1 /*
2  * Copyright (C) 2011 The Guava Authors
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.google.common.math;
18 
19 import java.math.BigInteger;
20 import java.util.Random;
21 
22 /**
23  * Utilities for benchmarks.
24  *
25  * @author Louis Wasserman
26  */
27 final class MathBenchmarking {
28   static final int ARRAY_SIZE = 0x10000;
29   static final int ARRAY_MASK = 0x0ffff;
30   static final Random RANDOM_SOURCE = new Random(314159265358979L);
31   static final int MAX_EXPONENT = 100;
32 
33   /*
34    * Duplicated from LongMath.
35    * binomial(biggestBinomials[k], k) fits in a long, but not
36    * binomial(biggestBinomials[k] + 1, k).
37    */
38   static final int[] biggestBinomials =
39       {Integer.MAX_VALUE, Integer.MAX_VALUE, Integer.MAX_VALUE, 3810779, 121977, 16175, 4337, 1733,
40           887, 534, 361, 265, 206, 169, 143, 125, 111, 101, 94, 88, 83, 79, 76, 74, 72, 70, 69, 68,
41           67, 67, 66, 66, 66, 66};
42 
randomPositiveBigInteger(int numBits)43   static BigInteger randomPositiveBigInteger(int numBits) {
44     int digits = RANDOM_SOURCE.nextInt(numBits) + 1;
45     return new BigInteger(digits, RANDOM_SOURCE).add(BigInteger.ONE);
46   }
47 
randomNonNegativeBigInteger(int numBits)48   static BigInteger randomNonNegativeBigInteger(int numBits) {
49     int digits = RANDOM_SOURCE.nextInt(numBits) + 1;
50     return new BigInteger(digits, RANDOM_SOURCE);
51   }
52 
randomNonZeroBigInteger(int numBits)53   static BigInteger randomNonZeroBigInteger(int numBits) {
54     BigInteger result = randomPositiveBigInteger(numBits);
55     return RANDOM_SOURCE.nextBoolean() ? result : result.negate();
56   }
57 
randomBigInteger(int numBits)58   static BigInteger randomBigInteger(int numBits) {
59     BigInteger result = randomNonNegativeBigInteger(numBits);
60     return RANDOM_SOURCE.nextBoolean() ? result : result.negate();
61   }
62 
randomDouble(int maxExponent)63   static double randomDouble(int maxExponent) {
64     return RANDOM_SOURCE.nextDouble();
65   }
66 
67   /**
68    * Returns a random integer between zero and {@code MAX_EXPONENT}.
69    */
randomExponent()70   static int randomExponent() {
71     return RANDOM_SOURCE.nextInt(MAX_EXPONENT + 1);
72   }
73 
randomPositiveDouble()74   static double randomPositiveDouble() {
75     return Math.exp(randomDouble(6));
76   }
77 }
78