
dlaqps.f(3) LAPACK dlaqps.f(3)
NAME
dlaqps.f 
SYNOPSIS
Functions/Subroutines
subroutine dlaqps (M, N, OFFSET, NB, KB, A, LDA, JPVT, TAU, VN1, VN2, AUXV, F, LDF)
DLAQPS computes a step of QR factorization with column pivoting of a real mbyn
matrix A by using BLAS level 3.
Function/Subroutine Documentation
subroutine dlaqps (integerM, integerN, integerOFFSET, integerNB, integerKB, double precision,
dimension( lda, * )A, integerLDA, integer, dimension( * )JPVT, double precision,
dimension( * )TAU, double precision, dimension( * )VN1, double precision, dimension( *
)VN2, double precision, dimension( * )AUXV, double precision, dimension( ldf, * )F,
integerLDF)
DLAQPS computes a step of QR factorization with column pivoting of a real mbyn matrix A
by using BLAS level 3.
Purpose:
DLAQPS computes a step of QR factorization with column pivoting
of a real MbyN matrix A by using Blas3. It tries to factorize
NB columns from A starting from the row OFFSET+1, and updates all
of the matrix with Blas3 xGEMM.
In some cases, due to catastrophic cancellations, it cannot
factorize NB columns. Hence, the actual number of factorized
columns is returned in KB.
Block A(1:OFFSET,1:N) is accordingly pivoted, but not factorized.
Parameters:
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
OFFSET
OFFSET is INTEGER
The number of rows of A that have been factorized in
previous steps.
NB
NB is INTEGER
The number of columns to factorize.
KB
KB is INTEGER
The number of columns actually factorized.
A
A is DOUBLE PRECISION array, dimension (LDA,N)
On entry, the MbyN matrix A.
On exit, block A(OFFSET+1:M,1:KB) is the triangular
factor obtained and block A(1:OFFSET,1:N) has been
accordingly pivoted, but no factorized.
The rest of the matrix, block A(OFFSET+1:M,KB+1:N) has
been updated.
LDA
LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,M).
JPVT
JPVT is INTEGER array, dimension (N)
JPVT(I) = K <==> Column K of the full matrix A has been
permuted into position I in AP.
TAU
TAU is DOUBLE PRECISION array, dimension (KB)
The scalar factors of the elementary reflectors.
VN1
VN1 is DOUBLE PRECISION array, dimension (N)
The vector with the partial column norms.
VN2
VN2 is DOUBLE PRECISION array, dimension (N)
The vector with the exact column norms.
AUXV
AUXV is DOUBLE PRECISION array, dimension (NB)
Auxiliar vector.
F
F is DOUBLE PRECISION array, dimension (LDF,NB)
Matrix F**T = L*Y**T*A.
LDF
LDF is INTEGER
The leading dimension of the array F. LDF >= max(1,N).
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Contributors:
G. QuintanaOrti, Depto. de Informatica, Universidad Jaime I, Spain X. Sun, Computer
Science Dept., Duke University, USA
Partial column norm updating strategy modified on April 2011 Z. Drmac and Z.
Bujanovic, Dept. of Mathematics, University of Zagreb, Croatia.
References:
LAPACK Working Note 176
Definition at line 177 of file dlaqps.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Tue Sep 25 2012 dlaqps.f(3) 
