001 /*
002 * Java Genetic Algorithm Library (jenetics-3.5.0).
003 * Copyright (c) 2007-2016 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@gmx.at)
019 */
020 package org.jenetics.internal.math;
021
022 import org.jenetics.internal.util.require;
023
024 /**
025 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
026 * @since 3.0
027 * @version 3.0
028 */
029 public final class arithmetic {
030 private arithmetic() {require.noInstance();}
031
032
033 /**
034 * Normalize the given double array, so that it sum to one. The
035 * normalization is performed in place and the same {@code values} are
036 * returned.
037 *
038 * @param values the values to normalize.
039 * @return the {@code values} array.
040 * @throws NullPointerException if the given double array is {@code null}.
041 */
042 public static double[] normalize(final double[] values) {
043 final double sum = 1.0/DoubleAdder.sum(values);
044 for (int i = values.length; --i >= 0;) {
045 values[i] = values[i]*sum;
046 }
047
048 return values;
049 }
050
051 public static double[] normalize(final long[] values) {
052 final double[] result = new double[values.length];
053 final double sum = 1.0/statistics.sum(values);
054 for (int i = values.length; --i >= 0;) {
055 result[i] = values[i]*sum;
056 }
057
058 return result;
059 }
060
061 /**
062 * Component wise division of the given double array.
063 *
064 * @param values the double values to divide.
065 * @param divisor the divisor.
066 * @throws NullPointerException if the given double array is {@code null}.
067 */
068 public static void divide(final double[] values, final double divisor) {
069 for (int i = values.length; --i >= 0;) {
070 values[i] /= divisor;
071 }
072 }
073
074 /**
075 * Binary exponentiation algorithm.
076 *
077 * @param b the base number.
078 * @param e the exponent.
079 * @return {@code b^e}.
080 */
081 public static long pow(final long b, final long e) {
082 long base = b;
083 long exp = e;
084 long result = 1;
085
086 while (exp != 0) {
087 if ((exp & 1) != 0) {
088 result *= base;
089 }
090 exp >>>= 1;
091 base *= base;
092 }
093
094 return result;
095 }
096
097 public static boolean isMultiplicationSave(final int a, final int b) {
098 final long m = (long)a*(long)b;
099 return (int)m == m;
100 }
101 }
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