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NAME
     dgelq2 - compute an LQ factorization of a real m by n matrix
     A

SYNOPSIS
     SUBROUTINE DGELQ2( M, N, A, LDA, TAU, WORK, INFO )

     INTEGER INFO, LDA, M, N

     DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * )



     #include <sunperf.h>

     void dgelq2(int m, int n, double *da, int lda, double  *tau,
               int *info) ;

PURPOSE
     DGELQ2 computes an LQ factorization of a real m by n  matrix
     A:  A = L * Q.


ARGUMENTS
     M         (input) INTEGER
               The number of rows of the matrix A.  M >= 0.

     N         (input) INTEGER
               The number of columns of the matrix A.  N >= 0.

     A         (input/output) DOUBLE PRECISION  array,  dimension
               (LDA,N)
               On entry, the m by n matrix A.  On exit, the  ele-
               ments  on and below the diagonal of the array con-
               tain the m by min(m,n) lower trapezoidal matrix  L
               (L  is  lower  triangular if m <= n); the elements
               above the diagonal, with the array TAU,  represent
               the orthogonal matrix Q as a product of elementary
               reflectors (see Further Details).  LDA     (input)
               INTEGER The leading dimension of the array A.  LDA
               >= max(1,M).

     TAU       (output)   DOUBLE   PRECISION   array,   dimension
               (min(M,N))
               The scalar factors of  the  elementary  reflectors
               (see Further Details).

     WORK      (workspace) DOUBLE PRECISION array, dimension (M)

     INFO      (output) INTEGER
               = 0: successful exit
               < 0: if INFO  =  -i,  the  i-th  argument  had  an
               illegal value

FURTHER DETAILS
     The matrix Q is  represented  as  a  product  of  elementary
     reflectors

        Q = H(k) . . . H(2) H(1), where k = min(m,n).

     Each H(i) has the form

        H(i) = I - tau * v * v'

     where tau is a real scalar, and v is a real vector with
     v(1:i-1) = 0 and v(i) = 1; v(i+1:n) is  stored  on  exit  in
     A(i,i+1:n), and tau in TAU(i).

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