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https://issues.apache.org/jira/browse/FLINK-1758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14499841#comment-14499841
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ASF GitHub Bot commented on FLINK-1758:
---------------------------------------
Github user vasia commented on a diff in the pull request:
https://github.com/apache/flink/pull/576#discussion_r28594318
--- Diff: docs/gelly_guide.md ---
@@ -282,25 +290,28 @@ The following code will collect the out-edges for
each vertex and apply the `Sel
{% highlight java %}
Graph<Long, Long, Double> graph = ...
-DataSet<Tuple2<Long, Double>> minWeights = graph.reduceOnEdges(
+DataSet<Tuple2<Long, Double>> minWeights = graph.groupReduceOnEdges(
new SelectMinWeight(), EdgeDirection.OUT);
// user-defined function to select the minimum weight
-static final class SelectMinWeight implements EdgesFunction<Long, Double,
Tuple2<Long, Double>> {
+static final class SelectMinWeightNeighbor implements
EdgesFunctionWithVertexValue<Long, Long, Long, Tuple2<Long, Long>> {
- public Tuple2<Long, Double> iterateEdges(Iterable<Tuple2<Long,
Edge<Long, Double>>> edges) {
+ @Override
+ public void iterateEdges(Vertex<Long, Long> v,
+ Iterable<Edge<Long, Long>> edges,
Collector<Tuple2<Long, Long>> out) throws Exception {
- long minWeight = Double.MAX_VALUE;
- long vertexId = -1;
+ long weight = Long.MAX_VALUE;
+ long minNeighborId = 0;
- for (Tuple2<Long, Edge<Long, Double>> edge: edges) {
- if (edge.f1.getValue() < weight) {
- weight = edge.f1.getValue();
- vertexId = edge.f0;
- }
- return new Tuple2<Long, Double>(vertexId, minWeight);
- }
-}
+ for (Edge<Long, Long> edge: edges) {
+ if (edge.getValue() < weight) {
+ weight = edge.getValue();
+ minNeighborId = edge.getTarget();
+ }
+ }
+ out.collect(new Tuple2<Long, Long>(v.getId(),
minNeighborId));
+ }
+ }
--- End diff --
I think it's confusing what this example is doing now. The description says
that each vertex selects the min weight among its edges, yet you modified it to
return the ID of the target neighbor of that edge. Do you want to show
something that I'm missing here?
> Extend Gelly's neighborhood methods
> -----------------------------------
>
> Key: FLINK-1758
> URL: https://issues.apache.org/jira/browse/FLINK-1758
> Project: Flink
> Issue Type: Improvement
> Components: Gelly
> Affects Versions: 0.9
> Reporter: Vasia Kalavri
> Assignee: Andra Lungu
>
> Currently, the neighborhood methods only allow returning a single value per
> vertex. In many cases, it is desirable to return several or no value per
> vertex. This is the case in clustering coefficient computation,
> vertex-centric jaccard, algorithms where a vertex computes a value per edge
> or when a vertex computes a value only for some of its neighbors.
> This issue proposes to
> - change the current reduceOnEdges/reduceOnNeighbors methods to use
> combinable reduce operations where possible
> - provide groupReduce-versions, which will use a Collector and allow
> returning none or more values per vertex.
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