001 /*
002 * Java Genetic Algorithm Library (jenetics-4.2.0).
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 final ISeq<? extends Op<A>> _operations;
063 private final ISeq<? extends Op<A>> _terminals;
064
065 ProgramGene(
066 final Op<A> op,
067 final int childOffset,
068 final ISeq<? extends Op<A>> operations,
069 final ISeq<? extends Op<A>> terminals
070 ) {
071 super(requireNonNull(get(op)), childOffset, op.arity());
072 _operations = requireNonNull(operations);
073 _terminals = requireNonNull(terminals);
074 }
075
076 private static <A> Op<A> get(final Op<A> op) {
077 final Op<A> instance = op.get();
078 if (instance != op && instance.arity() != op.arity()) {
079 throw new IllegalArgumentException(format(
080 "Original op and created op have different arity: %d != %d,",
081 instance.arity(), op.arity()
082 ));
083 }
084 return instance;
085 }
086
087 /**
088 * Evaluates this program gene (recursively) with the given variable values.
089 *
090 * @see ProgramGene#eval(Object[])
091 * @see ProgramChromosome#eval(Object[])
092 *
093 * @param args the input variables
094 * @return the evaluated value
095 * @throws NullPointerException if the given variable array is {@code null}
096 */
097 @Override
098 public A apply(final A[] args) {
099 checkTreeState();
100 return Program.eval(this, args);
101 }
102
103 /**
104 * Convenient method, which lets you apply the program function without
105 * explicitly create a wrapper array.
106 *
107 * @see ProgramGene#apply(Object[])
108 * @see ProgramChromosome#eval(Object[])
109 *
110 * @param args the function arguments
111 * @return the evaluated value
112 * @throws NullPointerException if the given variable array is {@code null}
113 */
114 @SafeVarargs
115 public final A eval(final A... args) {
116 return apply(args);
117 }
118
119 /**
120 * Return the allowed operations.
121 *
122 * @return the allowed operations
123 */
124 public ISeq<? extends Op<A>> getOperations() {
125 return _operations;
126 }
127
128 /**
129 * Return the allowed terminal operations.
130 *
131 * @return the allowed terminal operations
132 */
133 public ISeq<? extends Op<A>> getTerminals() {
134 return _terminals;
135 }
136
137 @Override
138 public ProgramGene<A> newInstance() {
139 final Random random = RandomRegistry.getRandom();
140
141 Op<A> operation = getValue();
142 if (isLeaf()) {
143 operation = _terminals.get(random.nextInt(_terminals.length()));
144 } else {
145 final ISeq<Op<A>> operations = _operations.stream()
146 .filter(op -> op.arity() == getValue().arity())
147 .map(op -> (Op<A>)op)
148 .collect(ISeq.toISeq());
149
150 if (operations.length() > 1) {
151 operation = operations.get(random.nextInt(operations.length()));
152 }
153 }
154
155 return newInstance(operation);
156 }
157
158 /**
159 * Create a new program gene with the given operation.
160 *
161 * @param op the operation of the new program gene
162 * @return a new program gene with the given operation
163 * @throws NullPointerException if the given {@code op} is {@code null}
164 * @throws IllegalArgumentException if the arity of the given operation is
165 * different from the arity of current operation. This restriction
166 * ensures that only valid program genes are created by this method.
167 */
168 @Override
169 public ProgramGene<A> newInstance(final Op<A> op) {
170 if (getValue().arity() != op.arity()) {
171 throw new IllegalArgumentException(format(
172 "New operation must have same arity: %s[%d] != %s[%d]",
173 getValue().name(), getValue().arity(), op.name(), op.arity()
174 ));
175 }
176 return new ProgramGene<>(op, childOffset(), _operations, _terminals);
177 }
178
179 /**
180 * Return a new program gene with the given operation and the <em>local</em>
181 * tree structure.
182 *
183 * @param op the new operation
184 * @param childOffset the offset of the first node child within the
185 * chromosome
186 * @param childCount the number of children of the new tree gene
187 * @return a new tree gene with the given parameters
188 * @throws IllegalArgumentException if the {@code childCount} is smaller
189 * than zero
190 * @throws IllegalArgumentException if the operation arity is different from
191 * the {@code childCount}.
192 * @throws NullPointerException if the given {@code op} is {@code null}
193 */
194 @Override
195 public ProgramGene<A> newInstance(
196 final Op<A> op,
197 final int childOffset,
198 final int childCount
199 ) {
200 if (op.arity() != childCount) {
201 throw new IllegalArgumentException(format(
202 "Operation arity and child count are different: %d, != %d",
203 op.arity(), childCount
204 ));
205 }
206
207 return new ProgramGene<>(op, childOffset, _operations, _terminals);
208 }
209
210 }
|