ctrexc.f - Man Page

SRC/ctrexc.f

Synopsis

Functions/Subroutines

subroutine ctrexc (compq, n, t, ldt, q, ldq, ifst, ilst, info)
CTREXC

Function/Subroutine Documentation

subroutine ctrexc (character compq, integer n, complex, dimension( ldt, * ) t, integer ldt, complex, dimension( ldq, * ) q, integer ldq, integer ifst, integer ilst, integer info)

CTREXC

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
postmultiplying it with Z.```
Parameters

COMPQ

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

N

```          N is INTEGER
The order of the matrix T. N >= 0.
If N == 0 arguments ILST and IFST may be any value.```

T

```          T is COMPLEX array, dimension (LDT,N)
On entry, the upper triangular matrix T.
On exit, the reordered upper triangular matrix.```

LDT

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

Q

```          Q is 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 transformation matrix Z which reorders T.
If COMPQ = 'N', Q is not referenced.```

LDQ

```          LDQ is INTEGER
The leading dimension of the array Q.  LDQ >= 1, and if
COMPQ = 'V', LDQ >= max(1,N).```

IFST

`          IFST is INTEGER`

ILST

```          ILST is 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

```          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.

Definition at line 125 of file ctrexc.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

The man page ctrexc(3) is an alias of ctrexc.f(3).

Tue Nov 28 2023 12:08:41 Version 3.12.0 LAPACK