gistfile1.txt

package org.neo4j.cypher.performance

import org.junit.Test

class ScalaStreamTest {

  @Test def stream_append_should_use_linear_memory() {

    def streamAppendTimes(times: Int): Float =
    {
      var stream = Stream(0,1,2,3,4,5,6,7,8,9)

      System.gc()
      val before = Runtime.getRuntime.freeMemory();
      for ( i <- 1.to(times) )
      {
        stream = stream :+ i
      }
      val after = Runtime.getRuntime.freeMemory();
      System.gc()
      (before - after) / times
    }

    streamAppendTimes(100000)
    streamAppendTimes(100000)
    streamAppendTimes(100000)

    val nums = 1.to(10).map { (i: Int) => streamAppendTimes(i * 25000) }
    println(nums)


    val rest = nums.zip(nums.tail :+ 0.asInstanceOf[Float]).reverse.tail.reverse
    println(rest)

    val diff = rest.map { (p: (Float, Float)) => Math.abs((p._2 - p._1)) / p._1 }
    println(diff)

    assert(diff.forall( _ < 0.5))
  }
}