[jira] [Commented] (APEXCORE-60) Iterative processing support

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/APEXCORE-60?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15155356#comment-15155356 ] 

ASF GitHub Bot commented on APEXCORE-60:
----------------------------------------

Github user tweise commented on a diff in the pull request:

    https://github.com/apache/incubator-apex-malhar/pull/177#discussion_r53543880
  
    --- Diff: demos/iteration/src/test/java/com/datatorrent/demos/iteration/ApplicationTest.java ---
    @@ -0,0 +1,43 @@
    +/**
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
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    + * "License"); you may not use this file except in compliance
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    +package com.datatorrent.demos.iteration;
    +
    +
    +import org.apache.hadoop.conf.Configuration;
    +import org.junit.Test;
    +
    +import com.datatorrent.api.LocalMode;
    +
    +
    +/**
    + *
    + */
    +public class ApplicationTest
    +{
    +  @Test
    +  public void testSomeMethod() throws Exception
    +  {
    +	  LocalMode lma = LocalMode.newInstance();
    +	    Configuration conf =new Configuration(false);
    +	    lma.prepareDAG(new Application(), conf);
    +	    LocalMode.Controller lc = lma.getController();
    +	    lc.run(10000);
    --- End diff --
    
    Please modify the test to check for the result instead of waiting for arbitrary time. One way to do this is to write output to file. Run run app async and check file content for expected result. Example: https://github.com/DataTorrent/examples/blob/master/tutorials/hdht/src/test/java/com/example/HDHTAppTest.java#L87
      


> Iterative processing support
> ----------------------------
>
>                 Key: APEXCORE-60
>                 URL: https://issues.apache.org/jira/browse/APEXCORE-60
>             Project: Apache Apex Core
>          Issue Type: New Feature
>            Reporter: David Yan
>            Assignee: David Yan
>              Labels: roadmap
>             Fix For: 3.3.0
>
>         Attachments: Iteration Support in Apex.pdf
>
>
> We would like to support iterative processing by introducing cycles in the graph (known as DAG now, but no longer if we support iterative processing).
> Initial idea is as follow:
> {noformat}
>      |----|
>      v    |
> A -> B -> C -> D
> ^         |
> |---------|
> {noformat} 
> C has two separate backward streams to A and B.  The input ports of A and B that C connects to will have a special attribute on how many window IDs ahead the incoming windows should be treated as, and A and B will be responsible for the initial data for such input ports.
> Another idea is to have C advance the window ID on its output ports and have C generate the initial data on its output ports to A and B.



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