dlanv2.f(3) LAPACK dlanv2.f(3)
NAME
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.
Version 3.4.2 Tue Sep 25 2012 dlanv2.f(3)