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8283083: java.util.random L128X256MixRandom constructor fails to use byte[] seed

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Reviewed-by: jlaskey, bpb
This commit is contained in:
Raffaello Giulietti 2022-04-12 17:36:16 +00:00 committed by Joe Darcy
parent 3f26d84f6a
commit 19b140a7f3
2 changed files with 60 additions and 9 deletions
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18
src/jdk.random/share/classes/jdk/random/L128X256MixRandom.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2021, 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
@ -178,7 +178,7 @@ public final class L128X256MixRandom extends AbstractSplittableWithBrineGenerato
this.x3 = x3;
// If x0, x1, x2, and x3 are all zero, we must choose nonzero values.
if ((x0 | x1 | x2 | x3) == 0) {
long v = sh;
long v = sh;
// At least three of the four values generated here will be nonzero.
this.x0 = RandomSupport.mixStafford13(v += RandomSupport.GOLDEN_RATIO_64);
this.x1 = RandomSupport.mixStafford13(v += RandomSupport.GOLDEN_RATIO_64);
@ -234,8 +234,8 @@ public final class L128X256MixRandom extends AbstractSplittableWithBrineGenerato
* @param seed the initial seed
*/
public L128X256MixRandom(byte[] seed) {
// Convert the seed to 6 long values, of which the last 4 are not all zero.
long[] data = RandomSupport.convertSeedBytesToLongs(seed, 6, 4);
// Convert the seed to 8 long values, of which the last 4 are not all zero.
long[] data = RandomSupport.convertSeedBytesToLongs(seed, 8, 4);
long ah = data[0], al = data[1], sh = data[2], sl = data[3],
x0 = data[4], x1 = data[5], x2 = data[6], x3 = data[7];
// Force a to be odd.
@ -253,7 +253,7 @@ public final class L128X256MixRandom extends AbstractSplittableWithBrineGenerato
@Override
public SplittableGenerator split(SplittableGenerator source, long brine) {
// Pick a new instance "at random", but use the brine for (the low half of) `a`.
// Pick a new instance "at random", but use the brine for (the low half of) `a`.
return new L128X256MixRandom(source.nextLong(), brine << 1,
source.nextLong(), source.nextLong(),
source.nextLong(), source.nextLong(),
@ -262,18 +262,18 @@ public final class L128X256MixRandom extends AbstractSplittableWithBrineGenerato
@Override
public long nextLong() {
// Compute the result based on current state information
// (this allows the computation to be overlapped with state update).
// Compute the result based on current state information
// (this allows the computation to be overlapped with state update).
final long result = RandomSupport.mixLea64(sh + x0);
// Update the LCG subgenerator
// Update the LCG subgenerator
// The LCG is, in effect, s = ((1LL << 64) + ML) * s + a, if only we had 128-bit arithmetic.
final long u = ML * sl;
sh = (ML * sh) + Math.unsignedMultiplyHigh(ML, sl) + sl + ah;
sl = u + al;
if (Long.compareUnsigned(sl, u) < 0) ++sh; // Handle the carry propagation from low half to high half.
// Update the XBG subgenerator
// Update the XBG subgenerator
long q0 = x0, q1 = x1, q2 = x2, q3 = x3;
{ // xoshiro256 1.0
long t = q1 << 17;

51
test/jdk/java/util/Random/LXMRandomWithSeed.java Normal file
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@ -0,0 +1,51 @@
/*
* 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.
*/
import java.util.random.RandomGeneratorFactory;
/**
* @test
* @summary Check that the (byte[]) constructors do not throw (see bug report)
* @bug 8283083
*/
public class LXMRandomWithSeed {
public static void main(String[] args) {
byte[] seed = new byte[0x100];
for (var i = 0; i < seed.length; ++i) {
seed[i] = (byte) i;
}
var lxmFactories = RandomGeneratorFactory.all()
.filter(factory -> factory.group().equals("LXM"))
.toList();
for (var lxmFactory : lxmFactories) {
var lxmGen0 = lxmFactory.create(seed);
var lxmGen1 = lxmFactory.create(seed);
if (lxmGen0.nextLong() != lxmGen1.nextLong()) {
throw new RuntimeException("%s(byte[]) is incorrect".formatted(lxmFactory.name()));
}
}
}
}