LAPACK  3.4.2
LAPACK: Linear Algebra PACKage
 All Files Functions Groups
Functions/Subroutines
dlaqps.f File Reference

Go to the source code of this file.

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 m-by-n matrix A by using BLAS level 3.

Function/Subroutine Documentation

subroutine dlaqps ( integer  M,
integer  N,
integer  OFFSET,
integer  NB,
integer  KB,
double precision, dimension( lda, * )  A,
integer  LDA,
integer, dimension( * )  JPVT,
double precision, dimension( * )  TAU,
double precision, dimension( * )  VN1,
double precision, dimension( * )  VN2,
double precision, dimension( * )  AUXV,
double precision, dimension( ldf, * )  F,
integer  LDF 
)

DLAQPS computes a step of QR factorization with column pivoting of a real m-by-n matrix A by using BLAS level 3.

Download DLAQPS + dependencies [TGZ] [ZIP] [TXT]
Purpose: 
 DLAQPS computes a step of QR factorization with column pivoting
 of a real 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:
[in]M
          M is INTEGER
          The number of rows of the matrix A. M >= 0.
[in]N
          N is INTEGER
          The number of columns of the matrix A. N >= 0
[in]OFFSET
          OFFSET is INTEGER
          The number of rows of A that have been factorized in
          previous steps.
[in]NB
          NB is INTEGER
          The number of columns to factorize.
[out]KB
          KB is INTEGER
          The number of columns actually factorized.
[in,out]A
          A is DOUBLE PRECISION 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.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A. LDA >= max(1,M).
[in,out]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.
[out]TAU
          TAU is DOUBLE PRECISION array, dimension (KB)
          The scalar factors of the elementary reflectors.
[in,out]VN1
          VN1 is DOUBLE PRECISION array, dimension (N)
          The vector with the partial column norms.
[in,out]VN2
          VN2 is DOUBLE PRECISION array, dimension (N)
          The vector with the exact column norms.
[in,out]AUXV
          AUXV is DOUBLE PRECISION array, dimension (NB)
          Auxiliar vector.
[in,out]F
          F is DOUBLE PRECISION array, dimension (LDF,NB)
          Matrix F**T = L*Y**T*A.
[in]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. 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 [PDF]

Definition at line 177 of file dlaqps.f.

Here is the call graph for this function:

Here is the caller graph for this function: