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Make level configurable in QTreeAggregators #444

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merged 1 commit into from
May 18, 2015
Merged

Make level configurable in QTreeAggregators #444

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23 changes: 16 additions & 7 deletions algebird-core/src/main/scala/com/twitter/algebird/QTree.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,11 @@ package com.twitter.algebird
*/

object QTree {
val DefaultLevel: Int = -16
/**
* level gives a bin size of 2^level. By default the bin size is 1/65536 (level = -16)
*/
def apply[A](kv: (Double, A), level: Int = -16): QTree[A] =
def apply[A](kv: (Double, A), level: Int = DefaultLevel): QTree[A] =
QTree(math.floor(kv._1 / math.pow(2.0, level)).toLong,
level,
1,
Expand Down Expand Up @@ -82,7 +83,7 @@ object QTree {
* features of QTree, you can save some space by using QTree[Unit]
* level gives a bin size of 2^level. By default this is 1/65536 (level = -16)
*/
def value(v: Double, level: Int = -16): QTree[Unit] = apply(v -> (), level)
def value(v: Double, level: Int = DefaultLevel): QTree[Unit] = apply(v -> (), level)
}

class QTreeSemigroup[A](k: Int)(implicit val underlyingMonoid: Monoid[A]) extends Semigroup[QTree[A]] {
Expand Down Expand Up @@ -371,11 +372,19 @@ case class QTree[A](
}

trait QTreeAggregatorLike[T] {
val percentile: Double
val k: Int
implicit val num: Numeric[T]
def prepare(input: T) = QTree.value(num.toDouble(input))
val semigroup = new QTreeSemigroup[Unit](k)
def percentile: Double
/**
* This is the depth parameter for the QTreeSemigroup
*/
def k: Int
/**
* We convert T to a Double, then the Double is converted
* to a Long by using a 2^level bucket size.
*/
def level: Int = QTree.DefaultLevel
implicit def num: Numeric[T]
def prepare(input: T) = QTree.value(num.toDouble(input), level)
def semigroup = new QTreeSemigroup[Unit](k)
}

object QTreeAggregator {
Expand Down