!>
!> SGELQ computes an LQ factorization of a real M-by-N matrix A:
!>
!>    A = ( L 0 ) *  Q
!>
!> where:
!>
!>    Q is a N-by-N orthogonal matrix;
!>    L is a lower-triangular M-by-M matrix;
!>    0 is a M-by-(N-M) zero matrix, if M < N.
!>
!> 

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.  N >= 0.
!> 

A

!>          A is REAL array, dimension (LDA,N)
!>          On entry, the M-by-N matrix A.
!>          On exit, the elements on and below the diagonal of the array
!>          contain the M-by-min(M,N) lower trapezoidal matrix L
!>          (L is lower triangular if M <= N);
!>          the elements above the diagonal are used to store part of the 
!>          data structure to represent Q.
!> 

LDA

!>          LDA is INTEGER
!>          The leading dimension of the array A.  LDA >= max(1,M).
!> 

T

!>          T is REAL array, dimension (MAX(5,TSIZE))
!>          On exit, if INFO = 0, T(1) returns optimal (or either minimal 
!>          or optimal, if query is assumed) TSIZE. See TSIZE for details.
!>          Remaining T contains part of the data structure used to represent Q.
!>          If one wants to apply or construct Q, then one needs to keep T 
!>          (in addition to A) and pass it to further subroutines.
!> 

TSIZE

!>          TSIZE is INTEGER
!>          If TSIZE >= 5, the dimension of the array T.
!>          If TSIZE = -1 or -2, then a workspace query is assumed. The routine
!>          only calculates the sizes of the T and WORK arrays, returns these
!>          values as the first entries of the T and WORK arrays, and no error
!>          message related to T or WORK is issued by XERBLA.
!>          If TSIZE = -1, the routine calculates optimal size of T for the 
!>          optimum performance and returns this value in T(1).
!>          If TSIZE = -2, the routine calculates minimal size of T and 
!>          returns this value in T(1).
!> 

WORK

!>          (workspace) REAL array, dimension (MAX(1,LWORK))
!>          On exit, if INFO = 0, WORK(1) contains optimal (or either minimal
!>          or optimal, if query was assumed) LWORK.
!>          See LWORK for details.
!> 

LWORK

!>          LWORK is INTEGER
!>          The dimension of the array WORK.
!>          If LWORK = -1 or -2, then a workspace query is assumed. The routine
!>          only calculates the sizes of the T and WORK arrays, returns these
!>          values as the first entries of the T and WORK arrays, and no error
!>          message related to T or WORK is issued by XERBLA.
!>          If LWORK = -1, the routine calculates optimal size of WORK for the
!>          optimal performance and returns this value in WORK(1).
!>          If LWORK = -2, the routine calculates minimal size of WORK and 
!>          returns this value in WORK(1).
!> 

INFO

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

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!>
!> The goal of the interface is to give maximum freedom to the developers for
!> creating any LQ factorization algorithm they wish. The triangular 
!> (trapezoidal) L has to be stored in the lower part of A. The lower part of A
!> and the array T can be used to store any relevant information for applying or
!> constructing the Q factor. The WORK array can safely be discarded after exit.
!>
!> Caution: One should not expect the sizes of T and WORK to be the same from one 
!> LAPACK implementation to the other, or even from one execution to the other.
!> A workspace query (for T and WORK) is needed at each execution. However, 
!> for a given execution, the size of T and WORK are fixed and will not change 
!> from one query to the next.
!>
!> 

!>
!> These details are particular for this LAPACK implementation. Users should not 
!> take them for granted. These details may change in the future, and are not likely
!> true for another LAPACK implementation. These details are relevant if one wants
!> to try to understand the code. They are not part of the interface.
!>
!> In this version,
!>
!>          T(2): row block size (MB)
!>          T(3): column block size (NB)
!>          T(6:TSIZE): data structure needed for Q, computed by
!>                           SLASWLQ or SGELQT
!>
!>  Depending on the matrix dimensions M and N, and row and column
!>  block sizes MB and NB returned by ILAENV, SGELQ will use either
!>  SLASWLQ (if the matrix is short-and-wide) or SGELQT to compute
!>  the LQ factorization.
!>