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LAPACK version 3.0
dorghr(3)

PURPOSE
  DORGHR - generate a real orthogonal matrix Q which is defined as the
  product of IHI-ILO elementary reflectors of order N, as returned by DGEHRD

SYNTAX
  SUBROUTINE DORGHR( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO )

      INTEGER	     IHI, ILO, INFO, LDA, LWORK, N

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

DESCRIPTION
  DORGHR generates a real orthogonal matrix Q which is defined as the product
  of IHI-ILO elementary reflectors of order N, as returned by DGEHRD: Q =
  H(ilo) H(ilo+1) . . . H(ihi-1).

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

  ILO	  (input) INTEGER
	  IHI	  (input) INTEGER ILO and IHI must have the same values as in
	  the previous call of DGEHRD. Q is equal to the unit matrix except
	  in the submatrix Q(ilo+1:ihi,ilo+1:ihi).  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 vectors which define the elementary reflectors, as
	  returned by DGEHRD.  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 DGEHRD.

  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 >= IHI-ILO.  For optimum
	  performance LWORK >= (IHI-ILO)*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