DLAQP2 (3) Linux Manual Page

dlaqp2.f –

Synopsis

Functions/Subroutines

subroutine dlaqp2 (M, N, OFFSET, A, LDA, JPVT, TAU, VN1, VN2, WORK)
DLAQP2 computes a QR factorization with column pivoting of the matrix block.

Function/Subroutine Documentation

subroutine dlaqp2 (integerM, integerN, integerOFFSET, double precision, dimension( lda, * )A, integerLDA, integer, dimension( * )JPVT, double precision, dimension( * )TAU, double precision, dimension( * )VN1, double precision, dimension( * )VN2, double precision, dimension( * )WORK)

DLAQP2 computes a QR factorization with column pivoting of the matrix block.

Purpose:

 DLAQP2 computes a QR factorization with column pivoting of

 the block A(OFFSET+1:M,1:N).

 The 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 the matrix A that must be pivoted

 but no factorized. OFFSET >= 0.

A

 A is DOUBLE PRECISION array, dimension (LDA,N)

 On entry, the M-by-N matrix A.

 On exit, the upper triangle of block A(OFFSET+1:M,1:N) is

 the triangular factor obtained; the elements in block

 A(OFFSET+1:M,1:N) below the diagonal, together with the

 array TAU, represent the orthogonal matrix Q as a product of

 elementary reflectors. Block A(1:OFFSET,1:N) has been

 accordingly pivoted, but no factorized.

LDA

 LDA is INTEGER

 The leading dimension of the array A. LDA >= max(1,M).

JPVT

 JPVT is INTEGER array, dimension (N)

 On entry, if JPVT(i) .ne. 0, the i-th column of A is permuted

 to the front of A*P (a leading column); if JPVT(i) = 0,

 the i-th column of A is a free column.

 On exit, if JPVT(i) = k, then the i-th column of A*P

 was the k-th column of A.

TAU

 TAU is DOUBLE PRECISION array, dimension (min(M,N))

 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.

WORK

 WORK is DOUBLE PRECISION array, dimension (N)

 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2013

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 149 of file dlaqp2.f.

Author

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