# 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 precision A, double precision B, double precision C, double precision D, double precision RT1R, double precision RT1I, double precision RT2R, double precision RT2I, double precision CS, double precision SN)

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

NAG Ltd.

Date:

December 2016

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 129 of file dlanv2.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dlanv2(3) is an alias of dlanv2.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK