In memory word frequency. Single core and parallel

wordfreqs.scala

/* Non-parallel Version -- Time: 5546ms */
val freqs = calculateFrequencies(words, 0, words.length)

/* Parallel Version -- Time 2891ms */
val pfactor = 4
val workSize = words.length / pfactor
val freqs = combineMaps (
  (0 until pfactor).par.map { unit =>
      calculateFrequencies(words, (unit * workSize), ((unit+1) * workSize))
  }
)


/* Functions */
def calculateFrequencies(words: Array[String], start: Int, end: Int): Map[String, Int] = {
  val freqs = Map[String,Int]()
  var idx = start
  while(idx < end) {
    freqs(words(idx)) = freqs.getOrElseUpdate(words(idx), 0) + 1
    idx += 1
  }
  freqs
}

def combineMaps(maps: ParIterable[Map[String,Int]]): Map[String,Int] = {
  maps.reduce { (m, s) =>
    s.keys.foreach { k =>
      if(m contains k)
        m(k) = m(k) + s(k)
      else
        m(k) = s(k)
    }
    m
  }
}