spark.default.parallelism

[Ognen Duzlevski]

This is what docs/configuration.md says about the property:
" Default number of tasks to use for distributed shuffle operations
(<code>groupByKey</code>,
    <code>reduceByKey</code>, etc) when not set by user.
"

If I set this property to, let's say, 4 - what does this mean? 4 tasks per
core, per worker, per...? :)

Thanks!
Ognen