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Table 1
List of changes to the SME since the original paper Valenti & Piskunov (1996).
| “Old” SME | Current version | |
| Versioning | None | IDL code, library and SME structure |
| Evaluating the number of absorbers | Saha-Boltzmann | Molecular-ionization equilibrium solver |
| Continuous opacity | Interpolated between the ends of spectral intervals | Evaluated at the same wavelength points where spectral synthesis is computed |
| Line opacity | Voigt | Voigt with two-parameter approximation for van der Waals broadening, new hydrogen line profile approximation |
| Radiative transfer | Runge-Kutta | Attenuation operator with Bezier splines, spherical radiative transfer |
| Model atmospheres | 2D (Teff- log g) grid from R.L. Kurucz | 3D (Teff- log g- [m/H]) grids from several sources, new model interpolation techniques |
| LTE | Strict LTE approximation | LTE and NLTE using pre-computed departure coefficients |
| Uncertainties of derived parameters | Using the main diagonal of the approximate covariance matrix | Cumulative distribution estimates in addition to covariance matrix approach |
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