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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    *      http://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  package org.apache.commons.geometry.examples.jmh;
18  
19  import org.apache.commons.rng.UniformRandomProvider;
20  
21  /** Class containing static utility methods for performance benchmarks.
22   */
23  public final class BenchmarkUtils {
24  
25      /** Default min exponent for random double values. */
26      public static final int DEFAULT_MIN_EXP = -64;
27  
28      /** Default max exponent for random double values. */
29      public static final int DEFAULT_MAX_EXP = 64;
30  
31      /** Utility class; no instantiation. */
32      private BenchmarkUtils() {}
33  
34      /** Creates a random double number with a random sign and mantissa and a large, default
35       * range for the exponent. The numbers will not be uniform over the range.
36       * @param rng random number generator
37       * @return the random number
38       */
39      public static double randomDouble(final UniformRandomProvider rng) {
40          return randomDouble(DEFAULT_MIN_EXP, DEFAULT_MAX_EXP, rng);
41      }
42  
43      /** Create a random double value with exponent in the range {@code [minExp, maxExp]}.
44       * @param minExp minimum exponent; must be less than {@code maxExp}
45       * @param maxExp maximum exponent; must be greater than {@code minExp}
46       * @param rng random number generator
47       * @return random double
48       */
49      public static double randomDouble(final int minExp, final int maxExp, final UniformRandomProvider rng) {
50          // Create random doubles using random bits in the sign bit and the mantissa.
51          final long mask = ((1L << 52) - 1) | 1L << 63;
52          final long bits = rng.nextLong() & mask;
53          // The exponent must be unsigned so + 1023 to the signed exponent
54          final long exp = rng.nextInt(maxExp - minExp + 1) + minExp + 1023;
55          return Double.longBitsToDouble(bits | (exp << 52));
56      }
57  
58      /** Create an array of doubles populated using {@link #randomDouble(UniformRandomProvider)}.
59       * @param rng uniform random provider
60       * @param len array length
61       * @return array containing {@code len} random doubles
62       */
63      public static double[] randomDoubleArray(final int len, final UniformRandomProvider rng) {
64          return randomDoubleArray(len, DEFAULT_MIN_EXP, DEFAULT_MAX_EXP, rng);
65      }
66  
67      /** Create an array with the given length containing random doubles with exponents in the range
68       * {@code [minExp, maxExp]}.
69       * @param len array length
70       * @param minExp minimum exponent; must be less than {@code maxExp}
71       * @param maxExp maximum exponent; must be greater than {@code minExp}
72       * @param rng random number generator
73       * @return array of random doubles
74       */
75      public static double[] randomDoubleArray(final int len, final int minExp, final int maxExp,
76              final UniformRandomProvider rng) {
77          final double[] arr = new double[len];
78          for (int i = 0; i < arr.length; ++i) {
79              arr[i] = randomDouble(minExp, maxExp, rng);
80          }
81          return arr;
82      }
83  }