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[SPARK-22905][MLLIB] Fix ChiSqSelectorModel save implementation #20088

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WeichenXu123
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@WeichenXu123 WeichenXu123 commented Dec 27, 2017

What changes were proposed in this pull request?

Currently, in ChiSqSelectorModel, save:

spark.createDataFrame(dataArray).repartition(1).write...

The default partition number used by createDataFrame is "defaultParallelism",
Current RoundRobinPartitioning won't guarantee the "repartition" generating the same order result with local array. We need fix it.

How was this patch tested?

N/A

@WeichenXu123
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Currently I cannot construct a failed test for this issue, but the future PR (changing RoundRobinPartitioning) by @jiangxb1987 will trigger this bug.

@SparkQA
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SparkQA commented Dec 27, 2017

Test build #85422 has finished for PR 20088 at commit 5fd56c3.

  • This patch passes all tests.
  • This patch merges cleanly.
  • This patch adds no public classes.

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LGTM, if we want to keep the output sequence then it is recommended to avoid performing repartition() without extra sort, because the repartition() function doesn't guarantee that sequence is kept.
We should also fix other similar places where we perform a repartition() during save().

@jkbradley
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This is hopefully a rare case of an error in assuming an ordering of rows; in general, we shouldn't (and don't, AFAIK) assume an order for rows in saving/loading models.

LGTM, but before this is merged, can you please remove the ML and CORE tags from the PR title @WeichenXu123 ?

@WeichenXu123 WeichenXu123 changed the title [SPARK-22905][ML][MLLIB][CORE] Fix ChiSqSelectorModel save implementation [SPARK-22905][MLLIB] Fix ChiSqSelectorModel save implementation Dec 28, 2017
@jkbradley
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Merging with master
Thanks!

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4 participants