Previous: ztzrqf Up: ../lapack-z.html Next: zung2r

zung2l

 NAME
      ZUNG2L - generate an m by n complex matrix Q with orthonor-
      mal 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 elemen-
              tary 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