chbtrd.c

/* chbtrd.f -- translated by f2c (version 20061008).
   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"
#include "blaswrap.h"

/* Table of constant values */

static complex c_b1 = {0.f,0.f};
static complex c_b2 = {1.f,0.f};
static integer c__1 = 1;

/* Subroutine */ int chbtrd_(char *vect, char *uplo, integer *n, integer *kd, 
	complex *ab, integer *ldab, real *d__, real *e, complex *q, integer *
	ldq, complex *work, integer *info)
{
    /* System generated locals */
    integer ab_dim1, ab_offset, q_dim1, q_offset, i__1, i__2, i__3, i__4, 
	    i__5, i__6;
    real r__1;
    complex q__1;

    /* Builtin functions */
    void r_cnjg(complex *, complex *);
    double c_abs(complex *);

    /* Local variables */
    integer i__, j, k, l;
    complex t;
    integer i2, j1, j2, nq, nr, kd1, ibl, iqb, kdn, jin, nrt, kdm1, inca, 
	    jend, lend, jinc;
    real abst;
    integer incx, last;
    complex temp;
    extern /* Subroutine */ int crot_(integer *, complex *, integer *, 
	    complex *, integer *, real *, complex *);
    integer j1end, j1inc;
    extern /* Subroutine */ int cscal_(integer *, complex *, complex *, 
	    integer *);
    integer iqend;
    extern logical lsame_(char *, char *);
    logical initq, wantq, upper;
    extern /* Subroutine */ int clar2v_(integer *, complex *, complex *, 
	    complex *, integer *, real *, complex *, integer *), clacgv_(
	    integer *, complex *, integer *);
    integer iqaend;
    extern /* Subroutine */ int claset_(char *, integer *, integer *, complex 
	    *, complex *, complex *, integer *), clartg_(complex *, 
	    complex *, real *, complex *, complex *), xerbla_(char *, integer 
	    *), clargv_(integer *, complex *, integer *, complex *, 
	    integer *, real *, integer *), clartv_(integer *, complex *, 
	    integer *, complex *, integer *, real *, complex *, integer *);


/*  -- LAPACK routine (version 3.2) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

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

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

/*  CHBTRD reduces a complex Hermitian band matrix A to real symmetric */
/*  tridiagonal form T by a unitary similarity transformation: */
/*  Q**H * A * Q = T. */

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

/*  VECT    (input) CHARACTER*1 */
/*          = 'N':  do not form Q; */
/*          = 'V':  form Q; */
/*          = 'U':  update a matrix X, by forming X*Q. */

/*  UPLO    (input) CHARACTER*1 */
/*          = 'U':  Upper triangle of A is stored; */
/*          = 'L':  Lower triangle of A is stored. */

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

/*  KD      (input) INTEGER */
/*          The number of superdiagonals of the matrix A if UPLO = 'U', */
/*          or the number of subdiagonals if UPLO = 'L'.  KD >= 0. */

/*  AB      (input/output) COMPLEX array, dimension (LDAB,N) */
/*          On entry, the upper or lower triangle of the Hermitian band */
/*          matrix A, stored in the first KD+1 rows of the array.  The */
/*          j-th column of A is stored in the j-th column of the array AB */
/*          as follows: */
/*          if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; */
/*          if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd). */
/*          On exit, the diagonal elements of AB are overwritten by the */
/*          diagonal elements of the tridiagonal matrix T; if KD > 0, the */
/*          elements on the first superdiagonal (if UPLO = 'U') or the */
/*          first subdiagonal (if UPLO = 'L') are overwritten by the */
/*          off-diagonal elements of T; the rest of AB is overwritten by */
/*          values generated during the reduction. */

/*  LDAB    (input) INTEGER */
/*          The leading dimension of the array AB.  LDAB >= KD+1. */

/*  D       (output) REAL array, dimension (N) */
/*          The diagonal elements of the tridiagonal matrix T. */

/*  E       (output) REAL array, dimension (N-1) */
/*          The off-diagonal elements of the tridiagonal matrix T: */
/*          E(i) = T(i,i+1) if UPLO = 'U'; E(i) = T(i+1,i) if UPLO = 'L'. */

/*  Q       (input/output) COMPLEX array, dimension (LDQ,N) */
/*          On entry, if VECT = 'U', then Q must contain an N-by-N */
/*          matrix X; if VECT = 'N' or 'V', then Q need not be set. */

