[jira] [Commented] (SPARK-16961) Utils.randomizeInPlace does not shuffle arrays uniformly
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https://issues.apache.org/jira/browse/SPARK-16961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15429280#comment-15429280
]
Apache Spark commented on SPARK-16961:
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User 'yanboliang' has created a pull request for this issue:
https://github.com/apache/spark/pull/14730
> Utils.randomizeInPlace does not shuffle arrays uniformly
>
>
> Key: SPARK-16961
> URL: https://issues.apache.org/jira/browse/SPARK-16961
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
>Affects Versions: 2.0.0
>Reporter: Nicholas
>Assignee: Nicholas
>Priority: Minor
> Fix For: 2.0.1, 2.1.0
>
> Original Estimate: 0h
> Remaining Estimate: 0h
>
> The Utils.randomizeInPlace method, which is meant to uniformly shuffle the
> elements on an input array, never shuffles elements to their starting
> position. That is, every permutation of the input array is equally likely to
> be returned, except for any permutation in which any element is in the same
> position where it began. These permutations are never output.
> This is because line 827 of Utils.scala should be
> {{val j = rand.nextInt(i + 1)}}
> instead of
> {{val j = rand.nextInt( i )}}
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[jira] [Commented] (SPARK-16961) Utils.randomizeInPlace does not shuffle arrays uniformly
[
https://issues.apache.org/jira/browse/SPARK-16961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15412783#comment-15412783
]
Apache Spark commented on SPARK-16961:
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User 'nicklavers' has created a pull request for this issue:
https://github.com/apache/spark/pull/14551
> Utils.randomizeInPlace does not shuffle arrays uniformly
>
>
> Key: SPARK-16961
> URL: https://issues.apache.org/jira/browse/SPARK-16961
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
>Affects Versions: 2.0.0
>Reporter: Nicholas
>Priority: Minor
> Original Estimate: 0h
> Remaining Estimate: 0h
>
> The Utils.randomizeInPlace method, which is meant to uniformly shuffle the
> elements on an input array, never shuffles elements to their starting
> position. That is, every permutation of the input array is equally likely to
> be returned, except for any permutation in which any element is in the same
> position where it began. These permutations are never output.
> This is because line 827 of Utils.scala should be
> {{val j = rand.nextInt(i + 1)}}
> instead of
> {{val j = rand.nextInt( i )}}
--
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[jira] [Commented] (SPARK-16961) Utils.randomizeInPlace does not shuffle arrays uniformly
[
https://issues.apache.org/jira/browse/SPARK-16961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15412705#comment-15412705
]
Nicholas commented on SPARK-16961:
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I am submitting a PR
> Utils.randomizeInPlace does not shuffle arrays uniformly
>
>
> Key: SPARK-16961
> URL: https://issues.apache.org/jira/browse/SPARK-16961
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
>Affects Versions: 2.0.0
>Reporter: Nicholas
>Priority: Minor
> Original Estimate: 0h
> Remaining Estimate: 0h
>
> The Utils.randomizeInPlace method, which is meant to uniformly shuffle the
> elements on an input array, never shuffles elements to their starting
> position. That is, every permutation of the input array is equally likely to
> be returned, except for any permutation in which any element is in the same
> position where it began. These permutations are never output.
> This is because line 827 of Utils.scala should be
> {{val j = rand.nextInt(i + 1)}}
> instead of
> {{val j = rand.nextInt( i )}}
--
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