1CUNGTR(1)                LAPACK routine (version 3.2)                CUNGTR(1)
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NAME

6       CUNGTR  -  generates a complex unitary matrix Q which is defined as the
7       product of n-1 elementary reflectors of order N, as returned by CHETRD
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SYNOPSIS

10       SUBROUTINE CUNGTR( UPLO, N, A, LDA, TAU, WORK, LWORK, INFO )
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12           CHARACTER      UPLO
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14           INTEGER        INFO, LDA, LWORK, N
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16           COMPLEX        A( LDA, * ), TAU( * ), WORK( * )
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PURPOSE

19       CUNGTR generates a complex unitary matrix Q which  is  defined  as  the
20       product of n-1 elementary reflectors of order N, as returned by CHETRD:
21       if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
22       if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
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ARGUMENTS

25       UPLO    (input) CHARACTER*1
26               = 'U': Upper triangle of A contains elementary reflectors  from
27               CHETRD;  = 'L': Lower triangle of A contains elementary reflec‐
28               tors from CHETRD.
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30       N       (input) INTEGER
31               The order of the matrix Q. N >= 0.
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33       A       (input/output) COMPLEX array, dimension (LDA,N)
34               On entry, the vectors which define the  elementary  reflectors,
35               as returned by CHETRD.  On exit, the N-by-N unitary matrix Q.
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37       LDA     (input) INTEGER
38               The leading dimension of the array A. LDA >= N.
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40       TAU     (input) COMPLEX array, dimension (N-1)
41               TAU(i) must contain the scalar factor of the elementary reflec‐
42               tor H(i), as returned by CHETRD.
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44       WORK    (workspace/output) COMPLEX array, dimension (MAX(1,LWORK))
45               On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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47       LWORK   (input) INTEGER
48               The dimension of the array WORK. LWORK  >=  N-1.   For  optimum
49               performance  LWORK  >= (N-1)*NB, where NB is the optimal block‐
50               size.  If LWORK = -1, then a workspace query  is  assumed;  the
51               routine  only  calculates  the  optimal size of the WORK array,
52               returns this value as the first entry of the WORK array, and no
53               error message related to LWORK is issued by XERBLA.
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55       INFO    (output) INTEGER
56               = 0:  successful exit
57               < 0:  if INFO = -i, the i-th argument had an illegal value
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61 LAPACK routine (version 3.2)    November 2008                       CUNGTR(1)
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