ztrexc.f(3)

NAME
ztrexc.f -

SYNOPSIS

  Functions/Subroutines

subroutine ztrexc (COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO)
ZTREXC

Function/Subroutine Documentation

  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.

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.

    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 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.

Date:
    November 2011

Definition at line 125 of file ztrexc.f.

Author

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