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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine slanv2 | ( | real | A, |
real | B, | ||
real | C, | ||
real | D, | ||
real | RT1R, | ||
real | RT1I, | ||
real | RT2R, | ||
real | RT2I, | ||
real | CS, | ||
real | SN | ||
) |
SLANV2 computes the Schur factorization of a real 2-by-2 nonsymmetric matrix in standard form.
Download SLANV2 + dependencies [TGZ] [ZIP] [TXT]
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.
[in,out] | A | A is REAL |
[in,out] | B | B is REAL |
[in,out] | C | C is REAL |
[in,out] | D | D is REAL 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 REAL |
[out] | RT1I | RT1I is REAL |
[out] | RT2R | RT2R is REAL |
[out] | RT2I | RT2I is REAL The real and imaginary parts of the eigenvalues. If the eigenvalues are a complex conjugate pair, RT1I > 0. |
[out] | CS | CS is REAL |
[out] | SN | SN is REAL Parameters of the rotation matrix. |
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 slanv2.f.