dlanv2()

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.

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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

[in,out]	A	!> A is DOUBLE PRECISION !>
[in,out]	B	!> B is DOUBLE PRECISION !>
[in,out]	C	!> C is DOUBLE PRECISION !>
[in,out]	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. !>
[out]	RT1R	!> RT1R is DOUBLE PRECISION !>
[out]	RT1I	!> RT1I is DOUBLE PRECISION !>
[out]	RT2R	!> RT2R is DOUBLE PRECISION !>
[out]	RT2I	!> RT2I is DOUBLE PRECISION !> The real and imaginary parts of the eigenvalues. If the !> eigenvalues are a complex conjugate pair, RT1I > 0. !>
[out]	CS	!> CS is DOUBLE PRECISION !>
[out]	SN	!> SN is DOUBLE PRECISION !> Parameters of the rotation matrix. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

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).
!>