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cungtr

 NAME
      CUNGTR - generate a complex unitary matrix Q which is
      defined as the product of n-1 elementary reflectors of order
      N, as returned by CHETRD

 SYNOPSIS
      SUBROUTINE CUNGTR( UPLO, N, A, LDA, TAU, WORK, LWORK, INFO )

          CHARACTER      UPLO

          INTEGER        INFO, LDA, LWORK, N

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

 PURPOSE
      CUNGTR generates a complex unitary matrix Q which is defined
      as the product of n-1 elementary reflectors of order N, as
      returned by CHETRD:

      if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),

      if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).

 ARGUMENTS
      UPLO    (input) CHARACTER*1
              = 'U': Upper triangle of A contains elementary
              reflectors from CHETRD; = 'L': Lower triangle of A
              contains elementary reflectors from CHETRD.

      N       (input) INTEGER
              The order of the matrix Q. N >= 0.

      A       (input/output) COMPLEX array, dimension (LDA,N)
              On entry, the vectors which define the elementary
              reflectors, as returned by CHETRD.  On exit, the N-
              by-N unitary matrix Q.

      LDA     (input) INTEGER
              The leading dimension of the array A. LDA >= N.

      TAU     (input) COMPLEX array, dimension (N-1)
              TAU(i) must contain the scalar factor of the elemen-
              tary reflector H(i), as returned by CHETRD.

      WORK    (workspace) COMPLEX array, dimension (LWORK)
              On exit, if INFO = 0, WORK(1) returns the optimal
              LWORK.

      LWORK   (input) INTEGER
              The dimension of the array WORK. LWORK >= N-1.  For
              optimum performance LWORK >= (N-1)*NB, where NB is

              the optimal blocksize.

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