Why is Scala slow to initialize an Array of tuples?

Question

This is the slow code

object Hello {
  def main(args: Array[String]) = {
    val ret = Array.fill[(Int, Int, Int)](8000000){(0, 0, 0)}
    println(ret.size)
  }
}

It runs for 2 minutes. And then outputs

java.lang.OutOfMemoryError: GC overhead limit exceeded

And this is the fast code

object Hello {
  def main(args: Array[String]) = {
    val ret = Array.fill[Int](24000000){0}
    println(ret.size)
  }
}

It runs for 0.5 seconds.

My compilation option:

scalac Hello.scala

Why is there a huge gap?

user_5249621 · Answer

Array[Int] is an array of primitives.

Array[(Int, Int, Int)] is an array of objects.

(You can experiment with Array[java.lang.Integer], which is an array of objects too.)

Something's with your settings, normally

object Hello {
  def main(args: Array[String]) = {
    val ret = Array.fill[(Int, Int, Int)](8000000){(0, 0, 0)}
    println(ret.size)
  }
}