Change Details

To generate [mobile apps session metrics](https://wikitech.wikimedia.org/wiki/Analytics/Data_Lake/Traffic/mobile_apps_session_metrics), we use [Q tree](https://twitter.github.io/algebird/datatypes/approx/q_tree.html) in this [quantiles function](https://github.com/wikimedia/analytics-refinery-source/blob/master/refinery-job/src/main/scala/org/wikimedia/analytics/refinery/job/AppSessionMetrics.scala#L42-L54). However, when the data type is `Long`, the result is incorrect. In the last example of this [documentation](https://twitter.github.io/algebird/datatypes/approx/q_tree.html), the range of the median of `List(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8)` is `(5.0,6.0)`, while the true median is 4.5. See more details about this issue: https://github.com/twitter/algebird/issues/517 As a solution, we may change the data type from `Long` to `Double`.

To generate [mobile apps session metrics](https://wikitech.wikimedia.org/wiki/Analytics/Data_Lake/Traffic/mobile_apps_session_metrics), we use [Q tree](https://twitter.github.io/algebird/datatypes/approx/q_tree.html) in this [quantiles function](https://github.com/wikimedia/analytics-refinery-source/blob/master/refinery-job/src/main/scala/org/wikimedia/analytics/refinery/job/AppSessionMetrics.scala#L42-L54). However, when the data type is `Long`, the result is incorrect. In the last example of this [documentation](https://twitter.github.io/algebird/datatypes/approx/q_tree.html), the range of the median of `List(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8)` is `(5.0,6.0)`, while the true median is 4.5. Correction: With our version this is what i get: scala> val data = List(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8) data: List[Int] = List(1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8) scala> val qtSemigroup = new QTreeSemigroup[Long](6) qtSemigroup: com.twitter.algebird.QTreeSemigroup[Long] = com.twitter.algebird.QTreeSemigroup@7c46ceff scala> val sum = qtSemigroup.sumOption(seqQTree).get sum: com.twitter.algebird.QTree[Long] = QTree(0,4,16,0,Some(QTree(0,3,14,0,Some(QTree(0,2,6,0,Some(QTree(0,1,2,0,None,Some(QTree(1,0,2,2,None,None)))),Some(QTree(1,1,4,0,Some(QTree(2,0,2,4,None,None)),Some(QTree(3,0,2,6,None,None)))))),Some(QTree(1,2,8,0,Some(QTree(2,1,4,0,Some(QTree(4,0,2,8,None,None)),Some(QTree(5,0,2,10,None,None)))),Some(QTree(3,1,4,0,Some(QTree(6,0,2,12,None,None)),Some(QTree(7,0,2,14,None,None)))))))),Some(QTree(1,3,2,0,Some(QTree(2,2,2,0,Some(QTree(4,1,2,0,Some(QTree(8,0,2,16,None,None)),None)),None)),None))) scala> sum.quantileBounds(0.5) res22: (Double, Double) = (4.0,5.0) See more details about this issue: https://github.com/twitter/algebird/issues/517 As a solution, we may change the data type from `Long` to `Double`.

To generate [mobile apps session metrics](https://wikitech.wikimedia.org/wiki/Analytics/Data_Lake/Traffic/mobile_apps_session_metrics), we use [Q tree](https://twitter.github.io/algebird/datatypes/approx/q_tree.html) in this [quantiles function](https://github.com/wikimedia/analytics-refinery-source/blob/master/refinery-job/src/main/scala/org/wikimedia/analytics/refinery/job/AppSessionMetrics.scala#L42-L54). However, when the data type is `Long`, the result is incorrect. In the last example of this [documentation](https://twitter.github.io/algebird/datatypes/approx/q_tree.html), the range of the median of `List(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8)` is `(5.0,6.0)`, while the true median is 4.5. Correction: With our version this is what i get: scala> val data = List(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8) data: List[Int] = List(1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8) scala> val qtSemigroup = new QTreeSemigroup[Long](6) qtSemigroup: com.twitter.algebird.QTreeSemigroup[Long] = com.twitter.algebird.QTreeSemigroup@7c46ceff scala> val sum = qtSemigroup.sumOption(seqQTree).get sum: com.twitter.algebird.QTree[Long] = QTree(0,4,16,0,Some(QTree(0,3,14,0,Some(QTree(0,2,6,0,Some(QTree(0,1,2,0,None,Some(QTree(1,0,2,2,None,None)))),Some(QTree(1,1,4,0,Some(QTree(2,0,2,4,None,None)),Some(QTree(3,0,2,6,None,None)))))),Some(QTree(1,2,8,0,Some(QTree(2,1,4,0,Some(QTree(4,0,2,8,None,None)),Some(QTree(5,0,2,10,None,None)))),Some(QTree(3,1,4,0,Some(QTree(6,0,2,12,None,None)),Some(QTree(7,0,2,14,None,None)))))))),Some(QTree(1,3,2,0,Some(QTree(2,2,2,0,Some(QTree(4,1,2,0,Some(QTree(8,0,2,16,None,None)),None)),None)),None))) scala> sum.quantileBounds(0.5) res22: (Double, Double) = (4.0,5.0) See more details about this issue: https://github.com/twitter/algebird/issues/517 As a solution, we may change the data type from `Long` to `Double`.