Why inconsistent results using subtraction in reduce?

Question

Given the following:

val rdd = List(1,2,3)

I assumed that rdd.reduce((x,y) => (x - y)) would return -4 (i.e. <

Answer 1

You can easy replace subtraction v1 - v2 - ... - vN with v1 - (v2 + ... + vN), so your code can look like

val v1 = 1
val values = Seq(2, 3)
val sum = sc.paralellize(values).reduce(_ + _)
val result = v1 - sum