Question

尝试从mapper中将2个二维数组作为值发出。在hadoop中，我们有TwoDArrayWritable，其中输入1 - 2D array。为了实现我的用例，我尝试修改TwoDArrayWritable以获取2 - 2D array

的输入

/**
 * A Writable for 2D arrays containing a matrix of instances of a class.
 */
public class MyTwoDArrayWritable implements Writable {


    private Class valueClass;
    private Writable[][] values;


    private Class valueClass1;
    private Writable[][] values1;


    public MyTwoDArrayWritable(Class valueClass,Class valueClass1) {
        this.valueClass = valueClass;
        this.valueClass1 = valueClass1;
    }

    public MyTwoDArrayWritable(Class valueClass, DoubleWritable[][] values,Class valueClass1, DoubleWritable[][] values1) {
        this(valueClass, valueClass1);
        this.values = values;
        this.values1 = values1;
    }

    public Object toArray() {
        int dimensions[] = {values.length, 0};
        Object result = Array.newInstance(valueClass, dimensions);
        for (int i = 0; i < values.length; i++) {
            Object resultRow = Array.newInstance(valueClass, values[i].length);
            Array.set(result, i, resultRow);
            for (int j = 0; j < values[i].length; j++) {
                Array.set(resultRow, j, values[i][j]);
            }
        }
        return result;
    }



    /**
     * @return the valueClass
     */
    public Class getValueClass() {
        return valueClass;
    }

    /**
     * @param valueClass the valueClass to set
     */
    public void setValueClass(Class valueClass) {
        this.valueClass = valueClass;
    }

    /**
     * @return the values
     */
    public Writable[][] getValues() {
        return values;
    }

    /**
     * @param values the values to set
     */
    public void setValues(DoubleWritable[][] values,DoubleWritable[][] values1) {
        this.values = values;
        this.values = values1;
    }

    /**
     * @return the valueClass1
     */
    public Class getValueClass1() {
        return valueClass1;
    }

    /**
     * @param valueClass1 the valueClass1 to set
     */
    public void setValueClass1(Class valueClass1) {
        this.valueClass1 = valueClass1;
    }

    /**
     * @return the values1
     */
    public Writable[][] getValues1() {
        return values1;
    }


    public void readFields(DataInput in) throws IOException {
        // construct matrix
        values = new Writable[in.readInt()][];
        for (int i = 0; i < values.length; i++) {
            values[i] = new Writable[in.readInt()];
        }

        // construct values
        for (int i = 0; i < values.length; i++) {
            for (int j = 0; j < values[i].length; j++) {
                Writable value;                             // construct value
                try {
                    value = (Writable) valueClass.newInstance();
                } catch (InstantiationException e) {
                    throw new RuntimeException(e.toString());
                } catch (IllegalAccessException e) {
                    throw new RuntimeException(e.toString());
                }
                value.readFields(in);                       // read a value
                values[i][j] = value;                       // store it in values
            }
        }
    }

    public void write(DataOutput out) throws IOException {
        out.writeInt(values.length);                 // write values
        for (int i = 0; i < values.length; i++) {
            out.writeInt(values[i].length);
        }
        for (int i = 0; i < values.length; i++) {
            for (int j = 0; j < values[i].length; j++) {
                values[i][j].write(out);
            }
        }
    }


}

从mapper中发出2个2D双数组。

MyTwoDArrayWritable array = new MyTwoDArrayWritable (DoubleWritable.class,DoubleWritable.class);
DoubleWritable[][] myInnerArray = new DoubleWritable[EtransEkey.length][EtransEkey[0].length];
DoubleWritable[][] myInnerArray1 = new DoubleWritable[EtransDevalue.length][EtransDevalue[0].length];
// set values in myInnerArray
for (int k1 = 0; k1 < EtransEkey.length; k1++) {
 for(int j1=0;j1< EtransEkey[0].length;j1++){
     myInnerArray[k1][j1] = new DoubleWritable(EtransEkey[k1][j1]);

 }
}

for (int k1 = 0; k1 < EtransDevalue.length; k1++) {
 for(int j1=0;j1< EtransDevalue[0].length;j1++){
     myInnerArray1[k1][j1] = new DoubleWritable(EtransDevalue[k1][j1]);
 }
}

array.set(myInnerArray,myInnerArray1);

在array.set(myInnerArray,myInnerArray1);

中显示错误

/*
 * The method set(DoubleWritable[][], DoubleWritable[][]) is undefined for the type MyTwoDArrayWritableritable
 */

编辑：如何在Reducer中迭代这些值以获取myInnerArray矩阵和myInnerArray1矩阵？

到目前为止，我所做的是

for (MyTwoDArrayWritable c : values) {
            System.out.println(c.getValues());
            DoubleWritable[][] myInnerArray = new DoubleWritable[KdimRow][KdimCol];
            for (int k1 = 0; k1 < KdimRow; k1++) {
                 for(int j1=0;j1< KdimCol;j1++){
                     myInnerArray[k1][j1] = new DoubleWritable();

                 }
        }

但是如何将它们存回双数组？

Answer 1

您尚未在set中定义MyTwoDArrayWritable方法，这就是显示错误的原因。您应该使用已经定义的方法来完成您所需的方法，而不是调用array.set：setValues，所以替换

array.set(myInnerArray,myInnerArray1);

带

array.setValues(myInnerArray,myInnerArray1);

在Hadoop中自定义TwoDArrayWritable并且无法在reducer中迭代相同的内容

1 个答案: