[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12829827#action_12829827
]
Sebb commented on LANG-472:
---
Math.abs() can return a negative number if parameter is MIN_VALUE.
Replacing this with 0 makes it non-negative and solves problem of reduced
frequency of zero.
Applied to nextInt() and nextLong():
URL: http://svn.apache.org/viewvc?rev=906693&view=rev
Log:
Math.abs(long) can return a negative number
Fix nextInt() and nextLong() so all values 0 -> MAX_VALUE are equally likely
I think the only remaining problem is the method nextLong(long) does not
generate properly distributed numbers above about Long.MAX_VALUE/1000, possibly
lower.
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.math.*
> Environment: all system
>Reporter: zhangruimin
> Fix For: 2.x
>
> Attachments: LANG-472-alt.patch, lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
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[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12829634#action_12829634
]
Sebb commented on LANG-472:
---
Just realised that nextInt() will never return Integer.MAX_VALUE.
Should it?
If so, then maybe the way to do this is:
{code}
int random=SHARED_RANDOM.nextInt();
if (random == Integer.MIN_VALUE) {
random = 0; // should solve problem of reduced frequency of 0
} else {
random = - random;
}
{code}
Could use the same approach for nextLong()
Thoughts?
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.math.*
> Environment: all system
>Reporter: zhangruimin
> Fix For: 2.x
>
> Attachments: LANG-472-alt.patch, lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12829592#action_12829592
]
Sebb commented on LANG-472:
---
It's just occurred to me that using Math.abs() to ensure non-negative numbers
means that the value 0 will appear with half the expected freqency.
So maybe looping whilst looking for a non-negative number would be a better
solution (let's hope any run of negative numbers is not too long!)
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.math.*
> Environment: all system
>Reporter: zhangruimin
> Fix For: 2.x
>
> Attachments: LANG-472-alt.patch, lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12829431#action_12829431
]
Sebb commented on LANG-472:
---
[Actually it was Phil's patch, amended to use the shared static Random
instance.]
One could also use Phil's solution and put:
{code}
if (n == Long.MAX_VALUE) {
return Math.abs(SHARED_RANDOM.nextLong());
}
{code}
However, that only fixes the one value - as far as I can tell, nextLong(long)
starts failing tests at around Long.MAX_VALUE/920 (not that there are any tests
in SVN yet!)
BTW, I think your hack would be more efficient as
{code}
if (n == Long.MAX_VALUE) {
double random = -1;
while (random < 0) {
random = Math.random();
}
return new BigDecimal(random).movePointRight(19).longValue();
}
{code}
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.math.*
> Environment: all system
>Reporter: zhangruimin
> Fix For: 2.x
>
> Attachments: LANG-472-alt.patch, lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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You can reply to this email to add a comment to the issue online.
[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12829424#action_12829424
]
Niall Pemberton commented on LANG-472:
--
Just reviewed Sebb's change - RandomUtils.nextLong() is now fixed because it no
longer calls JVMRandom nextLong(Long.MAX_VALUE) - but instead delagates to
SHARED_RANDOM.nextLong(). AFAICS calling JVMRandom nextLong(Long.MAX_VALUE)
will still see the same problem.
Do we want to do anything about this (my nasty hack?)
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.math.*
> Environment: all system
>Reporter: zhangruimin
> Fix For: 2.x
>
> Attachments: LANG-472-alt.patch, lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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You can reply to this email to add a comment to the issue online.
[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12829408#action_12829408
]
Niall Pemberton commented on LANG-472:
--
Doh! Sorry didn't see Sebb had already fixed this - ignore me
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.math.*
> Environment: all system
>Reporter: zhangruimin
> Fix For: 2.x
>
> Attachments: LANG-472-alt.patch, lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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You can reply to this email to add a comment to the issue online.
[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12829378#action_12829378
]
Sebb commented on LANG-472:
---
Applied Phil's patch, but adjusted so that the class now uses a static Random()
instance for all random number generation.
URL: http://svn.apache.org/viewvc?rev=906318&view=rev
Log:
LANG-472 - RandomUtils.nextLong() get all even number
Modified:
commons/proper/lang/branches/LANG_2_X/src/main/java/org/apache/commons/lang/math/JVMRandom.java
commons/proper/lang/branches/LANG_2_X/src/test/java/org/apache/commons/lang/math/RandomUtilsTest.java
I suspect nextLong(long) probably does not generate very evenly distributed
numbers.
Also documented non-negative behaviour:
URL: http://svn.apache.org/viewvc?rev=906319&view=rev
Log:
LANG-472 - Document >=0 behaviour
Modified:
commons/proper/lang/branches/LANG_2_X/src/main/java/org/apache/commons/lang/math/JVMRandom.java
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.math.*
> Environment: all system
>Reporter: zhangruimin
> Fix For: 2.x
>
> Attachments: lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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You can reply to this email to add a comment to the issue online.
[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12677876#action_12677876
]
Henri Yandell commented on LANG-472:
I'm not tied to JVMRandom. I needed it for a particular set of code, but
haven't used it since.
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Environment: all system
>Reporter: zhangruimin
> Fix For: 3.0
>
> Attachments: lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12651431#action_12651431
]
Phil Steitz commented on LANG-472:
--
Just realized that the patch violates / changes the contract of JVMRandom (as I
understand it). If we want to maintain the static, single-underlying-Random
behavior, we would need to create a static random instance and use that
instance's nextLong() method in place of super.nextLong() in the patch.
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Environment: all system
>Reporter: zhangruimin
> Attachments: lang-472.patch
>
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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[jira] Commented: (LANG-472) RandomUtils.nextLong() get all even number
[
https://issues.apache.org/jira/browse/LANG-472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12650856#action_12650856
]
James Carman commented on LANG-472:
---
So, you're saying you never see an "ok"?
> RandomUtils.nextLong() get all even number
> --
>
> Key: LANG-472
> URL: https://issues.apache.org/jira/browse/LANG-472
> Project: Commons Lang
> Issue Type: Bug
> Environment: all system
>Reporter: zhangruimin
>
> when we use the following code , we can see that the method produce only even
> number.
> while (true) {
> //for (int i = 0; i < 100; i++) {
> if (RandomUtils.nextLong() % 2 == 1) {
> System.out.println("ok");
> }
> }
--
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You can reply to this email to add a comment to the issue online.
