```      SUBROUTINE DORGL2( M, N, K, A, LDA, TAU, WORK, INFO )
*
*  -- LAPACK routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
INTEGER            INFO, K, LDA, M, N
*     ..
*     .. Array Arguments ..
DOUBLE PRECISION   A( LDA, * ), TAU( * ), WORK( * )
*     ..
*
*  Purpose
*  =======
*
*  DORGL2 generates an m by n real matrix Q with orthonormal rows,
*  which is defined as the first m rows of a product of k elementary
*  reflectors of order n
*
*        Q  =  H(k) . . . H(2) H(1)
*
*  as returned by DGELQF.
*
*  Arguments
*  =========
*
*  M       (input) INTEGER
*          The number of rows of the matrix Q. M >= 0.
*
*  N       (input) INTEGER
*          The number of columns of the matrix Q. N >= M.
*
*  K       (input) INTEGER
*          The number of elementary reflectors whose product defines the
*          matrix Q. M >= K >= 0.
*
*  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
*          On entry, the i-th row must contain the vector which defines
*          the elementary reflector H(i), for i = 1,2,...,k, as returned
*          by DGELQF in the first k rows of its array argument A.
*          On exit, the m-by-n matrix Q.
*
*  LDA     (input) INTEGER
*          The first dimension of the array A. LDA >= max(1,M).
*
*  TAU     (input) DOUBLE PRECISION array, dimension (K)
*          TAU(i) must contain the scalar factor of the elementary
*          reflector H(i), as returned by DGELQF.
*
*  WORK    (workspace) DOUBLE PRECISION array, dimension (M)
*
*  INFO    (output) INTEGER
*          = 0: successful exit
*          < 0: if INFO = -i, the i-th argument has an illegal value
*
*  =====================================================================
*
*     .. Parameters ..
DOUBLE PRECISION   ONE, ZERO
PARAMETER          ( ONE = 1.0D+0, ZERO = 0.0D+0 )
*     ..
*     .. Local Scalars ..
INTEGER            I, J, L
*     ..
*     .. External Subroutines ..
EXTERNAL           DLARF, DSCAL, XERBLA
*     ..
*     .. Intrinsic Functions ..
INTRINSIC          MAX
*     ..
*     .. Executable Statements ..
*
*     Test the input arguments
*
INFO = 0
IF( M.LT.0 ) THEN
INFO = -1
ELSE IF( N.LT.M ) THEN
INFO = -2
ELSE IF( K.LT.0 .OR. K.GT.M ) THEN
INFO = -3
ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
INFO = -5
END IF
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'DORGL2', -INFO )
RETURN
END IF
*
*     Quick return if possible
*
IF( M.LE.0 )
\$   RETURN
*
IF( K.LT.M ) THEN
*
*        Initialise rows k+1:m to rows of the unit matrix
*
DO 20 J = 1, N
DO 10 L = K + 1, M
A( L, J ) = ZERO
10       CONTINUE
IF( J.GT.K .AND. J.LE.M )
\$         A( J, J ) = ONE
20    CONTINUE
END IF
*
DO 40 I = K, 1, -1
*
*        Apply H(i) to A(i:m,i:n) from the right
*
IF( I.LT.N ) THEN
IF( I.LT.M ) THEN
A( I, I ) = ONE
CALL DLARF( 'Right', M-I, N-I+1, A( I, I ), LDA,
\$                     TAU( I ), A( I+1, I ), LDA, WORK )
END IF
CALL DSCAL( N-I, -TAU( I ), A( I, I+1 ), LDA )
END IF
A( I, I ) = ONE - TAU( I )
*
*        Set A(i,1:i-1) to zero
*
DO 30 L = 1, I - 1
A( I, L ) = ZERO
30    CONTINUE
40 CONTINUE
RETURN
*
*     End of DORGL2
*
END

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