1CUNGHR(1)                LAPACK routine (version 3.1)                CUNGHR(1)
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NAME

6       CUNGHR  - a complex unitary matrix Q which is defined as the product of
7       IHI-ILO elementary reflectors of order N, as returned by CGEHRD
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SYNOPSIS

10       SUBROUTINE CUNGHR( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO )
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12           INTEGER        IHI, ILO, INFO, LDA, LWORK, N
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14           COMPLEX        A( LDA, * ), TAU( * ), WORK( * )
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PURPOSE

17       CUNGHR generates a complex unitary matrix Q which  is  defined  as  the
18       product  of  IHI-ILO  elementary  reflectors of order N, as returned by
19       CGEHRD:
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21       Q = H(ilo) H(ilo+1) . . . H(ihi-1).
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ARGUMENTS

25       N       (input) INTEGER
26               The order of the matrix Q. N >= 0.
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28       ILO     (input) INTEGER
29               IHI     (input) INTEGER ILO and IHI must have the  same  values
30               as  in  the  previous  call  of  CGEHRD. Q is equal to the unit
31               matrix except in the submatrix  Q(ilo+1:ihi,ilo+1:ihi).   1  <=
32               ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
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34       A       (input/output) COMPLEX array, dimension (LDA,N)
35               On  entry,  the vectors which define the elementary reflectors,
36               as returned by CGEHRD.  On exit, the N-by-N unitary matrix Q.
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38       LDA     (input) INTEGER
39               The leading dimension of the array A. LDA >= max(1,N).
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41       TAU     (input) COMPLEX array, dimension (N-1)
42               TAU(i) must contain the scalar factor of the elementary reflec‐
43               tor H(i), as returned by CGEHRD.
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45       WORK    (workspace/output) COMPLEX array, dimension (MAX(1,LWORK))
46               On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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48       LWORK   (input) INTEGER
49               The dimension of the array WORK. LWORK >= IHI-ILO.  For optimum
50               performance LWORK >= (IHI-ILO)*NB,  where  NB  is  the  optimal
51               blocksize.
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53               If  LWORK  = -1, then a workspace query is assumed; the routine
54               only calculates the optimal size of  the  WORK  array,  returns
55               this  value  as the first entry of the WORK array, and no error
56               message related to LWORK is issued by XERBLA.
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58       INFO    (output) INTEGER
59               = 0:  successful exit
60               < 0:  if INFO = -i, the i-th argument had an illegal value
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64 LAPACK routine (version 3.1)    November 2006                       CUNGHR(1)