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VertexInputFormat 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.io;
20  
21  import java.io.IOException;
22  
23  import org.apache.hadoop.io.Writable;
24  import org.apache.hadoop.io.WritableComparable;
25  import org.apache.hadoop.mapreduce.InputSplit;
26  import org.apache.hadoop.mapreduce.TaskAttemptContext;
27  
28  /**
29   * Use this to load data for a BSP application.  Note that the InputSplit must
30   * also implement Writable.  The InputSplits will determine the partitioning of
31   * vertices across the mappers, so keep that in consideration when implementing
32   * getSplits().  Provides access to ImmutableClassesGiraphConfiguration.
33   *
34   * It's guaranteed that whatever parameters are set in the configuration are
35   * also going to be available in all method arguments related to this input
36   * format (context in getSplits and createVertexReader; methods invoked on
37   * VertexReader). So if backing input format relies on some parameters from
38   * configuration, you can safely set them for example in
39   * {@link #setConf(org.apache.giraph.conf.ImmutableClassesGiraphConfiguration)}.
40   *
41   * @param <I> Vertex id
42   * @param <V> Vertex value
43   * @param <E> Edge value
44   */
45  @SuppressWarnings("rawtypes")
46  public abstract class VertexInputFormat<I extends WritableComparable,
47      V extends Writable, E extends Writable> extends GiraphInputFormat<I, V, E> {
48    /**
49     * Create a vertex reader for a given split. Guaranteed to have been
50     * configured with setConf() prior to use.  The framework will also call
51     * {@link VertexReader#initialize(InputSplit, TaskAttemptContext)} before
52     * the split is used.
53     *
54     * @param split the split to be read
55     * @param context the information about the task
56     * @return a new record reader
57     * @throws IOException
58     */
59    public abstract VertexReader<I, V, E> createVertexReader(
60        InputSplit split,
61        TaskAttemptContext context) throws IOException;
62  }