Question

I have a function , which is to mulitply a matrix and vector:

 double *matrix_vector_multiply(int rows, int cols,
                           double **mat, double *vec)
{

    double *answer = malloc(rows * sizeof (double));
    int i,j;
    for (i=0; i<rows; rows++)
    ans[i]=0;

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

        for (j=0; j<cols; cols++)
             {
            answer[i] = answer[i] + mat[i][j] * vec[j];
            }
        }
    return ans;
}

I keep getting all 0’s for the output.. any ideas on how to fix it?

Answer 1

Is this actual code that you have posted ? As well as the obvious problems with ans and answer etc, your for loops are completely wrong, e.g.

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

should be:

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

and:

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

should be:

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