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https://issues.apache.org/jira/browse/FLINK-3945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15300173#comment-15300173
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ASF GitHub Bot commented on FLINK-3945:
---------------------------------------
Github user greghogan commented on a diff in the pull request:
https://github.com/apache/flink/pull/2021#discussion_r64587577
--- Diff:
flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/asm/degree/annotate/directed/EdgeDegreesPair.java
---
@@ -0,0 +1,81 @@
+/*
+ * 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.asm.degree.annotate.directed;
+
+import org.apache.flink.api.common.ExecutionConfig;
+import
org.apache.flink.api.common.operators.base.JoinOperatorBase.JoinHint;
+import org.apache.flink.api.java.DataSet;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.tuple.Tuple3;
+import org.apache.flink.graph.Edge;
+import org.apache.flink.graph.Graph;
+import org.apache.flink.graph.GraphAlgorithm;
+import org.apache.flink.graph.Vertex;
+import
org.apache.flink.graph.asm.degree.annotate.DegreeAnnotationFunctions.JoinEdgeDegreeWithVertexDegree;
+import
org.apache.flink.graph.asm.degree.annotate.directed.VertexDegrees.Degrees;
+
+/**
+ * Annotates edges of a directed graph with the degree, out-degree, and
+ * in-degree of both the source and target vertices.
+ *
+ * @param <K> ID type
+ * @param <VV> vertex value type
+ * @param <EV> edge value type
+ */
+public class EdgeDegreesPair<K, VV, EV>
+implements GraphAlgorithm<K, VV, EV, DataSet<Edge<K, Tuple3<EV, Degrees,
Degrees>>>> {
+
+ // Optional configuration
+ private int parallelism = ExecutionConfig.PARALLELISM_UNKNOWN;
+
+ /**
+ * Override the operator parallelism.
+ *
+ * @param parallelism operator parallelism
+ * @return this
+ */
+ public EdgeDegreesPair<K, VV, EV> setParallelism(int parallelism) {
+ this.parallelism = parallelism;
+
+ return this;
+ }
+
+ @Override
+ public DataSet<Edge<K, Tuple3<EV, Degrees, Degrees>>> run(Graph<K, VV,
EV> input)
+ throws Exception {
+ // s, t, d(s)
+ DataSet<Edge<K, Tuple2<EV, Degrees>>> edgeSourceDegrees = input
+ .run(new EdgeSourceDegrees<K, VV, EV>()
+ .setParallelism(parallelism));
+
+ // t, d(t)
+ DataSet<Vertex<K, Degrees>> vertexDegrees = input
+ .run(new VertexDegrees<K, VV, EV>()
+ .setParallelism(parallelism));
+
+ // s, t, (d(s), d(t))
+ return edgeSourceDegrees
+ .join(vertexDegrees, JoinHint.REPARTITION_HASH_SECOND)
--- End diff --
Algorithms should not expect the user to have knowledge of the input graph
or divine the best configuration. Worst case for an undirected graph is twice
as many vertices as edges.
> Degree annotation for directed graphs
> -------------------------------------
>
> Key: FLINK-3945
> URL: https://issues.apache.org/jira/browse/FLINK-3945
> Project: Flink
> Issue Type: Improvement
> Components: Gelly
> Affects Versions: 1.1.0
> Reporter: Greg Hogan
> Assignee: Greg Hogan
> Priority: Minor
> Fix For: 1.1.0
>
>
> There is a third degree count for vertices in directed graphs which is the
> distinct count of out- and in-neighbors. This also adds edge annotation of
> the vertex degrees for directed graphs.
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