SLANV2 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.

A

          A is REAL

B

          B is REAL

C

          C is REAL

D

          D is REAL


          On entry, the elements of the input matrix.


          On exit, they are overwritten by the elements of the


          standardised Schur form.

RT1R

          RT1R is REAL

RT1I

          RT1I is REAL

RT2R

          RT2R is REAL

RT2I

          RT2I is REAL


          The real and imaginary parts of the eigenvalues. If the


          eigenvalues are a complex conjugate pair, RT1I > 0.

CS

          CS is REAL

SN

          SN is REAL


          Parameters of the rotation matrix.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

September 2012

  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).