# zlaqp2(3) [centos man page]

zlaqp2.f(3) LAPACK zlaqp2.f(3)NAME

zlaqp2.f-SYNOPSIS

Functions/Subroutines subroutine zlaqp2 (M, N, OFFSET, A, LDA, JPVT, TAU, VN1, VN2, WORK) ZLAQP2 computes a QR factorization with column pivoting of the matrix block.Function/Subroutine Documentation subroutine zlaqp2 (integerM, integerN, integerOFFSET, complex*16, dimension( lda, * )A, integerLDA, integer, dimension( * )JPVT, complex*16, dimension( * )TAU, double precision, dimension( * )VN1, double precision, dimension( * )VN2, complex*16, dimension( * )WORK) ZLAQP2 computes a QR factorization with column pivoting of the matrix block. 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. 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 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 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 COMPLEX*16 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 COMPLEX*16 array, dimension (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 Definition at line 149 of file zlaqp2.f.AuthorGenerated automatically by Doxygen for LAPACK from the source code.Version 3.4.2Tue Sep 25 2012 zlaqp2.f(3)

## Check Out this Related Man Page

ZLAQP2(l)) ZLAQP2(l)NAME

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 triangular factor obtained; the ele- ments 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 (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 column); if JPVT(i) = 0, the i-th col- umn 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 (output) COMPLEX*16 array, dimension (min(M,N)) 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, USALAPACK version 3.015 June 2000 ZLAQP2(l)