CXML
        	    
LAPACK version 3.0
dorgtr(3)

PURPOSE
  DORGTR - generate a real orthogonal matrix Q which is defined as the
  product of n-1 elementary reflectors of order N, as returned by DSYTRD

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

      CHARACTER	     UPLO

      INTEGER	     INFO, LDA, LWORK, N

      DOUBLE	     PRECISION A( LDA, * ), TAU( * ), WORK( * )

DESCRIPTION
  DORGTR generates a real orthogonal matrix Q which is defined as the product
  of n-1 elementary reflectors of order N, as returned by DSYTRD: 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
	  DSYTRD; = 'L': Lower triangle of A contains elementary reflectors
	  from DSYTRD.

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

  A	  (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	  On entry, the vectors which define the elementary reflectors, as
	  returned by DSYTRD.  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 DSYTRD.

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

  LWORK	  (input) INTEGER
	  The dimension of the array WORK. LWORK >= max(1,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