HPPC LongIntMap memory usage

build.sbt

name := "map-sizes"
version := "1.0"
scalaVersion := "2.12.2"

libraryDependencies += "com.carrotsearch" % "hppc" % "0.7.2"

RandomMapGenerator result.md

After a single run of RandomMapGenerator the reported retained size by the Map is ~1.6GiB. YourKit profiler was used.

RandomMapGenerator.scala

import com.carrotsearch.hppc.LongIntHashMap

import scala.util.Random

object RandomMapGenerator {

  private[this] val random = new Random()

  private val ElementsToGenerate = 100 * 1000 * 1000

  def main(args: Array[String]): Unit = {
    val map = new LongIntHashMap()

    for (i <- 0 until ElementsToGenerate) {
      val key = random.nextLong()
      val value = random.nextInt()
      map.put(key, value)
    }

    println(s"Map generated, feel free to dump the heap. Key distribution is: ${map.visualizeKeyDistribution(8)}.")

    // Wait
    Console.in.readLine()
  }

}