Playing with Scala Lists to Maps

Example timings

res1: String = Elapsed time: 46446 microseconds
res2: String = Elapsed time: 33675 microseconds
res3: String = Elapsed time: 70051 microseconds
res4: String = Elapsed time: 40251 microseconds
res5: String = Elapsed time: 38201 microseconds

res1: String = Elapsed time: 44123 microseconds
res2: String = Elapsed time: 65585 microseconds
res3: String = Elapsed time: 43811 microseconds
res4: String = Elapsed time: 48572 microseconds
res5: String = Elapsed time: 49074 microseconds

res1: String = Elapsed time: 45099 microseconds
res2: String = Elapsed time: 84781 microseconds
res3: String = Elapsed time: 44751 microseconds
res4: String = Elapsed time: 52398 microseconds
res5: String = Elapsed time: 51860 microseconds

Worksheet.scala

def time[R](block: => R): R = {
  val t0 = System.nanoTime()
  val result = block    // call-by-name
  val t1 = System.nanoTime()
  val e = (t1 - t0) / 1000
  val s = "Elapsed time: " + e + " microseconds"
  println(s)
  result
}

def time2[R](block: => R): String = {
  val t0 = System.nanoTime()
  block    // call-by-name
  val t1 = System.nanoTime()
  val e = (t1 - t0) / 1000
  "Elapsed time: " + e + " microseconds"
}


class Foo(val x: String, val y: String)

val list = (1 to 100000).map { i => new Foo(i.toString, i.toString) }.toList

// Perform a simple iteration so we eliminate any chance of cold head/tail caches
list.foreach(o => "")

time2 { list.map(o => o.x -> o.y).toMap }
time2 { list.map(o => (o.x, o.y)).toMap }
time2 { list.foldLeft(Map[String, String]())((m, o) => m + (o.x -> o.y)) }
time2 {
  var m = Map[String, String]()
  list.foreach(o => m += (o.x -> o.y))
}
time2 { list.toSeq.map(o => o.x -> o.y).toMap }