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ctgevc.f(3)				      LAPACK				      ctgevc.f(3)

NAME
       ctgevc.f -

SYNOPSIS
   Functions/Subroutines
       subroutine ctgevc (SIDE, HOWMNY, SELECT, N, S, LDS, P, LDP, VL, LDVL, VR, LDVR, MM, M,
	   WORK, RWORK, INFO)
	   CTGEVC

Function/Subroutine Documentation
   subroutine ctgevc (characterSIDE, characterHOWMNY, logical, dimension( * )SELECT, integerN,
       complex, dimension( lds, * )S, integerLDS, complex, dimension( ldp, * )P, integerLDP,
       complex, dimension( ldvl, * )VL, integerLDVL, complex, dimension( ldvr, * )VR,
       integerLDVR, integerMM, integerM, complex, dimension( * )WORK, real, dimension( * )RWORK,
       integerINFO)
       CTGEVC

       Purpose:

	    CTGEVC computes some or all of the right and/or left eigenvectors of
	    a pair of complex matrices (S,P), where S and P are upper triangular.
	    Matrix pairs of this type are produced by the generalized Schur
	    factorization of a complex matrix pair (A,B):

	       A = Q*S*Z**H,  B = Q*P*Z**H

	    as computed by CGGHRD + CHGEQZ.

	    The right eigenvector x and the left eigenvector y of (S,P)
	    corresponding to an eigenvalue w are defined by:

	       S*x = w*P*x,  (y**H)*S = w*(y**H)*P,

	    where y**H denotes the conjugate tranpose of y.
	    The eigenvalues are not input to this routine, but are computed
	    directly from the diagonal elements of S and P.

	    This routine returns the matrices X and/or Y of right and left
	    eigenvectors of (S,P), or the products Z*X and/or Q*Y,
	    where Z and Q are input matrices.
	    If Q and Z are the unitary factors from the generalized Schur
	    factorization of a matrix pair (A,B), then Z*X and Q*Y
	    are the matrices of right and left eigenvectors of (A,B).

       Parameters:
	   SIDE

		     SIDE is CHARACTER*1
		     = 'R': compute right eigenvectors only;
		     = 'L': compute left eigenvectors only;
		     = 'B': compute both right and left eigenvectors.

	   HOWMNY

		     HOWMNY is CHARACTER*1
		     = 'A': compute all right and/or left eigenvectors;
		     = 'B': compute all right and/or left eigenvectors,
			    backtransformed by the matrices in VR and/or VL;
		     = 'S': compute selected right and/or left eigenvectors,
			    specified by the logical array SELECT.

	   SELECT

		     SELECT is LOGICAL array, dimension (N)
		     If HOWMNY='S', SELECT specifies the eigenvectors to be
		     computed.	The eigenvector corresponding to the j-th
		     eigenvalue is computed if SELECT(j) = .TRUE..
		     Not referenced if HOWMNY = 'A' or 'B'.

	   N

		     N is INTEGER
		     The order of the matrices S and P.  N >= 0.

	   S

		     S is COMPLEX array, dimension (LDS,N)
		     The upper triangular matrix S from a generalized Schur
		     factorization, as computed by CHGEQZ.

	   LDS

		     LDS is INTEGER
		     The leading dimension of array S.	LDS >= max(1,N).

	   P

		     P is COMPLEX array, dimension (LDP,N)
		     The upper triangular matrix P from a generalized Schur
		     factorization, as computed by CHGEQZ.  P must have real
		     diagonal elements.

	   LDP

		     LDP is INTEGER
		     The leading dimension of array P.	LDP >= max(1,N).

	   VL

		     VL is COMPLEX array, dimension (LDVL,MM)
		     On entry, if SIDE = 'L' or 'B' and HOWMNY = 'B', VL must
		     contain an N-by-N matrix Q (usually the unitary matrix Q
		     of left Schur vectors returned by CHGEQZ).
		     On exit, if SIDE = 'L' or 'B', VL contains:
		     if HOWMNY = 'A', the matrix Y of left eigenvectors of (S,P);
		     if HOWMNY = 'B', the matrix Q*Y;
		     if HOWMNY = 'S', the left eigenvectors of (S,P) specified by
				 SELECT, stored consecutively in the columns of
				 VL, in the same order as their eigenvalues.
		     Not referenced if SIDE = 'R'.

	   LDVL

		     LDVL is INTEGER
		     The leading dimension of array VL.  LDVL >= 1, and if
		     SIDE = 'L' or 'l' or 'B' or 'b', LDVL >= N.

	   VR

		     VR is COMPLEX array, dimension (LDVR,MM)
		     On entry, if SIDE = 'R' or 'B' and HOWMNY = 'B', VR must
		     contain an N-by-N matrix Q (usually the unitary matrix Z
		     of right Schur vectors returned by CHGEQZ).
		     On exit, if SIDE = 'R' or 'B', VR contains:
		     if HOWMNY = 'A', the matrix X of right eigenvectors of (S,P);
		     if HOWMNY = 'B', the matrix Z*X;
		     if HOWMNY = 'S', the right eigenvectors of (S,P) specified by
				 SELECT, stored consecutively in the columns of
				 VR, in the same order as their eigenvalues.
		     Not referenced if SIDE = 'L'.

	   LDVR

		     LDVR is INTEGER
		     The leading dimension of the array VR.  LDVR >= 1, and if
		     SIDE = 'R' or 'B', LDVR >= N.

	   MM

		     MM is INTEGER
		     The number of columns in the arrays VL and/or VR. MM >= M.

	   M

		     M is INTEGER
		     The number of columns in the arrays VL and/or VR actually
		     used to store the eigenvectors.  If HOWMNY = 'A' or 'B', M
		     is set to N.  Each selected eigenvector occupies one column.

	   WORK

		     WORK is COMPLEX array, dimension (2*N)

	   RWORK

		     RWORK is REAL array, dimension (2*N)

	   INFO

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

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Definition at line 219 of file ctgevc.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      ctgevc.f(3)
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