/* ./src_f77/cgelq2.f -- translated by f2c (version 20030320).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include <punc/vf2c.h>

/* Subroutine */ int cgelq2_(integer *m, integer *n, complex *a, integer *lda,
	 complex *tau, complex *work, integer *info)
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3;

    /* Local variables */
    static integer i__, k;
    static complex alpha;
    extern /* Subroutine */ int clarf_(char *, integer *, integer *, complex *
	    , integer *, complex *, complex *, integer *, complex *, ftnlen), 
	    clarfg_(integer *, complex *, complex *, integer *, complex *), 
	    clacgv_(integer *, complex *, integer *), xerbla_(char *, integer 
	    *, ftnlen);


/*  -- LAPACK routine (version 3.0) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/*     Courant Institute, Argonne National Lab, and Rice University */
/*     September 30, 1994 */

/*     .. Scalar Arguments .. */
/*     .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  CGELQ2 computes an LQ factorization of a complex 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) COMPLEX 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, */
/*          with the array TAU, represent the unitary 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) COMPLEX array, dimension (min(M,N)) */
/*          The scalar factors of the elementary reflectors (see Further */
/*          Details). */

/*  WORK    (workspace) COMPLEX 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 complex scalar, and v is a complex vector with */
/*  v(1:i-1) = 0 and v(i) = 1; conjg(v(i+1:n)) is stored on exit in */
/*  A(i,i+1:n), and tau in TAU(i). */

/*  ===================================================================== */

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. External Subroutines .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Test the input arguments */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    --tau;
    --work;

    /* Function Body */
    *info = 0;
    if (*m < 0) {
	*info = -1;
    } else if (*n < 0) {
	*info = -2;
    } else if (*lda < max(1,*m)) {
	*info = -4;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("CGELQ2", &i__1, (ftnlen)6);
	return 0;
    }

    k = min(*m,*n);

    i__1 = k;
    for (i__ = 1; i__ <= i__1; ++i__) {

/*        Generate elementary reflector H(i) to annihilate A(i,i+1:n) */

	i__2 = *n - i__ + 1;
	clacgv_(&i__2, &a[i__ + i__ * a_dim1], lda);
	i__2 = i__ + i__ * a_dim1;
	alpha.r = a[i__2].r, alpha.i = a[i__2].i;
	i__2 = *n - i__ + 1;
/* Computing MIN */
	i__3 = i__ + 1;
	clarfg_(&i__2, &alpha, &a[i__ + min(i__3,*n) * a_dim1], lda, &tau[i__]
		);
	if (i__ < *m) {

/*           Apply H(i) to A(i+1:m,i:n) from the right */

	    i__2 = i__ + i__ * a_dim1;
	    a[i__2].r = 1.f, a[i__2].i = 0.f;
	    i__2 = *m - i__;
	    i__3 = *n - i__ + 1;
	    clarf_("Right", &i__2, &i__3, &a[i__ + i__ * a_dim1], lda, &tau[
		    i__], &a[i__ + 1 + i__ * a_dim1], lda, &work[1], (ftnlen)
		    5);
	}
	i__2 = i__ + i__ * a_dim1;
	a[i__2].r = alpha.r, a[i__2].i = alpha.i;
	i__2 = *n - i__ + 1;
	clacgv_(&i__2, &a[i__ + i__ * a_dim1], lda);
/* L10: */
    }
    return 0;

/*     End of CGELQ2 */

} /* cgelq2_ */