/*          On exit: */
/*          if VECT = 'V', Q contains the N-by-N unitary matrix Q; */
/*          if VECT = 'U', Q contains the product X*Q; */
/*          if VECT = 'N', the array Q is not referenced. */

/*  LDQ     (input) INTEGER */
/*          The leading dimension of the array Q. */
/*          LDQ >= 1, and LDQ >= N if VECT = 'V' or 'U'. */

/*  WORK    (workspace) COMPLEX array, dimension (N) */

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

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

/*  Modified by Linda Kaufman, Bell Labs. */

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

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

/*     Test the input parameters */

    /* Parameter adjustments */
    ab_dim1 = *ldab;
    ab_offset = 1 + ab_dim1;
    ab -= ab_offset;
    --d__;
    --e;
    q_dim1 = *ldq;
    q_offset = 1 + q_dim1;
    q -= q_offset;
    --work;

    /* Function Body */
    initq = lsame_(vect, "V");
    wantq = initq || lsame_(vect, "U");
    upper = lsame_(uplo, "U");
    kd1 = *kd + 1;
    kdm1 = *kd - 1;
    incx = *ldab - 1;
    iqend = 1;

    *info = 0;
    if (! wantq && ! lsame_(vect, "N")) {
	*info = -1;
    } else if (! upper && ! lsame_(uplo, "L")) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (*kd < 0) {
	*info = -4;
    } else if (*ldab < kd1) {
	*info = -6;
    } else if (*ldq < max(1,*n) && wantq) {
	*info = -10;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("CHBTRD", &i__1);
	return 0;
    }

/*     Quick return if possible */

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

/*     Initialize Q to the unit matrix, if needed */

    if (initq) {
	claset_("Full", n, n, &c_b1, &c_b2, &q[q_offset], ldq);
    }

/*     Wherever possible, plane rotations are generated and applied in */
/*     vector operations of length NR over the index set J1:J2:KD1. */

/*     The real cosines and complex sines of the plane rotations are */
/*     stored in the arrays D and WORK. */

    inca = kd1 * *ldab;
/* Computing MIN */
    i__1 = *n - 1;
    kdn = min(i__1,*kd);
    if (upper) {

	if (*kd > 1) {

/*           Reduce to complex Hermitian tridiagonal form, working with */
/*           the upper triangle */

	    nr = 0;
	    j1 = kdn + 2;
	    j2 = 1;

	    i__1 = kd1 + ab_dim1;
	    i__2 = kd1 + ab_dim1;
	    r__1 = ab[i__2].r;
	    ab[i__1].r = r__1, ab[i__1].i = 0.f;
	    i__1 = *n - 2;
	    for (i__ = 1; i__ <= i__1; ++i__) {

/*              Reduce i-th row of matrix to tridiagonal form */

		for (k = kdn + 1; k >= 2; --k) {
		    j1 += kdn;
		    j2 += kdn;

		    if (nr > 0) {

/*                    generate plane rotations to annihilate nonzero */
/*                    elements which have been created outside the band */

			clargv_(&nr, &ab[(j1 - 1) * ab_dim1 + 1], &inca, &
				work[j1], &kd1, &d__[j1], &kd1);

/*                    apply rotations from the right */


/*                    Dependent on the the number of diagonals either */
/*                    CLARTV or CROT is used */

			if (nr >= (*kd << 1) - 1) {
			    i__2 = *kd - 1;
			    for (l = 1; l <= i__2; ++l) {
				clartv_(&nr, &ab[l + 1 + (j1 - 1) * ab_dim1], 
					&inca, &ab[l + j1 * ab_dim1], &inca, &
					d__[j1], &work[j1], &kd1);
/* L10: */
			    }

			} else {
			    jend = j1 + (nr - 1) * kd1;
			    i__2 = jend;
			    i__3 = kd1;
			    for (jinc = j1; i__3 < 0 ? jinc >= i__2 : jinc <= 
				    i__2; jinc += i__3) {
				crot_(&kdm1, &ab[(jinc - 1) * ab_dim1 + 2], &
					c__1, &ab[jinc * ab_dim1 + 1], &c__1, 
					&d__[jinc], &work[jinc]);
/* L20: */
			    }
			}
		    }


		    if (k > 2) {
			if (k <= *n - i__ + 1) {

/*                       generate plane rotation to annihilate a(i,i+k-1) */
/*                       within the band */

			    clartg_(&ab[*kd - k + 3 + (i__ + k - 2) * ab_dim1]
, &ab[*kd - k + 2 + (i__ + k - 1) * 
				    ab_dim1], &d__[i__ + k - 1], &work[i__ + 
				    k - 1], &temp);
			    i__3 = *kd - k + 3 + (i__ + k - 2) * ab_dim1;
			    ab[i__3].r = temp.r, ab[i__3].i = temp.i;

