
cungbr.f(3) LAPACK cungbr.f(3)
NAME
cungbr.f 
SYNOPSIS
Functions/Subroutines
subroutine cungbr (VECT, M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
CUNGBR
Function/Subroutine Documentation
subroutine cungbr (characterVECT, integerM, integerN, integerK, complex, dimension( lda, * )A,
integerLDA, complex, dimension( * )TAU, complex, dimension( * )WORK, integerLWORK,
integerINFO)
CUNGBR
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 MbyK 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(m1) and CUNGBR returns Q as an
MbyM matrix.
If VECT = 'P', A is assumed to have been a KbyN 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(n1) . . . G(2) G(1) and CUNGBR returns P**H as
an NbyN matrix.
Parameters:
VECT
VECT is 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
M is INTEGER
The number of rows of the matrix Q or P**H to be returned.
M >= 0.
N
N is 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
K is INTEGER
If VECT = 'Q', the number of columns in the original MbyK
matrix reduced by CGEBRD.
If VECT = 'P', the number of rows in the original KbyN
matrix reduced by CGEBRD.
K >= 0.
A
A is COMPLEX array, dimension (LDA,N)
On entry, the vectors which define the elementary reflectors,
as returned by CGEBRD.
On exit, the MbyN matrix Q or P**H.
LDA
LDA is INTEGER
The leading dimension of the array A. LDA >= M.
TAU
TAU is 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
WORK is COMPLEX array, dimension (MAX(1,LWORK))
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
LWORK
LWORK is INTEGER
The dimension of the array WORK. LWORK >= max(1,min(M,N)).
For optimum performance 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
INFO is INTEGER
= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
April 2012
Definition at line 158 of file cungbr.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Tue Sep 25 2012 cungbr.f(3) 
