zlaqps.f - Man Page
SRC/zlaqps.f
Synopsis
Functions/Subroutines
subroutine zlaqps (m, n, offset, nb, kb, a, lda, jpvt, tau, vn1, vn2, auxv, f, ldf)
ZLAQPS computes a step of QR factorization with column pivoting of a real m-by-n matrix A by using BLAS level 3.
Function/Subroutine Documentation
subroutine zlaqps (integer m, integer n, integer offset, integer nb, integer kb, complex*16, dimension( lda, * ) a, integer lda, integer, dimension( * ) jpvt, complex*16, dimension( * ) tau, double precision, dimension( * ) vn1, double precision, dimension( * ) vn2, complex*16, dimension( * ) auxv, complex*16, dimension( ldf, * ) f, integer ldf)
ZLAQPS computes a step of QR factorization with column pivoting of a real m-by-n matrix A by using BLAS level 3.
Purpose:
ZLAQPS computes a step of QR factorization with column pivoting of a complex M-by-N matrix A by using Blas-3. It tries to factorize NB columns from A starting from the row OFFSET+1, and updates all of the matrix with Blas-3 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 COMPLEX*16 array, dimension (LDA,N) On entry, the M-by-N 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 COMPLEX*16 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 COMPLEX*16 array, dimension (NB) Auxiliary vector.
F
F is COMPLEX*16 array, dimension (LDF,NB) Matrix F**H = L * Y**H * 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.
- Contributors:
G. Quintana-Orti, 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 175 of file zlaqps.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Referenced By
The man page zlaqps(3) is an alias of zlaqps.f(3).