toy benchmark of OpenHashMap

bench.scala

def timeAndRecordAllocations(
    numWarmups: Int,
    numTrials: Int
  )(functionToBenchmark: => Unit): Unit = {

    import java.lang.management.ManagementFactory
    import com.sun.management.ThreadMXBean
    val threadMxBean = ManagementFactory.getThreadMXBean.asInstanceOf[ThreadMXBean]
    val threadId = Thread.currentThread.getId

    // Warmup:
    {
      var i = 0
      while (i < numWarmups) {
        functionToBenchmark
        i += 1
      }
    }

    // Benchmark:
    System.gc()
    val bytesBefore = threadMxBean.getThreadAllocatedBytes(threadId)
    val cpuTimeBefore = threadMxBean.getThreadCpuTime(threadId)

    {
      var i = 0
      while (i < numTrials) {
        functionToBenchmark
        i += 1
      }
    }

    val cpuTimeAfter = threadMxBean.getThreadCpuTime(threadId)
    System.gc()
    val bytesAfter = threadMxBean.getThreadAllocatedBytes(threadId)
    // scalastyle:off
    println(s"Estimated: ${bytesAfter - bytesBefore}")
    println(s"CPU time: ${cpuTimeAfter - cpuTimeBefore}")
  }


  test("benchmark") {
    timeAndRecordAllocations(10, 10) {
      val map = new OpenHashMap[Int, Int]
      var i = 0
      while (i < 10000000) {
        map(i) = i
        i += 1
      }
    }
  }