ZUNG2L (3lapack)

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

SYNOPSIS

  SUBROUTINE ZUNG2L( M, N, K, A, LDA, TAU, WORK, INFO )

      INTEGER        INFO, K, LDA, M, N

      COMPLEX*16     A( LDA, * ), TAU( * ), WORK( * )

PURPOSE

  ZUNG2L generates an m by n complex 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 ZGEQLF.

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) COMPLEX*16 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 ZGEQLF 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) COMPLEX*16 array, dimension (K)
          TAU(i) must contain the scalar factor of the elementary reflector
          H(i), as returned by ZGEQLF.

  WORK    (workspace) COMPLEX*16 array, dimension (N)

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