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/*
* Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* @test
* @bug 8200698
* @summary Tests that exceptions are thrown for ops which would overflow
* @requires (sun.arch.data.model == "64" & os.maxMemory >= 4g)
* @run testng/othervm -Xmx4g LargeValueExceptions
*/
import java.math.BigInteger;
import static java.math.BigInteger.ONE;
import org.testng.annotations.Test;
//
// The intent of this test is to probe the boundaries between overflow and
// non-overflow, principally for multiplication and squaring, specifically
// the largest values which should not overflow and the smallest values which
// should. The transition values used are not necessarily at the exact
// boundaries but should be "close." Quite a few different values were used
// experimentally before settling on the ones in this test. For multiplication
// and squaring all cases are exercised: definite overflow and non-overflow
// which can be detected "up front," and "indefinite" overflow, i.e., overflow
// which cannot be detected up front so further calculations are required.
//
// Testing negative values is unnecessary. For both multiplication and squaring
// the paths lead to the Toom-Cook algorithm where the signum is used only to
// determine the sign of the result and not in the intermediate calculations.
// This is also true for exponentiation.
//
// @Test annotations with optional element "enabled" set to "false" should
// succeed when "enabled" is set to "true" but they take too to run in the
// course of the typical regression test execution scenario.
//
public class LargeValueExceptions {
// BigInteger.MAX_MAG_LENGTH
private static final int MAX_INTS = 1 << 26;
// Number of bits corresponding to MAX_INTS
private static final long MAX_BITS = (0xffffffffL & MAX_INTS) << 5L;
// Half BigInteger.MAX_MAG_LENGTH
private static final int MAX_INTS_HALF = MAX_INTS / 2;
// --- squaring ---
// Largest no overflow determined by examining data lengths alone.
@Test(enabled=false)
public void squareNoOverflow() {
BigInteger x = ONE.shiftLeft(16*MAX_INTS - 1).subtract(ONE);
BigInteger y = x.multiply(x);
}
// Smallest no overflow determined by extra calculations.
@Test(enabled=false)
public void squareIndefiniteOverflowSuccess() {
BigInteger x = ONE.shiftLeft(16*MAX_INTS - 1);
BigInteger y = x.multiply(x);
}
// Largest overflow detected by extra calculations.
@Test(expectedExceptions=ArithmeticException.class,enabled=false)
public void squareIndefiniteOverflowFailure() {
BigInteger x = ONE.shiftLeft(16*MAX_INTS).subtract(ONE);
BigInteger y = x.multiply(x);
}
// Smallest overflow detected by examining data lengths alone.
@Test(expectedExceptions=ArithmeticException.class)
public void squareDefiniteOverflow() {
BigInteger x = ONE.shiftLeft(16*MAX_INTS);
BigInteger y = x.multiply(x);
}
// --- multiplication ---
// Largest no overflow determined by examining data lengths alone.
@Test(enabled=false)
public void multiplyNoOverflow() {
final int halfMaxBits = MAX_INTS_HALF << 5;
BigInteger x = ONE.shiftLeft(halfMaxBits).subtract(ONE);
BigInteger y = ONE.shiftLeft(halfMaxBits - 1).subtract(ONE);
BigInteger z = x.multiply(y);
}
// Smallest no overflow determined by extra calculations.
@Test(enabled=false)
public void multiplyIndefiniteOverflowSuccess() {
BigInteger x = ONE.shiftLeft((int)(MAX_BITS/2) - 1);
long m = MAX_BITS - x.bitLength();
BigInteger y = ONE.shiftLeft((int)(MAX_BITS/2) - 1);
long n = MAX_BITS - y.bitLength();
if (m + n != MAX_BITS) {
throw new RuntimeException("Unexpected leading zero sum");
}
BigInteger z = x.multiply(y);
}
// Largest overflow detected by extra calculations.
@Test(expectedExceptions=ArithmeticException.class,enabled=false)
public void multiplyIndefiniteOverflowFailure() {
BigInteger x = ONE.shiftLeft((int)(MAX_BITS/2)).subtract(ONE);
long m = MAX_BITS - x.bitLength();
BigInteger y = ONE.shiftLeft((int)(MAX_BITS/2)).subtract(ONE);
long n = MAX_BITS - y.bitLength();
if (m + n != MAX_BITS) {
throw new RuntimeException("Unexpected leading zero sum");
}
BigInteger z = x.multiply(y);
}
// Smallest overflow detected by examining data lengths alone.
@Test(expectedExceptions=ArithmeticException.class)
public void multiplyDefiniteOverflow() {
// multiply by 4 as MAX_INTS_HALF refers to ints
byte[] xmag = new byte[4*MAX_INTS_HALF];
xmag[0] = (byte)0xff;
BigInteger x = new BigInteger(1, xmag);
byte[] ymag = new byte[4*MAX_INTS_HALF + 1];
ymag[0] = (byte)0xff;
BigInteger y = new BigInteger(1, ymag);
BigInteger z = x.multiply(y);
}
// --- exponentiation ---
@Test(expectedExceptions=ArithmeticException.class)
public void powOverflow() {
BigInteger.TEN.pow(Integer.MAX_VALUE);
}
@Test(expectedExceptions=ArithmeticException.class)
public void powOverflow1() {
int shift = 20;
int exponent = 1 << shift;
BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent));
BigInteger y = x.pow(exponent);
}
@Test(expectedExceptions=ArithmeticException.class)
public void powOverflow2() {
int shift = 20;
int exponent = 1 << shift;
BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent)).add(ONE);
BigInteger y = x.pow(exponent);
}
@Test(expectedExceptions=ArithmeticException.class,enabled=false)
public void powOverflow3() {
int shift = 20;
int exponent = 1 << shift;
BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent)).subtract(ONE);
BigInteger y = x.pow(exponent);
}
@Test(enabled=false)
public void powOverflow4() {
int shift = 20;
int exponent = 1 << shift;
BigInteger x = ONE.shiftLeft((int)(MAX_BITS / exponent - 1)).add(ONE);
BigInteger y = x.pow(exponent);
}
}
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