Lapack's dgeqrf in c++

Question

My project is about finding Q in QR decomposition for very large matrices (e.g. 500*500) in C++. I've started to use Lapack package recently and its especial function "dgeqrf". I started by a simple matrix as below in Code:blocks:

 #include <iostream>
 #include <lapacke.h>

using namespace std;

int main()
{
    double a[6][2] = {{0,2},{2,-1},{2,-1},{0,1.5},{2,-1},{2,-1}};
    int m=6;
    int n=2;
    int info = 0;
    int lda = m;
    int lwork = n;
    double *work;
    double *tau;
    dgeqrf_(&m, &n, a, &lda, tau, work, &lwork, &info);

}

After running the code, I saw this error in "dgeqrf" line:

error: cannot convert 'double (*)[2]' to 'double*' for argument '3' to 'void dgeqrf_(int*, int*, double*, int*, double*, double*, int*, int*)'

Who can help me about this error?Do I have mistake in parameter definition? Also, after running, how I can work with the Q matrix? Can I define a new matix double q[][]=dgeqrf(....) and use it in my project? I'm sorry if my question was very basic but I couldn't find the solution.

Answer 1

double a[12] = {0, 2, 2,  0, 2, 2,  // row1
                2,-1,-1,1.5,-1,-1}; // row2