ztrexc(3P) Sun Performance Library ztrexc(3P)NAMEztrexc - 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 ZTREXC(COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO)
CHARACTER * 1 COMPQ
DOUBLE COMPLEX T(LDT,*), Q(LDQ,*)
INTEGER N, LDT, LDQ, IFST, ILST, INFO
SUBROUTINE ZTREXC_64(COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO)
CHARACTER * 1 COMPQ
DOUBLE COMPLEX T(LDT,*), Q(LDQ,*)
INTEGER*8 N, LDT, LDQ, IFST, ILST, INFO
F95 INTERFACE
SUBROUTINE TREXC(COMPQ, [N], T, [LDT], Q, [LDQ], IFST, ILST, [INFO])
CHARACTER(LEN=1) :: COMPQ
COMPLEX(8), DIMENSION(:,:) :: T, Q
INTEGER :: N, LDT, LDQ, IFST, ILST, INFO
SUBROUTINE TREXC_64(COMPQ, [N], T, [LDT], Q, [LDQ], IFST, ILST, [INFO])
CHARACTER(LEN=1) :: COMPQ
COMPLEX(8), DIMENSION(:,:) :: T, Q
INTEGER(8) :: N, LDT, LDQ, IFST, ILST, INFO
C INTERFACE
#include <sunperf.h>
void ztrexc(char compq, int n, doublecomplex *t, int ldt, doublecomplex
*q, int ldq, int ifst, int ilst, int *info);
void ztrexc_64(char compq, long n, doublecomplex *t, long ldt, double‐
complex *q, long ldq, long ifst, long ilst, long *info);
PURPOSEztrexc 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)
= 'V': update the matrix Q of Schur vectors;
= 'N': do not update Q.
N (input) The order of the matrix T. N >= 0.
T (input/output)
On entry, the upper triangular matrix T. On exit, the
reordered upper triangular matrix.
LDT (input)
The leading dimension of the array T. LDT >= max(1,N).
Q (input) On entry, if COMPQ = 'V', the matrix Q of Schur vectors. On
exit, if COMPQ = 'V', Q has been postmultiplied by the uni‐
tary transformation matrix Z which reorders T. If COMPQ =
'N', Q is not referenced.
LDQ (input)
The leading dimension of the array Q. LDQ >= max(1,N).
IFST (input)
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.
ILST (input)
See the description of IFST.
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
6 Mar 2009 ztrexc(3P)
