dorgrq man page on YellowDog

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DORGRQ(l)			       )			     DORGRQ(l)

NAME
       DORGRQ - generate an M-by-N real matrix Q with orthonormal rows,

SYNOPSIS
       SUBROUTINE DORGRQ( M, N, K, A, LDA, TAU, WORK, LWORK, INFO )

	   INTEGER	  INFO, K, LDA, LWORK, M, N

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

PURPOSE
       DORGRQ  generates  an M-by-N real matrix Q with orthonormal rows, which
       is defined as the last M rows of a product of K	elementary  reflectors
       of order N

	     Q	=  H(1) H(2) . . . H(k)

       as returned by DGERQF.

ARGUMENTS
       M       (input) INTEGER
	       The number of rows of the matrix Q. M >= 0.

       N       (input) INTEGER
	       The number of columns of the matrix Q. N >= M.

       K       (input) INTEGER
	       The  number  of elementary reflectors whose product defines the
	       matrix Q. M >= K >= 0.

       A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	       On entry, the (m-k+i)-th row  must  contain  the	 vector	 which
	       defines	the  elementary	 reflector H(i), for i = 1,2,...,k, as
	       returned by DGERQF in the last k rows of its array argument  A.
	       On exit, the M-by-N matrix Q.

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

       TAU     (input) DOUBLE PRECISION array, dimension (K)
	       TAU(i) must contain the scalar factor of the elementary reflec‐
	       tor H(i), as returned by DGERQF.

       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,M).  For	 opti‐
	       mum  performance	 LWORK >= M*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 has an illegal value

LAPACK version 3.0		 15 June 2000			     DORGRQ(l)
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