slanv2.f (3) - Linux Man Pages
subroutine slanv2 (realA, realB, realC, realD, realRT1R, realRT1I, realRT2R, realRT2I, realCS, realSN)
SLANV2 computes the Schur factorization of a real 2-by-2 nonsymmetric matrix in standard form.
SLANV2 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 REAL
B is REAL
C is REAL
D is REAL On entry, the elements of the input matrix. On exit, they are overwritten by the elements of the standardised Schur form.
RT1R is REAL
RT1I is REAL
RT2R is REAL
RT2I is REAL The real and imaginary parts of the eigenvalues. If the eigenvalues are a complex conjugate pair, RT1I > 0.
CS is REAL
SN is REAL 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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