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/**
 * 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.hama.graph;

import java.io.IOException;
import java.util.List;

import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hama.HamaConfiguration;
import org.apache.hama.bsp.Counters.Counter;

/**
 * The vertex interface.
 * 
 * @param  this type must be writable and should also implement equals and
 *          hashcode.
 * @param  the type used for storing edge values, usually the value of an
 *          edge.
 * @param  the type used for messaging, usually the value of a vertex.
 */
@SuppressWarnings("rawtypes")
public interface VertexInterface
    extends WritableComparable> {

  /**
   * This method is called once before the Vertex computation begins. Since the
   * Vertex object is serializable, variables in your Vertex program always
   * should be declared a s static.
   * 
   */
  public void setup(HamaConfiguration conf);

  /**
   * @return the unique identification for the vertex.
   */
  public V getVertexID();

  /**
   * @return the total number of vertices.
   */
  public long getTotalNumVertices();

  /**
   * The user-defined function.
   */
  public void compute(Iterable messages) throws IOException;

  /**
   * @return a list of outgoing edges of this vertex in the input graph.
   */
  public List> getEdges();

  /**
   * Sends a message to another vertex.
   */
  public void sendMessage(Edge e, M msg) throws IOException;

  /**
   * Sends a message to neighbors
   */
  public void sendMessageToNeighbors(M msg) throws IOException;

  /**
   * Sends a message to the given destination vertex by ID and the message value
   */
  public void sendMessage(V destinationVertexID, M msg) throws IOException;

  /**
   * Sends a message to add a new vertex through the partitioner to the
   * appropriate BSP peer
   */
  public void addVertex(V vertexID, List> edges, M value)
      throws IOException;

  /**
   * Removes current Vertex from local peer.
   */
  public void remove() throws IOException;

  /**
   * @return the superstep number of the current superstep (starting from 0).
   */
  public long getSuperstepCount();

  /**
   * Vote to halt.
   */
  public void voteToHalt();

  /**
   * Sets the vertex value
   */
  public void setValue(M value);

  /**
   * Gets the vertex value
   */
  public M getValue();
  
   /**
    * Provides a value to the specified aggregator.
    *
    * @throws IOException
    *
    * @param index identifies a aggregator
    * @param value value to be aggregated
    */
   public void aggregate(int index, M value) throws IOException;

   /**
    * Returns the value of the specified aggregator.
    */
   public Writable getAggregatedValue(int index);

   /** Counters */
   public Counter getCounter(Enum name);
   
   public Counter getCounter(String group, String name);
}