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Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 4.8 |
i386 |
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dlanv2(l) |
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DLANV2 - compute the Schur factorization of a real 2-by-2 nonsymmetric matrix in standard form
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SUBROUTINE DLANV2( |
A, B, C, D, RT1R, RT1I, RT2R, RT2I, CS, SN ) | ||
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DOUBLE |
PRECISION A, B, C, CS, D, RT1I, RT1R, RT2I, RT2R, SN |
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 (input/output) DOUBLE PRECISION
B (input/output) DOUBLE PRECISION C (input/output) DOUBLE PRECISION D (input/output) DOUBLE PRECISION On entry, the elements of the input matrix. On exit, they are overwritten by the elements of the standardised Schur form.
RT1R (output) DOUBLE PRECISION
RT1I (output) DOUBLE PRECISION RT2R (output) DOUBLE PRECISION RT2I (output) DOUBLE PRECISION The real and imaginary parts of the eigenvalues. If the eigenvalues are a complex conjugate pair, RT1I > 0.
CS (output) DOUBLE PRECISION
SN (output) DOUBLE PRECISION 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).
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dlanv2(l) | |