subroutine ztrexc (COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO)
subroutine ztrexc (characterCOMPQ, integerN, complex*16, dimension( ldt, * )T, integerLDT, complex*16, dimension( ldq, * )Q, integerLDQ, integerIFST, integerILST, integerINFO)ZTREXC Purpose:
ZTREXC 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.
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.T
T is COMPLEX*16 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*16 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 >= max(1,N).IFST
IFST is INTEGERILST
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
Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd.Date:
November 2011Definition at line 125 of file ztrexc.f.