[concurrency-interest] ConcurrentHashMapV8 now supports Spliterator

Alex Lam S.L. alexlamsl at gmail.com
Wed Jul 4 09:27:02 EDT 2012

On Wed, Jul 4, 2012 at 12:29 PM, Doug Lea <dl at cs.oswego.edu> wrote:
> On 07/04/12 04:20, Aleksandar Prokopec wrote:
>> Wow, this is great news!
>> It may allow us to write a wrapper for chmv8 in Scala parallel
>> collections. I
>> wish concurrent skip lists had a similar thing.
> Yes, adding the new functionality of ConcurrentHashMap to
> ConcurrentSkipListMap is on the todo list. ConcurrentHashMap
> will almost always be a lot faster for parallelism though.
> Performing parallel operations on collections that maintain
> ordering (which is basically ignored for purposes of parallelism)
> is usually more costly than just using a hash table (or array)
> and then sorting (in parallel) later when the ordering is needed.

That's good to know.

In the case of frequently performing:

1) subset (range) of an ordered map
2) perform parallel operation on subset
3) ordering of elements in subset does not matter

Today I just call ConcurrentSkipListMap.subMap() then perform the
operation. Would there be an alternative which might potentially be
more performant?


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