配列を使った行列乗算

Question

多次元配列（[2][2]）を使って簡単な行列乗法を作ろうとしています。私はこれでちょっと新しいです、そして、私はそれが私が間違っていることを見つけることができません。私はそれが何であるかを教えてくれて本当に助けに感謝します。私はむしろライブラリなどを使用しないで、私は主にこれをどのように動作するかを学ぶためにやっています。事前にありがとうございます。

次のように私はmainメソッドで私のaraysを宣言しています：

Double[][] A={{4.00,3.00},{2.00,1.00}}; 
Double[][] B={{-0.500,1.500},{1.000,-2.0000}}; 

* Bは単位行列を返す必要があります。それはしません。

public static Double[][] multiplicar(Double[][] A, Double[][] B){ 
//the method runs and returns a matrix of the correct dimensions 
//(I actually changed the .length function to a specific value to eliminate 
//it as a possible issue), but not the correct values 

    Double[][] C= new Double[2][2]; 
    int i,j; 

    ////I fill the matrix with zeroes, if I don't do this it gives me an error 
    for(i=0;i<2;i++) { 
     for(j=0;j<2;j++){ 
      C[i][j]=0.00000; 
     } 
    } 
    ///this is where I'm supposed to perform the adding of every element in 
    //a row of A multiplied by the corresponding element in the 
    //corresponding column of B, for all columns in B and all rows in A 
    for(i=0;i<2;i++){ 
     for(j=0;j<2;j++) 
      C[i][j]+=(A[i][j]*B[j][i]); 
    } 
    return C; 
} 

Answer 1

あなたはこのコードを試すことができます。

public class MyMatrix { 
    Double[][] A = { { 4.00, 3.00 }, { 2.00, 1.00 } }; 
    Double[][] B = { { -0.500, 1.500 }, { 1.000, -2.0000 } }; 

    public static Double[][] multiplicar(Double[][] A, Double[][] B) { 

     int aRows = A.length; 
     int aColumns = A[0].length; 
     int bRows = B.length; 
     int bColumns = B[0].length; 

     if (aColumns != bRows) { 
      throw new IllegalArgumentException("A:Rows: " + aColumns + " did not match B:Columns " + bRows + "."); 
     } 

     Double[][] C = new Double[aRows][bColumns]; 
     for (int i = 0; i < aRows; i++) { 
      for (int j = 0; j < bColumns; j++) { 
       C[i][j] = 0.00000; 
      } 
     } 

     for (int i = 0; i < aRows; i++) { // aRow 
      for (int j = 0; j < bColumns; j++) { // bColumn 
       for (int k = 0; k < aColumns; k++) { // aColumn 
        C[i][j] += A[i][k] * B[k][j]; 
       } 
      } 
     } 

     return C; 
    } 

    public static void main(String[] args) { 

     MyMatrix matrix = new MyMatrix(); 
     Double[][] result = multiplicar(matrix.A, matrix.B); 

     for (int i = 0; i < 2; i++) { 
      for (int j = 0; j < 2; j++) 
       System.out.print(result[i][j] + " "); 
      System.out.println(); 
     } 
    } 
} 

Answer 2

は

public static Double[][] multiplicar(Double A[][],Double B[][]){ 
    Double[][] C= new Double[2][2]; 
    int i,j,k; 
    for (i = 0; i < 2; i++) { 
     for (j = 0; j < 2; j++) { 
      C[i][j] = 0.00000; 
     } 
    } 
    for(i=0;i<2;i++){ 
     for(j=0;j<2;j++){ 
      for (k=0;k<2;k++){ 
        C[i][j]+=(A[i][k]*B[k][j]); 

      } 

     } 
    } 
    return C; 
} 

Answer 3

static int b[][]={{21,21},{22,22}}; 

static int a[][] ={{1,1},{2,2}}; 

public static void mul(){ 
    int c[][] = new int[2][2]; 

    for(int i=0;i<b.length;i++){ 
     for(int j=0;j<b.length;j++){ 
      c[i][j] =0; 
     } 
    } 

    for(int i=0;i<a.length;i++){ 
     for(int j=0;j<b.length;j++){ 
      for(int k=0;k<b.length;k++){ 
      c[i][j]= c[i][j] +(a[i][k] * b[k][j]); 
      } 
     } 
    } 

    for(int i=0;i<c.length;i++){ 
     for(int j=0;j<c.length;j++){ 
      System.out.print(c[i][j]); 
     } 
     System.out.println("\n"); 
    } 
} 

