Caching function results using a hashmap scala - scala

Question

Here is some code I wrote to solve project Euler #14 in scala
The output is shown below as well. My issue is, I expect better performance from the cached version, but the opposite is true. I think I did something wrong, since I don't think HashMap's overhead is enough to make this this slow.
Any suggestions?
object Problem14 {
def main(args: Array[String]) {
val collatzCacheMap = collection.mutable.HashMap[Long,Long]()
def collatzLengthWithCache(num: Long): Long = {
def collatzR(currNum: Long, solution: Long): Long = {
val cacheVal = collatzCacheMap.get(currNum)
if(cacheVal != None) {
val answer = solution + cacheVal.get
collatzCacheMap.put(num, answer);
answer;
}
else if(currNum == 1) { collatzCacheMap.put(num, solution + 1); solution + 1; }
else if(currNum % 2 == 0) collatzR(currNum/2, solution + 1)
else collatzR(3*currNum + 1, solution + 1)
}
collatzR(num, 0)
}
def collatzLength(num: Long): Long = {
def collatzR(currNum: Long, solution: Long): Long = {
if(currNum == 1) solution + 1
else if(currNum % 2 == 0) collatzR(currNum/2, solution + 1)
else collatzR(currNum*3 + 1, solution + 1)
}
collatzR(num, 0)
}
var startTime = System.currentTimeMillis()
//val answer = (1L to 1000000).reduceLeft((x,y) => if(collatzLengthWithCache(x) > collatzLengthWithCache(y)) x else y)
val answer = (1L to 1000000).zip((1L to 1000000).map(collatzLengthWithCache)).reduceLeft((x,y) => if(x._2 > y._2) x else y)
println(answer)
println("Cached time: " + (System.currentTimeMillis() - startTime))
collatzCacheMap.clear()
startTime = System.currentTimeMillis()
//val answer2 = (1L to 1000000).par.reduceLeft((x,y) => if(collatzLengthWithCache(x) > collatzLengthWithCache(y)) x else y)
val answer2 = (1L to 1000000).par.zip((1L to 1000000).par.map(collatzLengthWithCache)).reduceLeft((x,y) => if(x._2 > y._2) x else y)
println(answer2)
println("Cached time parallel: " + (System.currentTimeMillis() - startTime))
startTime = System.currentTimeMillis()
//val answer3 = (1L to 1000000).reduceLeft((x,y) => if(collatzLength(x) > collatzLength(y)) x else y)
val answer3 = (1L to 1000000).zip((1L to 1000000).map(collatzLength)).reduceLeft((x,y) => if(x._2 > y._2) x else y)
println(answer3)
println("No Cached time: " + (System.currentTimeMillis() - startTime))
startTime = System.currentTimeMillis()
//val answer4 = (1L to 1000000).par.reduceLeft((x,y) => if(collatzLength(x) > collatzLength(y)) x else y)
val answer4 = (1L to 1000000).par.zip((1L to 1000000).par.map(collatzLength)).reduceLeft((x,y) => if(x._2 > y._2) x else y)
println(answer4)
println("No Cached time parallel: " + (System.currentTimeMillis() - startTime))
}
}
Output:
(837799,525)
Cached time: 1070
(837799,525)
Cached time parallel: 954
(837799,525)
No Cached time: 450
(837799,525)
No Cached time parallel: 241