Dependency Injection for OpaPremodit

This how-to shows the new DI-friendly constructors for PreMODIT opacity.

Minimal Example (ExoMol)

from exojax.database.exomol.api import MdbExomol
from exojax.opacity import OpaPremodit
from exojax.utils.grids import wavenumber_grid

# Make a grid and load an mdb
nu_grid, _, _ = wavenumber_grid(4200.0, 4300.0, 20000, xsmode="premodit")
mdb = MdbExomol(".database/CO/12C-16O/Li2015", nurange=nu_grid)

# 1) Build from a snapshot (data-only DTO)
snap = mdb.to_snapshot()
opa1 = OpaPremodit.from_snapshot(
    snap, nu_grid, manual_params=(5.0, 1000.0, 1200.0)
)

# 2) Back-compat: build directly from an mdb
opa2 = OpaPremodit.from_mdb(
    mdb, nu_grid, manual_params=(5.0, 1000.0, 1200.0)
)

Notes

• from_snapshot avoids dependencies on concrete mdb classes.

• from_mdb mirrors legacy usage but routes through a snapshot internally.

• Both APIs accept the same keyword options as the original constructor.

Optional Memory Policy

Override memory/runtime knobs explicitly (defaults unchanged if omitted):

from exojax.opacity.policies import MemoryPolicy

opa3 = OpaPremodit.from_mdb(
    mdb,
    nu_grid,
    manual_params=(5.0, 1000.0, 1200.0),
    memory_policy=MemoryPolicy(allow_32bit=True, nstitch=2, cutwing=0.5),
)