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8280550: SplittableRandom#nextDouble(double,double) can return result…
… >= bound

Reviewed-by: phh
Backport-of: 0c42e43f77b91a50fedc3fddb74e17f910d8df2a
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GoeLin committed Nov 3, 2022
1 parent 82c9cf2 commit 91f1538
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Showing 4 changed files with 57 additions and 5 deletions.
2 changes: 1 addition & 1 deletion src/java.base/share/classes/java/util/Random.java
Expand Up @@ -303,7 +303,7 @@ final double internalNextDouble(double origin, double bound) {
if (origin < bound) {
r = r * (bound - origin) + origin;
if (r >= bound) // correct for rounding
r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
r = Math.nextAfter(r, origin);
}
return r;
}
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4 changes: 2 additions & 2 deletions src/java.base/share/classes/java/util/SplittableRandom.java
Expand Up @@ -350,7 +350,7 @@ final double internalNextDouble(double origin, double bound) {
if (origin < bound) {
r = r * (bound - origin) + origin;
if (r >= bound) // correct for rounding
r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
r = Math.nextAfter(r, origin);
}
return r;
}
Expand Down Expand Up @@ -547,7 +547,7 @@ public double nextDouble(double bound) {
throw new IllegalArgumentException(BAD_BOUND);
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
return (result < bound) ? result : // correct for rounding
Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
Math.nextDown(result);
}

/**
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Expand Up @@ -282,7 +282,7 @@ final double internalNextDouble(double origin, double bound) {
if (origin < bound) {
r = r * (bound - origin) + origin;
if (r >= bound) // correct for rounding
r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
Math.nextAfter(r, origin);
}
return r;
}
Expand Down Expand Up @@ -414,7 +414,7 @@ public double nextDouble(double bound) {
throw new IllegalArgumentException(BAD_BOUND);
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
return (result < bound) ? result : // correct for rounding
Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
Math.nextDown(result);
}

/**
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52 changes: 52 additions & 0 deletions test/jdk/java/util/Random/RandomNextDoubleBoundary.java
@@ -0,0 +1,52 @@
/*
* Copyright (c) 2022, 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
* @summary Verify nextDouble stays within range
* @bug 8280550
*/

import java.util.SplittableRandom;

public class RandomNextDoubleBoundary {
public static void main(String... args) {
// Both bounds are negative
double lowerBound = -1.0000000000000002;
double upperBound = -1.0;
var sr = new SplittableRandom(42L);
var r = sr.nextDouble(lowerBound, upperBound);

if (r >= upperBound) {
System.err.println("r = " + r + "\t" + Double.toHexString(r));
System.err.println("ub = " + upperBound + "\t" + Double.toHexString(upperBound));
throw new RuntimeException("Greater than upper bound");
}

if (r < lowerBound) {
System.err.println("r = " + r + "\t" + Double.toHexString(r));
System.err.println("lb = " + lowerBound + "\t" + Double.toHexString(lowerBound));
throw new RuntimeException("Less than lower bound");
}
}
}

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