# Linear Least Squares (LLS) Problems

This topic describes LAPACK driver routines used for solving linear least squares problems. Table “Driver Routines for Solving LLS Problems” lists all such routines for Fortran 77 interface. Respective routine names in Fortran 95 interface are without the first symbol (see Routine Naming Conventions).

Driver Routines for Solving LLS Problems
Routine Name | Operation performed
--- | ---
?gels | Uses QR or LQ factorization to solve a overdetermined or underdetermined linear system with full rank matrix.
?gelsy | Computes the minimum-norm solution to a linear least squares problem using a complete orthogonal factorization of A.
?gelss | Computes the minimum-norm solution to a linear least squares problem using the singular value decomposition of A.
?gelsd | Computes the minimum-norm solution to a linear least squares problem using the singular value decomposition of A and a divide and conquer method.