Partitions

https://stackoverflow.com/questions/38732409/how-many-default-number-of-partition-there-are-when-i-initially-start-my-spark-a

How many partitons

For operations like parallelize with no parent RDDs, it depends on the cluster manager:

Local mode: number of cores on the local machine

Mesos fine grained mode: 8

Others: total number of cores on all executor nodes or 2, whichever is larger