/*  -- translated by f2c (version 20100827).
   You must link the resulting object file with libf2c:
	on Microsoft Windows system, link with libf2c.lib;
	on Linux or Unix systems, link with .../path/to/libf2c.a -lm
	or, if you install libf2c.a in a standard place, with -lf2c -lm
	-- in that order, at the end of the command line, as in
		cc *.o -lf2c -lm
	Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,

		http://www.netlib.org/f2c/libf2c.zip
*/

#include "f2c.h"

/* Table of constant values */

static integer c__1 = 1;
static integer c_n1 = -1;

/* Subroutine */ int igraphdorghr_(integer *n, integer *ilo, integer *ihi, 
	doublereal *a, integer *lda, doublereal *tau, doublereal *work, 
	integer *lwork, integer *info)
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2;

    /* Local variables */
    integer i__, j, nb, nh, iinfo;
    extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);
    extern integer igraphilaenv_(integer *, char *, char *, integer *, integer *, 
	    integer *, integer *, ftnlen, ftnlen);
    extern /* Subroutine */ int igraphdorgqr_(integer *, integer *, integer *, 
	    doublereal *, integer *, doublereal *, doublereal *, integer *, 
	    integer *);
    integer lwkopt;
    logical lquery;


/*  -- LAPACK routine (version 3.2) --   
    -- LAPACK is a software package provided by Univ. of Tennessee,    --   
    -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--   
       November 2006   


    Purpose   
    =======   

    DORGHR generates a real orthogonal matrix Q which is defined as the   
    product of IHI-ILO elementary reflectors of order N, as returned by   
    DGEHRD:   

    Q = H(ilo) H(ilo+1) . . . H(ihi-1).   

    Arguments   
    =========   

    N       (input) INTEGER   
            The order of the matrix Q. N >= 0.   

    ILO     (input) INTEGER   
    IHI     (input) INTEGER   
            ILO and IHI must have the same values as in the previous call   
            of DGEHRD. Q is equal to the unit matrix except in the   
            submatrix Q(ilo+1:ihi,ilo+1:ihi).   
            1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.   

    A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)   
            On entry, the vectors which define the elementary reflectors,   
            as returned by DGEHRD.   
            On exit, the N-by-N orthogonal matrix Q.   

    LDA     (input) INTEGER   
            The leading dimension of the array A. LDA >= max(1,N).   

    TAU     (input) DOUBLE PRECISION array, dimension (N-1)   
            TAU(i) must contain the scalar factor of the elementary   
            reflector H(i), as returned by DGEHRD.   

    WORK    (workspace/output) DOUBLE PRECISION array, dimension (MAX(1,LWORK))   
            On exit, if INFO = 0, WORK(1) returns the optimal LWORK.   

    LWORK   (input) INTEGER   
            The dimension of the array WORK. LWORK >= IHI-ILO.   
            For optimum performance LWORK >= (IHI-ILO)*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 had an illegal value   

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


       Test the input arguments   

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

    /* Function Body */
    *info = 0;
    nh = *ihi - *ilo;
    lquery = *lwork == -1;
    if (*n < 0) {
	*info = -1;
    } else if (*ilo < 1 || *ilo > max(1,*n)) {
	*info = -2;
    } else if (*ihi < min(*ilo,*n) || *ihi > *n) {
	*info = -3;
    } else if (*lda < max(1,*n)) {
	*info = -5;
    } else if (*lwork < max(1,nh) && ! lquery) {
	*info = -8;
    }

    if (*info == 0) {
	nb = igraphilaenv_(&c__1, "DORGQR", " ", &nh, &nh, &nh, &c_n1, (ftnlen)6, (
		ftnlen)1);
	lwkopt = max(1,nh) * nb;
	work[1] = (doublereal) lwkopt;
    }

    if (*info != 0) {
	i__1 = -(*info);
	igraphxerbla_("DORGHR", &i__1, (ftnlen)6);
	return 0;
    } else if (lquery) {
	return 0;
    }

/*     Quick return if possible */

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

/*     Shift the vectors which define the elementary reflectors one   
       column to the right, and set the first ilo and the last n-ihi   
       rows and columns to those of the unit matrix */

    i__1 = *ilo + 1;
    for (j = *ihi; j >= i__1; --j) {
	i__2 = j - 1;
	for (i__ = 1; i__ <= i__2; ++i__) {
	    a[i__ + j * a_dim1] = 0.;
/* L10: */
	}
	i__2 = *ihi;
	for (i__ = j + 1; i__ <= i__2; ++i__) {
	    a[i__ + j * a_dim1] = a[i__ + (j - 1) * a_dim1];
/* L20: */
	}
	i__2 = *n;
	for (i__ = *ihi + 1; i__ <= i__2; ++i__) {
	    a[i__ + j * a_dim1] = 0.;
/* L30: */
	}
/* L40: */
    }
    i__1 = *ilo;
    for (j = 1; j <= i__1; ++j) {
	i__2 = *n;
	for (i__ = 1; i__ <= i__2; ++i__) {
	    a[i__ + j * a_dim1] = 0.;
/* L50: */
	}
	a[j + j * a_dim1] = 1.;
/* L60: */
    }
    i__1 = *n;
    for (j = *ihi + 1; j <= i__1; ++j) {
	i__2 = *n;
	for (i__ = 1; i__ <= i__2; ++i__) {
	    a[i__ + j * a_dim1] = 0.;
/* L70: */
	}
	a[j + j * a_dim1] = 1.;
/* L80: */
    }

    if (nh > 0) {

/*        Generate Q(ilo+1:ihi,ilo+1:ihi) */

	igraphdorgqr_(&nh, &nh, &nh, &a[*ilo + 1 + (*ilo + 1) * a_dim1], lda, &tau[*
		ilo], &work[1], lwork, &iinfo);
    }
    work[1] = (doublereal) lwkopt;
    return 0;

/*     End of DORGHR */

} /* igraphdorghr_ */

