GitHub user jiangxb1987 opened a pull request:
https://github.com/apache/spark/pull/15059
[SPARK-17506][SQL] Improve the check double values equality rule.
## What changes were proposed in this pull request?
In `ExpressionEvalHelper`, we check the equality between two double values
by comparing whether the expected value is within the range [target -
tolerance, target + tolerance], but this can cause a negative false when the
compared numerics are very large.
Beforeï¼
```
val1 = 1.6358558070241E306
val2 = 1.6358558070240974E306
ExpressionEvalHelper.compareResults(val1, val2)
false
```
In fact, `val1` and `val2` are but with different precisions, we should
tolerant this case by comparing with percentage range, eg.,expected is within
range [target - target * tolerance_percentage, target + target *
tolerance_percentage].
After:
```
val1 = 1.6358558070241E306
val2 = 1.6358558070240974E306
ExpressionEvalHelper.compareResults(val1, val2)
true
```
## How was this patch tested?
Exsiting testcases.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/jiangxb1987/spark deq
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/15059.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 #15059
----
commit 78f37334164a015605d5c23ff7217a131c3ea3a7
Author: jiangxingbo <jiangxb1...@gmail.com>
Date: 2016-09-12T15:14:28Z
check the equality of double values with tolerance within percentage range.
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