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dlanv2 examples
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Man Page Details
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NAME
       DLANV2  -  the Schur factorization of a real 2-by-2 nonsymmetric matrix
       in standard form

SYNOPSIS
       SUBROUTINE DLANV2( A, B, C, D, RT1R, RT1I, RT2R, RT2I, CS, SN )

           DOUBLE         PRECISION A, B, C, CS, D, RT1I, RT1R, RT2I, RT2R, SN

 Purpose
 =======

  DLANV2 computes the Schur factorization of a real 2-by-2 nonsymmetric
  matrix in standard form:

       [ A  B ] = [ CS -SN ] [ AA  BB ] [ CS  SN ]
       [ C  D ]   [ SN  CS ] [ CC  DD ] [-SN  CS ]

  where either
  1) CC = 0 so that AA and DD are real eigenvalues of the matrix, or
  2) AA = DD and BB*CC < 0, so that AA + or - sqrt(BB*CC) are complex
  conjugate eigenvalues.

 Arguments
 =========

  A       (input/output) DOUBLE PRECISION
  B       (input/output) DOUBLE PRECISION
  C       (input/output) DOUBLE PRECISION
  D       (input/output) DOUBLE PRECISION
          On entry, the elements of the input matrix.
          On exit, they are overwritten by the elements of the
          standardised Schur form.

  RT1R    (output) DOUBLE PRECISION
  RT1I    (output) DOUBLE PRECISION
  RT2R    (output) DOUBLE PRECISION
  RT2I    (output) DOUBLE PRECISION
          The real and imaginary parts of the eigenvalues. If the
          eigenvalues are a complex conjugate pair, RT1I > 0.

  CS      (output) DOUBLE PRECISION
  SN      (output) DOUBLE PRECISION
          Parameters of the rotation matrix.

  Further Details
  ===============

  Modified by V. Sima, Research Institute for Informatics, Bucharest,
  Romania, to reduce the risk of cancellation errors,
  when computing real eigenvalues, and to ensure, if possible, that
  abs(RT1R) >= abs(RT2R).

