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zunghr examples
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Man Page Details
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 Online html documentation available at 
            http://www.netlib.org/lapack/explore-html/ 

 Definition:
 ===========

       SUBROUTINE ZUNGHR( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO )
 
       .. Scalar Arguments ..
       INTEGER            IHI, ILO, INFO, LDA, LWORK, N
       ..
       .. Array Arguments ..
       COMPLEX*16         A( LDA, * ), TAU( * ), WORK( * )
       ..
  

 Purpose:
 =============

 ZUNGHR generates a complex unitary matrix Q which is defined as the
 product of IHI-ILO elementary reflectors of order N, as returned by
 ZGEHRD:

 Q = H(ilo) H(ilo+1) . . . H(ihi-1).

 Arguments:
 ==========

  [in] N

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

  [in] ILO

          ILO is INTEGER

  [in] IHI

          IHI is INTEGER

          ILO and IHI must have the same values as in the previous call
          of ZGEHRD. Q is equal to the unit matrix except in the
          submatrix Q(ilo+1:ihi,ilo+1:ihi).
          1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.

  [in,out] A

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

  [in] LDA

          LDA is INTEGER
          The leading dimension of the array A. LDA >= max(1,N).

  [in] 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 ZGEHRD.

  [out] WORK

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

  [in] LWORK

          LWORK is INTEGER
          The dimension of the array WORK. LWORK >= IHI-ILO.
          For optimum performance LWORK >= (IHI-ILO)*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.

  [out] INFO

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

 Authors:
 ========

  Univ. of Tennessee 
  Univ. of California Berkeley 
  Univ. of Colorado Denver 
  NAG Ltd. 

 November 2011

