001/*
002 * Java Genetic Algorithm Library (jenetics-6.1.0).
003 * Copyright (c) 2007-2020 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 */
020package io.jenetics.prog.regression;
021
022import static java.util.Objects.requireNonNull;
023
024import io.jenetics.ext.util.Tree;
025
026import io.jenetics.prog.op.Op;
027
028/**
029 * This interface represents a set of sample points, which can be evaluated with
030 * a given evolved <em>program</em>.
031 *
032 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
033 * @version 6.0
034 * @since 6.0
035 */
036@FunctionalInterface
037public interface Sampling<T> {
038
039        /**
040         * This class represents the result of a sample calculation, which contains
041         * the array of calculated values and a corresponding array with expected
042         * sample values. This two arrays can then be used for calculating the
043         * error between modeled regression function and actual sample values.
044         *
045         * @param <T> the sample result  type
046         */
047        final class Result<T> {
048                private final T[] _calculated;
049                private final T[] _expected;
050
051                private Result(final T[] calculated, final T[] expected) {
052                        _calculated = requireNonNull(calculated);
053                        _expected = requireNonNull(expected);
054                }
055
056                /**
057                 * Return the the calculated result values.
058                 *
059                 * @return the the calculated result values
060                 */
061                public T[] calculated() {
062                        return _calculated;
063                }
064
065                /**
066                 * Return the expected sample result values.
067                 *
068                 * @return the expected sample result values
069                 */
070                public T[] expected() {
071                        return _expected;
072                }
073
074                /**
075                 * Create a new sampling result object.
076                 *
077                 * @param calculated the calculated values
078                 * @param expected the expected sample values
079                 * @param <T> the sample type
080                 * @return a new sampling result object
081                 * @throws NullPointerException if one of the arguments is {@code null}
082                 */
083                public static <T> Result<T> of(final T[] calculated, final T[] expected) {
084                        return new Result<>(calculated.clone(), expected.clone());
085                }
086        }
087
088        /**
089         * Evaluates the given {@code program} tree with its sample points. The
090         * returned result object may be {@code null} if no sample point has been
091         * added to the <em>sampling</em> when calling the {@code eval} method.
092         *
093         * @param program the program to evaluate
094         * @return the evaluated sample result. May be {@code null} if the sampling
095         *         is empty and contains no sample points.
096         */
097        Result<T> eval(final Tree<? extends Op<T>, ?> program);
098
099}