GitHub user dbtsai opened a pull request: https://github.com/apache/spark/pull/1425
[SPARK-2479][MLlib] Comparing floating-point numbers using relative error in UnitTests Floating point math is not exact, and most floating-point numbers end up being slightly imprecise due to rounding errors. Simple values like 0.1 cannot be precisely represented using binary floating point numbers, and the limited precision of floating point numbers means that slight changes in the order of operations or the precision of intermediates can change the result. That means that comparing two floats to see if they are equal is usually not what we want. As long as this imprecision stays small, it can usually be ignored. See the following famous article for detail. http://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/ For example: float a = 0.15 + 0.15 float b = 0.1 + 0.2 if(a == b) // can be false! if(a >= b) // can also be false! (ps, not all the tests involving floating point comparisons are changed to use almostEquals) You can merge this pull request into a Git repository by running: $ git pull https://github.com/AlpineNow/spark SPARK-2479_comparing_floating_point Alternatively you can review and apply these changes as the patch at: https://github.com/apache/spark/pull/1425.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 #1425 ---- commit f4da8f4f8693763b4823e36e3d270b74a7ce67bf Author: DB Tsai <dbt...@alpinenow.com> Date: 2014-07-14T23:24:11Z Alpine Data Labs ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. ---