/*                       apply rotation from the right */

			    i__3 = k - 3;
			    crot_(&i__3, &ab[*kd - k + 4 + (i__ + k - 2) * 
				    ab_dim1], &c__1, &ab[*kd - k + 3 + (i__ + 
				    k - 1) * ab_dim1], &c__1, &d__[i__ + k - 
				    1], &work[i__ + k - 1]);
			}
			++nr;
			j1 = j1 - kdn - 1;
		    }

/*                 apply plane rotations from both sides to diagonal */
/*                 blocks */

		    if (nr > 0) {
			clar2v_(&nr, &ab[kd1 + (j1 - 1) * ab_dim1], &ab[kd1 + 
				j1 * ab_dim1], &ab[*kd + j1 * ab_dim1], &inca, 
				 &d__[j1], &work[j1], &kd1);
		    }

/*                 apply plane rotations from the left */

		    if (nr > 0) {
			clacgv_(&nr, &work[j1], &kd1);
			if ((*kd << 1) - 1 < nr) {

/*                    Dependent on the the number of diagonals either */
/*                    CLARTV or CROT is used */

			    i__3 = *kd - 1;
			    for (l = 1; l <= i__3; ++l) {
				if (j2 + l > *n) {
				    nrt = nr - 1;
				} else {
				    nrt = nr;
				}
				if (nrt > 0) {
				    clartv_(&nrt, &ab[*kd - l + (j1 + l) * 
					    ab_dim1], &inca, &ab[*kd - l + 1 
					    + (j1 + l) * ab_dim1], &inca, &
					    d__[j1], &work[j1], &kd1);
				}
/* L30: */
			    }
			} else {
			    j1end = j1 + kd1 * (nr - 2);
			    if (j1end >= j1) {
				i__3 = j1end;
				i__2 = kd1;
				for (jin = j1; i__2 < 0 ? jin >= i__3 : jin <=
					 i__3; jin += i__2) {
				    i__4 = *kd - 1;
				    crot_(&i__4, &ab[*kd - 1 + (jin + 1) * 
					    ab_dim1], &incx, &ab[*kd + (jin + 
					    1) * ab_dim1], &incx, &d__[jin], &
					    work[jin]);
/* L40: */
				}
			    }
/* Computing MIN */
			    i__2 = kdm1, i__3 = *n - j2;
			    lend = min(i__2,i__3);
			    last = j1end + kd1;
			    if (lend > 0) {
				crot_(&lend, &ab[*kd - 1 + (last + 1) * 
					ab_dim1], &incx, &ab[*kd + (last + 1) 
					* ab_dim1], &incx, &d__[last], &work[
					last]);
			    }
			}
		    }

		    if (wantq) {

/*                    accumulate product of plane rotations in Q */

			if (initq) {

/*                 take advantage of the fact that Q was */
/*                 initially the Identity matrix */

			    iqend = max(iqend,j2);
/* Computing MAX */
			    i__2 = 0, i__3 = k - 3;
			    i2 = max(i__2,i__3);
			    iqaend = i__ * *kd + 1;
			    if (k == 2) {
				iqaend += *kd;
			    }
			    iqaend = min(iqaend,iqend);
			    i__2 = j2;
			    i__3 = kd1;
			    for (j = j1; i__3 < 0 ? j >= i__2 : j <= i__2; j 
				    += i__3) {
				ibl = i__ - i2 / kdm1;
				++i2;
/* Computing MAX */
				i__4 = 1, i__5 = j - ibl;
				iqb = max(i__4,i__5);
				nq = iqaend + 1 - iqb;
/* Computing MIN */
				i__4 = iqaend + *kd;
				iqaend = min(i__4,iqend);
				r_cnjg(&q__1, &work[j]);
				crot_(&nq, &q[iqb + (j - 1) * q_dim1], &c__1, 
					&q[iqb + j * q_dim1], &c__1, &d__[j], 
					&q__1);
/* L50: */
			    }
			} else {

			    i__3 = j2;
			    i__2 = kd1;
			    for (j = j1; i__2 < 0 ? j >= i__3 : j <= i__3; j 
				    += i__2) {
				r_cnjg(&q__1, &work[j]);
				crot_(n, &q[(j - 1) * q_dim1 + 1], &c__1, &q[
					j * q_dim1 + 1], &c__1, &d__[j], &
					q__1);
/* L60: */
			    }
			}

