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RedHat 9 (Linux i386) - man page for cungbr (redhat section l)

CUNGBR(l)					)					CUNGBR(l)

NAME
       CUNGBR  - generate one of the complex unitary matrices Q or P**H determined by CGEBRD when
       reducing a complex matrix A to bidiagonal form

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

	   CHARACTER	  VECT

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

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

PURPOSE
       CUNGBR generates one of the complex unitary matrices Q or P**H determined by  CGEBRD  when
       reducing  a  complex matrix A to bidiagonal form: A = Q * B * P**H. Q and P**H are defined
       as products of elementary reflectors H(i) or G(i) respectively.

       If VECT = 'Q', A is assumed to have been an M-by-K matrix, and Q is of order M:
       if m >= k, Q = H(1) H(2) . . . H(k) and CUNGBR returns the first n columns of Q,  where	m
       >= n >= k;
       if m < k, Q = H(1) H(2) . . . H(m-1) and CUNGBR returns Q as an M-by-M matrix.

       If VECT = 'P', A is assumed to have been a K-by-N matrix, and P**H is of order N:
       if k < n, P**H = G(k) . . . G(2) G(1) and CUNGBR returns the first m rows of P**H, where n
       >= m >= k;
       if k >= n, P**H = G(n-1) . . . G(2) G(1) and CUNGBR returns P**H as an N-by-N matrix.

ARGUMENTS
       VECT    (input) CHARACTER*1
	       Specifies whether the matrix Q or the matrix P**H is required, as defined  in  the
	       transformation applied by CGEBRD:
	       = 'Q':  generate Q;
	       = 'P':  generate P**H.

       M       (input) INTEGER
	       The number of rows of the matrix Q or P**H to be returned.  M >= 0.

       N       (input) INTEGER
	       The  number of columns of the matrix Q or P**H to be returned.  N >= 0.	If VECT =
	       'Q', M >= N >= min(M,K); if VECT = 'P', N >= M >= min(N,K).

       K       (input) INTEGER
	       If VECT = 'Q', the number of columns in the original M-by-K matrix reduced by CGE-
	       BRD.   If  VECT = 'P', the number of rows in the original K-by-N matrix reduced by
	       CGEBRD.	K >= 0.

       A       (input/output) COMPLEX array, dimension (LDA,N)
	       On entry, the vectors which define the elementary reflectors, as returned by  CGE-
	       BRD.  On exit, the M-by-N matrix Q or P**H.

       LDA     (input) INTEGER
	       The leading dimension of the array A. LDA >= M.

       TAU     (input) COMPLEX array, dimension
	       (min(M,K))  if  VECT = 'Q' (min(N,K)) if VECT = 'P' TAU(i) must contain the scalar
	       factor of the elementary reflector H(i) or G(i), which determines Q  or	P**H,  as
	       returned by CGEBRD in its array argument TAUQ or TAUP.

       WORK    (workspace/output) COMPLEX 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,min(M,N)).  For optimum perfor-
	       mance LWORK >= min(M,N)*NB, where NB is the optimal blocksize.

	       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 				CUNGBR(l)


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