#include "clapack.h"
#include "f2cP.h"

/* Table of constant values */

static double c_b10 = 0.;
static double c_b11 = 1.;
static integer c__1 = 1;

/* Subroutine */ int dgghrd_(const char *compq, const char *compz, integer *n, integer *
	ilo, integer *ihi, double *a, integer *lda, double *b, 
	integer *ldb, double *q, integer *ldq, double *z__, integer *
	ldz, integer *info)
{
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, q_dim1, q_offset, z_dim1, 
	    z_offset, i__1, i__2, i__3;

    /* Local variables */
    double c__, s;
    bool ilq, ilz;
    integer jcol;
    double temp;
    integer jrow;
    integer icompq, icompz;


/*  -- LAPACK routine (version 3.1) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

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

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

/*  DGGHRD reduces a pair of real matrices (A,B) to generalized upper */
/*  Hessenberg form using orthogonal transformations, where A is a */
/*  general matrix and B is upper triangular.  The form of the */
/*  generalized eigenvalue problem is */
/*     A*x = lambda*B*x, */
/*  and B is typically made upper triangular by computing its QR */
/*  factorization and moving the orthogonal matrix Q to the left side */
/*  of the equation. */

/*  This subroutine simultaneously reduces A to a Hessenberg matrix H: */
/*     Q**T*A*Z = H */
/*  and transforms B to another upper triangular matrix T: */
/*     Q**T*B*Z = T */
/*  in order to reduce the problem to its standard form */
/*     H*y = lambda*T*y */
/*  where y = Z**T*x. */

/*  The orthogonal matrices Q and Z are determined as products of Givens */
/*  rotations.  They may either be formed explicitly, or they may be */
/*  postmultiplied into input matrices Q1 and Z1, so that */

/*       Q1 * A * Z1**T = (Q1*Q) * H * (Z1*Z)**T */

/*       Q1 * B * Z1**T = (Q1*Q) * T * (Z1*Z)**T */

/*  If Q1 is the orthogonal matrix from the QR factorization of B in the */
/*  original equation A*x = lambda*B*x, then DGGHRD reduces the original */
/*  problem to generalized Hessenberg form. */

/*  Arguments */
/*  ========= */

/*  COMPQ   (input) CHARACTER*1 */
/*          = 'N': do not compute Q; */
/*          = 'I': Q is initialized to the unit matrix, and the */
/*                 orthogonal matrix Q is returned; */
/*          = 'V': Q must contain an orthogonal matrix Q1 on entry, */
/*                 and the product Q1*Q is returned. */

/*  COMPZ   (input) CHARACTER*1 */
/*          = 'N': do not compute Z; */
/*          = 'I': Z is initialized to the unit matrix, and the */
/*                 orthogonal matrix Z is returned; */
/*          = 'V': Z must contain an orthogonal matrix Z1 on entry, */
/*                 and the product Z1*Z is returned. */

/*  N       (input) INTEGER */
/*          The order of the matrices A and B.  N >= 0. */

/*  ILO     (input) INTEGER */
/*  IHI     (input) INTEGER */
/*          ILO and IHI mark the rows and columns of A which are to be */
/*          reduced.  It is assumed that A is already upper triangular */
/*          in rows and columns 1:ILO-1 and IHI+1:N.  ILO and IHI are */
/*          normally set by a previous call to SGGBAL; otherwise they */
/*          should be set to 1 and N respectively. */
/*          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 N-by-N general matrix to be reduced. */
/*          On exit, the upper triangle and the first subdiagonal of A */
/*          are overwritten with the upper Hessenberg matrix H, and the */
/*          rest is set to zero. */

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

/*  B       (input/output) DOUBLE PRECISION array, dimension (LDB, N) */
/*          On entry, the N-by-N upper triangular matrix B. */
/*          On exit, the upper triangular matrix T = Q**T B Z.  The */
/*          elements below the diagonal are set to zero. */

/*  LDB     (input) INTEGER */
/*          The leading dimension of the array B.  LDB >= max(1,N). */

/*  Q       (input/output) DOUBLE PRECISION array, dimension (LDQ, N) */
/*          On entry, if COMPQ = 'V', the orthogonal matrix Q1, */
/*          typically from the QR factorization of B. */
/*          On exit, if COMPQ='I', the orthogonal matrix Q, and if */
/*          COMPQ = 'V', the product Q1*Q. */
/*          Not referenced if COMPQ='N'. */

/*  LDQ     (input) INTEGER */
/*          The leading dimension of the array Q. */
/*          LDQ >= N if COMPQ='V' or 'I'; LDQ >= 1 otherwise. */

/*  Z       (input/output) DOUBLE PRECISION array, dimension (LDZ, N) */
/*          On entry, if COMPZ = 'V', the orthogonal matrix Z1. */
/*          On exit, if COMPZ='I', the orthogonal matrix Z, and if */
/*          COMPZ = 'V', the product Z1*Z. */
/*          Not referenced if COMPZ='N'. */

/*  LDZ     (input) INTEGER */
/*          The leading dimension of the array Z. */
/*          LDZ >= N if COMPZ='V' or 'I'; LDZ >= 1 otherwise. */

