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SimpleInDegreeCountComputation xref
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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.giraph.examples;
20  
21  import org.apache.giraph.graph.BasicComputation;
22  import org.apache.giraph.edge.Edge;
23  import org.apache.giraph.graph.Vertex;
24  import org.apache.hadoop.io.DoubleWritable;
25  import org.apache.hadoop.io.LongWritable;
26  
27  import java.io.IOException;
28  
29  /**
30   * Simple function to return the out degree for each vertex.
31   */
32  @Algorithm(
33      name = "Indegree Count"
34  )
35  public class SimpleInDegreeCountComputation extends BasicComputation<
36    LongWritable, LongWritable, DoubleWritable, DoubleWritable> {
37  
38    @Override
39    public void compute(
40        Vertex<LongWritable, LongWritable, DoubleWritable> vertex,
41        Iterable<DoubleWritable> messages) throws IOException {
42      if (getSuperstep() == 0) {
43        Iterable<Edge<LongWritable, DoubleWritable>> edges = vertex.getEdges();
44        for (Edge<LongWritable, DoubleWritable> edge : edges) {
45          sendMessage(edge.getTargetVertexId(), new DoubleWritable(1.0));
46        }
47      } else {
48        long sum = 0;
49        for (DoubleWritable message : messages) {
50          sum++;
51        }
52        LongWritable vertexValue = vertex.getValue();
53        vertexValue.set(sum);
54        vertex.setValue(vertexValue);
55        vertex.voteToHalt();
56      }
57    }
58  }