redhat man page for dgelq2

DGELQ2(l)								 )								 DGELQ2(l)

NAME
       DGELQ2 - compute an LQ factorization of a real m by n matrix A

SYNOPSIS
       SUBROUTINE DGELQ2( M, N, A, LDA, TAU, WORK, INFO )

	   INTEGER	  INFO, LDA, M, N

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

PURPOSE
       DGELQ2 computes an LQ factorization of a real m by n matrix A: A = L * Q.

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

       N       (input) INTEGER
	       The number of columns of the matrix A.  N >= 0.

       A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	       On entry, the m by n matrix A.  On exit, the elements on and below the diagonal of the array contain the m by min(m,n) lower trape-
	       zoidal matrix L (L is lower triangular if m <= n); the elements above the diagonal, with the array TAU,	represent  the	orthogonal
	       matrix  Q  as a product of elementary reflectors (see Further Details).	LDA	(input) INTEGER The leading dimension of the array
	       A.  LDA >= max(1,M).

       TAU     (output) DOUBLE PRECISION array, dimension (min(M,N))
	       The scalar factors of the elementary reflectors (see Further Details).

       WORK    (workspace) DOUBLE PRECISION array, dimension (M)

       INFO    (output) INTEGER
	       = 0: successful exit
	       < 0: if INFO = -i, the i-th argument had an illegal value

FURTHER DETAILS
       The matrix Q is represented as a product of elementary reflectors

	  Q = H(k) . . . H(2) H(1), where k = min(m,n).

       Each H(i) has the form

	  H(i) = I - tau * v * v'

       where tau is a real scalar, and v is a real vector with
       v(1:i-1) = 0 and v(i) = 1; v(i+1:n) is stored on exit in A(i,i+1:n), and tau in TAU(i).

LAPACK version 3.0						   15 June 2000 							 DGELQ2(l)