cgbbrd(l) [redhat man page]

CGBBRD(l)								 )								 CGBBRD(l)

NAME

       CGBBRD - reduce a complex general m-by-n band matrix A to real upper bidiagonal form B by a unitary transformation

SYNOPSIS

       SUBROUTINE CGBBRD( VECT, M, N, NCC, KL, KU, AB, LDAB, D, E, Q, LDQ, PT, LDPT, C, LDC, WORK, RWORK, INFO )

	   CHARACTER	  VECT

	   INTEGER	  INFO, KL, KU, LDAB, LDC, LDPT, LDQ, M, N, NCC

	   REAL 	  D( * ), E( * ), RWORK( * )

	   COMPLEX	  AB( LDAB, * ), C( LDC, * ), PT( LDPT, * ), Q( LDQ, * ), WORK( * )

PURPOSE

       CGBBRD  reduces	a  complex  general m-by-n band matrix A to real upper bidiagonal form B by a unitary transformation: Q' * A * P = B.  The
       routine computes B, and optionally forms Q or P', or computes Q'*C for a given matrix C.

ARGUMENTS

       VECT    (input) CHARACTER*1
	       Specifies whether or not the matrices Q and P' are to be formed.  = 'N': do not form Q or P';
	       = 'Q': form Q only;
	       = 'P': form P' only;
	       = 'B': form both.

       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.

       NCC     (input) INTEGER
	       The number of columns of the matrix C.  NCC >= 0.

       KL      (input) INTEGER
	       The number of subdiagonals of the matrix A. KL >= 0.

       KU      (input) INTEGER
	       The number of superdiagonals of the matrix A. KU >= 0.

       AB      (input/output) COMPLEX array, dimension (LDAB,N)
	       On entry, the m-by-n band matrix A, stored in rows 1 to KL+KU+1. The j-th column of A is stored in the j-th column of the array	AB
	       as  follows:  AB(ku+1+i-j,j)  =	A(i,j)	for max(1,j-ku)<=i<=min(m,j+kl).  On exit, A is overwritten by values generated during the
	       reduction.

       LDAB    (input) INTEGER
	       The leading dimension of the array A. LDAB >= KL+KU+1.

       D       (output) REAL array, dimension (min(M,N))
	       The diagonal elements of the bidiagonal matrix B.

       E       (output) REAL array, dimension (min(M,N)-1)
	       The superdiagonal elements of the bidiagonal matrix B.

       Q       (output) COMPLEX array, dimension (LDQ,M)
	       If VECT = 'Q' or 'B', the m-by-m unitary matrix Q.  If VECT = 'N' or 'P', the array Q is not referenced.

       LDQ     (input) INTEGER
	       The leading dimension of the array Q.  LDQ >= max(1,M) if VECT = 'Q' or 'B'; LDQ >= 1 otherwise.

       PT      (output) COMPLEX array, dimension (LDPT,N)
	       If VECT = 'P' or 'B', the n-by-n unitary matrix P'.  If VECT = 'N' or 'Q', the array PT is not referenced.

       LDPT    (input) INTEGER
	       The leading dimension of the array PT.  LDPT >= max(1,N) if VECT = 'P' or 'B'; LDPT >= 1 otherwise.

       C       (input/output) COMPLEX array, dimension (LDC,NCC)
	       On entry, an m-by-ncc matrix C.	On exit, C is overwritten by Q'*C.  C is not referenced if NCC = 0.

       LDC     (input) INTEGER
	       The leading dimension of the array C.  LDC >= max(1,M) if NCC > 0; LDC >= 1 if NCC = 0.

       WORK    (workspace) COMPLEX array, dimension (max(M,N))

       RWORK   (workspace) REAL array, dimension (max(M,N))

       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 							 CGBBRD(l)