DLAQPS (3)  Linux Manuals
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.
NN is INTEGER The number of columns of the matrix A. N >= 0
OFFSETOFFSET is INTEGER The number of rows of A that have been factorized in previous steps.
NBNB is INTEGER The number of columns to factorize.
KBKB is INTEGER The number of columns actually factorized.
AA 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.
LDALDA is INTEGER The leading dimension of the array A. LDA >= max(1,M).
JPVTJPVT is INTEGER array, dimension (N) JPVT(I) = K <==> Column K of the full matrix A has been permuted into position I in AP.
TAUTAU is DOUBLE PRECISION array, dimension (KB) The scalar factors of the elementary reflectors.
VN1VN1 is DOUBLE PRECISION array, dimension (N) The vector with the partial column norms.
VN2VN2 is DOUBLE PRECISION array, dimension (N) The vector with the exact column norms.
AUXVAUXV is DOUBLE PRECISION array, dimension (NB) Auxiliar vector.
FF is DOUBLE PRECISION array, dimension (LDF,NB) Matrix F**T = L*Y**T*A.
LDFLDF 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
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