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

6       ZTREXC  -  reorders  the  Schur  factorization  of a complex matrix A =
7       Q*T*Q**H, so that the diagonal element of T  with  row  index  IFST  is
8       moved to row ILST
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SYNOPSIS

11       SUBROUTINE ZTREXC( COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO )
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13           CHARACTER      COMPQ
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15           INTEGER        IFST, ILST, INFO, LDQ, LDT, N
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17           COMPLEX*16     Q( LDQ, * ), T( LDT, * )
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PURPOSE

20       ZTREXC  reorders  the  Schur  factorization  of  a  complex  matrix A =
21       Q*T*Q**H, so that the diagonal element of T  with  row  index  IFST  is
22       moved to row ILST.  The Schur form T is reordered by a unitary similar‐
23       ity transformation Z**H*T*Z, and optionally the matrix Q of Schur  vec‐
24       tors is updated by postmultplying it with Z.
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ARGUMENTS

27       COMPQ   (input) CHARACTER*1
28               = 'V':  update the matrix Q of Schur vectors;
29               = 'N':  do not update Q.
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31       N       (input) INTEGER
32               The order of the matrix T. N >= 0.
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34       T       (input/output) COMPLEX*16 array, dimension (LDT,N)
35               On  entry,  the  upper  triangular  matrix  T.   On  exit,  the
36               reordered upper triangular matrix.
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38       LDT     (input) INTEGER
39               The leading dimension of the array T. LDT >= max(1,N).
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41       Q       (input/output) COMPLEX*16 array, dimension (LDQ,N)
42               On entry, if COMPQ = 'V', the matrix Q of  Schur  vectors.   On
43               exit,  if COMPQ = 'V', Q has been postmultiplied by the unitary
44               transformation matrix Z which reorders T.  If COMPQ = 'N', Q is
45               not referenced.
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47       LDQ     (input) INTEGER
48               The leading dimension of the array Q.  LDQ >= max(1,N).
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50       IFST    (input) INTEGER
51               ILST     (input) INTEGER Specify the reordering of the diagonal
52               elements of T: The element with row index IFST is moved to  row
53               ILST by a sequence of transpositions between adjacent elements.
54               1 <= IFST <= N; 1 <= ILST <= N.
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56       INFO    (output) INTEGER
57               = 0:  successful exit
58               < 0:  if INFO = -i, the i-th argument had an illegal value
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62 LAPACK routine (version 3.2)    November 2008                       ZTREXC(1)