giraph-core/src/main/java/org/apache/giraph/graph/VertexValueCombiner.java

/*
 * 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.giraph.graph;

import org.apache.hadoop.io.Writable;

/**
 * When vertex values with the same vertex id are loaded, this
 * class specifies how to combine their vertex values.  Edges loaded will
 * be added to the EdgeStore.
 *
 * @param <V> Vertex data
 */
public interface VertexValueCombiner<V extends Writable> {
  /**
   * Combine a vertex with the original vertex
   * by modifying originalVertex.
   *
   * @param originalVertexValue Combine the other vertex into this one
   * @param vertexValue Combine into the originalVertex.
   */
  void combine(V originalVertexValue, V vertexValue);
}