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From Mike Hynes <91m...@gmail.com>
Subject Re: RDD.broadcast
Date Thu, 28 Apr 2016 11:24:24 GMT
I second knowing the use case for interest. I can imagine a case where
knowledge of the RDD key distribution would help local computations, for
relaticely few keys, but would be interested to hear your motive.

Essentially, are you trying to achieve what would be an all-reduce type
operation in MPI?
On Apr 28, 2016 9:08 PM, "Marcin Tustin" <mtustin@handybook.com> wrote:

> Why would you ever need to do this? I'm genuinely curious. I view
> collects as being solely for interactive work.
>
> On Thursday, April 28, 2016, <Ioannis.Deligiannis@nomura.com> wrote:
>
>> Hi,
>>
>>
>>
>> It is a common pattern to process an RDD, collect (typically a subset) to
>> the driver and then broadcast back.
>>
>>
>>
>> Adding an RDD method that can do that using the torrent broadcast
>> mechanics would be much more efficient. In addition, it would not require
>> the Driver to also utilize its Heap holding this broadcast.
>>
>>
>>
>> I guess this can become complicated if the resulting broadcast is
>> required to keep lineage information, but assuming a torrent distribution,
>> once the broadcast is synced then lineage would not be required. I’d also
>> expect the call to rdd.brodcast to be an action that eagerly distributes
>> the broadcast and returns when the operation has succeeded.
>>
>>
>>
>> Is this something that could be implemented or are there any reasons that
>> prohibits this?
>>
>>
>>
>> Thanks
>>
>> Ioannis
>>
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