GitHub user srowen opened a pull request:
https://github.com/apache/spark/pull/15341
[SPARK-17768] [CORE] Small (Sum,Count,Mean)Evaluator problems and
suboptimalities
## What changes were proposed in this pull request?
Fix:
- GroupedMeanEvaluator and GroupedSumEvaluator are unused, as is the
StudentTCacher support class
- CountEvaluator can return a lower bound < 0, when counts can't be negative
- MeanEvaluator will actually fail on exactly 1 datum (yields t-test with 0
DOF)
- CountEvaluator uses a normal distribution, which may be an inappropriate
approximation (leading to above)
- Test for SumEvaluator asserts incorrect expected sums â e.g. after
observing 10% of data has sum of 2, expectation should be 20, not 38
- CountEvaluator, MeanEvaluator have no unit tests to catch these
- Duplication of distribution code across CountEvaluator,
GroupedCountEvaluator
- The stats in each could use a bit of documentation as I had to guess at
them
- (Code could use a few cleanups and optimizations too)
## How was this patch tested?
Existing and new tests
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/srowen/spark SPARK-17768
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/15341.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #15341
----
commit 22d4093acc778fa355eb80c2ff4a649448597eda
Author: Sean Owen <[email protected]>
Date: 2016-10-04T09:25:11Z
Fix various issues with Count/Sum/MeanEvaluator; remove dead code
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