Answer 4

ジャワ、これを試してみてください。行列乗算。

異なるサイズのマトリックスでテストしました。

public class Matrix { 

/** 
* Matrix multiplication method. 
* @param m1 Multiplicand 
* @param m2 Multiplier 
* @return Product 
*/ 
    public static double[][] multiplyByMatrix(double[][] m1, double[][] m2) { 
     int m1ColLength = m1[0].length; // m1 columns length 
     int m2RowLength = m2.length; // m2 rows length 
     if(m1ColLength != m2RowLength) return null; // matrix multiplication is not possible 
     int mRRowLength = m1.length; // m result rows length 
     int mRColLength = m2[0].length; // m result columns length 
     double[][] mResult = new double[mRRowLength][mRColLength]; 
     for(int i = 0; i < mRRowLength; i++) {   // rows from m1 
      for(int j = 0; j < mRColLength; j++) {  // columns from m2 
       for(int k = 0; k < m1ColLength; k++) { // columns from m1 
        mResult[i][j] += m1[i][k] * m2[k][j]; 
       } 
      } 
     } 
     return mResult; 
    } 

    public static String toString(double[][] m) { 
     String result = ""; 
     for(int i = 0; i < m.length; i++) { 
      for(int j = 0; j < m[i].length; j++) { 
       result += String.format("%11.2f", m[i][j]); 
      } 
      result += "\n"; 
     } 
     return result; 
    } 

    public static void main(String[] args) { 
     // #1 
     double[][] multiplicand = new double[][] { 
       {3, -1, 2}, 
       {2, 0, 1}, 
       {1, 2, 1} 
     }; 
     double[][] multiplier = new double[][] { 
       {2, -1, 1}, 
       {0, -2, 3}, 
       {3, 0, 1} 
     }; 
     System.out.println("#1\n" + toString(multiplyByMatrix(multiplicand, multiplier))); 
     // #2 
     multiplicand = new double[][] { 
       {1, 2, 0}, 
       {-1, 3, 1}, 
       {2, -2, 1} 
     }; 
     multiplier = new double[][] { 
       {2}, 
       {-1}, 
       {1} 
     }; 
     System.out.println("#2\n" + toString(multiplyByMatrix(multiplicand, multiplier))); 
     // #3 
     multiplicand = new double[][] { 
       {1, 2, -1}, 
       {0, 1, 0} 
     }; 
     multiplier = new double[][] { 
       {1, 1, 0, 0}, 
       {0, 2, 1, 1}, 
       {1, 1, 2, 2} 
     }; 
     System.out.println("#3\n" + toString(multiplyByMatrix(multiplicand, multiplier))); 
    } 
} 

出力：

#1 
     12.00  -1.00  2.00 
     7.00  -2.00  3.00 
     5.00  -5.00  8.00 

#2 
     0.00 
     -4.00 
     7.00 

#3 
     0.00  4.00  0.00  0.00 
     0.00  2.00  1.00  1.00 

Answer 5

それは方法multsあなた

import java.util.Scanner; 

public class MulTwoArray { 

public static void main(String[] args) { 

    int i, j, k; 
    int[][] a = new int[3][3]; 
    int[][] b = new int[3][3]; 
    int[][] c = new int[3][3]; 



    Scanner sc = new Scanner(System.in); 

    System.out.println("Enter size of array a"); 
    int rowa = sc.nextInt(); 
    int cola = sc.nextInt(); 

    System.out.println("Enter size of array b"); 
    int rowb = sc.nextInt(); 
    int colb = sc.nextInt(); 


    //read and b 

    System.out.println("Enter elements of array a"); 
    for (i = 0; i < rowa; ++i) { 
     for (j = 0; j < cola; ++j) { 

      a[i][j] = sc.nextInt(); 

     } 
     System.out.println(); 
    } 
    System.out.println("Enter elements of array b"); 
    for (i = 0; i < rowb; ++i) { 
     for (j = 0; j < colb; ++j) { 

      b[i][j] = sc.nextInt(); 

     } 
     System.out.println("\n"); 
    } 

    //print a and b 

    System.out.println("the elements of array a"); 
    for (i = 0; i < rowa; ++i) { 
     for (j = 0; j < cola; ++j) { 

      System.out.print(a[i][j]); 
      System.out.print("\t"); 

     } 
     System.out.println("\n"); 
    } 
    System.out.println("the elements of array b"); 
    for (i = 0; i < rowb; ++i) { 
     for (j = 0; j < colb; ++j) { 

      System.out.print(b[i][j]); 
      System.out.print("\t"); 

     } 
     System.out.println("\n"); 

    } 

    //multiply a and b 

    for (i = 0; i < rowa; ++i) { 

     for (j = 0; j < colb; ++j) { 
      c[i][j] = 0; 
      for (k = 0; k < cola; ++k) { 
       c[i][j] += a[i][k] * b[k][j]; 
      } 
     } 
    } 


    //print multi result 

    System.out.println("result of multiplication of array a and b is "); 
    for (i = 0; i < rowa; ++i) { 
     for (j = 0; j < colb; ++j) { 

      System.out.print(c[i][j]); 
      System.out.print("\t"); 
     } 
     System.out.println("\n"); 
    } 
} 
} 

