我从映射器发出二维 double 组作为值,并尝试在 reducer 中访问它。转换回 double 以获得所有二维数组的总和。
public static class DoubleTwoDArrayWritable extends TwoDArrayWritable {
public DoubleTwoDArrayWritable () {
super (DoubleWritable.class) ;
}
}
reducer
public class ReducerSvm extends Reducer<Text, DoubleTwoDArrayWritable, Text, Text>{
public void reduce(Text key,Iterable<DoubleTwoDArrayWritable> values,Context context){
System.out.println("key------"+key.toString());
Writable [][] getArray = null;
double C[][] = new double[3][1];
for (DoubleTwoDArrayWritable value : values)
{
getArray = value.get();
for (int i=0; i<3 ; i++ )
{
for (int j=0 ; j<1 ; j++ ){
System.out.println("v--> "+((DoubleWritable)getArray[i][j]).get());
C[i][j] = ((DoubleWritable)getArray[i][j]).get();
}
}
System.out.println("C array");
for (int i=0; i<3 ; i++ ){
for (int j=0 ; j<1 ; j++ ){
System.out.println(C[i][j]+" ");
}
System.out.println("");
}
}
我能够在 Reducer 中获得我的双数组。但是我硬编码
我的行和值。
如何在使用 TwoDArrayWritable
row
和 column
计数
编辑:
按照 Balduz 的建议,我编辑了代码
public void reduce(Text key,Iterable<DoubleTwoDArrayWritable> values,Context context){
for (DoubleTwoDArrayWritable value : values) {
Writable[][] currentArray = value.get();
int rowSize = currentArray.length;
int columnSize = currentArray[0].length;
System.out.println("row size: "+rowSize);
double[][] myArray = new double[rowSize][columnSize];
for (int i = 0; i < currentArray.length; i++) {
for (int j = 0; i < currentArray[i].length; j++) {
myArray[i][j] = ((DoubleWritable)currentArray[i][j]).get();
}
}
System.out.println("myArray array");
for (int i=0; i<myArray.length ; i++ ){
for (int j=0 ; j<myArray[0].length ; j++ ){
System.out.println(myArray[i][j]+" ");
}
System.out.println("");
}
}
}
}
我能够正确获取行大小。
但显示
java.lang.ArrayIndexOutOfBoundsException: 1
at edu.am.bigdata.svmmodel.ReducerTrail.reduce(ReducerTrail.java:26)
at edu.am.bigdata.svmmodel.ReducerTrail.reduce(ReducerTrail.java:1)
at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:164)
at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:610)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:444)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:449)
最佳答案
首先,请不要调用变量getArray
,因为它看起来像一个方法名,会导致混淆。要遍历每个矩阵,您需要执行以下操作:
for (DoubleTwoDArrayWritable value : values) {
Writable[][] currentArray = value.get();
for (int i = 0; i < currentArray.length; i++) {
for (int j = 0; j < currentArray[i].length; j++) {
DoubleWritable valueYouWant = (DoubleWritable)currentArray[i][j];
}
}
}
编辑: 为了将整个矩阵存储在一个变量中,我假设每一行都有相同数量的列。在这种情况下,您可以像这样初始化它:
for (DoubleTwoDArrayWritable value : values) {
Writable[][] currentArray = value.get();
int rowSize = currentArray.length;
int columnSize = currentArray[0].length;
double[][] myArray = new double[rowSize][columnSize];
for (int i = 0; i < currentArray.length; i++) {
for (int j = 0; j < currentArray[i].length; j++) {
myArray[i][j] = ((DoubleWritable)currentArray[i][j]).get();
}
}
}
关于java - TwoDArrayWritable 中的行列值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/25200531/