Scala Spark中两个数组之间的叉积

Question

Consider two arrays in scala-spark

val mole_1 = Array(2.0,1.0,0.0,0.0,0.0,0.0)
val mole_2 = Array(2.0,2.0,0.0,0.0,0.0,0.0)

Now an efficient method of element-wise multiplication of the two arrays would be

val dot_Mole = (mole_1, mole_2).zipped.map(_ * _).sum

Which yields  >> 6.0

How would one use zipped and map to implement cross product between these arrays to give >> 12.0 ?

USe only zipped, map and reduce .

Answer 1

You can do like this:

val dot_mole = Mole_1.map{ x => Mole_2.map(b => b * x)}.flatten.sum
dot_mole: Double = 12.0