h は遅い

CaseBench.scala

import scala.collection.mutable.ArrayBuffer
import scala.util.Random

object Main {
  def main(args: Array[String]) {
    val data = testdata()
    val start = System.currentTimeMillis()
    val ret = f(data) // g, h
    val end = System.currentTimeMillis()
    println(ret)
    println(end-start)
  }

  def testdata(): Seq[(Int, Int)] = {
    val random = new Random
    val buf = new ArrayBuffer[(Int, Int)]
    (0 until 5000000).foreach { _ =>
      buf += ((random.nextInt, random.nextInt))
    }
    buf
  }

  def f(data: Seq[(Int, Int)]): Long = {
    var ret = 0L
    data.foreach { case (x, y) =>
      ret += x * y
    }
    ret
  }

  def g(data: Seq[(Int, Int)]): Long = {
    var ret = 0L
    data.foreach { xy: (Int, Int) =>
      ret += xy._1 * xy._2
    }
  }

  val pf: PartialFunction[(Int, Int), Int] = {
    case (x, y) => x * y
  }
  def h(data: Seq[(Int, Int)]): Long = {
    var ret = 0L
    data.foreach { xy: (Int, Int) =>
      ret += pf(xy)
    }
    ret
  }
}