SYNOPSIS

SUBROUTINE DORG2R(

M, N, K, A, LDA, TAU, WORK, INFO )

    

INTEGER INFO, K, LDA, M, N

    

DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * )

PURPOSE

DORG2R generates an m by n real matrix Q with orthonormal columns, which is defined as the first n columns of a product of k elementary reflectors of order m

      Q  =  H(1) H(2) . . . H(k)
as returned by DGEQRF.

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. M >= N >= 0.

K (input) INTEGER

The number of elementary reflectors whose product defines the matrix Q. N >= K >= 0.

A (input/output) DOUBLE PRECISION array, dimension (LDA,N)

On entry, the i-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGEQRF in the first k columns 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 DGEQRF.

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

INFO (output) INTEGER

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