code childCount}.
194 * @throws NullPointerException if the given {@code op} is {@code null}
195 */
196 @Override
197 public ProgramGene<A> newInstance(
198 final Op<A> op,
199 final int childOffset,
200 final int childCount
201 ) {
202 if (op.arity() != childCount) {
203 throw new IllegalArgumentException(format(
204 "Operation arity and child count are different: %d, != %d",
205 op.arity(), childCount
206 ));
207 }
208
209 return new ProgramGene<>(op, childOffset, _operations, _terminals);
210 }
211
212 }
|