sgeqrs3

!>
!> Solve the least squares problem
!>     min || A*X - B ||
!> using the QR factorization
!>     A = Q*R
!> computed by SGEQRF.
!> 

M

!>          M is INTEGER
!>          The number of rows of the matrix A.  M >= 0.
!> 

N

!>          N is INTEGER
!>          The number of columns of the matrix A.  M >= N >= 0.
!> 

NRHS

!>          NRHS is INTEGER
!>          The number of columns of B.  NRHS >= 0.
!> 

A

!>          A is REAL array, dimension (LDA,N)
!>          Details of the QR factorization of the original matrix A as
!>          returned by SGEQRF.
!> 

LDA

!>          LDA is INTEGER
!>          The leading dimension of the array A.  LDA >= M.
!> 

TAU

!>          TAU is REAL array, dimension (N)
!>          Details of the orthogonal matrix Q.
!> 

B

!>          B is REAL array, dimension (LDB,NRHS)
!>          On entry, the m-by-nrhs right hand side matrix B.
!>          On exit, the n-by-nrhs solution matrix X.
!> 

LDB

!>          LDB is INTEGER
!>          The leading dimension of the array B. LDB >= M.
!> 

WORK

!>          WORK is REAL array, dimension (LWORK)
!> 

LWORK

!>          LWORK is INTEGER
!>          The length of the array WORK.  LWORK must be at least NRHS,
!>          and should be at least NRHS*NB, where NB is the block size
!>          for this environment.
!> 

INFO

!>          INFO is INTEGER
!>          = 0: successful exit
!>          < 0: if INFO = -i, the i-th argument had an illegal value
!> 

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