Iterate over lines in a file in parallel (Scala)?

You could use grouping to easily slice the iterator into chunks you can load into memory and then process in parallel.

val chunkSize = 128 * 1024
val iterator = Source.fromFile(path).getLines.grouped(chunkSize)
iterator.foreach { lines => 
    lines.par.foreach { line => process(line) }
}

In my opinion, something like this is the simplest way to do it.