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

/*  Further Details */
/*  =============== */

/*  This routine reduces A to Hessenberg and B to triangular form by */
/*  an unblocked reduction, as described in _Matrix_Computations_, */
/*  by Golub and Van Loan (Johns Hopkins Press.) */

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

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

/*     Decode COMPQ */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;
    q_dim1 = *ldq;
    q_offset = 1 + q_dim1;
    q -= q_offset;
    z_dim1 = *ldz;
    z_offset = 1 + z_dim1;
    z__ -= z_offset;

    /* Function Body */
    if (lsame_(compq, "N")) {
	ilq = false;
	icompq = 1;
    } else if (lsame_(compq, "V")) {
	ilq = true;
	icompq = 2;
    } else if (lsame_(compq, "I")) {
	ilq = true;
	icompq = 3;
    } else {
	icompq = 0;
    }

/*     Decode COMPZ */

    if (lsame_(compz, "N")) {
	ilz = false;
	icompz = 1;
    } else if (lsame_(compz, "V")) {
	ilz = true;
	icompz = 2;
    } else if (lsame_(compz, "I")) {
	ilz = true;
	icompz = 3;
    } else {
	icompz = 0;
    }

/*     Test the input parameters. */

    *info = 0;
    if (icompq <= 0) {
	*info = -1;
    } else if (icompz <= 0) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (*ilo < 1) {
	*info = -4;
    } else if (*ihi > *n || *ihi < *ilo - 1) {
	*info = -5;
    } else if (*lda < std::max(1_integer,*n)) {
	*info = -7;
    } else if (*ldb < std::max(1_integer,*n)) {
	*info = -9;
    } else if (ilq && *ldq < *n || *ldq < 1) {
	*info = -11;
    } else if (ilz && *ldz < *n || *ldz < 1) {
	*info = -13;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DGGHRD", &i__1);
	return 0;
    }

/*     Initialize Q and Z if desired. */

    if (icompq == 3) {
	dlaset_("Full", n, n, &c_b10, &c_b11, &q[q_offset], ldq);
    }
    if (icompz == 3) {
	dlaset_("Full", n, n, &c_b10, &c_b11, &z__[z_offset], ldz);
    }

/*     Quick return if possible */

    if (*n <= 1) {
	return 0;
    }

/*     Zero out lower triangle of B */

    i__1 = *n - 1;
    for (jcol = 1; jcol <= i__1; ++jcol) {
	i__2 = *n;
	for (jrow = jcol + 1; jrow <= i__2; ++jrow) {
	    b[jrow + jcol * b_dim1] = 0.;
/* L10: */
	}
/* L20: */
    }

/*     Reduce A and B */

    i__1 = *ihi - 2;
    for (jcol = *ilo; jcol <= i__1; ++jcol) {

	i__2 = jcol + 2;
	for (jrow = *ihi; jrow >= i__2; --jrow) {

/*           Step 1: rotate rows JROW-1, JROW to kill A(JROW,JCOL) */

	    temp = a[jrow - 1 + jcol * a_dim1];
	    dlartg_(&temp, &a[jrow + jcol * a_dim1], &c__, &s, &a[jrow - 1 + 
		    jcol * a_dim1]);
	    a[jrow + jcol * a_dim1] = 0.;
	    i__3 = *n - jcol;
	    drot_(&i__3, &a[jrow - 1 + (jcol + 1) * a_dim1], lda, &a[jrow + (
		    jcol + 1) * a_dim1], lda, &c__, &s);
	    i__3 = *n + 2 - jrow;
	    drot_(&i__3, &b[jrow - 1 + (jrow - 1) * b_dim1], ldb, &b[jrow + (
		    jrow - 1) * b_dim1], ldb, &c__, &s);
	    if (ilq) {
		drot_(n, &q[(jrow - 1) * q_dim1 + 1], &c__1, &q[jrow * q_dim1 
			+ 1], &c__1, &c__, &s);
	    }

/*           Step 2: rotate columns JROW, JROW-1 to kill B(JROW,JROW-1) */

	    temp = b[jrow + jrow * b_dim1];
	    dlartg_(&temp, &b[jrow + (jrow - 1) * b_dim1], &c__, &s, &b[jrow 
		    + jrow * b_dim1]);
	    b[jrow + (jrow - 1) * b_dim1] = 0.;
	    drot_(ihi, &a[jrow * a_dim1 + 1], &c__1, &a[(jrow - 1) * a_dim1 + 
		    1], &c__1, &c__, &s);
	    i__3 = jrow - 1;
	    drot_(&i__3, &b[jrow * b_dim1 + 1], &c__1, &b[(jrow - 1) * b_dim1 
		    + 1], &c__1, &c__, &s);
	    if (ilz) {
		drot_(n, &z__[jrow * z_dim1 + 1], &c__1, &z__[(jrow - 1) * 
			z_dim1 + 1], &c__1, &c__, &s);
	    }
/* L30: */
	}
/* L40: */
    }

    return 0;

/*     End of DGGHRD */

} /* dgghrd_ */
