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slanv2.f(3) LAPACK slanv2.f(3)

NAME

slanv2.f -

SYNOPSIS

Functions/Subroutines


subroutine slanv2 (A, B, C, D, RT1R, RT1I, RT2R, RT2I, CS, SN)
 
SLANV2 computes the Schur factorization of a real 2-by-2 nonsymmetric matrix in standard form.

Function/Subroutine Documentation

subroutine slanv2 (realA, realB, realC, realD, realRT1R, realRT1I, realRT2R, realRT2I, realCS, realSN)

SLANV2 computes the Schur factorization of a real 2-by-2 nonsymmetric matrix in standard form.
Purpose: 
 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.
Parameters:
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.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
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).
Definition at line 128 of file slanv2.f.

Author

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