LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
subroutine  ztrexc (COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO) 
ZTREXC 
subroutine ztrexc  (  character  COMPQ, 
integer  N,  
complex*16, dimension( ldt, * )  T,  
integer  LDT,  
complex*16, dimension( ldq, * )  Q,  
integer  LDQ,  
integer  IFST,  
integer  ILST,  
integer  INFO  
) 
ZTREXC
Download ZTREXC + dependencies [TGZ] [ZIP] [TXT]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.
[in]  COMPQ  COMPQ is CHARACTER*1 = 'V': update the matrix Q of Schur vectors; = 'N': do not update Q. 
[in]  N  N is INTEGER The order of the matrix T. N >= 0. 
[in,out]  T  T is COMPLEX*16 array, dimension (LDT,N) On entry, the upper triangular matrix T. On exit, the reordered upper triangular matrix. 
[in]  LDT  LDT is INTEGER The leading dimension of the array T. LDT >= max(1,N). 
[in,out]  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. 
[in]  LDQ  LDQ is INTEGER The leading dimension of the array Q. LDQ >= max(1,N). 
[in]  IFST  IFST is INTEGER 
[in]  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. 
[out]  INFO  INFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value 
Definition at line 125 of file ztrexc.f.