Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/13403#discussion_r67924857
--- Diff: core/src/test/java/org/apache/spark/JavaAPISuite.java ---
@@ -733,8 +733,10 @@ public Boolean call(Double x) {
assertEquals(20/6.0, rdd.mean(), 0.01);
assertEquals(20/6.0, rdd.mean(), 0.01);
assertEquals(6.22222, rdd.variance(), 0.01);
+ assertEquals(rdd.variance(), rdd.popVariance());
assertEquals(7.46667, rdd.sampleVariance(), 0.01);
assertEquals(2.49444, rdd.stdev(), 0.01);
+ assertEquals(rdd.stdev(), rdd.popStdev(), 0.01);
--- End diff --
I think it should be approximate equality but with a very small tolerance,
e.g. 1e-14. Both calls trigger reduce jobs and we don't have guarantees on the
ordering or reduce operations, which might lead to small numerical errors.
Maybe it doesn't apply to the test case here, but it is still a best practice
to not test strict equality of floating-point numbers.
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