Hi, everyone!

I have a sparse $n \times n$ matrix $A$ with $nnz(A)$ denoting the number of non-zero entries in $A$. Now I use QR factorization to decompose $A$ into an orthogonal matrix $Q$ and triangular matrix $R$. My problem is that : can we use some methods to control the sparsity of $Q$ satisfying $nnz(Q) \le nnz(A)$.