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RedHat 9 (Linux i386) - man page for cunghr (redhat section l)

CUNGHR(l)					)					CUNGHR(l)

NAME
       CUNGHR  -  generate  a complex unitary matrix Q which is defined as the product of IHI-ILO
       elementary reflectors of order N, as returned by CGEHRD

SYNOPSIS
       SUBROUTINE CUNGHR( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO )

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

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

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).

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  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.

       A       (input/output) 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.

       LDA     (input) INTEGER
	       The leading dimension of the array A. LDA >= max(1,N).

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

       WORK    (workspace/output) COMPLEX 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

LAPACK version 3.0			   15 June 2000 				CUNGHR(l)


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