.TH DTZRQF 1 "November 2006" " LAPACK routine (version 3.1) " " LAPACK routine (version 3.1) "
.SH NAME
DTZRQF - i deprecated and has been replaced by routine DTZRZF
.SH SYNOPSIS
.TP 19
SUBROUTINE DTZRQF(
M, N, A, LDA, TAU, INFO )
.TP 19
.ti +4
INTEGER
INFO, LDA, M, N
.TP 19
.ti +4
DOUBLE
PRECISION A( LDA, * ), TAU( * )
.SH PURPOSE
This routine is deprecated and has been replaced by routine DTZRZF.
DTZRQF reduces the M-by-N ( M<=N ) real upper trapezoidal matrix A
to upper triangular form by means of orthogonal transformations.
The upper trapezoidal matrix A is factored as
.br
A = ( R 0 ) * Z,
.br
where Z is an N-by-N orthogonal matrix and R is an M-by-M upper
triangular matrix.
.br
.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 >= M.
.TP 8
A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the leading M-by-N upper trapezoidal part of the
array A must contain the matrix to be factorized.
On exit, the leading M-by-M upper triangular part of A
contains the upper triangular matrix R, and elements M+1 to
N of the first M rows of A, with the array TAU, represent the
orthogonal matrix Z as a product of M elementary reflectors.
.TP 8
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,M).
.TP 8
TAU (output) DOUBLE PRECISION array, dimension (M)
The scalar factors of the elementary reflectors.
.TP 8
INFO (output) INTEGER
= 0: successful exit
.br
< 0: if INFO = -i, the i-th argument had an illegal value
.SH FURTHER DETAILS
The factorization is obtained by Householder\(aqs method. The kth
transformation matrix, Z( k ), which is used to introduce zeros into
the ( m - k + 1 )th row of A, is given in the form
.br
Z( k ) = ( I 0 ),
.br
( 0 T( k ) )
.br
where
.br
T( k ) = I - tau*u( k )*u( k )\(aq, u( k ) = ( 1 ),
( 0 )
( z( k ) )
tau is a scalar and z( k ) is an ( n - m ) element vector.
tau and z( k ) are chosen to annihilate the elements of the kth row
of X.
.br
The scalar tau is returned in the kth element of TAU and the vector
u( k ) in the kth row of A, such that the elements of z( k ) are
in a( k, m + 1 ), ..., a( k, n ). The elements of R are returned in
the upper triangular part of A.
.br
Z is given by
.br
Z = Z( 1 ) * Z( 2 ) * ... * Z( m ).
.br