Tests for some ways to implement summation in Scala. Something to consider.

compareSum.scala

package main

import scala.language.implicitConversions

object SomeTests {

    implicit def traversableToFolder[A](traversable: Traversable[A]) = new Folder[A](traversable)

    class Folder[A](val list: Traversable[A]) {
        def foldFor[B](start: B)(op: ((B, A) => B)): B = {
            var ret = start
            for (v <- list)
                ret = op(ret, v)
            return ret
        }
    }

    def main(args: Array[String]): Unit = {

        print("sum:    \t")
        val prev1 = System.currentTimeMillis()
        val s1 = (1 to 100000000).sum
        println((System.currentTimeMillis() - prev1))

        print("par sum:\t")
        val prev2 = System.currentTimeMillis()
        val s2 = (1 to 100000000).par.sum
        println((System.currentTimeMillis() - prev2))

        print("fold:    \t")
        val prev3 = System.currentTimeMillis()
        val s3 = (1 to 100000000).fold(0)(_ + _)
        println((System.currentTimeMillis() - prev3))

        print("par fold:\t")
        val prev4 = System.currentTimeMillis()
        val s4 = (1 to 100000000).par.fold(0)(_ + _)
        println((System.currentTimeMillis() - prev4))

        print("foldleft:\t")
        val prev5 = System.currentTimeMillis()
        val s5 = (1 to 100000000).foldLeft(0)(_ + _)
        println((System.currentTimeMillis() - prev5))

        print("par foldleft:\t")
        val prev6 = System.currentTimeMillis()
        val s6 = (1 to 100000000).par.foldLeft(0)(_ + _)
        println((System.currentTimeMillis() - prev6))

        print("fold for:\t")
        val prev7 = System.currentTimeMillis()
        val s7 = (1 to 100000000).foldFor(0)(_ + _)
        println((System.currentTimeMillis() - prev7))

        /*
        
        Don't even bother
        
        print("foldright:\t")
        val prev8 = System.currentTimeMillis()
        val s8 = (1 to 100000000).foldRight(0)(_ + _)
        println((System.currentTimeMillis() - prev8))

        print("par foldright:\t")
        val prev9 = System.currentTimeMillis()
        val s9 = (1 to 100000000).par.foldRight(0)(_ + _)
        println((System.currentTimeMillis() - prev9))
        
        */
    }

}