SizeEstimator

  1. import org.apache.spark.util.SizeEstimator
  3. abstract class People {
  4.     def name: String
  5. }
  7. class Student extends People {
  8.     override val name: String = "lilei"
  9. }
  11. class Teacher extends People {
  12.     override def name: String = "lili"
  13. }
  16. object Test {
  17.     def main(args: Array[String]): Unit = {
  18.         val student = SizeEstimator.estimate(new Student())
  19.         println(student) //72
  20.         val teacher = SizeEstimator.estimate(new Teacher())
  21.         println(teacher) //16
  22.     }
  23. }

出处

  1. //org.apache.spark.util.collection.SizeTracker#takeSample  
  2. /**
  3.    * Take a new sample of the current collection's size.
  4.    */
  5.   private def takeSample(): Unit = {
  6.     samples.enqueue(Sample(SizeEstimator.estimate(this), numUpdates))
  7.     // Only use the last two samples to extrapolate
  8.     if (samples.size > 2) {
  9.       samples.dequeue()
  10.     }
  11.     val bytesDelta = samples.toList.reverse match {
  12.       case latest :: previous :: tail =>
  13.         (latest.size - previous.size).toDouble / (latest.numUpdates - previous.numUpdates)
  14.       // If fewer than 2 samples, assume no change
  15.       case _ => 0
  16.     }
  17.     bytesPerUpdate = math.max(0, bytesDelta)
  18.     nextSampleNum = math.ceil(numUpdates * SAMPLE_GROWTH_RATE).toLong
  19.   }