content: /*
   * Copyright 2022 Alibaba Group Holding Limited.
   *
   * Licensed 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 com.alibaba.graphscope.example.giraph;
  
  import org.apache.giraph.conf.LongConfOption;
  import org.apache.giraph.graph.BasicComputation;
  import org.apache.giraph.graph.Vertex;
  import org.apache.hadoop.io.FloatWritable;
  import org.apache.hadoop.io.IntWritable;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  
  public class BFS extends BasicComputation<IntWritable, IntWritable, FloatWritable, IntWritable> {
  
      /**
       * The start id
       */
      public static final LongConfOption SOURCE_ID =
              new LongConfOption("bfs.sourceId", 6, "The shortest paths id");
  
      private static Logger logger = LoggerFactory.getLogger(BFS.class);
  
      /**
       * Must be defined by user to do computation on a single Vertex.
       *
       * @param vertex   Vertex
       * @param messages Messages that were sent to this vertex in the previous superstep. Each
       *                 message is only guaranteed to have
       */
      @Override
      public void compute(
              Vertex<IntWritable, IntWritable, FloatWritable> vertex, Iterable<IntWritable> messages)
              throws IOException {
          boolean changed = false;
          if (getSuperstep() == 0) {
              if (isSource(vertex)) {
                  vertex.setValue(new IntWritable(0));
                  changed = true;
              } else {
                  vertex.setValue(new IntWritable(Integer.MAX_VALUE));
              }
          }
  
          for (IntWritable message : messages) {
              if (vertex.getValue().get() > message.get()) {
                  vertex.setValue(message);
                  changed = true;
              }
          }
          if (changed) {
              sendMessageToAllEdges(vertex, new IntWritable(vertex.getValue().get() + 1));
          }
          vertex.voteToHalt();
      }
  
      /**
       * Is this vertex the source id?
       *
       * @param vertex Vertex
       * @return True if the source id
       */
      private boolean isSource(Vertex<IntWritable, ?, ?> vertex) {
          return vertex.getId().get() == SOURCE_ID.get(getConf());
      }
  }
  