package jtlyuan.csdn;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
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.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
//利用MapReduce求最大值海量資料中的K個數
public class TopKNum extends Configured implements Tool {
public static class MapClass extends Mapper<LongWritable, Text, IntWritable, IntWritable> {
public static final int K = 100;
private int[] top = new int[K];
public void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String[] str = value.toString().split(",", -2);
try {// 對於非數字字元我們忽略掉
int temp = Integer.parseInt(str[8]);
add(temp);
} catch (NumberFormatException e) {
}
}
private void add(int temp) {//實現插入
if(temp>top[0]){
top[0]=temp;
int i=0;
for(;i<99&&temp>top[i+1];i++){
top[i]=top[i+1];
}
top[i]=temp;
}
}
@Override
protected void cleanup(Context context) throws IOException,
InterruptedException {
for(int i=0;i<100;i++){
context.write(new IntWritable(top[i]), new IntWritable(top[i]));
}
}
}
public static class Reduce extends Reducer<IntWritable, IntWritable, IntWritable, IntWritable> {
public static final int K = 100;
private int[] top = new int[K];
public void reduce(IntWritable key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
for (IntWritable val : values) {
add(val.get());
}
}
private void add(int temp) {//實現插入if(temp>top[0]){
top[0]=temp;
int i=0;
for(;i<99&&temp>top[i+1];i++){
top[i]=top[i+1];
}
top[i]=temp;
}
}
@Override
protected void cleanup(Context context) throws IOException,
InterruptedException {
for(int i=0;i<100;i++){
context.write(new IntWritable(top[i]), new IntWritable(top[i]));
}
}
}
public int run(String[] args) throws Exception {
Configuration conf = getConf();
Job job = new Job(conf, "TopKNum");
job.setJarByClass(TopKNum.class);
FileInputFormat.setInputPaths(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.setMapperClass(MapClass.class);
job.setCombinerClass(Reduce.class);
job.setReducerClass(Reduce.class);
job.setInputFormatClass(TextInputFormat.class);
job.setOutputFormatClass(TextOutputFormat.class);
job.setOutputKeyClass(IntWritable.class);
job.setOutputValueClass(IntWritable.class);
System.exit(job.waitForCompletion(true) ? 0 : 1);
return 0;
}
public static void main(String[] args) throws Exception {
int res = ToolRunner.run(new Configuration(), new TopKNum(), args);
System.exit(res);
}
}
/*
* 列舉一部分出來：
* 306 306
307 307
309 309
313 313
320 320
346 346
348 348
393 393
394 394
472 472
642 642
706 706
868 868
*/