CXML
        	    
LAPACK version 3.0
zgeqr2(3)

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

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

      INTEGER	     INFO, LDA, M, N

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

DESCRIPTION
  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
	  trapezoidal 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).