D9a. Overdetermined or underdetermined systems of linear equations (unconstrained)

Functions
void	_dgecov (int job, int n, int lda, double a[], double ci[], int *info)
	Unscaled covariance matrix of linear least squares problem solved by dgels
void	_dgecovs (int job, int n, int lda, double a[], double s[], double ci[], double work[], int *info)
	Unscaled covariance matrix of linear least squares problem solved by dgelss
void	_dgecovy (int job, int n, int lda, double a[], int ipiv[], double ci[], int iwork[], int *info)
	Unscaled covariance matrix of linear least squares problem solved by dgelsy
void	_dgels (char trans, int m, int n, int nrhs, int lda, double a[], int ldb, double b[], double work[], int lwork, int *info)
	Solution to overdetermined or underdetermined linear equations Ax = b (Full rank)
void	_dgelsd (int m, int n, int nrhs, int lda, double a[], int ldb, double b[], double s[], double rcond, int *rank, double work[], int lwork, int iwork[], int *info)
	Solution to overdetermined or underdetermined linear equations Ax = b using the singular value decomposition (SVD) (Divide and conquer method)
void	_dgelss (int m, int n, int nrhs, int lda, double a[], int ldb, double b[], double s[], double rcond, int *rank, double work[], int lwork, int *info)
	Solution to overdetermined or underdetermined linear equations Ax = b using the singular value decomposition (SVD)
void	_dgelsy (int m, int n, int nrhs, int lda, double a[], int ldb, double b[], int jpvt[], double rcond, int *rank, double work[], int lwork, int *info)
	Solution to overdetermined or underdetermined linear equations Ax = b using a complete orthogonal factorization
void	_dgetsls (char trans, int m, int n, int nrhs, int lda, double a[], int ldb, double b[], double work[], int lwork, int *info)
	Solution to overdetermined or underdetermined linear equations Ax = b (Full rank) (Tall skinny QR or short wide LQ factorization)

Detailed Description

This is the group of D9a. Overdetermined or underdetermined systems of linear equations (unconstrained).