		    }

		    if (j2 + kdn > *n) {

/*                    adjust J2 to keep within the bounds of the matrix */

			--nr;
			j2 = j2 - kdn - 1;
		    }

		    i__2 = j2;
		    i__3 = kd1;
		    for (j = j1; i__3 < 0 ? j >= i__2 : j <= i__2; j += i__3) 
			    {

/*                    create nonzero element a(j-1,j+kd) outside the band */
/*                    and store it in WORK */

			i__4 = j + *kd;
			i__5 = j;
			i__6 = (j + *kd) * ab_dim1 + 1;
			q__1.r = work[i__5].r * ab[i__6].r - work[i__5].i * 
				ab[i__6].i, q__1.i = work[i__5].r * ab[i__6]
				.i + work[i__5].i * ab[i__6].r;
			work[i__4].r = q__1.r, work[i__4].i = q__1.i;
			i__4 = (j + *kd) * ab_dim1 + 1;
			i__5 = j;
			i__6 = (j + *kd) * ab_dim1 + 1;
			q__1.r = d__[i__5] * ab[i__6].r, q__1.i = d__[i__5] * 
				ab[i__6].i;
			ab[i__4].r = q__1.r, ab[i__4].i = q__1.i;
/* L70: */
		    }
/* L80: */
		}
/* L90: */
	    }
	}

	if (*kd > 0) {

/*           make off-diagonal elements real and copy them to E */

	    i__1 = *n - 1;
	    for (i__ = 1; i__ <= i__1; ++i__) {
		i__3 = *kd + (i__ + 1) * ab_dim1;
		t.r = ab[i__3].r, t.i = ab[i__3].i;
		abst = c_abs(&t);
		i__3 = *kd + (i__ + 1) * ab_dim1;
		ab[i__3].r = abst, ab[i__3].i = 0.f;
		e[i__] = abst;
		if (abst != 0.f) {
		    q__1.r = t.r / abst, q__1.i = t.i / abst;
		    t.r = q__1.r, t.i = q__1.i;
		} else {
		    t.r = 1.f, t.i = 0.f;
		}
		if (i__ < *n - 1) {
		    i__3 = *kd + (i__ + 2) * ab_dim1;
		    i__2 = *kd + (i__ + 2) * ab_dim1;
		    q__1.r = ab[i__2].r * t.r - ab[i__2].i * t.i, q__1.i = ab[
			    i__2].r * t.i + ab[i__2].i * t.r;
		    ab[i__3].r = q__1.r, ab[i__3].i = q__1.i;
		}
		if (wantq) {
		    r_cnjg(&q__1, &t);
		    cscal_(n, &q__1, &q[(i__ + 1) * q_dim1 + 1], &c__1);
		}
/* L100: */
	    }
	} else {

/*           set E to zero if original matrix was diagonal */

	    i__1 = *n - 1;
	    for (i__ = 1; i__ <= i__1; ++i__) {
		e[i__] = 0.f;
/* L110: */
	    }
	}

/*        copy diagonal elements to D */

	i__1 = *n;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    i__3 = i__;
	    i__2 = kd1 + i__ * ab_dim1;
	    d__[i__3] = ab[i__2].r;
/* L120: */
	}

    } else {

	if (*kd > 1) {

/*           Reduce to complex Hermitian tridiagonal form, working with */
/*           the lower triangle */

	    nr = 0;
	    j1 = kdn + 2;
	    j2 = 1;

	    i__1 = ab_dim1 + 1;
	    i__3 = ab_dim1 + 1;
	    r__1 = ab[i__3].r;
	    ab[i__1].r = r__1, ab[i__1].i = 0.f;
	    i__1 = *n - 2;
	    for (i__ = 1; i__ <= i__1; ++i__) {

/*              Reduce i-th column of matrix to tridiagonal form */

		for (k = kdn + 1; k >= 2; --k) {
		    j1 += kdn;
		    j2 += kdn;

		    if (nr > 0) {

/*                    generate plane rotations to annihilate nonzero */
/*                    elements which have been created outside the band */

			clargv_(&nr, &ab[kd1 + (j1 - kd1) * ab_dim1], &inca, &
				work[j1], &kd1, &d__[j1], &kd1);

