DORGR2 (3lapack)

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 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