dlanv2.f (3) - Linux Man Pages
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.
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.
A is DOUBLE PRECISION
B is DOUBLE PRECISION
C is DOUBLE PRECISION
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 is DOUBLE PRECISION
RT1I is DOUBLE PRECISION
RT2R is DOUBLE PRECISION
RT2I is DOUBLE PRECISION The real and imaginary parts of the eigenvalues. If the eigenvalues are a complex conjugate pair, RT1I > 0.
CS is DOUBLE PRECISION
SN is DOUBLE PRECISION Parameters of the rotation matrix.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
- September 2012
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).
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