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VertexResolver 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.graph;
20  
21  import org.apache.hadoop.io.Writable;
22  import org.apache.hadoop.io.WritableComparable;
23  
24  /**
25   * Handles all the situations that can arise upon creation/removal of
26   * vertices and edges.
27   *
28   * @param <I> Vertex id
29   * @param <V> Vertex data
30   * @param <E> Edge data
31   */
32  @SuppressWarnings("rawtypes")
33  public interface VertexResolver<I extends WritableComparable,
34      V extends Writable, E extends Writable> {
35    /**
36     * A vertex may have been removed, created zero or more times and had
37     * zero or more messages sent to it.  This method will handle all situations
38     * excluding the normal case (a vertex already exists and has zero or more
39     * messages sent it to).
40     *
41     * @param vertexId Vertex id (can be used for {@link Vertex}'s initialize())
42     * @param vertex Original vertex or null if none
43     * @param vertexChanges Changes that happened to this vertex or null if none
44     * @param hasMessages True iff vertex received messages in the last superstep
45     * @return Vertex to be returned, if null, and a vertex currently exists
46     *         it will be removed
47     */
48    Vertex<I, V, E> resolve(I vertexId,
49        Vertex<I, V, E> vertex,
50        VertexChanges<I, V, E> vertexChanges,
51        boolean hasMessages);
52  }