#include "blaswrap.h"
#include "f2c.h"

/* Subroutine */ int zungqr_(integer *m, integer *n, integer *k, 
	doublecomplex *a, integer *lda, doublecomplex *tau, doublecomplex *
	work, integer *lwork, integer *info)
{
/*  -- LAPACK routine (version 3.0) --   
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
       Courant Institute, Argonne National Lab, and Rice University   
       June 30, 1999   


    Purpose   
    =======   

    ZUNGQR generates an M-by-N complex matrix Q with orthonormal columns,   
    which is defined as the first N columns of a product of K elementary   
    reflectors of order M   

          Q  =  H(1) H(2) . . . H(k)   

    as returned by ZGEQRF.   

    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. M >= N >= 0.   

    K       (input) INTEGER   
            The number of elementary reflectors whose product defines the   
            matrix Q. N >= K >= 0.   

    A       (input/output) COMPLEX*16 array, dimension (LDA,N)   
            On entry, the i-th column must contain the vector which   
            defines the elementary reflector H(i), for i = 1,2,...,k, as   
            returned by ZGEQRF in the first k columns 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) COMPLEX*16 array, dimension (K)   
            TAU(i) must contain the scalar factor of the elementary   
            reflector H(i), as returned by ZGEQRF.   

    WORK    (workspace/output) COMPLEX*16 array, dimension (LWORK)   
            On exit, if INFO = 0, WORK(1) returns the optimal LWORK.   

    LWORK   (input) INTEGER   
            The dimension of the array WORK. LWORK >= max(1,N).   
            For optimum performance LWORK >= N*NB, where NB is the   
            optimal blocksize.   

            If LWORK = -1, then a workspace query is assumed; the routine   
            only calculates the optimal size of the WORK array, returns   
            this value as the first entry of the WORK array, and no error   
            message related to LWORK is issued by XERBLA.   

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

    =====================================================================   


       Test the input arguments   

       Parameter adjustments */
    /* Table of constant values */
    static integer c__1 = 1;
    static integer c_n1 = -1;
    static integer c__3 = 3;
    static integer c__2 = 2;
    
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3, i__4;
    /* Local variables */
    static integer i__, j, l, nbmin, iinfo, ib, nb, ki, kk;
    extern /* Subroutine */ int zung2r_(integer *, integer *, integer *, 
	    doublecomplex *, integer *, doublecomplex *, doublecomplex *, 
	    integer *);
    static integer nx;
    extern /* Subroutine */ int xerbla_(char *, integer *);
    extern integer ilaenv_(integer *, char *, char *, integer *, integer *, 
	    integer *, integer *, ftnlen, ftnlen);
    extern /* Subroutine */ int zlarfb_(char *, char *, char *, char *, 
	    integer *, integer *, integer *, doublecomplex *, integer *, 
	    doublecomplex *, integer *, doublecomplex *, integer *, 
	    doublecomplex *, integer *);
    static integer ldwork;
    extern /* Subroutine */ int zlarft_(char *, char *, integer *, integer *, 
	    doublecomplex *, integer *, doublecomplex *, doublecomplex *, 
	    integer *);
    static integer lwkopt;
    static logical lquery;
    static integer iws;
#define a_subscr(a_1,a_2) (a_2)*a_dim1 + a_1
#define a_ref(a_1,a_2) a[a_subscr(a_1,a_2)]


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

    /* Function Body */
    *info = 0;
    nb = ilaenv_(&c__1, "ZUNGQR", " ", m, n, k, &c_n1, (ftnlen)6, (ftnlen)1);
    lwkopt = max(1,*n) * nb;
    work[1].r = (doublereal) lwkopt, work[1].i = 0.;
    lquery = *lwork == -1;
    if (*m < 0) {
	*info = -1;
    } else if (*n < 0 || *n > *m) {
	*info = -2;
    } else if (*k < 0 || *k > *n) {
	*info = -3;
    } else if (*lda < max(1,*m)) {
	*info = -5;
    } else if (*lwork < max(1,*n) && ! lquery) {
	*info = -8;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("ZUNGQR", &i__1);
	return 0;
    } else if (lquery) {
	return 0;
    }

/*     Quick return if possible */

    if (*n <= 0) {
	work[1].r = 1., work[1].i = 0.;
	return 0;
    }

    nbmin = 2;
    nx = 0;
    iws = *n;
    if (nb > 1 && nb < *k) {

/*        Determine when to cross over from blocked to unblocked code.   

