Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/2455#discussion_r18122185
--- Diff:
core/src/main/scala/org/apache/spark/util/random/RandomSampler.scala ---
@@ -53,56 +81,237 @@ trait RandomSampler[T, U] extends Pseudorandom with
Cloneable with Serializable
* @tparam T item type
*/
@DeveloperApi
-class BernoulliSampler[T](lb: Double, ub: Double, complement: Boolean =
false)
+class BernoulliPartitionSampler[T](lb: Double, ub: Double, complement:
Boolean = false)
extends RandomSampler[T, T] {
- private[random] var rng: Random = new XORShiftRandom
+ // epsilon slop to avoid failure from floating point jitter
+ @transient val eps: Double = RandomSampler.epsArgs
+ require(lb <= (ub + eps), "Lower bound (lb) must be <= upper bound (ub)")
+ require(lb >= (0d - eps), "Lower bound (lb) must be >= 0.0")
+ require(ub <= (1d + eps), "Upper bound (ub) must be <= 1.0")
- def this(ratio: Double) = this(0.0d, ratio)
+ private val rng: Random = new XORShiftRandom
override def setSeed(seed: Long) = rng.setSeed(seed)
override def sample(items: Iterator[T]): Iterator[T] = {
- items.filter { item =>
- val x = rng.nextDouble()
- (x >= lb && x < ub) ^ complement
+ ub-lb match {
--- End diff --
i think this is easier to read if you do
```scala
if (ub <= lb) {
if (complement) items else Iterator.empty
} else {
if (complement) {
items.filter { item =>
val x = rng.nextDouble()
(x < lb) || (x >= ub)
}
} else {
items.filter { _ =>
val x = rng.nextDouble()
(x >= lb) && (x < ub)
}
}
}
```
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