How to register aggregators with the 'new' Giraph?

[Paolo Castagna]

Hi,
first and foremost, thanks for all the work and improvements on Giraph.
I went away from computers for a while (personal reasons) and changed
job, now I am back and playing with Giraph when I can.

I updated my little examples (overall, it was easy and quick, here the
changes [1]. Just in case others are in a similar situation and want
to have a look).

I am not sure I get the 'new' aggregators and in particular how I can
'register' them. My tests failing confirm my non understanding! And
forgive me if I come here and ask such a simple question.

Here is what I used to do [2]:

public class PageRankVertexWorkerContext extends WorkerContext {

  private static final Logger log =
LoggerFactory.getLogger(PageRankVertexWorkerContext.class);

  public static double errorPrevious = Double.MAX_VALUE;
  public static double danglingPrevious = 0d;

  @SuppressWarnings("unchecked")
  @Override
  public void preApplication() throws InstantiationException,
IllegalAccessException {
    log.debug("preApplication()");
    registerAggregator("dangling-current", SumAggregator.class);
    registerAggregator("error-current", SumAggregator.class);
    registerAggregator("pagerank-sum", SumAggregator.class);
    registerAggregator("vertices-count", LongSumAggregator.class);

    
((Aggregator<DoubleWritable>)getAggregator("error-current")).setAggregatedValue(
new DoubleWritable( Double.MAX_VALUE ) );
  }

  [...]


Here is what I am trying to do now [3]:

public class PageRankVertexWorkerContext extends WorkerContext {

  private static final Logger log =
LoggerFactory.getLogger(PageRankVertexWorkerContext.class);

  public static double errorPrevious = Double.MAX_VALUE;
  public static double danglingPrevious = 0d;

  // TODO: double check this... how is calling initialize()?
  public static class SimplePageRankVertexMasterCompute extends
DefaultMasterCompute {
    @Override
    public void initialize() throws InstantiationException,
IllegalAccessException {
      registerAggregator("dangling-current", DoubleSumAggregator.class);
      registerAggregator("error-current", DoubleSumAggregator.class);
      registerAggregator("pagerank-sum", DoubleSumAggregator.class);
      registerAggregator("vertices-count", LongSumAggregator.class);
    }
  }

  [...]


I am not convinced someone is actually calling the initialize() method
and there must be something I am missing (yesterday was late, after a
long day at work).

Anyway, is there a place/example where I can learn how to use
Aggregators with the new Giraph?

Thanks again and it's good to see Giraph mailing list and JIRA 'brewing' ;-)

Paolo


 [1] 
https://github.com/castagna/jena-grande/commit/3edc0a7780f5e7c25d37956c158d878b590858b5#src/main/java/org/apache/jena/grande/giraph/pagerank/PageRankVertexWorkerContext.java
 [2] 
https://github.com/castagna/jena-grande/blob/2fa8a1b879a464d8e3db84e78edd539c70274e7c/src/main/java/org/apache/jena/grande/giraph/pagerank/PageRankVertexWorkerContext.java
 [3] 
https://github.com/castagna/jena-grande/blob/3edc0a7780f5e7c25d37956c158d878b590858b5/src/main/java/org/apache/jena/grande/giraph/pagerank/PageRankVertexWorkerContext.java