dorg2r(3F)

NAME
     DORG2R - generate an m by n real matrix Q with orthonormal columns,

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