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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-2634) Add a Vertex-centric Version of the Tringle Count Library Method
Date Fri, 11 Sep 2015 14:36:45 GMT

    [ https://issues.apache.org/jira/browse/FLINK-2634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14740912#comment-14740912

ASF GitHub Bot commented on FLINK-2634:

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

    --- Diff: flink-staging/flink-gelly/src/main/java/org/apache/flink/graph/library/TriangleCount.java
    @@ -0,0 +1,208 @@
    + * 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
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.flink.graph.library;
    +import org.apache.flink.api.common.functions.FlatJoinFunction;
    +import org.apache.flink.api.common.functions.GroupReduceFunction;
    +import org.apache.flink.api.common.functions.MapFunction;
    +import org.apache.flink.api.common.functions.ReduceFunction;
    +import org.apache.flink.api.java.DataSet;
    +import org.apache.flink.api.java.tuple.Tuple1;
    +import org.apache.flink.api.java.tuple.Tuple2;
    +import org.apache.flink.graph.GraphAlgorithm;
    +import org.apache.flink.graph.Graph;
    +import org.apache.flink.graph.Vertex;
    +import org.apache.flink.graph.Edge;
    +import org.apache.flink.graph.EdgeDirection;
    +import org.apache.flink.graph.NeighborsFunctionWithVertexValue;
    +import org.apache.flink.graph.utils.VertexToTuple2Map;
    +import org.apache.flink.types.NullValue;
    +import org.apache.flink.util.Collector;
    +import java.util.Iterator;
    +import java.util.TreeMap;
    + * Triangle Count Algorithm.
    + *
    + * This algorithm operates in three phases. First, vertices select neighbors with id
greater than theirs
    + * and send messages to them. Each received message is then propagated to neighbors with
higher id.
    + * Finally, if a node encounters the target id in the list of received messages, it increments
the number
    + * of triangles found.
    + *
    + * For skewed graphs, we recommend calling the GSATriangleCount library method as it
uses the more restrictive
    + * `reduceOnNeighbors` function which internally makes use of combiners to speed up computation.
    + *
    + * This implementation is non - iterative.
    + *
    + * The algorithm takes an undirected, unweighted graph as input and outputs a DataSet
    + * Tuple1 which contains a single integer representing the number of triangles.
    + */
    +public class TriangleCount implements
    +		GraphAlgorithm<Long, NullValue, NullValue, DataSet<Tuple1<Integer>>>
    --- End diff --
    For the Tuple1 comment: I wanted to be consistent with the other examples. If you run
it on a cluster, you'd like the result printed in a file. You could print it with regular
Java functions, but `writeAsCsv` and `print` were more appealing (to me at least) :)  
    For the key type: At some point, you check that your id is lower than the neighbors' ids...
How would that comparison be made if you don't know the type. If let's say you received String,
you'd need to do `Long.parseLong`.... If you know a way, I'd gladly change it, but I don't
think this is the only library method that has the key type problem... Even ConnectedComponents
uses Long. Maybe we can open a JIRA for that...

> Add a Vertex-centric Version of the Tringle Count Library Method
> ----------------------------------------------------------------
>                 Key: FLINK-2634
>                 URL: https://issues.apache.org/jira/browse/FLINK-2634
>             Project: Flink
>          Issue Type: Task
>          Components: Gelly
>    Affects Versions: 0.10
>            Reporter: Andra Lungu
>            Assignee: Andra Lungu
>            Priority: Minor
> The vertex-centric version of this algorithm receives an undirected graph as input and
outputs the total number of triangles formed by the graph's edges.
> The implementation consists of three phases:
> 1). Select neighbours with id greater than the current vertex id.
> 2). Propagate each received value to neighbours with higher id. 
> 3). Compute the number of Triangles by verifying if the final vertex contains the sender's
id in its list.
> As opposed to the GAS version, all these three steps will be performed via message passing.

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