Hadoop实例: 单轮MapReduce的矩阵乘法，hadoopmapreduce,import java.

Hadoop实例: 单轮MapReduce的矩阵乘法，hadoopmapreduce,import java.

import java.io.IOException;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Job;import org.apache.hadoop.mapreduce.Mapper;import org.apache.hadoop.mapreduce.Reducer;import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import org.apache.hadoop.util.GenericOptionsParser;public class MartrixMultiplication{  public static class MartrixMapper extends Mapper<Object, Text, Text, Text>{    private Text map_key = new Text();    private Text map_value = new Text();    int rNumber = 300;    int cNumber = 500;    String fileTarget;    String i, j, k, ij, jk;    public void map(Object key, Text value, Context context) throws IOException, InterruptedException {        String eachterm[] = value.toString().split("#");        fileTarget = eachterm[0];        if(fileTarget.equals("M")){            i = eachterm[1];            j = eachterm[2];            ij = eachterm[3];            for(int c = 1; c<=cNumber; c++){                map_key.set(i + "#" + String.valueOf(c));                map_value.set("M" + "#" + j + "#" + ij);                context.write(map_key, map_value);            }        }else if(fileTarget.equals("N")){            j = eachterm[1];            k = eachterm[2];            jk = eachterm[3];            for(int r = 1; r<=rNumber; r++){                map_key.set(String.valueOf(r) + "#" +k);            map_value.set("N" + "#" + j + "#" + jk);            context.write(map_key, map_value);          }        }    }  }   public static class MartrixReducer extends Reducer<Text,Text,Text,Text> {    private Text reduce_value = new Text();    int jNumber = 150;      int M_ij[] = new int[jNumber+1];    int N_jk[] = new int[jNumber+1];    int j, ij, jk;    String fileTarget;    int jsum = 0;    public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {      jsum = 0;       for (Text val : values) {          String eachterm[] = val.toString().split("#");          fileTarget = eachterm[0];          j = Integer.parseInt(eachterm[1]);          if(fileTarget.equals("M")){              ij = Integer.parseInt(eachterm[2]);              M_ij[j] = ij;          }else if(fileTarget.equals("N")){              jk = Integer.parseInt(eachterm[2]);              N_jk[j] = jk;        }      }      for(int d = 1; d<=jNumber; d++){          jsum +=  M_ij[d] * N_jk[d];      }      reduce_value.set(String.valueOf(jsum));        context.write(key, reduce_value);    }  }  public static void main(String[] args) throws Exception {        Configuration conf = new Configuration();        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();        if (otherArgs.length != 2) {          System.err.println("Usage: MartrixMultiplication <in> <out>");          System.exit(2);        }        Job job = new Job(conf, "martrixmultiplication");        job.setJarByClass(MartrixMultiplication.class);        job.setMapperClass(MartrixMapper.class);        job.setReducerClass(MartrixReducer.class);        job.setOutputKeyClass(Text.class);        job.setOutputValueClass(Text.class);        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));        System.exit(job.waitForCompletion(true) ? 0 : 1);  }}//该片段来自于http://byrx.net