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From Maximilian Michels <...@apache.org>
Subject Re: Nested Iterations Outlook
Date Mon, 20 Jul 2015 14:02:31 GMT
Now that makes more sense :) I thought by "nested iterations" you meant
iterations in Flink that can be nested, i.e. starting an iteration inside
an iteration.

The caching/pinning of intermediate results is still a work in progress in
Flink. It is actually in a state where it could be merged but some pending
pull requests got delayed because priorities changed a bit.

Essentially, we need to merge these two pull requests:

https://github.com/apache/flink/pull/858
This introduces a session management which allows to keep the
ExecutionGraph for the session.

https://github.com/apache/flink/pull/640
Implements the actual backtracking and caching of the results.

Once these are in, we can change the Java/Scala API to support
backtracking. I don't exactly know how Spark's API does it but, essentially
it should work then by just creating new operations on an existing DataSet
and submit to the cluster again.

Cheers,
Max

On Mon, Jul 20, 2015 at 3:31 PM, Maximilian Alber <
alber.maximilian@gmail.com> wrote:

> Oh sorry, my fault. When I wrote it, I had iterations in mind.
>
> What I actually wanted to say, how "resuming from intermediate results"
> will work with (non-nested) "non-Flink" iterations? And with iterations I
> mean something like this:
>
> while(...):
>   - change params
>   - submit to cluster
>
> where the executed Flink-program is more or less the same at each
> iterations. But with changing input sets, which are reused between
> different loop iterations.
>
> I might got something wrong, because in our group we mentioned caching a
> lá Spark for Flink and someone came up that "pinning" will do that. Is that
> somewhat right?
>
> Thanks and Cheers,
> Max
>
> On Mon, Jul 20, 2015 at 1:06 PM, Maximilian Michels <mxm@apache.org>
> wrote:
>
>>  "So it is up to debate how the support for resuming from intermediate
>> results will look like." -> What's the current state of that debate?
>>
>> Since there is no support for nested iterations that I know of, the
>> debate how intermediate results are integrated has not started yet.
>>
>>
>>> "Intermediate results are not produced within the iterations cycles." ->
>>> Ok, if there are none, what does it have to do with that debate? :-)
>>>
>>
>> I was referring to the existing support for intermediate results within
>> iterations. If we were to implement nested iterations, this could
>> (possibly) change. This is all very theoretical because there are no plans
>> to support nested iterations.
>>
>> Hope this clarifies. Otherwise, please restate your question because I
>> might have misunderstood.
>>
>> Cheers,
>> Max
>>
>>
>> On Mon, Jul 20, 2015 at 12:11 PM, Maximilian Alber <
>> alber.maximilian@gmail.com> wrote:
>>
>>> Thanks for the answer! But I need some clarification:
>>>
>>> "So it is up to debate how the support for resuming from intermediate
>>> results will look like." -> What's the current state of that debate?
>>> "Intermediate results are not produced within the iterations cycles." ->
>>> Ok, if there are none, what does it have to do with that debate? :-)
>>>
>>> Cheers,
>>> Max
>>>
>>> On Mon, Jul 20, 2015 at 10:50 AM, Maximilian Michels <mxm@apache.org>
>>> wrote:
>>>
>>>> Hi Max,
>>>>
>>>> You are right, there is no support for nested iterations yet. As far as
>>>> I know, there are no concrete plans to add support for it. So it is up to
>>>> debate how the support for resuming from intermediate results will look
>>>> like. Intermediate results are not produced within the iterations cycles.
>>>> Same would be true for nested iterations. So the behavior for resuming from
>>>> intermediate results should be alike for nested iterations.
>>>>
>>>> Cheers,
>>>> Max
>>>>
>>>> On Fri, Jul 17, 2015 at 4:26 PM, Maximilian Alber <
>>>> alber.maximilian@gmail.com> wrote:
>>>>
>>>>> Hi Flinksters,
>>>>>
>>>>> as far as I know, there is still no support for nested iterations
>>>>> planned. Am I right?
>>>>>
>>>>> So my question is how such use cases should be handled in the future.
>>>>> More specific: when pinning/caching will be available, you suggest to
>>>>> use that feature and program in "Spark" style? Or is there some other,
more
>>>>> flexible, mechanism planned for loops?
>>>>>
>>>>> Cheers,
>>>>> Max
>>>>>
>>>>
>>>>
>>>
>>
>

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