LAPACK  3.4.2
LAPACK: Linear Algebra PACKage
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ctrexc.f File Reference

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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

Download CTREXC + dependencies [TGZ] [ZIP] [TXT]
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
 postmultplying it with Z.
Parameters:
[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 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 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 i-th argument had an illegal value
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011

Definition at line 125 of file ctrexc.f.

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