ztgexc.f(3)							      LAPACK							       ztgexc.f(3)

NAME

       ztgexc.f -

SYNOPSIS

   Functions/Subroutines
       subroutine ztgexc (WANTQ, WANTZ, N, A, LDA, B, LDB, Q, LDQ, Z, LDZ, IFST, ILST, INFO)
	   ZTGEXC

Function/Subroutine Documentation
   subroutine ztgexc (logicalWANTQ, logicalWANTZ, integerN, complex*16, dimension( lda, * )A, integerLDA, complex*16, dimension( ldb, * )B,
       integerLDB, complex*16, dimension( ldq, * )Q, integerLDQ, complex*16, dimension( ldz, * )Z, integerLDZ, integerIFST, integerILST,
       integerINFO)
       ZTGEXC

       Purpose:

	    ZTGEXC reorders the generalized Schur decomposition of a complex
	    matrix pair (A,B), using an unitary equivalence transformation
	    (A, B) := Q * (A, B) * Z**H, so that the diagonal block of (A, B) with
	    row index IFST is moved to row ILST.

	    (A, B) must be in generalized Schur canonical form, that is, A and
	    B are both upper triangular.

	    Optionally, the matrices Q and Z of generalized Schur vectors are
	    updated.

		   Q(in) * A(in) * Z(in)**H = Q(out) * A(out) * Z(out)**H
		   Q(in) * B(in) * Z(in)**H = Q(out) * B(out) * Z(out)**H

       Parameters:
	   WANTQ

		     WANTQ is LOGICAL
		     .TRUE. : update the left transformation matrix Q;
		     .FALSE.: do not update Q.

	   WANTZ

		     WANTZ is LOGICAL
		     .TRUE. : update the right transformation matrix Z;
		     .FALSE.: do not update Z.

	   N

		     N is INTEGER
		     The order of the matrices A and B. N >= 0.

	   A

		     A is COMPLEX*16 array, dimension (LDA,N)
		     On entry, the upper triangular matrix A in the pair (A, B).
		     On exit, the updated matrix A.

	   LDA

		     LDA is INTEGER
		     The leading dimension of the array A. LDA >= max(1,N).

	   B

		     B is COMPLEX*16 array, dimension (LDB,N)
		     On entry, the upper triangular matrix B in the pair (A, B).
		     On exit, the updated matrix B.

	   LDB

		     LDB is INTEGER
		     The leading dimension of the array B. LDB >= max(1,N).

	   Q

		     Q is COMPLEX*16 array, dimension (LDZ,N)
		     On entry, if WANTQ = .TRUE., the unitary matrix Q.
		     On exit, the updated matrix Q.
		     If WANTQ = .FALSE., Q is not referenced.

	   LDQ

		     LDQ is INTEGER
		     The leading dimension of the array Q. LDQ >= 1;
		     If WANTQ = .TRUE., LDQ >= N.

	   Z

		     Z is COMPLEX*16 array, dimension (LDZ,N)
		     On entry, if WANTZ = .TRUE., the unitary matrix Z.
		     On exit, the updated matrix Z.
		     If WANTZ = .FALSE., Z is not referenced.

	   LDZ

		     LDZ is INTEGER
		     The leading dimension of the array Z. LDZ >= 1;
		     If WANTZ = .TRUE., LDZ >= N.

	   IFST

		     IFST is INTEGER

	   ILST

		     ILST is INTEGER
		     Specify the reordering of the diagonal blocks of (A, B).
		     The block with row index IFST is moved to row ILST, by a
		     sequence of swapping between adjacent blocks.

	   INFO

		     INFO is INTEGER
		      =0:  Successful exit.
		      <0:  if INFO = -i, the i-th argument had an illegal value.
		      =1:  The transformed matrix pair (A, B) would be too far
			   from generalized Schur form; the problem is ill-
			   conditioned. (A, B) may have been partially reordered,
			   and ILST points to the first row of the current
			   position of the block being moved.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Contributors:
	   Bo Kagstrom and Peter Poromaa, Department of Computing Science, Umea University, S-901 87 Umea, Sweden.

       References:
	   [1] B. Kagstrom; A Direct Method for Reordering Eigenvalues in the Generalized Real Schur Form of a Regular Matrix Pair (A, B), in M.S.
	   Moonen et al (eds), Linear Algebra for Large Scale and Real-Time Applications, Kluwer Academic Publ. 1993, pp 195-218.
	    [2] B. Kagstrom and P. Poromaa; Computing Eigenspaces with Specified Eigenvalues of a Regular Matrix Pair (A, B) and Condition
	   Estimation: Theory, Algorithms and Software, Report UMINF - 94.04, Department of Computing Science, Umea University, S-901 87 Umea,
	   Sweden, 1994. Also as LAPACK Working Note 87. To appear in Numerical Algorithms, 1996.
	    [3] B. Kagstrom and P. Poromaa, LAPACK-Style Algorithms and Software for Solving the Generalized Sylvester Equation and Estimating the
	   Separation between Regular Matrix Pairs, Report UMINF - 93.23, Department of Computing Science, Umea University, S-901 87 Umea, Sweden,
	   December 1993, Revised April 1994, Also as LAPACK working Note 75. To appear in ACM Trans. on Math. Software, Vol 22, No 1, 1996.

       Definition at line 200 of file ztgexc.f.

Author
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Version 3.4.2							  Tue Sep 25 2012						       ztgexc.f(3)