111 lines
3.3 KiB
Java
111 lines
3.3 KiB
Java
/*
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* Copyright (C) 2011 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.math;
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import static com.google.common.math.MathBenchmarking.ARRAY_MASK;
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import static com.google.common.math.MathBenchmarking.ARRAY_SIZE;
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import static com.google.common.math.MathBenchmarking.RANDOM_SOURCE;
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import static java.math.RoundingMode.CEILING;
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import com.google.caliper.BeforeExperiment;
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import com.google.caliper.Benchmark;
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import com.google.caliper.Param;
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import java.math.BigInteger;
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/**
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* Benchmarks for the non-rounding methods of {@code BigIntegerMath}.
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*
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* @author Louis Wasserman
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*/
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public class BigIntegerMathBenchmark {
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private static final int[] factorials = new int[ARRAY_SIZE];
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private static final int[] slowFactorials = new int[ARRAY_SIZE];
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private static final int[] binomials = new int[ARRAY_SIZE];
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@Param({"50", "1000", "10000"})
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int factorialBound;
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@BeforeExperiment
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void setUp() {
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for (int i = 0; i < ARRAY_SIZE; i++) {
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factorials[i] = RANDOM_SOURCE.nextInt(factorialBound);
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slowFactorials[i] = RANDOM_SOURCE.nextInt(factorialBound);
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binomials[i] = RANDOM_SOURCE.nextInt(factorials[i] + 1);
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}
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}
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/** Previous version of BigIntegerMath.factorial, kept for timing purposes. */
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private static BigInteger oldSlowFactorial(int n) {
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if (n <= 20) {
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return BigInteger.valueOf(LongMath.factorial(n));
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} else {
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int k = 20;
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return BigInteger.valueOf(LongMath.factorial(k)).multiply(oldSlowFactorial(k, n));
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}
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}
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/** Returns the product of {@code n1} exclusive through {@code n2} inclusive. */
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private static BigInteger oldSlowFactorial(int n1, int n2) {
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assert n1 <= n2;
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if (IntMath.log2(n2, CEILING) * (n2 - n1) < Long.SIZE - 1) {
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// the result will definitely fit into a long
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long result = 1;
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for (int i = n1 + 1; i <= n2; i++) {
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result *= i;
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}
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return BigInteger.valueOf(result);
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}
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/*
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* We want each multiplication to have both sides with approximately the same number of digits.
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* Currently, we just divide the range in half.
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*/
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int mid = (n1 + n2) >>> 1;
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return oldSlowFactorial(n1, mid).multiply(oldSlowFactorial(mid, n2));
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}
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@Benchmark
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int slowFactorial(int reps) {
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int tmp = 0;
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for (int i = 0; i < reps; i++) {
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int j = i & ARRAY_MASK;
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tmp += oldSlowFactorial(slowFactorials[j]).intValue();
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}
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return tmp;
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}
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@Benchmark
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int factorial(int reps) {
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int tmp = 0;
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for (int i = 0; i < reps; i++) {
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int j = i & ARRAY_MASK;
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tmp += BigIntegerMath.factorial(factorials[j]).intValue();
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}
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return tmp;
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}
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@Benchmark
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int binomial(int reps) {
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int tmp = 0;
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for (int i = 0; i < reps; i++) {
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int j = i & 0xffff;
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tmp += BigIntegerMath.binomial(factorials[j], binomials[j]).intValue();
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}
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return tmp;
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}
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}
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