202 lines
7.4 KiB
Java
202 lines
7.4 KiB
Java
/*
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* Copyright (c) 2018, 2023, 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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* @bug 8200698
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* @summary Tests that exceptions are thrown for ops which would overflow
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* @requires (sun.arch.data.model == "64" & os.maxMemory >= 4g)
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* @run testng/othervm -Xmx4g LargeValueExceptions
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*/
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import java.math.BigInteger;
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import static java.math.BigInteger.ONE;
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import org.testng.ITestResult;
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import org.testng.annotations.AfterMethod;
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import org.testng.annotations.Test;
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//
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// The intent of this test is to probe the boundaries between overflow and
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// non-overflow, principally for multiplication and squaring, specifically
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// the largest values which should not overflow and the smallest values which
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// should. The transition values used are not necessarily at the exact
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// boundaries but should be "close." Quite a few different values were used
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// experimentally before settling on the ones in this test. For multiplication
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// and squaring all cases are exercised: definite overflow and non-overflow
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// which can be detected "up front," and "indefinite" overflow, i.e., overflow
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// which cannot be detected up front so further calculations are required.
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//
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// Testing negative values is unnecessary. For both multiplication and squaring
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// the paths lead to the Toom-Cook algorithm where the signum is used only to
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// determine the sign of the result and not in the intermediate calculations.
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// This is also true for exponentiation.
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//
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// @Test annotations with optional element "enabled" set to "false" should
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// succeed when "enabled" is set to "true" but they take too to run in the
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// course of the typical regression test execution scenario.
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//
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public class LargeValueExceptions {
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// BigInteger.MAX_MAG_LENGTH
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private static final int MAX_INTS = 1 << 26;
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// Number of bits corresponding to MAX_INTS
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private static final long MAX_BITS = (0xffffffffL & MAX_INTS) << 5L;
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// Half BigInteger.MAX_MAG_LENGTH
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private static final int MAX_INTS_HALF = MAX_INTS / 2;
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// Print the run time of each sub-test in milliseconds
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@AfterMethod
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public void getRunTime(ITestResult tr) {
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long time = tr.getEndMillis() - tr.getStartMillis();
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System.out.printf("Run time: %d ms%n", time);
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}
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// --- squaring ---
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// Largest no overflow determined by examining data lengths alone.
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@Test(enabled=false)
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public void squareNoOverflow() {
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BigInteger x = ONE.shiftLeft(16*MAX_INTS - 1).subtract(ONE);
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BigInteger y = x.multiply(x);
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}
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// Smallest no overflow determined by extra calculations.
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@Test(enabled=false)
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public void squareIndefiniteOverflowSuccess() {
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BigInteger x = ONE.shiftLeft(16*MAX_INTS - 1);
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BigInteger y = x.multiply(x);
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}
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// Largest overflow detected by extra calculations.
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@Test(expectedExceptions=ArithmeticException.class,enabled=false)
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public void squareIndefiniteOverflowFailure() {
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BigInteger x = ONE.shiftLeft(16*MAX_INTS).subtract(ONE);
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BigInteger y = x.multiply(x);
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}
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// Smallest overflow detected by examining data lengths alone.
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@Test(expectedExceptions=ArithmeticException.class)
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public void squareDefiniteOverflow() {
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BigInteger x = ONE.shiftLeft(16*MAX_INTS);
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BigInteger y = x.multiply(x);
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}
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// --- multiplication ---
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// Largest no overflow determined by examining data lengths alone.
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@Test(enabled=false)
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public void multiplyNoOverflow() {
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final int halfMaxBits = MAX_INTS_HALF << 5;
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BigInteger x = ONE.shiftLeft(halfMaxBits).subtract(ONE);
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BigInteger y = ONE.shiftLeft(halfMaxBits - 1).subtract(ONE);
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BigInteger z = x.multiply(y);
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}
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// Smallest no overflow determined by extra calculations.
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@Test(enabled=false)
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public void multiplyIndefiniteOverflowSuccess() {
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BigInteger x = ONE.shiftLeft((int)(MAX_BITS/2) - 1);
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long m = MAX_BITS - x.bitLength();
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BigInteger y = ONE.shiftLeft((int)(MAX_BITS/2) - 1);
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long n = MAX_BITS - y.bitLength();
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if (m + n != MAX_BITS) {
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throw new RuntimeException("Unexpected leading zero sum");
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}
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BigInteger z = x.multiply(y);
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}
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// Largest overflow detected by extra calculations.
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@Test(expectedExceptions=ArithmeticException.class,enabled=false)
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public void multiplyIndefiniteOverflowFailure() {
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BigInteger x = ONE.shiftLeft((int)(MAX_BITS/2)).subtract(ONE);
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long m = MAX_BITS - x.bitLength();
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BigInteger y = ONE.shiftLeft((int)(MAX_BITS/2)).subtract(ONE);
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long n = MAX_BITS - y.bitLength();
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if (m + n != MAX_BITS) {
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throw new RuntimeException("Unexpected leading zero sum");
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}
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BigInteger z = x.multiply(y);
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}
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// Smallest overflow detected by examining data lengths alone.
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@Test(expectedExceptions=ArithmeticException.class)
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public void multiplyDefiniteOverflow() {
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// multiply by 4 as MAX_INTS_HALF refers to ints
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byte[] xmag = new byte[4*MAX_INTS_HALF];
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xmag[0] = (byte)0xff;
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BigInteger x = new BigInteger(1, xmag);
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byte[] ymag = new byte[4*MAX_INTS_HALF + 1];
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ymag[0] = (byte)0xff;
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BigInteger y = new BigInteger(1, ymag);
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BigInteger z = x.multiply(y);
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}
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// --- exponentiation ---
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@Test(expectedExceptions=ArithmeticException.class)
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public void powOverflow() {
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BigInteger.TEN.pow(Integer.MAX_VALUE);
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}
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@Test(expectedExceptions=ArithmeticException.class)
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public void powOverflow1() {
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int shift = 20;
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int exponent = 1 << shift;
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BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent));
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BigInteger y = x.pow(exponent);
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}
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@Test(expectedExceptions=ArithmeticException.class)
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public void powOverflow2() {
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int shift = 20;
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int exponent = 1 << shift;
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BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent)).add(ONE);
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BigInteger y = x.pow(exponent);
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}
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@Test(expectedExceptions=ArithmeticException.class,enabled=false)
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public void powOverflow3() {
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int shift = 20;
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int exponent = 1 << shift;
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BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent)).subtract(ONE);
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BigInteger y = x.pow(exponent);
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}
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@Test(enabled=false)
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public void powOverflow4() {
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int shift = 20;
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int exponent = 1 << shift;
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BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent - 1)).add(ONE);
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BigInteger y = x.pow(exponent);
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}
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}
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