\brief \b ESMF_DLAS2 \htmlonly Download ESMF_DLAS2 + dependencies [TGZ] [ZIP] [TXT] \endhtmlonly \par Purpose:
\verbatim
ESMF_DLAS2 computes the singular values of the 2-by-2 matrix [ F G ] [ 0 H ]. On return, SSMIN is the smaller singular value and SSMAX is the larger singular value. \endverbatim \param[in] F \verbatim F is DOUBLE PRECISION The (1,1) element of the 2-by-2 matrix. \endverbatim
\param[in] G \verbatim G is DOUBLE PRECISION The (1,2) element of the 2-by-2 matrix. \endverbatim
\param[in] H \verbatim H is DOUBLE PRECISION The (2,2) element of the 2-by-2 matrix. \endverbatim
\param[out] SSMIN \verbatim SSMIN is DOUBLE PRECISION The smaller singular value. \endverbatim
\param[out] SSMAX \verbatim SSMAX is DOUBLE PRECISION The larger singular value. \endverbatim \author Univ. of Tennessee \author Univ. of California Berkeley \author Univ. of Colorado Denver \author NAG Ltd. \date November 2011 \ingroup auxOTHERauxiliary \par Further Details:
\verbatim
Barring over/underflow, all output quantities are correct to within a few units in the last place (ulps), even in the absence of a guard digit in addition/subtraction.
In IEEE arithmetic, the code works correctly if one matrix element is infinite.
Overflow will not occur unless the largest singular value itself overflows, or is within a few ulps of overflow. (On machines with partial overflow, like the Cray, overflow may occur if the largest singular value is within a factor of 2 of overflow.)
Underflow is harmless if underflow is gradual. Otherwise, results may correspond to a matrix modified by perturbations of size near the underflow threshold. \endverbatim
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| double precision | :: | F | ||||
| double precision | :: | G | ||||
| double precision | :: | H | ||||
| double precision | :: | SSMIN | ||||
| double precision | :: | SSMAX |