def mult1(m1: Array[Array[Double]],
          m2: Array[Array[Double]],
          size: Int): Array[Array[Double]] = {
  var res = Array.fill(size)(new Array[Double](size))
  var i = 0
  while (i < size) {
    var j = 0
    while (j < size) {
      var k = 0
      while (k < size) {
        res(i)(j) += m1(i)(k) * m2(k)(j)
        k += 1
      }
      j += 1
    }
    i += 1
  }
  res
}