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 * https://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 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22 package org.hipparchus.transform;
23
24 import java.util.Arrays;
25
26 import org.hipparchus.complex.Complex;
27 import org.hipparchus.exception.LocalizedCoreFormats;
28 import org.hipparchus.exception.MathIllegalArgumentException;
29
30 /**
31 * Useful functions for the implementation of various transforms.
32 *
33 */
34 public class TransformUtils {
35 /**
36 * Table of the powers of 2 to facilitate binary search lookup.
37 *
38 * @see #exactLog2(int)
39 */
40 private static final int[] POWERS_OF_TWO = {
41 0x00000001, 0x00000002, 0x00000004, 0x00000008, 0x00000010, 0x00000020,
42 0x00000040, 0x00000080, 0x00000100, 0x00000200, 0x00000400, 0x00000800,
43 0x00001000, 0x00002000, 0x00004000, 0x00008000, 0x00010000, 0x00020000,
44 0x00040000, 0x00080000, 0x00100000, 0x00200000, 0x00400000, 0x00800000,
45 0x01000000, 0x02000000, 0x04000000, 0x08000000, 0x10000000, 0x20000000,
46 0x40000000
47 };
48
49 /** Private constructor. */
50 private TransformUtils() {
51 super();
52 }
53
54 /**
55 * Multiply every component in the given real array by the
56 * given real number. The change is made in place.
57 *
58 * @param f the real array to be scaled
59 * @param d the real scaling coefficient
60 * @return a reference to the scaled array
61 */
62 public static double[] scaleArray(double[] f, double d) {
63
64 for (int i = 0; i < f.length; i++) {
65 f[i] *= d;
66 }
67 return f;
68 }
69
70 /**
71 * Multiply every component in the given complex array by the
72 * given real number. The change is made in place.
73 *
74 * @param f the complex array to be scaled
75 * @param d the real scaling coefficient
76 * @return a reference to the scaled array
77 */
78 public static Complex[] scaleArray(Complex[] f, double d) {
79
80 for (int i = 0; i < f.length; i++) {
81 f[i] = new Complex(d * f[i].getReal(), d * f[i].getImaginary());
82 }
83 return f;
84 }
85
86
87 /**
88 * Builds a new two dimensional array of {@code double} filled with the real
89 * and imaginary parts of the specified {@link Complex} numbers. In the
90 * returned array {@code dataRI}, the data is laid out as follows
91 * <ul>
92 * <li>{@code dataRI[0][i] = dataC[i].getReal()},</li>
93 * <li>{@code dataRI[1][i] = dataC[i].getImaginary()}.</li>
94 * </ul>
95 *
96 * @param dataC the array of {@link Complex} data to be transformed
97 * @return a two dimensional array filled with the real and imaginary parts
98 * of the specified complex input
99 */
100 public static double[][] createRealImaginaryArray(final Complex[] dataC) {
101 final double[][] dataRI = new double[2][dataC.length];
102 final double[] dataR = dataRI[0];
103 final double[] dataI = dataRI[1];
104 for (int i = 0; i < dataC.length; i++) {
105 final Complex c = dataC[i];
106 dataR[i] = c.getReal();
107 dataI[i] = c.getImaginary();
108 }
109 return dataRI;
110 }
111
112 /**
113 * Builds a new array of {@link Complex} from the specified two dimensional
114 * array of real and imaginary parts. In the returned array {@code dataC},
115 * the data is laid out as follows
116 * <ul>
117 * <li>{@code dataC[i].getReal() = dataRI[0][i]},</li>
118 * <li>{@code dataC[i].getImaginary() = dataRI[1][i]}.</li>
119 * </ul>
120 *
121 * @param dataRI the array of real and imaginary parts to be transformed
122 * @return an array of {@link Complex} with specified real and imaginary parts.
123 * @throws MathIllegalArgumentException if the number of rows of the specified
124 * array is not two, or the array is not rectangular
125 */
126 public static Complex[] createComplexArray(final double[][] dataRI)
127 throws MathIllegalArgumentException {
128
129 if (dataRI.length != 2) {
130 throw new MathIllegalArgumentException(LocalizedCoreFormats.DIMENSIONS_MISMATCH,
131 dataRI.length, 2);
132 }
133 final double[] dataR = dataRI[0];
134 final double[] dataI = dataRI[1];
135 if (dataR.length != dataI.length) {
136 throw new MathIllegalArgumentException(LocalizedCoreFormats.DIMENSIONS_MISMATCH,
137 dataI.length, dataR.length);
138 }
139
140 final int n = dataR.length;
141 final Complex[] c = new Complex[n];
142 for (int i = 0; i < n; i++) {
143 c[i] = new Complex(dataR[i], dataI[i]);
144 }
145 return c;
146 }
147
148
149 /**
150 * Returns the base-2 logarithm of the specified {@code int}. Throws an
151 * exception if {@code n} is not a power of two.
152 *
153 * @param n the {@code int} whose base-2 logarithm is to be evaluated
154 * @return the base-2 logarithm of {@code n}
155 * @throws MathIllegalArgumentException if {@code n} is not a power of two
156 */
157 public static int exactLog2(final int n)
158 throws MathIllegalArgumentException {
159
160 int index = Arrays.binarySearch(TransformUtils.POWERS_OF_TWO, n);
161 if (index < 0) {
162 throw new MathIllegalArgumentException(LocalizedFFTFormats.NOT_POWER_OF_TWO_CONSIDER_PADDING,
163 Integer.valueOf(n));
164 }
165 return index;
166 }
167 }