Answer 6

役立つかもしれない、これを試してみてくださいは、手順（パスカル）またはサブルーチン（Fortranの）

です

方法multMatrixは、入力行列としてコマンドを実行cmmdラインようUNIXで

inE.txt

4 4 
1 1 1 1 
2 4 8 16 
3 9 27 81 
4 16 64 256 
4 3 
4.0 -3.0 4.0 
-13.0 19.0 -7.0 
3.0 -2.0 7.0 
-1.0 1.0 -1.0 

を入力することができる機能（パスカル、フォートラン）

import java.util.*; 

public class MatmultE 
{ 
private static Scanner sc = new Scanner(System.in); 
    public static void main(String [] args) 
    { 
    double[][] A={{4.00,3.00},{2.00,1.00}}; 
    double[][] B={{-0.500,1.500},{1.000,-2.0000}}; 
    double[][] C=multMatrix(A,B); 
    printMatrix(A); 
    printMatrix(B);  
    printMatrix(C); 

    double a[][] = {{1, 2, -2, 0}, {-3, 4, 7, 2}, {6, 0, 3, 1}}; 
    double b[][] = {{-1, 3}, {0, 9}, {1, -11}, {4, -5}}; 
    double[][] c=multMatrix(a,b); 
    printMatrix(a); 
    printMatrix(b);  
    printMatrix(c); 

    double[][] a1 = readMatrix(); 
    double[][] b1 = readMatrix(); 
    double[][] c1 = new double[a1.length][b1[0].length]; 
    mults(a1,b1,c1,a1.length,a1[0].length,b1.length,b1[0].length); 
    printMatrix(c1); 
    printMatrixE(c1); 
    } 

    public static double[][] readMatrix() { 
     int rows = sc.nextInt(); 
     int cols = sc.nextInt(); 
     double[][] result = new double[rows][cols]; 
     for (int i = 0; i < rows; i++) { 
      for (int j = 0; j < cols; j++) { 
       result[i][j] = sc.nextDouble(); 
      } 
     } 
     return result; 
    } 


    public static void printMatrix(double[][] mat) { 
    System.out.println("Matrix["+mat.length+"]["+mat[0].length+"]"); 
     int rows = mat.length; 
     int columns = mat[0].length; 
     for (int i = 0; i < rows; i++) { 
      for (int j = 0; j < columns; j++) { 
       System.out.printf("%8.3f " , mat[i][j]); 
      } 
      System.out.println(); 
     } 
    System.out.println(); 
    } 

    public static void printMatrixE(double[][] mat) { 
    System.out.println("Matrix["+mat.length+"]["+mat[0].length+"]"); 
     int rows = mat.length; 
     int columns = mat[0].length; 
     for (int i = 0; i < rows; i++) { 
      for (int j = 0; j < columns; j++) { 
       System.out.printf("%9.2e " , mat[i][j]); 
      } 
      System.out.println(); 
     } 
    System.out.println(); 
    } 


    public static double[][] multMatrix(double a[][], double b[][]){//a[m][n], b[n][p] 
    if(a.length == 0) return new double[0][0]; 
    if(a[0].length != b.length) return null; //invalid dims 

    int n = a[0].length; 
    int m = a.length; 
    int p = b[0].length; 

    double ans[][] = new double[m][p]; 

    for(int i = 0;i < m;i++){ 
     for(int j = 0;j < p;j++){ 
     ans[i][j]=0; 
     for(int k = 0;k < n;k++){ 
      ans[i][j] += a[i][k] * b[k][j]; 
     } 
     } 
    } 
    return ans; 
    } 

    public static void mults(double a[][], double b[][], double c[][], int r1, 
         int c1, int r2, int c2){ 
     for(int i = 0;i < r1;i++){ 
     for(int j = 0;j < c2;j++){ 
      c[i][j]=0; 
      for(int k = 0;k < c1;k++){ 
       c[i][j] += a[i][k] * b[k][j]; 
      } 
     } 
     } 
    } 
} 

ある：

$ java MatmultE < inE.txt> outE.txt

あなたは出力

outC.txt

Matrix[2][2] 
    4.000 3.000 
    2.000 1.000 

Matrix[2][2] 
    -0.500 1.500 
    1.000 -2.000 

Matrix[2][2] 
    1.000 0.000 
    0.000 1.000 

Matrix[3][4] 
    1.000 2.000 -2.000 0.000 
    -3.000 4.000 7.000 2.000 
    6.000 0.000 3.000 1.000 

Matrix[4][2] 
    -1.000 3.000 
    0.000 9.000 
    1.000 -11.000 
    4.000 -5.000 

Matrix[3][2] 
    -3.000 43.000 
    18.000 -60.000 
    1.000 -20.000 

Matrix[4][3] 
    -7.000 15.000 3.000 
-36.000 70.000 20.000 
-105.000 189.000 57.000 
-256.000 420.000 96.000 

Matrix[4][3] 
-7.00e+00 1.50e+01 3.00e+00 
-3.60e+01 7.00e+01 2.00e+01 
-1.05e+02 1.89e+02 5.70e+01 
-2.56e+02 4.20e+02 9.60e+01