Serializing the main object isn't going to help here - it's SparkContext
it's complaining about.
The problem is that the context is, according to the code you sent,
computeDwt has a signature of:
class DWTSample ... {
def computDWT (sc: SparkContext, data: ArrayBuffer[(Int, Double)]):
This is something that I have bumped into time and again. the object that
contains your main() should also be serializable then you won't have this
issue.
For example
object Test extends serializable{
def main(){
// set up spark context
// read your data
// create your RDD's (grouped by key)
