dlanv2.f man page

dlanv2.f —

Synopsis

Functions/Subroutines

subroutine dlanv2 (A, B, C, D, RT1R, RT1I, RT2R, RT2I, CS, SN)
DLANV2 computes the Schur factorization of a real 2-by-2 nonsymmetric matrix in standard form.

Function/Subroutine Documentation

subroutine dlanv2 (double precisionA, double precisionB, double precisionC, double precisionD, double precisionRT1R, double precisionRT1I, double precisionRT2R, double precisionRT2I, double precisionCS, double precisionSN)

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

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.

Parameters:

A

A is DOUBLE PRECISION

B

B is DOUBLE PRECISION

C

C is DOUBLE PRECISION

D

D is DOUBLE PRECISION
On entry, the elements of the input matrix.
On exit, they are overwritten by the elements of the
standardised Schur form.

RT1R

RT1R is DOUBLE PRECISION

RT1I

RT1I is DOUBLE PRECISION

RT2R

RT2R is DOUBLE PRECISION

RT2I

RT2I is DOUBLE PRECISION
The real and imaginary parts of the eigenvalues. If the
eigenvalues are a complex conjugate pair, RT1I > 0.

CS

CS is DOUBLE PRECISION

SN

SN is DOUBLE PRECISION
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 dlanv2.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

dlanv2(3) is an alias of dlanv2.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK