CTREXC(l)								 )								 CTREXC(l)

NAME

       CTREXC  -  reorder the Schur factorization of a complex matrix A = Q*T*Q**H, so that the diagonal element of T with row index IFST is moved
       to row ILST

SYNOPSIS

       SUBROUTINE CTREXC( COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO )

	   CHARACTER	  COMPQ

	   INTEGER	  IFST, ILST, INFO, LDQ, LDT, N

	   COMPLEX	  Q( LDQ, * ), T( LDT, * )

PURPOSE

       CTREXC reorders the Schur factorization of a complex matrix A = Q*T*Q**H, so that the diagonal element of T with row index IFST is moved to
       row  ILST.   The Schur form T is reordered by a unitary similarity transformation Z**H*T*Z, and optionally the matrix Q of Schur vectors is
       updated by postmultplying it with Z.

ARGUMENTS

       COMPQ   (input) CHARACTER*1
	       = 'V':  update the matrix Q of Schur vectors;
	       = 'N':  do not update Q.

       N       (input) INTEGER
	       The order of the matrix T. N >= 0.

       T       (input/output) COMPLEX array, dimension (LDT,N)
	       On entry, the upper triangular matrix T.  On exit, the reordered upper triangular matrix.

       LDT     (input) INTEGER
	       The leading dimension of the array T. LDT >= max(1,N).

       Q       (input/output) COMPLEX array, dimension (LDQ,N)
	       On entry, if COMPQ = 'V', the matrix Q of Schur vectors.  On exit, if COMPQ = 'V', Q has been postmultiplied by the unitary  trans-
	       formation matrix Z which reorders T.  If COMPQ = 'N', Q is not referenced.

       LDQ     (input) INTEGER
	       The leading dimension of the array Q.  LDQ >= max(1,N).

       IFST    (input) INTEGER
	       ILST	(input) INTEGER Specify the reordering of the diagonal elements of T: The element with row index IFST is moved to row ILST
	       by a sequence of transpositions between adjacent elements.  1 <= IFST <= N; 1 <= ILST <= N.

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

LAPACK version 3.0						   15 June 2000 							 CTREXC(l)