dorgr2(3)

NAME

DORGR2 - generate an m by n real matrix Q with orthonormal

rows,

SYNOPSIS

SUBROUTINE DORGR2( M, N, K, A, LDA, TAU, WORK, INFO )
    INTEGER        INFO, K, LDA, M, N
    DOUBLE          PRECISION A( LDA, * ), TAU( * ), WORK(
* )

PURPOSE

DORGR2 generates an m by n real matrix Q with orthonormal

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

mentary reflectors of order n

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

as returned by DGERQF.

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 (m-k+i)-th row must contain the vec

tor which defines the elementary reflector H(i), for i =

1,2,...,k, as returned by DGERQF in the last 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 DGERQF.

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

DORGR2(3)