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RedHat 9 (Linux i386) - man page for zlaqp2 (redhat section l)

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:OFF- SET,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 triangu- lar 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:OFF- SET,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 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 (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, USA LAPACK version 3.0 15 June 2000 ZLAQP2(l)


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