.TH "SRC/ztgexc.f" 3 "Version 3.12.0" "LAPACK" \" -*- nroff -*-
.ad l
.nh
.SH NAME
SRC/ztgexc.f
.SH SYNOPSIS
.br
.PP
.SS "Functions/Subroutines"

.in +1c
.ti -1c
.RI "subroutine \fBztgexc\fP (wantq, wantz, n, a, lda, b, ldb, q, ldq, z, ldz, ifst, ilst, info)"
.br
.RI "\fBZTGEXC\fP "
.in -1c
.SH "Function/Subroutine Documentation"
.PP 
.SS "subroutine ztgexc (logical wantq, logical wantz, integer n, complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension( ldb, * ) b, integer ldb, complex*16, dimension( ldq, * ) q, integer ldq, complex*16, dimension( ldz, * ) z, integer ldz, integer ifst, integer ilst, integer info)"

.PP
\fBZTGEXC\fP  
.PP
\fBPurpose:\fP
.RS 4

.PP
.nf
 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
.fi
.PP
 
.RE
.PP
\fBParameters\fP
.RS 4
\fIWANTQ\fP 
.PP
.nf
          WANTQ is LOGICAL
          \&.TRUE\&. : update the left transformation matrix Q;
          \&.FALSE\&.: do not update Q\&.
.fi
.PP
.br
\fIWANTZ\fP 
.PP
.nf
          WANTZ is LOGICAL
          \&.TRUE\&. : update the right transformation matrix Z;
          \&.FALSE\&.: do not update Z\&.
.fi
.PP
.br
\fIN\fP 
.PP
.nf
          N is INTEGER
          The order of the matrices A and B\&. N >= 0\&.
.fi
.PP
.br
\fIA\fP 
.PP
.nf
          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\&.
.fi
.PP
.br
\fILDA\fP 
.PP
.nf
          LDA is INTEGER
          The leading dimension of the array A\&. LDA >= max(1,N)\&.
.fi
.PP
.br
\fIB\fP 
.PP
.nf
          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\&.
.fi
.PP
.br
\fILDB\fP 
.PP
.nf
          LDB is INTEGER
          The leading dimension of the array B\&. LDB >= max(1,N)\&.
.fi
.PP
.br
\fIQ\fP 
.PP
.nf
          Q is COMPLEX*16 array, dimension (LDQ,N)
          On entry, if WANTQ = \&.TRUE\&., the unitary matrix Q\&.
          On exit, the updated matrix Q\&.
          If WANTQ = \&.FALSE\&., Q is not referenced\&.
.fi
.PP
.br
\fILDQ\fP 
.PP
.nf
          LDQ is INTEGER
          The leading dimension of the array Q\&. LDQ >= 1;
          If WANTQ = \&.TRUE\&., LDQ >= N\&.
.fi
.PP
.br
\fIZ\fP 
.PP
.nf
          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\&.
.fi
.PP
.br
\fILDZ\fP 
.PP
.nf
          LDZ is INTEGER
          The leading dimension of the array Z\&. LDZ >= 1;
          If WANTZ = \&.TRUE\&., LDZ >= N\&.
.fi
.PP
.br
\fIIFST\fP 
.PP
.nf
          IFST is INTEGER
.fi
.PP
.br
\fIILST\fP 
.PP
.nf
          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\&.
.fi
.PP
.br
\fIINFO\fP 
.PP
.nf
          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\&.
.fi
.PP
 
.RE
.PP
\fBAuthor\fP
.RS 4
Univ\&. of Tennessee 
.PP
Univ\&. of California Berkeley 
.PP
Univ\&. of Colorado Denver 
.PP
NAG Ltd\&. 
.RE
.PP
\fBContributors:\fP
.RS 4
Bo Kagstrom and Peter Poromaa, Department of Computing Science, Umea University, S-901 87 Umea, Sweden\&. 
.RE
.PP
\fBReferences:\fP
.RS 4
[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\&. 
.br
 [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\&. 
.br
 [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\&. 
.RE
.PP

.PP
Definition at line \fB198\fP of file \fBztgexc\&.f\fP\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for LAPACK from the source code\&.