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.TH CLAQP2 l "15 June 2000" "LAPACK version 3.0" ")"
.SH NAME
CLAQP2 - compute a QR factorization with column pivoting of the block A(OFFSET+1:M,1:N)
.SH SYNOPSIS
.TP 19
SUBROUTINE CLAQP2(
M, N, OFFSET, A, LDA, JPVT, TAU, VN1, VN2,
WORK )
.TP 19
.ti +4
INTEGER
LDA, M, N, OFFSET
.TP 19
.ti +4
INTEGER
JPVT( * )
.TP 19
.ti +4
REAL
VN1( * ), VN2( * )
.TP 19
.ti +4
COMPLEX
A( LDA, * ), TAU( * ), WORK( * )
.SH PURPOSE
CLAQP2 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.
.SH ARGUMENTS
.TP 8
M (input) INTEGER
The number of rows of the matrix A. M >= 0.
.TP 8
N (input) INTEGER
The number of columns of the matrix A. N >= 0.
.TP 8
OFFSET (input) INTEGER
The number of rows of the matrix A that must be pivoted
but no factorized. OFFSET >= 0.
.TP 8
A (input/output) COMPLEX 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.
.TP 8
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,M).
.TP 8
JPVT (input/output) 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.
.TP 8
TAU (output) COMPLEX array, dimension (min(M,N))
The scalar factors of the elementary reflectors.
.TP 8
VN1 (input/output) REAL array, dimension (N)
The vector with the partial column norms.
.TP 8
VN2 (input/output) REAL array, dimension (N)
The vector with the exact column norms.
.TP 8
WORK (workspace) COMPLEX array, dimension (N)
.SH FURTHER DETAILS
Based on contributions by
.br
G. Quintana-Orti, Depto. de Informatica, Universidad Jaime I, Spain
X. Sun, Computer Science Dept., Duke University, USA
.br
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