dlanv2(3F)

NAME
     DLANV2 - compute 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 both
             real, abs(RT1R) >= abs(RT2R); if the eigenvalues are a complex
             conjugate pair, RT1I > 0.

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