/*                    apply plane rotations from one side */


/*                    Dependent on the the number of diagonals either */
/*                    CLARTV or CROT is used */

			if (nr > (*kd << 1) - 1) {
			    i__3 = *kd - 1;
			    for (l = 1; l <= i__3; ++l) {
				clartv_(&nr, &ab[kd1 - l + (j1 - kd1 + l) * 
					ab_dim1], &inca, &ab[kd1 - l + 1 + (
					j1 - kd1 + l) * ab_dim1], &inca, &d__[
					j1], &work[j1], &kd1);
/* L130: */
			    }
			} else {
			    jend = j1 + kd1 * (nr - 1);
			    i__3 = jend;
			    i__2 = kd1;
			    for (jinc = j1; i__2 < 0 ? jinc >= i__3 : jinc <= 
				    i__3; jinc += i__2) {
				crot_(&kdm1, &ab[*kd + (jinc - *kd) * ab_dim1]
, &incx, &ab[kd1 + (jinc - *kd) * 
					ab_dim1], &incx, &d__[jinc], &work[
					jinc]);
/* L140: */
			    }
			}

		    }

		    if (k > 2) {
			if (k <= *n - i__ + 1) {

/*                       generate plane rotation to annihilate a(i+k-1,i) */
/*                       within the band */

			    clartg_(&ab[k - 1 + i__ * ab_dim1], &ab[k + i__ * 
				    ab_dim1], &d__[i__ + k - 1], &work[i__ + 
				    k - 1], &temp);
			    i__2 = k - 1 + i__ * ab_dim1;
			    ab[i__2].r = temp.r, ab[i__2].i = temp.i;

/*                       apply rotation from the left */

			    i__2 = k - 3;
			    i__3 = *ldab - 1;
			    i__4 = *ldab - 1;
			    crot_(&i__2, &ab[k - 2 + (i__ + 1) * ab_dim1], &
				    i__3, &ab[k - 1 + (i__ + 1) * ab_dim1], &
				    i__4, &d__[i__ + k - 1], &work[i__ + k - 
				    1]);
			}
			++nr;
			j1 = j1 - kdn - 1;
		    }

/*                 apply plane rotations from both sides to diagonal */
/*                 blocks */

		    if (nr > 0) {
			clar2v_(&nr, &ab[(j1 - 1) * ab_dim1 + 1], &ab[j1 * 
				ab_dim1 + 1], &ab[(j1 - 1) * ab_dim1 + 2], &
				inca, &d__[j1], &work[j1], &kd1);
		    }

/*                 apply plane rotations from the right */


/*                    Dependent on the the number of diagonals either */
/*                    CLARTV or CROT is used */

		    if (nr > 0) {
			clacgv_(&nr, &work[j1], &kd1);
			if (nr > (*kd << 1) - 1) {
			    i__2 = *kd - 1;
			    for (l = 1; l <= i__2; ++l) {
				if (j2 + l > *n) {
				    nrt = nr - 1;
				} else {
				    nrt = nr;
				}
				if (nrt > 0) {
				    clartv_(&nrt, &ab[l + 2 + (j1 - 1) * 
					    ab_dim1], &inca, &ab[l + 1 + j1 * 
					    ab_dim1], &inca, &d__[j1], &work[
					    j1], &kd1);
				}
/* L150: */
			    }
			} else {
			    j1end = j1 + kd1 * (nr - 2);
			    if (j1end >= j1) {
				i__2 = j1end;
				i__3 = kd1;
				for (j1inc = j1; i__3 < 0 ? j1inc >= i__2 : 
					j1inc <= i__2; j1inc += i__3) {
				    crot_(&kdm1, &ab[(j1inc - 1) * ab_dim1 + 
					    3], &c__1, &ab[j1inc * ab_dim1 + 
					    2], &c__1, &d__[j1inc], &work[
					    j1inc]);
/* L160: */
				}
			    }
/* Computing MIN */
			    i__3 = kdm1, i__2 = *n - j2;
			    lend = min(i__3,i__2);
			    last = j1end + kd1;
			    if (lend > 0) {
				crot_(&lend, &ab[(last - 1) * ab_dim1 + 3], &
					c__1, &ab[last * ab_dim1 + 2], &c__1, 
					&d__[last], &work[last]);
			    }
			}
		    }



		    if (wantq) {

/*                    accumulate product of plane rotations in Q */

			if (initq) {

/*                 take advantage of the fact that Q was */
/*                 initially the Identity matrix */

