dorgl2(3)

NAME

DORGL2 - generate an m by n real matrix Q with orthonormal

rows,

SYNOPSIS

SUBROUTINE DORGL2( M, N, K, A, LDA, TAU, WORK, INFO )
    INTEGER        INFO, K, LDA, M, N
    DOUBLE          PRECISION A( LDA, * ), TAU( * ), WORK(
* )

PURPOSE

DORGL2 generates an m by n real matrix Q with orthonormal

rows, which is defined as the first m rows of a product of k ele

mentary reflectors of order n

Q = H(k) . . . H(2) H(1)

as returned by DGELQF.

ARGUMENTS

M (input) INTEGER

The number of rows of the matrix Q. M >= 0.

N (input) INTEGER

The number of columns of the matrix Q. N >= M.

K (input) INTEGER

The number of elementary reflectors whose product

defines the matrix Q. M >= K >= 0.

A (input/output) DOUBLE PRECISION array, dimension

(LDA,N)

On entry, the i-th row must contain the vector

which defines the elementary reflector H(i), for i = 1,2,...,k,

as returned by DGELQF in the first k rows of its array argument

A. On exit, the m-by-n matrix Q.

LDA (input) INTEGER

The first dimension of the array A. LDA >=

max(1,M).

TAU (input) DOUBLE PRECISION array, dimension (K)

TAU(i) must contain the scalar factor of the ele

mentary reflector H(i), as returned by DGELQF.

WORK (workspace) DOUBLE PRECISION array, dimension (M)

INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -i, the i-th argument has an ille

gal value

LAPACK version 3.0 15 June 2000

DORGL2(3)