Write a method called matmul that takes as arguments two matrices of doubles: do

Question

Write a method called matmul that takes as arguments two matrices of doubles: double[][] A and double[][] B, and returns the matrix that represents the multiplication of the two argument matrices (that is C = AB). Matrix multiplication is not commutative and it works as follows: one can only multiply two matrices if the number of rows of the left matrix is the same as the number of columns of the right matrix. The entry (i; j) on C = AB is obtained by taking the inner-product of the ith row of A with the jth column of B. The inner-product between two vectors is obtained by adding up the products of the respective entries in the two vectors.

Explanation / Answer

class matrix_multi
{
   public static void matrixMultiply(double[][] m, double[][] n)
   {
       double[][] multipliedMatrix = new double [m.length][n[0].length];
       for (int i=0; i<m.length; i++)
       {
           for (int j=0; j<n[0].length; j++)
           {
               for (int k=0; k<n.length; k++)
               {
               multipliedMatrix[i][j] = multipliedMatrix[i][j] + (m[i][k] * n[k][j]);
               }
           }
       }

        for (int i=0; i<m.length; i++)
       {
  
           for (int k=0; k<n.length; k++)
           {
               System.out.println(multipliedMatrix[i][k]);
           }
       }

   }

   public static void main(String args[])
   {
      
       int i,j,c=1;
       double a[][] =new double[3][3];
       double b[][] = new double[3][3];

       for(i=0;i<3;i++)
       {
           for(j=0;j<3;j++)
           {
               a[i][j]=c;
               b[i][j]=c+2;
               c++;
           }
       }

       matrixMultiply(a,b);
   }
}
          

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