ZLAQP2 - compute a QR factorization with column pivoting
of the block A(OFFSET+1:M,1:N)
SYNOPSIS
SUBROUTINE ZLAQP2( M, N, OFFSET, A, LDA, JPVT, TAU, VN1,
VN2, WORK )
INTEGER LDA, M, N, OFFSET
INTEGER JPVT( * )
DOUBLE PRECISION VN1( * ), VN2( * )
COMPLEX*16 A( LDA, * ), TAU( * ), WORK( * )
PURPOSE
ZLAQP2 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.
ARGUMENTS
M (input) INTEGER
The number of rows of the matrix A. M >= 0.
N (input) INTEGER
The number of columns of the matrix A. N >= 0.
OFFSET (input) INTEGER
The number of rows of the matrix A that must be
pivoted but no factorized. OFFSET >= 0.
A (input/output) COMPLEX*16 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 trian
gular 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 piv
oted, but no factorized.
LDA (input) INTEGER
The leading dimension of the array A. LDA >=
max(1,M).
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 col
umn); 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.
The scalar factors of the elementary reflectors.
VN1 (input/output) DOUBLE PRECISION array, dimension
(N)
The vector with the partial column norms.
VN2 (input/output) DOUBLE PRECISION array, dimension
(N)
The vector with the exact column norms.
WORK (workspace) COMPLEX*16 array, dimension (N)
FURTHER DETAILS
Based on contributions by
G. Quintana-Orti, Depto. de Informatica, Universidad
Jaime I, Spain
X. Sun, Computer Science Dept., Duke University, USA
Man(1) output converted with
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