Mapreduce 映射减少字数示例不';行不通
我尝试自己实现单词计数示例,下面是我对映射器的实现:Mapreduce 映射减少字数示例不';行不通,mapreduce,word-count,Mapreduce,Word Count,我尝试自己实现单词计数示例,下面是我对映射器的实现: public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> { public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { Text word = new Te
public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
Text word = new Text();
String line = value.toString();
StringTokenizer tokenizer = new StringTokenizer(line);
while (tokenizer.hasMoreTokens()) {
word.set(tokenizer.nextToken());
context.write(word, new IntWritable(1));
}
}
}
我还在映射和归约之间使用组合器。谁能解释一下这个代码有什么问题吗
非常感谢 将您的reduce方法替换为以下方法:
@Override
protected void reduce(Text key, java.lang.Iterable<IntWritable> values, org.apache.hadoop.mapreduce.Reducer<Text, IntWritable, Text, IntWritable>.Context context) throws IOException,
InterruptedException {
int sum = 0;
for (IntWritable value : values) {
sum += value.get();
}
context.write(key, new IntWritable(sum));
}
@覆盖
受保护的void reduce(文本键、java.lang.Iterable值、org.apache.hadoop.mapreduce.Reducer.Context)抛出IOException,
中断异常{
整数和=0;
for(可写入值:值){
sum+=value.get();
}
write(key,newintwriteable(sum));
}
所以底线是您没有覆盖正确的方法。@Override有助于解决此类错误
还要确保将Reduce.class设置为Reduce class,而不是Reducer.class
)()
嗯
Johannes用以下方法替换您的reduce方法:
@Override
protected void reduce(Text key, java.lang.Iterable<IntWritable> values, org.apache.hadoop.mapreduce.Reducer<Text, IntWritable, Text, IntWritable>.Context context) throws IOException,
InterruptedException {
int sum = 0;
for (IntWritable value : values) {
sum += value.get();
}
context.write(key, new IntWritable(sum));
}
@覆盖
受保护的void reduce(文本键、java.lang.Iterable值、org.apache.hadoop.mapreduce.Reducer.Context)抛出IOException,
中断异常{
整数和=0;
for(可写入值:值){
sum+=value.get();
}
write(key,newintwriteable(sum));
}
所以底线是您没有覆盖正确的方法。@Override有助于解决此类错误
还要确保将Reduce.class设置为Reduce class,而不是Reducer.class
)()
嗯
Johannes如果您不想在重写时使用reduce方法的args,那么替代解决方案可以是:
@Override
protected void reduce(Object key, Iterable values, Context context) throws
IOException, InterruptedException {
int sum = 0;
Iterable<IntWritable> v = values;
Iterator<IntWritable> itr = v.iterator();
while(itr.hasNext()){
sum += itr.next().get();
}
context.write(key, new IntWritable(sum));
}
@覆盖
受保护的void reduce(对象键、Iterable值、上下文)抛出
IOException,InterruptedException{
整数和=0;
Iterable v=数值;
迭代器itr=v.Iterator();
while(itr.hasNext()){
sum+=itr.next().get();
}
write(key,newintwriteable(sum));
}
如果您不想在重写时使用reduce方法的args,那么替代解决方案可以是:
@Override
protected void reduce(Object key, Iterable values, Context context) throws
IOException, InterruptedException {
int sum = 0;
Iterable<IntWritable> v = values;
Iterator<IntWritable> itr = v.iterator();
while(itr.hasNext()){
sum += itr.next().get();
}
context.write(key, new IntWritable(sum));
}
@覆盖
受保护的void reduce(对象键、Iterable值、上下文)抛出
IOException,InterruptedException{
整数和=0;
Iterable v=数值;
迭代器itr=v.Iterator();
while(itr.hasNext()){
sum+=itr.next().get();
}
write(key,newintwriteable(sum));
}
谢谢您的帮助。我被这个问题困扰了一两天。谢谢你。我在这个问题上纠缠了一两天。