CXML
        	    
LAPACK version 3.0
zungtr(3)

PURPOSE
  ZUNGTR - generate a complex unitary matrix Q which is defined as the
  product of n-1 elementary reflectors of order N, as returned by ZHETRD

SYNTAX
  SUBROUTINE ZUNGTR( UPLO, N, A, LDA, TAU, WORK, LWORK, INFO )

      CHARACTER	     UPLO

      INTEGER	     INFO, LDA, LWORK, N

      COMPLEX*16     A( LDA, * ), TAU( * ), WORK( * )

DESCRIPTION
  ZUNGTR generates a complex unitary matrix Q which is defined as the product
  of n-1 elementary reflectors of order N, as returned by ZHETRD: if UPLO =
  'U', Q = H(n-1) . . . H(2) H(1),

  if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).

ARGUMENTS
  UPLO	  (input) CHARACTER*1
	  = 'U': Upper triangle of A contains elementary reflectors from
	  ZHETRD; = 'L': Lower triangle of A contains elementary reflectors
	  from ZHETRD.

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

  A	  (input/output) COMPLEX*16 array, dimension (LDA,N)
	  On entry, the vectors which define the elementary reflectors, as
	  returned by ZHETRD.  On exit, the N-by-N unitary matrix Q.

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

  TAU	  (input) COMPLEX*16 array, dimension (N-1)
	  TAU(i) must contain the scalar factor of the elementary reflector
	  H(i), as returned by ZHETRD.

  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 >= N-1.  For optimum
	  performance LWORK >= (N-1)*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