Github user greghogan commented on a diff in the pull request:
https://github.com/apache/flink/pull/1956#discussion_r63347071
--- Diff:
flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/library/HITSAlgorithm.java
---
@@ -0,0 +1,276 @@
+/*
+ * 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.aggregators.DoubleSumAggregator;
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.java.DataSet;
+
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.typeutils.TupleTypeInfo;
+import org.apache.flink.graph.Edge;
+import org.apache.flink.graph.EdgeDirection;
+import org.apache.flink.graph.Graph;
+import org.apache.flink.graph.GraphAlgorithm;
+import org.apache.flink.graph.Vertex;
+import org.apache.flink.graph.spargel.MessageIterator;
+import org.apache.flink.graph.spargel.MessagingFunction;
+import org.apache.flink.graph.spargel.ScatterGatherConfiguration;
+import org.apache.flink.graph.spargel.VertexUpdateFunction;
+import org.apache.flink.graph.utils.NullValueEdgeMapper;
+import org.apache.flink.types.DoubleValue;
+import org.apache.flink.types.NullValue;
+import org.apache.flink.util.Preconditions;
+
+/**
+ * This is an implementation of HITS algorithm, using a scatter-gather
iteration.
+ * The user can define the maximum number of iterations. HITS algorithm is
determined by two parameters,
+ * hubs and authorities. A good hub represents a page that points to many
other pages, and a good authority
+ * represented a page that is linked by many different hubs.
+ * Each vertex has a value of Tuple2 type, the first field is hub score
and the second field is authority score.
+ * The implementation assumes that the two score are the same in each
vertex at the beginning.
+ * If the number of vertices of the input graph is known, it should be
provided as a parameter
+ * to speed up computation. Otherwise, the algorithm will first execute a
job to count the vertices.
+ * <p>
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/HITS_algorithm";>HITS
Algorithm</a>
+ */
+public class HITSAlgorithm<K, VV, EV> implements GraphAlgorithm<K, VV, EV,
DataSet<Vertex<K, Tuple2<DoubleValue, DoubleValue>>>> {
+
+ private final static int MAXIMUMITERATION = (Integer.MAX_VALUE - 1) / 2;
+ private final static double MINIMUMTHRESHOLD = 1e-9;
+
+ private int maxIterations;
+ private long numberOfVertices;
+ private double convergeThreshold;
+
+ public HITSAlgorithm(int maxIterations) {
+ this(maxIterations, MINIMUMTHRESHOLD);
+ }
+
+ public HITSAlgorithm(double convergeThreshold) {
+ this(MAXIMUMITERATION, convergeThreshold);
+ }
+
+ public HITSAlgorithm(int maxIterations, long numberOfVertices) {
+ this(maxIterations, MINIMUMTHRESHOLD, numberOfVertices);
+ }
+
+ public HITSAlgorithm(double convergeThreshold, long numberOfVertices) {
+ this(MAXIMUMITERATION, convergeThreshold, numberOfVertices);
+ }
+
+ /**
+ * Creates an instance of HITS algorithm.
+ *
+ * @param maxIterations the maximum number of iterations
+ * @param convergeThreshold convergence threshold for sum of scores
+ */
+ public HITSAlgorithm(int maxIterations, double convergeThreshold) {
+ Preconditions.checkArgument(maxIterations > 0, "Number of
iterations must be greater than zero.");
+ Preconditions.checkArgument(convergeThreshold > 0.0,
"Convergence threshold must be greater than zero.");
+ this.maxIterations = maxIterations * 2 + 1;
+ this.convergeThreshold = convergeThreshold;
+ }
+
+ /**
+ * Creates an instance of HITS algorithm.
+ *
+ * @param maxIterations the maximum number of iterations
+ * @param convergeThreshold convergence threshold for sum of scores
+ * @param numberOfVertices the number of vertices in the graph
+ */
+ public HITSAlgorithm(int maxIterations, double convergeThreshold, long
numberOfVertices) {
+ this(maxIterations, convergeThreshold);
+ Preconditions.checkArgument(numberOfVertices > 0, "Number of
vertices must be greater than zero.");
+ this.numberOfVertices = numberOfVertices;
+ }
+
+ @Override
+ public DataSet<Vertex<K, Tuple2<DoubleValue, DoubleValue>>>
run(Graph<K, VV, EV> netGraph) throws Exception {
--- End diff --
`netGraph` -> `graph`?
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