			    iqend = max(iqend,j2);
/* Computing MAX */
			    i__3 = 0, i__2 = k - 3;
			    i2 = max(i__3,i__2);
			    iqaend = i__ * *kd + 1;
			    if (k == 2) {
				iqaend += *kd;
			    }
			    iqaend = min(iqaend,iqend);
			    i__3 = j2;
			    i__2 = kd1;
			    for (j = j1; i__2 < 0 ? j >= i__3 : j <= i__3; j 
				    += i__2) {
				ibl = i__ - i2 / kdm1;
				++i2;
/* Computing MAX */
				i__4 = 1, i__5 = j - ibl;
				iqb = max(i__4,i__5);
				nq = iqaend + 1 - iqb;
/* Computing MIN */
				i__4 = iqaend + *kd;
				iqaend = min(i__4,iqend);
				crot_(&nq, &q[iqb + (j - 1) * q_dim1], &c__1, 
					&q[iqb + j * q_dim1], &c__1, &d__[j], 
					&work[j]);
/* L170: */
			    }
			} else {

			    i__2 = j2;
			    i__3 = kd1;
			    for (j = j1; i__3 < 0 ? j >= i__2 : j <= i__2; j 
				    += i__3) {
				crot_(n, &q[(j - 1) * q_dim1 + 1], &c__1, &q[
					j * q_dim1 + 1], &c__1, &d__[j], &
					work[j]);
/* L180: */
			    }
			}
		    }

		    if (j2 + kdn > *n) {

/*                    adjust J2 to keep within the bounds of the matrix */

			--nr;
			j2 = j2 - kdn - 1;
		    }

		    i__3 = j2;
		    i__2 = kd1;
		    for (j = j1; i__2 < 0 ? j >= i__3 : j <= i__3; j += i__2) 
			    {

/*                    create nonzero element a(j+kd,j-1) outside the */
/*                    band and store it in WORK */

			i__4 = j + *kd;
			i__5 = j;
			i__6 = kd1 + j * ab_dim1;
			q__1.r = work[i__5].r * ab[i__6].r - work[i__5].i * 
				ab[i__6].i, q__1.i = work[i__5].r * ab[i__6]
				.i + work[i__5].i * ab[i__6].r;
			work[i__4].r = q__1.r, work[i__4].i = q__1.i;
			i__4 = kd1 + j * ab_dim1;
			i__5 = j;
			i__6 = kd1 + j * ab_dim1;
			q__1.r = d__[i__5] * ab[i__6].r, q__1.i = d__[i__5] * 
				ab[i__6].i;
			ab[i__4].r = q__1.r, ab[i__4].i = q__1.i;
/* L190: */
		    }
/* L200: */
		}
/* L210: */
	    }
	}

	if (*kd > 0) {

/*           make off-diagonal elements real and copy them to E */

	    i__1 = *n - 1;
	    for (i__ = 1; i__ <= i__1; ++i__) {
		i__2 = i__ * ab_dim1 + 2;
		t.r = ab[i__2].r, t.i = ab[i__2].i;
		abst = c_abs(&t);
		i__2 = i__ * ab_dim1 + 2;
		ab[i__2].r = abst, ab[i__2].i = 0.f;
		e[i__] = abst;
		if (abst != 0.f) {
		    q__1.r = t.r / abst, q__1.i = t.i / abst;
		    t.r = q__1.r, t.i = q__1.i;
		} else {
		    t.r = 1.f, t.i = 0.f;
		}
		if (i__ < *n - 1) {
		    i__2 = (i__ + 1) * ab_dim1 + 2;
		    i__3 = (i__ + 1) * ab_dim1 + 2;
		    q__1.r = ab[i__3].r * t.r - ab[i__3].i * t.i, q__1.i = ab[
			    i__3].r * t.i + ab[i__3].i * t.r;
		    ab[i__2].r = q__1.r, ab[i__2].i = q__1.i;
		}
		if (wantq) {
		    cscal_(n, &t, &q[(i__ + 1) * q_dim1 + 1], &c__1);
		}
/* L220: */
	    }
	} else {

/*           set E to zero if original matrix was diagonal */

	    i__1 = *n - 1;
	    for (i__ = 1; i__ <= i__1; ++i__) {
		e[i__] = 0.f;
/* L230: */
	    }
	}

/*        copy diagonal elements to D */

	i__1 = *n;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    i__2 = i__;
	    i__3 = i__ * ab_dim1 + 1;
	    d__[i__2] = ab[i__3].r;
/* L240: */
	}
    }

    return 0;

/*     End of CHBTRD */

} /* chbtrd_ */