sorgbr.f(3) LAPACK sorgbr.f(3)NAMEsorgbr.f-
SYNOPSIS
Functions/Subroutines
subroutine sorgbr (VECT, M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
SORGBR
Function/Subroutine Documentation
subroutine sorgbr (characterVECT, integerM, integerN, integerK, real,
dimension( lda, * )A, integerLDA, real, dimension( * )TAU, real,
dimension( * )WORK, integerLWORK, integerINFO)
SORGBR
Purpose:
SORGBR generates one of the real orthogonal matrices Q or P**T
determined by SGEBRD when reducing a real matrix A to bidiagonal
form: A = Q * B * P**T. Q and P**T 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 SORGBR returns the first n
columns of Q, where m >= n >= k;
if m < k, Q = H(1)H(2) . . . H(m-1) and SORGBR returns Q as an
M-by-M matrix.
If VECT = 'P', A is assumed to have been a K-by-N matrix, and P**T
is of order N:
if k < n, P**T = G(k) . . . G(2)G(1) and SORGBR returns the first m
rows of P**T, where n >= m >= k;
if k >= n, P**T = G(n-1) . . . G(2)G(1) and SORGBR returns P**T as
an N-by-N matrix.
Parameters:
VECT
VECT is CHARACTER*1
Specifies whether the matrix Q or the matrix P**T is
required, as defined in the transformation applied by SGEBRD:
= 'Q': generate Q;
= 'P': generate P**T.
M
M is INTEGER
The number of rows of the matrix Q or P**T to be returned.
M >= 0.
N
N is INTEGER
The number of columns of the matrix Q or P**T 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 M-by-K
matrix reduced by SGEBRD.
If VECT = 'P', the number of rows in the original K-by-N
matrix reduced by SGEBRD.
K >= 0.
A
A is REAL array, dimension (LDA,N)
On entry, the vectors which define the elementary reflectors,
as returned by SGEBRD.
On exit, the M-by-N matrix Q or P**T.
LDA
LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,M).
TAU
TAU is REAL 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**T, as
returned by SGEBRD in its array argument TAUQ or TAUP.
WORK
WORK is REAL 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 i-th 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 sorgbr.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Sat Nov 16 2013 sorgbr.f(3)
