redhat man page for sorghr

SORGHR(l)								 )								 SORGHR(l)

NAME
       SORGHR  -  generate  a real orthogonal matrix Q which is defined as the product of IHI-ILO elementary reflectors of order N, as returned by
       SGEHRD

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

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

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

PURPOSE
       SORGHR generates a real orthogonal matrix Q which is defined as the product of IHI-ILO elementary reflectors of order  N,  as  returned	by
       SGEHRD: 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 SGEHRD. 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) REAL array, dimension (LDA,N)
	       On entry, the vectors which define the elementary reflectors, as returned by SGEHRD.  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) REAL array, dimension (N-1)
	       TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SGEHRD.

       WORK    (workspace/output) REAL 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  block-
	       size.

	       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 							 SORGHR(l)