cunghr()

subroutine cunghr	(	integer	n,
		integer	ilo,
		integer	ihi,
		complex, dimension( lda, * )	a,
		integer	lda,
		complex, dimension( * )	tau,
		complex, dimension( * )	work,
		integer	lwork,
		integer	info )

CUNGHR

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Purpose:

!>
!> CUNGHR generates a complex unitary matrix Q which is defined as the
!> product of IHI-ILO elementary reflectors of order N, as returned by
!> CGEHRD:
!>
!> Q = H(ilo) H(ilo+1) . . . H(ihi-1).
!> 

Parameters

[in]	N	!> N is INTEGER !> The order of the matrix Q. N >= 0. !>
[in]	ILO	!> ILO is INTEGER !>
[in]	IHI	!> IHI is INTEGER !> !> ILO and IHI must have the same values as in the previous call !> of CGEHRD. 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. !>
[in,out]	A	!> A is COMPLEX array, dimension (LDA,N) !> On entry, the vectors which define the elementary reflectors, !> as returned by CGEHRD. !> On exit, the N-by-N unitary matrix Q. !>
[in]	LDA	!> LDA is INTEGER !> The leading dimension of the array A. LDA >= max(1,N). !>
[in]	TAU	!> TAU is COMPLEX array, dimension (N-1) !> TAU(i) must contain the scalar factor of the elementary !> reflector H(i), as returned by CGEHRD. !>
[out]	WORK	!> WORK is COMPLEX array, dimension (MAX(1,LWORK)) !> On exit, if INFO = 0, WORK(1) returns the optimal LWORK. !>
[in]	LWORK	!> LWORK is 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. !>
[out]	INFO	!> INFO is INTEGER !> = 0: successful exit !> < 0: if INFO = -i, the i-th argument had an illegal value !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.