SRC/zungbr.f(3)            Library Functions Manual            SRC/zungbr.f(3)

NAME
       SRC/zungbr.f

SYNOPSIS
   Functions/Subroutines
       subroutine zungbr (vect, m, n, k, a, lda, tau, work, lwork, info)
           ZUNGBR

Function/Subroutine Documentation
   subroutine zungbr (character vect, integer m, integer n, integer k,
       complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension(
       * ) tau, complex*16, dimension( * ) work, integer lwork, integer info)
       ZUNGBR

       Purpose:


           !>
           !> ZUNGBR generates one of the complex unitary matrices Q or P**H
           !> determined by ZGEBRD when reducing a complex matrix A to bidiagonal
           !> form: A = Q * B * P**H.  Q and P**H are defined as products of
           !> elementary reflectors H(i) or G(i) respectively.
           !>
           !> If VECT = 'Q', A is assumed to have been an M-by-K matrix, and Q
           !> is of order M:
           !> if m >= k, Q = H(1) H(2) . . . H(k) and ZUNGBR returns the first n
           !> columns of Q, where m >= n >= k;
           !> if m < k, Q = H(1) H(2) . . . H(m-1) and ZUNGBR returns Q as an
           !> M-by-M matrix.
           !>
           !> If VECT = 'P', A is assumed to have been a K-by-N matrix, and P**H
           !> is of order N:
           !> if k < n, P**H = G(k) . . . G(2) G(1) and ZUNGBR returns the first m
           !> rows of P**H, where n >= m >= k;
           !> if k >= n, P**H = G(n-1) . . . G(2) G(1) and ZUNGBR returns P**H as
           !> an N-by-N matrix.
           !>

       Parameters
           VECT

           !>          VECT is CHARACTER*1
           !>          Specifies whether the matrix Q or the matrix P**H is
           !>          required, as defined in the transformation applied by ZGEBRD:
           !>          = 'Q':  generate Q;
           !>          = 'P':  generate P**H.
           !>

           M

           !>          M is INTEGER
           !>          The number of rows of the matrix Q or P**H to be returned.
           !>          M >= 0.
           !>

           N

           !>          N is INTEGER
           !>          The number of columns of the matrix Q or P**H to be returned.
           !>          N >= 0.
           !>          If VECT = 'Q', M >= N >= min(M,K);
           !>          if VECT = 'P', N >= M >= min(N,K).
           !>

           K

           !>          K is INTEGER
           !>          If VECT = 'Q', the number of columns in the original M-by-K
           !>          matrix reduced by ZGEBRD.
           !>          If VECT = 'P', the number of rows in the original K-by-N
           !>          matrix reduced by ZGEBRD.
           !>          K >= 0.
           !>

           A

           !>          A is COMPLEX*16 array, dimension (LDA,N)
           !>          On entry, the vectors which define the elementary reflectors,
           !>          as returned by ZGEBRD.
           !>          On exit, the M-by-N matrix Q or P**H.
           !>

           LDA

           !>          LDA is INTEGER
           !>          The leading dimension of the array A. LDA >= M.
           !>

           TAU

           !>          TAU is COMPLEX*16 array, dimension
           !>                                (min(M,K)) if VECT = 'Q'
           !>                                (min(N,K)) if VECT = 'P'
           !>          TAU(i) must contain the scalar factor of the elementary
           !>          reflector H(i) or G(i), which determines Q or P**H, as
           !>          returned by ZGEBRD in its array argument TAUQ or TAUP.
           !>

           WORK

           !>          WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
           !>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
           !>

           LWORK

           !>          LWORK is INTEGER
           !>          The dimension of the array WORK. LWORK >= max(1,min(M,N)).
           !>          For optimum performance LWORK >= min(M,N)*NB, where NB
           !>          is the optimal blocksize.
           !>
           !>          If LWORK = -1, then a workspace query is assumed; the routine
           !>          only calculates the optimal size of the WORK array, returns
           !>          this value as the first entry of the WORK array, and no error
           !>          message related to LWORK is issued by XERBLA.
           !>

           INFO

           !>          INFO is INTEGER
           !>          = 0:  successful exit
           !>          < 0:  if INFO = -i, the i-th argument had an illegal value
           !>

       Author
           Univ. of Tennessee


           Univ. of California Berkeley


           Univ. of Colorado Denver


           NAG Ltd.

       Definition at line 156 of file zungbr.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0                 SRC/zungbr.f(3)