Multiply 6X6 Matrices using "infile" (DAT file)

Lao-Tzu · #1 03-May-2008, 18:02

Hey guys,
I'm stuck on a Matrix assigment at the moment. The assignment asks us to multiply 2 6x6 matrices together and show the result. Our inputs are supposed to come form a .DAT file.. Can you guys show me how I would incorporate the "infile" into my current project? My current currently asks for someone to input numbers... but my instructor wants us to get input from the .DAT files.. Below is my current code.

CPP / C++ / C Code:


#include <iostream>
using namespace std;

int main()

{

     int A[6][6];

     int B[6][6];

     int C[6][6];

     int X[6][6][6];

     int i,j,m;

     

     

     cout<<"==========Enter matrix A==========\n";

     for(i=0;i<6;i++)

     {     cout<<endl;

          for(j=0;j<6;j++)

          {     

               cout<<"A["<<i<<"]["<<j<<"]= ";

               cin>>A[i][j];

               C[i][j]=0;

          }

     }

     

     cout<<"\n==========Enter matrix B==========\n";

     for(i=0;i<6;i++)

     {     cout<<endl;

          for(j=0;j<6;j++)

          {     

               cout<<" B["<<i<<"]["<<j<<"]= ";

               cin>>B[i][j];

          }

     }

     

     

     for(i=0;i<6;i++)

     {     

          for(j=0;j<6;j++)

          {     

               for(m=0;m<6;m++)

               {

               X[i][j][m]=A[i][m]*B[m][j];

               C[i][j]+=X[i][j][m];

               }

          }

     }

 

     cout<<"\n==========matrix C==========\n";

     for(i=0;i<6;i++)

     {     cout<<endl;

          for(j=0;j<6;j++)

          {     

               cout<<" C["<<i<<"]["<<j<<"]= "<<C[i][j];

         

          }

     }

     cout<<endl<<endl;

 

return 0;

}

davekw7x · #2 04-May-2008, 08:25

Quote:

Originally Posted by Lao-Tzu

Can you guys show me how I would incorporate the "infile" into my current project?

1. Declare an ifstream and give it the name of your file.

2. Make sure it was opened correctly. Tell the user what happened. (Did it open it or not?)

3. Use the overloaded operator >> to read the values.

4. Each and every time, make sure that it was able to read. If it was not able to read everything, inform the user. For now, just bail out if it sees an error condition.

For example:

CPP / C++ / C Code:

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    int i, j;
    double x[3][3];
    char *inname = "test.dat";
    ifstream infile(inname);
    if (!infile) {
        cout << "Can't open file " << inname << " for reading." << endl;
        return 0;
    }
    cout << "Opened " << inname << " for reading." << endl;
    for (i = 0; i < 3; i++) {
        for (j = 0; j < 3; j++) {
            infile >> x[i][j];
            if (!infile) {
                cout << "There was a problem reading x[" << i << "][" << j << "]" << endl;
                return 0;
            }
        }
    }
    for (i = 0; i < 3; i++) {
        for (j = 0; j < 3; j++) {
            cout << "x[" << i << "][" << j << "] = " << x[i][j] << endl;
        }
    }
    return 0;
}

Now, try something like the following as the file "test.dat":

Code:

1 2 3
5.2 4.00001 22.22
7 8 9

Output:

Code:

Opened test.dat for reading.
x[0][0] = 1
x[0][1] = 2
x[0][2] = 3
x[1][0] = 5.2
x[1][1] = 4.00001
x[1][2] = 22.22
x[2][0] = 7
x[2][1] = 8
x[2][2] = 9

Now go back to test.dat and put in an error. Maybe put a comma instead of a period in 4.00001:

Code:

1 2 3
5.2 4,00001 22.22
7 8 9

Output:

Code:

Opened test.dat for reading.
There was a problem reading x[1][2]

Now, go back and rename your file "test.dat" to something else (so there is no file named "test.dat").

Output:

Code:

Can't open file test.dat for reading.

Regards,

Dave

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Multiply 6X6 Matrices using "infile" (DAT file)

Re: Multiply 6X6 Matrices using "infile" (DAT file)