ZHBTRD(l)		LAPACK routine (version	1.1)		    ZHBTRD(l)

NAME
  ZHBTRD - reduce a complex Hermitian band matrix A to real symmetric tridi-
  agonal form T	by a unitary similarity	transformation

SYNOPSIS

  SUBROUTINE ZHBTRD( VECT, UPLO, N, KD,	AB, LDAB, D, E,	Q, LDQ,	WORK, INFO )

      CHARACTER	     UPLO, VECT

      INTEGER	     INFO, KD, LDAB, LDQ, N

      DOUBLE	     PRECISION D( * ), E( * )

      COMPLEX*16     AB( LDAB, * ), Q( LDQ, * ), WORK( * )

PURPOSE
  ZHBTRD reduces a complex Hermitian band matrix A to real symmetric tridiag-
  onal 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.

  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*16 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 A 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 offdiagonal elements of T; the rest of
	  A is overwritten by values generated during the reduction.

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

  D	  (output) DOUBLE PRECISION array, dimension (N)
	  The diagonal elements	of the tridiagonal matrix T.

  E	  (output) DOUBLE PRECISION 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	  (output) COMPLEX*16 array, dimension (LDQ,N)
	  If VECT = 'V', the N-by-N unitary matrix Q.  If VECT = 'N', the
	  array	Q is not referenced.

  LDQ	  (input) INTEGER
	  The leading dimension	of the array Q.	 LDQ >=	max(1,N) if VECT =
	  'V'.

  WORK	  (workspace) COMPLEX*16 array,	dimension (N)

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