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https://issues.apache.org/jira/browse/FLINK-10662?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16689674#comment-16689674
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Piotr Nowojski commented on FLINK-10662:
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I think both current solution and iterator are more complicated to 
handle/implement. Iterator is probably better then {{int[]}}. As far as I know 
and talked with [~StephanEwen] there are no plans to select only some of the 
channels, so that's why I was in favour of dropping it. Performance benefits 
were not huge, but visible ~10% in synthetic network benchmarks if I remember 
correctly. Always something.

Normally this {{int[] selectChannels()}} simplification would be nice to have, 
but not must have for me. However since broadcasting will need to be handled in 
a special way to avoid data copying, it would leave out {{int[] 
selectChannels()}} interface to ONLY handle single integers. 

{{Either<Integer, PredefinedPattern>}} could be less efficient and 
{{PredefinedPattern.BROADCASTING}} would also not be used/called after 
implementing broadcast optimisations.

> Refactor the ChannelSelector interface for single selected channel
> ------------------------------------------------------------------
>
>                 Key: FLINK-10662
>                 URL: https://issues.apache.org/jira/browse/FLINK-10662
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Network
>    Affects Versions: 1.5.4, 1.6.1
>            Reporter: zhijiang
>            Assignee: zhijiang
>            Priority: Minor
>
> In the discussion of broadcast improvement, [~pnowojski] pointed out the 
> issue of improving the current channel selector.
>  
> In {{ChannelSelector#selectChannels}}, it would return an array for selected 
> channels. But considering specific implementations, only 
> {{BroadcastPartitioner}} would select all the channels, and other 
> implementations will select one channel. So we can simple this interface to 
> return single channel index for benefiting performance, and specialize the 
> {{BroadcastPartitioner}} in a more efficient way.



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