83 lines
3.3 KiB
Java
83 lines
3.3 KiB
Java
/*
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* Copyright (c) 1998, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* @test
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* @run main BigIntegerParallelMultiplyTest
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* @summary tests parallelMultiply() method in BigInteger
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* @author Heinz Kabutz heinz@javaspecialists.eu
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*/
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import java.math.BigInteger;
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import java.util.function.BinaryOperator;
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/**
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* This is a simple test class created to ensure that the results
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* of multiply() are the same as multiplyParallel(). We calculate
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* the Fibonacci numbers using Dijkstra's sum of squares to get
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* very large numbers (hundreds of thousands of bits).
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*
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* @author Heinz Kabutz, heinz@javaspecialists.eu
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*/
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public class BigIntegerParallelMultiplyTest {
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public static BigInteger fibonacci(int n, BinaryOperator<BigInteger> multiplyOperator) {
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if (n == 0) return BigInteger.ZERO;
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if (n == 1) return BigInteger.ONE;
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int half = (n + 1) / 2;
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BigInteger f0 = fibonacci(half - 1, multiplyOperator);
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BigInteger f1 = fibonacci(half, multiplyOperator);
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if (n % 2 == 1) {
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BigInteger b0 = multiplyOperator.apply(f0, f0);
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BigInteger b1 = multiplyOperator.apply(f1, f1);
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return b0.add(b1);
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} else {
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BigInteger b0 = f0.shiftLeft(1).add(f1);
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return multiplyOperator.apply(b0, f1);
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}
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}
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public static void main(String[] args) throws Exception {
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compare(1000, 324);
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compare(10_000, 3473);
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compare(100_000, 34883);
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compare(1_000_000, 347084);
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}
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private static void compare(int n, int expectedBitCount) {
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BigInteger multiplyResult = fibonacci(n, BigInteger::multiply);
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BigInteger parallelMultiplyResult = fibonacci(n, BigInteger::parallelMultiply);
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checkBitCount(n, expectedBitCount, multiplyResult);
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checkBitCount(n, expectedBitCount, parallelMultiplyResult);
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if (!multiplyResult.equals(parallelMultiplyResult))
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throw new AssertionError("multiply() and parallelMultiply() give different results");
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}
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private static void checkBitCount(int n, int expectedBitCount, BigInteger number) {
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if (number.bitCount() != expectedBitCount)
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throw new AssertionError(
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"bitCount of fibonacci(" + n + ") was expected to be " + expectedBitCount
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+ " but was " + number.bitCount());
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}
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}
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