SRC/cungtr.f(3)

NAME
SRC/cungtr.f

SYNOPSIS

  Functions/Subroutines
subroutine cungtr (uplo, n, a, lda, tau, work, lwork, info)
CUNGTR

Function/Subroutine Documentation

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

CUNGTR

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).

Parameters
    UPLO

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

    N

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

    A

              A is 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

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

    TAU

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

    WORK

              WORK is COMPLEX 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 cungtr.f.

Author

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