Scala example source code file (t2530.scala)

This example Scala source code file (t2530.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

a, array, array, b, int, iteration, list, matrix, matrix, none, some, test, test, throwable

The Scala t2530.scala source code

import scala.actors.{Future, Futures}

object Test {

  def main(args:Array[String]) : Unit = {
    //scala.actors.Debug.level = 3
    val size = /*if (args.length > 0) Integer.parseInt(args(0)) else*/ 8
    val (m,n) = (size, size)
    def random = (for (i <- 0 until m*n) yield java.lang.Math.random).toArray
    val A = Matrix(m, n, random)
    val B = Matrix(m, n, random)
    val format = new java.text.DecimalFormat("000.00'ms'");
    var iter = 1
    val done = 21
    while (iter < done) {
      val start = System.nanoTime()
      val result = A * B
      val time = System.nanoTime() - start
      result match {
        case Some(result) => {
          printf("     Iteration %2d succeeded %n", iter/*, format.format(time / 1e6)*/)
          iter += 1
        }
        case None => {
          printf(">>>> Iteration %2d failed after %s <<<<< %n", iter, format.format(time / 1e6))
          iter = done
        }
      }
    }
    println("Test done with no deadlock. Try again, it will not occur...")
  }
}

case class Matrix(numRows: Int, numCols: Int, values: Array[Double])  {

  def this(m:Int, n:Int) = this(m, n, new Array[Double](m*n))

  def offset(i:Int, j:Int) = i * numCols + j
  def apply(i:Int, j:Int) = values( offset(i,j) )
  def update(i:Int, j:Int, value:Double) = values(offset(i, j)) = value;

  def *(by:Matrix) = {
    val aM = numRows
    val aN = numCols
    assert(aM == by.numCols)
    assert(aN == by.numRows)
    val resultMatrix = new Matrix(aM, aM)
    val m = aM.asInstanceOf[Int]
    val n = aN.asInstanceOf[Int]

    val rows = for (j <- 0 until m) yield {
      Futures.future {
        try {
        val b_j = new Array[Double](n)
        var k = 0
        while (k < n) { // sadly, while loops are still faster than for loops
          b_j(k) = by(k,j)
          k += 1
        }
        var i = 0
        while (i < m) {
          var s = 0.0d;
          k = 0
          while (k < n) {
            s += Matrix.this(i,k) * b_j(k)
            k += 1
          }
          resultMatrix(i,j) = s
          i += 1
        }
        //printf("future %d of %d completed.%n", j, m)
        j
        } catch {
          case e: Throwable if !e.isInstanceOf[scala.util.control.ControlThrowable] =>
            e.printStackTrace()
        }
      }
    }

    // rows.foreach { x=> x() } // This appears to force sequential execution, so use:
    // timeout is 10 years; see http://lampsvn.epfl.ch/trac/scala/ticket/2515
    val done: List[Option[Any]] = try {
      Futures.awaitAll(10*365*24*60*60*1000, rows.toArray : _*) // list to array, as varargs.
    } catch {
      case e: Throwable if !e.isInstanceOf[scala.util.control.ControlThrowable] =>
        e.printStackTrace()
        List()
    }

    if (done.contains(None))
      None
    else
      Some(resultMatrix)
  }

}