MapReduce实现协同过滤中每个用户看过的项目集合

一、知识准备

　　hadoop自带的例子在

　　D:HADOOP_HOMEhadoop-2.6.4sharehadoopmapreducesourceshadoop-mapreduce-examples 2.6.0-source.jar

　　我记得当年面试的时候就问中位数的问题不过是数据流下的中位数，一问便知是否搞过hadoop。

二、代码实现

2.1 Mapper

package cf;

import java.io.IOException;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class MovieMapper1 extends Mapper<LongWritable, Text, Text, Text> {

	public void map(LongWritable ikey, Text ivalue, Context context)
			throws IOException, InterruptedException {
			String[] values = ivalue.toString().split(",");
			if (values.length!=2) {
				return ;
			}
			String userID = values[0];
			String itemID = values[1];
			context.write(new Text(userID), new Text(itemID));
	}
}

　　

2.2 Reducer

package cf;

import java.io.IOException;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

public  class MovieReduce1 extends Reducer<Text, Text, Text, Text> {

	public void reduce(Text _key, Iterable<Text> values, Context context)
			throws IOException, InterruptedException {
		// process values
		StringBuffer sb = new StringBuffer();	
		for (Text val : values) {
			sb.append(val.toString());
			sb.append(",");
		}
		//value不能直接用StringBuffer  必须转换为String
		context.write(_key,new Text(sb.toString()));
	}

}

2.3 Main

package cf;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class UserItemSetMapReduce {

	public static void main(String[] args) throws Exception{
			
		Configuration conf = new Configuration();
		Job job = new Job(conf, "CFItemSet");
		job.setJarByClass(UserItemSetMapReduce.class);
		job.setMapperClass(MovieMapper1.class);
		//job.setCombinerClass(cls);
//		job.setCombinerClass(MovieReduce1.class);
		job.setReducerClass(MovieReduce1.class);
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(Text.class);
		FileInputFormat.addInputPath(job,new Path("hdfs://192.168.58.180:8020/cf/userItem.txt"));
		//InputPath(job, new Path(otherArgs[0]));
		//直接写到cf会提示已存在cf，我写成uIO.ttx，以为内容会写入到txt，然没有，默认他是文件夹
		FileOutputFormat.setOutputPath(job,new Path("hdfs://192.168.58.180:8020/cf/userItemOut.txt"));
		System.exit(job.waitForCompletion(true) ? 0 : 1);
	}
}

　　

三、结果分析

3.1 输入

3.2 输出

查看结果发现输出文件的分隔符默认是tab，‘ ’，同时相对于输入文件来说输出结果是逆着的，类似沾，莫非context就是这样的先进后出、

3.3日志分析

只列出了主要部分的日志

 
 DEBUG - PrivilegedAction as:hxsyl (auth:SIMPLE) from:org.apache.hadoop.mapreduce.Job.getCounters(Job.java:765)
  INFO - Counters: 38
	File System Counters
		FILE: Number of bytes read=538
		FILE: Number of bytes written=509366
		FILE: Number of read operations=0
		FILE: Number of large read operations=0
		FILE: Number of write operations=0
		HDFS: Number of bytes read=106
		HDFS: Number of bytes written=37
		HDFS: Number of read operations=13
		HDFS: Number of large read operations=0
		HDFS: Number of write operations=4
	Map-Reduce Framework
		Map input records=11
		Map output records=11
		Map output bytes=44
		Map output materialized bytes=72
		Input split bytes=107
		Combine input records=0
		Combine output records=0
		Reduce input groups=5
		Reduce shuffle bytes=72
		Reduce input records=11
		Reduce output records=5
		Spilled Records=22
		Shuffled Maps =1
		Failed Shuffles=0
		Merged Map outputs=1
		GC time elapsed (ms)=3
		CPU time spent (ms)=0
		Physical memory (bytes) snapshot=0
		Virtual memory (bytes) snapshot=0
		Total committed heap usage (bytes)=462422016
	Shuffle Errors
		BAD_ID=0
		CONNECTION=0
		IO_ERROR=0
		WRONG_LENGTH=0
		WRONG_MAP=0
		WRONG_REDUCE=0
	File Input Format Counters 
		Bytes Read=53
	File Output Format Counters 
		Bytes Written=37
 DEBUG - PrivilegedAction as:hxsyl (auth:SIMPLE) from:org.apache.hadoop.mapreduce.Job.updateStatus(Job.java:323)
 DEBUG - stopping client from cache: org.apache.hadoop.ipc.Client@37afeb11
 DEBUG - removing client from cache: org.apache.hadoop.ipc.Client@37afeb11
 DEBUG - stopping actual client because no more references remain: org.apache.hadoop.ipc.Client@37afeb11
 DEBUG - Stopping client
 DEBUG - IPC Client (521081105) connection to /192.168.58.180:8020 from hxsyl: closed
 DEBUG - IPC Client (521081105) connection to /192.168.58.180:8020 from hxsyl: stopped, remaining connections 0
 

　　

大神分析一下如何执行的，看着日志....Map如何输入的，执行几次等。