Nicholas created SPARK-16961:
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Summary: 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
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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