DORG2R (3lapack)

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