# cgbbrd(3) [centos man page]

```cgbbrd.f(3)							      LAPACK							       cgbbrd.f(3)

NAME
cgbbrd.f -

SYNOPSIS
Functions/Subroutines
subroutine cgbbrd (VECT, M, N, NCC, KL, KU, AB, LDAB, D, E, Q, LDQ, PT, LDPT, C, LDC, WORK, RWORK, INFO)
CGBBRD

Function/Subroutine Documentation
subroutine cgbbrd (characterVECT, integerM, integerN, integerNCC, integerKL, integerKU, complex, dimension( ldab, * )AB, integerLDAB, real,
dimension( * )D, real, dimension( * )E, complex, dimension( ldq, * )Q, integerLDQ, complex, dimension( ldpt, * )PT, integerLDPT, complex,
dimension( ldc, * )C, integerLDC, complex, dimension( * )WORK, real, dimension( * )RWORK, integerINFO)
CGBBRD

Purpose:

CGBBRD reduces a complex general m-by-n band matrix A to real upper
bidiagonal form B by a unitary transformation: Q**H * A * P = B.

The routine computes B, and optionally forms Q or P**H, or computes
Q**H*C for a given matrix C.

Parameters:
VECT

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

M

M is INTEGER
The number of rows of the matrix A.  M >= 0.

N

N is INTEGER
The number of columns of the matrix A.  N >= 0.

NCC

NCC is INTEGER
The number of columns of the matrix C.  NCC >= 0.

KL

KL is INTEGER
The number of subdiagonals of the matrix A. KL >= 0.

KU

KU is INTEGER
The number of superdiagonals of the matrix A. KU >= 0.

AB

AB is 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

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

D

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

E

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

Q

Q is 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

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

PT

PT is 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

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

C

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

LDC

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

WORK

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

RWORK

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

INFO

INFO is INTEGER
= 0:  successful exit.
< 0:  if INFO = -i, the i-th argument had an illegal value.

Author:
Univ. of Tennessee

Univ. of California Berkeley