altabinit.f

This file checks the Allard atmosphere table that ALFILEIN has just read and derives the limits that the lookup ALSURFP needs: the range of $\log T_\mathrm{eff}$, and for each $T_\mathrm{eff}$ row the valid columns in $\log g$ and the allowed range of $\log g$, extrapolation included.

• Who calls it: ALFILEIN, at the end of reading.
• What it calls: ALPRINT, to print the table when it is bad.
• Inputs: ALATM01_MOD (the table).
• Outputs: ALATM02_MOD (GLmin, GLmax, IGLmin, IGLmax, TEFFLmin, TEFFLmax, GLXmin, GLXmax), read by ALSURFP and ALPRINT; ALATM05_MOD (AL_TEFFLmin, AL_TEFFLmax, the table's own first and last $\log T_\mathrm{eff}$), read by SURFBC to decide when to switch away from Allard atmospheres.

With $t_i$ the table's $\log T_\mathrm{eff}$ and $g_j$ its $\log g$ values:

1. $t_\mathrm{min} = t_1 - (t_2 - t_1)$ and $t_\mathrm{max} = t_n + (t_n - t_{n-1})$: one row's width beyond each end.
2. For each row $i$, the first and last valid columns $j_1(i)$, $j_2(i)$ (entries above $-998$).

3. The allowed range of $\log g$ in each row: $$g_\mathrm{min}(i) = g_{j_1} - 4\,(g_{j_1+1} - g_{j_1}), \qquad g_\mathrm{max}(i) = g_{j_2} + (g_{j_2} - g_{j_2-1}),$$ and the extremes over all rows, GLXmin and GLXmax.

4. Validate: no invalid entry between $j_1$ and $j_2$ in any row, at least 4 rows, and at least 4 valid entries per row (4-point Lagrange interpolation needs them). Otherwise print the table and stop. Only PLs is checked, which is enough: ALFILEIN fills P100Ls and T100Ls from the same record as PLs (alfilein.f, lines 334–337↗), and refuses an old-format file, which has no $\tau = 100$ values, when LALTPTau100 asks for them (alfilein.f, lines 156–164↗) (settled from the code, Nov 9, 2026).