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/*
* Copyright (C) 2011 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.math;
import java.math.BigInteger;
import java.util.Random;
/**
* Utilities for benchmarks.
*
* @author Louis Wasserman
*/
final class MathBenchmarking {
static final int ARRAY_SIZE = 0x10000;
static final int ARRAY_MASK = 0x0ffff;
static final Random RANDOM_SOURCE = new Random(314159265358979L);
static final int MAX_EXPONENT = 100;
/*
* Duplicated from LongMath.
* binomial(biggestBinomials[k], k) fits in a long, but not
* binomial(biggestBinomials[k] + 1, k).
*/
static final int[] biggestBinomials =
{Integer.MAX_VALUE, Integer.MAX_VALUE, Integer.MAX_VALUE, 3810779, 121977, 16175, 4337, 1733,
887, 534, 361, 265, 206, 169, 143, 125, 111, 101, 94, 88, 83, 79, 76, 74, 72, 70, 69, 68,
67, 67, 66, 66, 66, 66};
static BigInteger randomPositiveBigInteger(int numBits) {
int digits = RANDOM_SOURCE.nextInt(numBits) + 1;
return new BigInteger(digits, RANDOM_SOURCE).add(BigInteger.ONE);
}
static BigInteger randomNonNegativeBigInteger(int numBits) {
int digits = RANDOM_SOURCE.nextInt(numBits) + 1;
return new BigInteger(digits, RANDOM_SOURCE);
}
static BigInteger randomNonZeroBigInteger(int numBits) {
BigInteger result = randomPositiveBigInteger(numBits);
return RANDOM_SOURCE.nextBoolean() ? result : result.negate();
}
static BigInteger randomBigInteger(int numBits) {
BigInteger result = randomNonNegativeBigInteger(numBits);
return RANDOM_SOURCE.nextBoolean() ? result : result.negate();
}
static double randomDouble(int maxExponent) {
double result = RANDOM_SOURCE.nextDouble();
result = Math.scalb(result, RANDOM_SOURCE.nextInt(maxExponent + 1));
return RANDOM_SOURCE.nextBoolean() ? result : -result;
}
/**
* Returns a random integer between zero and {@code MAX_EXPONENT}.
*/
static int randomExponent() {
return RANDOM_SOURCE.nextInt(MAX_EXPONENT + 1);
}
static double randomPositiveDouble() {
return Math.exp(randomDouble(6));
}
}
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