dorgr2 (l) - Linux Manuals

dorgr2: generates an m by n real matrix Q with orthonormal rows,

NAME

DORGR2 - generates 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 elementary 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 vector 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 elementary 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 illegal value