SRC/zungtr.f(3)

NAME
SRC/zungtr.f

SYNOPSIS

  Functions/Subroutines
subroutine zungtr (uplo, n, a, lda, tau, work, lwork, info)
ZUNGTR

Function/Subroutine Documentation

  subroutine zungtr (character uplo, integer n, complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension( * ) tau, complex*16, dimension( * ) work, integer lwork, integer info)

ZUNGTR

Purpose:

    !>
    !> ZUNGTR generates a complex unitary matrix Q which is defined as the
    !> product of n-1 elementary reflectors of order N, as returned by
    !> ZHETRD:
    !>
    !> if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
    !>
    !> if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
    !>

Parameters
    UPLO

    !>          UPLO is CHARACTER*1
    !>          = 'U': Upper triangle of A contains elementary reflectors
    !>                 from ZHETRD;
    !>          = 'L': Lower triangle of A contains elementary reflectors
    !>                 from ZHETRD.
    !>

    N

    !>          N is INTEGER
    !>          The order of the matrix Q. N >= 0.
    !>

    A

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

    LDA

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

    TAU

    !>          TAU is COMPLEX*16 array, dimension (N-1)
    !>          TAU(i) must contain the scalar factor of the elementary
    !>          reflector H(i), as returned by ZHETRD.
    !>

    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 >= N-1.
    !>          For optimum performance LWORK >= (N-1)*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 122 of file zungtr.f.

Author

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