Hello,
I've used delta iterations several times up until now, but I just realized
that I never fully understood what happens inside. And the documentation
only explains things from a user's perspective. Which is why I could really
use your help :).
Here goes nothing:
In Gelly, Graph.java, there is a nice runVertexCentricIteration(...)
method, which is in fact Spargel's - that disguises a delta iteration. What
I am trying to do is to set the vertex value before running
DataSet<Vertex<K, VV>> newVertices =
verticesWithInDegrees.runOperation(iteration);
The problem is that after this runOperation, the vertex values get reset.
Now, when I looked in VertexCentricIteration.java's createResult().
It's a plain delta iteration that (more or less) looks like this:
final DeltaIteration<Vertex<VertexKey, VertexValue>, Vertex<VertexKey,
VertexValue>> iteration =
this.initialVertices.iterateDelta(this.initialVertices,
this.maximumNumberOfIterations, zeroKeyPos);
................
// configure coGroup update function with name and broadcast variables
updates = updates.name("Vertex State Updates");
for (Tuple2<String, DataSet<?>> e : this.bcVarsUpdate) {
updates = updates.withBroadcastSet(e.f1, e.f0);
}
// let the operator know that we preserve the key field
updates.withForwardedFieldsFirst("0").withForwardedFieldsSecond("0");
return iteration.closeWith(updates, updates);
The
DataSet<?>
in the for is the problem. Vertex values get reset. Can someone give me a
hint on how to propagate the vertex value throughout the iteration?
Thanks!
Andra
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P.S. Could someone please subscribe me to the @user mailing list? For some
reason, sending the mail to that recipient fails. Thanks!
