CODEWITHSUNDEEP
cgccmatrix
user2019260
user2019260

Reputation: 153

Why isn't my C matrix performing the way I expect?

I'm attempting a project in C and I'm pretty confused by the results I'm getting. I've done quite a bit of research on how the arrays are handled and I feel like it should work. Below is my code:

for( i = 0; i<1000;i++)
    {
        for( j = 0; j<1000; j++)
            {   
                if(j==0)
                    matrix[i][j] =i;
                else{
                    double value = (i-j)/j;
                    printf("%s%d\n","value of i-j: ",value);
                    matrix[i][j] = value;
                    printf("%s%d\n","value stores in matrix: ",*matrix[i][j]);
                }


        }
    }

matrix is a double array declared outside of any functions like so:

double matrix[1000][1000];

When I run the program, I get a separate value for the printout of 'value' and a different value for the printout of matrix[i][j] and I do not understand why they are different.

Thank you in advance!

Upvotes: 0

Views: 71

Answers (3)

KARTHIK BHAT
KARTHIK BHAT

Reputation: 1420

printf("%s%d\n","value stores in matrix: ",*matrix[i][j]);

why do you deference the matrix??

change it to 

printf("value stored in matrix: %lf ", matrix[i][j]);

you cannot specify the string literal like that in C. if you still want to print a string try

char *s = "value stores in matrix:"

then 

printf("%s%lf\n",s,matrix[i][j]);

Upvotes: 0

PandaRaid
PandaRaid

Reputation: 628

You are dereferencing the result of matrix[i][j] which is wrong since the array notation by default dereferences the index. Remove the * before the matrix access. Also change your format specifier to %lf.

Upvotes: 0

ooga
ooga

Reputation: 15501

You shouldn't put the asterisk in front of matrix in printf, as that interprets the data as an address and "dereferences" it. Also, if you want to print a double, you need to use %f instead of %d. And if you want to calculate (i-j)/j as a double (instead of integer division) you need to use a cast on one of the operands of the division operator.

for( i = 0; i < 1000;i++)
{
    matrix[i][0] = i;
    for( j = 1; j < 1000; j++)
    {   
        double value = (i-j)/(double)j;
        printf("value of i-j: %f\n", value);
        matrix[i][j] = value;
        printf("value stored in matrix: %f\n", matrix[i][j]);
    }
}

Upvotes: 2

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