redhat man page for zgeqr2

ZGEQR2(l)								 )								 ZGEQR2(l)

NAME
       ZGEQR2 - compute a QR factorization of a complex m by n matrix A

SYNOPSIS
       SUBROUTINE ZGEQR2( M, N, A, LDA, TAU, WORK, INFO )

	   INTEGER	  INFO, LDA, M, N

	   COMPLEX*16	  A( LDA, * ), TAU( * ), WORK( * )

PURPOSE
       ZGEQR2 computes a QR factorization of a complex m by n matrix A: A = Q * R.

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) COMPLEX*16 array, dimension (LDA,N)
	       On entry, the m by n matrix A.  On exit, the elements on and above the diagonal of the array contain the min(m,n) by n upper trape-
	       zoidal matrix R (R is upper triangular if m >= n); the elements below the diagonal, with  the  array  TAU,  represent  the  unitary
	       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) COMPLEX*16 array, dimension (min(M,N))
	       The scalar factors of the elementary reflectors (see Further Details).

       WORK    (workspace) COMPLEX*16 array, dimension (N)

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

       Each H(i) has the form

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

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

LAPACK version 3.0						   15 June 2000 							 ZGEQR2(l)