"by bravegag ?? Sat Mar 24, 2012 4:43 pm Hello,I have the same problem as peng.du has, trying to reuse Daniel's routines I pass as input as A the old QR as returned by DGEQRF and B is a matrix that contains the extra row and does not work for me.My use-case is simple I create a QR factorization using DGEQRF, then I have a pointer to the QR compact LAPACK form which I can pass around.Daniel's A input" . . . .