Playing with Breeze

Main.scala

package de.yousry.linearalgebra

import scala.language.postfixOps
import breeze.linalg.{DenseMatrix, DenseVector}
import breeze.numerics._
import com.typesafe.scalalogging.LazyLogging

// To Start: LD_PRELOAD=/usr/lib/libcblas.so sbt

/**
  * Created by yousry on 06.02.17.
  */
object Main  extends App with LazyLogging {

  logger.debug("Main")

  val p = DenseVector[Float](0,1,0)
  logger.debug("Vector p: " + p )

  val pLength = sqrt(p.map(pow(_,2)).reduceLeft(_+_))
  logger.debug("|p|: " + pLength )

  val rotX = toRadians(90.0)

  val m = DenseMatrix.zeros[Float](4,4)

  m(0,0) = 1.0F
  m(0,1) = 0
  m(0,2) = 0
  m(0,3) = 0

  m(1,0) = 0
  m(1,1) = cos(rotX).toFloat
  m(1,2) = -sin(rotX).toFloat
  m(1,3) = 0

  m(2,0) = 0
  m(2,1) = sin(rotX).toFloat
  m(2,2) = cos(rotX).toFloat
  m(2,3) = 0

  m(3,0) = 0
  m(3,1) = 0
  m(3,2) = 0
  m(3,3) = 1

  logger.debug("m: \n" + m )

  // doesn't work: val r = m * p
  val q = DenseVector[Float](0,1,0,1)

  val startTime = System.nanoTime()
  val r = m * q;
  val duration : Double = (System.nanoTime() - startTime).toDouble / 1000000000.0

  logger.debug(f"Computation Time: $duration%.5f")
  val r3d = Vector() ++ (List() ++ r.toArray).init.map(_/r(3))

  logger.debug("r3d:" + r3d)
}