DORG2L (3lapack)

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

SYNOPSIS

  SUBROUTINE DORG2L( M, N, K, A, LDA, TAU, WORK, INFO )

      INTEGER        INFO, K, LDA, M, N

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

PURPOSE

  DORG2L generates an m by n real matrix Q with orthonormal columns, which is
  defined as the last n columns of a product of k elementary reflectors of
  order m

        Q  =  H(k) . . . H(2) H(1)

  as returned by DGEQLF.

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 (n-k+i)-th column must contain the vector which
          defines the elementary reflector H(i), for i = 1,2,...,k, as
          returned by DGEQLF in the last 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 DGEQLF.

  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