   Computing MAX */
	i__1 = 0, i__2 = ilaenv_(&c__3, "ZUNGQR", " ", m, n, k, &c_n1, (
		ftnlen)6, (ftnlen)1);
	nx = max(i__1,i__2);
	if (nx < *k) {

/*           Determine if workspace is large enough for blocked code. */

	    ldwork = *n;
	    iws = ldwork * nb;
	    if (*lwork < iws) {

/*              Not enough workspace to use optimal NB:  reduce NB and   
                determine the minimum value of NB. */

		nb = *lwork / ldwork;
/* Computing MAX */
		i__1 = 2, i__2 = ilaenv_(&c__2, "ZUNGQR", " ", m, n, k, &c_n1,
			 (ftnlen)6, (ftnlen)1);
		nbmin = max(i__1,i__2);
	    }
	}
    }

    if (nb >= nbmin && nb < *k && nx < *k) {

/*        Use blocked code after the last block.   
          The first kk columns are handled by the block method. */

	ki = (*k - nx - 1) / nb * nb;
/* Computing MIN */
	i__1 = *k, i__2 = ki + nb;
	kk = min(i__1,i__2);

/*        Set A(1:kk,kk+1:n) to zero. */

	i__1 = *n;
	for (j = kk + 1; j <= i__1; ++j) {
	    i__2 = kk;
	    for (i__ = 1; i__ <= i__2; ++i__) {
		i__3 = a_subscr(i__, j);
		a[i__3].r = 0., a[i__3].i = 0.;
/* L10: */
	    }
/* L20: */
	}
    } else {
	kk = 0;
    }

/*     Use unblocked code for the last or only block. */

    if (kk < *n) {
	i__1 = *m - kk;
	i__2 = *n - kk;
	i__3 = *k - kk;
	zung2r_(&i__1, &i__2, &i__3, &a_ref(kk + 1, kk + 1), lda, &tau[kk + 1]
		, &work[1], &iinfo);
    }

    if (kk > 0) {

/*        Use blocked code */

	i__1 = -nb;
	for (i__ = ki + 1; i__1 < 0 ? i__ >= 1 : i__ <= 1; i__ += i__1) {
/* Computing MIN */
	    i__2 = nb, i__3 = *k - i__ + 1;
	    ib = min(i__2,i__3);
	    if (i__ + ib <= *n) {

/*              Form the triangular factor of the block reflector   
                H = H(i) H(i+1) . . . H(i+ib-1) */

		i__2 = *m - i__ + 1;
		zlarft_("Forward", "Columnwise", &i__2, &ib, &a_ref(i__, i__),
			 lda, &tau[i__], &work[1], &ldwork);

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

		i__2 = *m - i__ + 1;
		i__3 = *n - i__ - ib + 1;
		zlarfb_("Left", "No transpose", "Forward", "Columnwise", &
			i__2, &i__3, &ib, &a_ref(i__, i__), lda, &work[1], &
			ldwork, &a_ref(i__, i__ + ib), lda, &work[ib + 1], &
			ldwork);
	    }

/*           Apply H to rows i:m of current block */

	    i__2 = *m - i__ + 1;
	    zung2r_(&i__2, &ib, &ib, &a_ref(i__, i__), lda, &tau[i__], &work[
		    1], &iinfo);

/*           Set rows 1:i-1 of current block to zero */

	    i__2 = i__ + ib - 1;
	    for (j = i__; j <= i__2; ++j) {
		i__3 = i__ - 1;
		for (l = 1; l <= i__3; ++l) {
		    i__4 = a_subscr(l, j);
		    a[i__4].r = 0., a[i__4].i = 0.;
/* L30: */
		}
/* L40: */
	    }
/* L50: */
	}
    }

    work[1].r = (doublereal) iws, work[1].i = 0.;
    return 0;

/*     End of ZUNGQR */

} /* zungqr_ */

#undef a_ref
#undef a_subscr