laser.measles.compartmental.snapshot

`laser.measles.compartmental.snapshot`

Snapshot save/load for the laser-measles compartmental model.

Snapshots capture the full patch SEIR state at a given point in time and allow the simulation to be resumed exactly from that point.

Typical usage::

import laser.measles as lm
from laser.measles.compartmental import save_snapshot, load_snapshot
from laser.measles.compartmental.components import InfectionProcess

# --- Segment 1 ---
model1 = lm.CompartmentalModel(scenario, params1)
model1.components = [InfectionProcess]
model1.run()
save_snapshot(model1, "checkpoint.h5")

# --- Segment 2 ---
params2 = lm.CompartmentalParams(start_time="2001-01", num_ticks=365)
model2 = load_snapshot("checkpoint.h5", params2, components=[InfectionProcess])
model2.run()

Notes

Do not include InfectionSeedingProcess in the components list for a resumed run — infections are already encoded in the restored patch states.
Snapshots persist SIACalendarProcess's implemented_sias state. When resumed with SIACalendarProcess in the components list, campaigns already applied before the snapshot will not fire again; only campaigns not yet implemented in the schedule remain eligible.

`laser.measles.compartmental.snapshot.load_snapshot(path, params, components=None, verbose=True)`

Load a compartmental model from an HDF5 snapshot file and return it ready to run.

Restores the patch SEIR state, scenario, and metadata saved by save_snapshot. Set params.start_time to the snapshot date printed by save_snapshot. Do not include InfectionSeedingProcess in the components list — infections are already encoded in the restored patch states.

Parameters:

Name	Type	Description	Default
`path`	`str \| Path`	Path to the HDF5 snapshot file written by `save_snapshot`.	required
`params`	`CompartmentalParams`	`CompartmentalParams` for the resumed segment. Set `start_time` to the snapshot date and `num_ticks` to the remaining duration.	required
`components`	`list \| None`	Ordered list of component classes to attach — same list as used when building the original model, minus `InfectionSeedingProcess`.	`None`
`verbose`	`bool`	Print a loading summary.	`True`

Returns:

Type	Description
`CompartmentalModel`	A configured `CompartmentalModel` instance. Call `model.run()` to continue the simulation.

Example:

```python
import laser.measles as lm
from laser.measles.compartmental import load_snapshot
from laser.measles.compartmental.components import InfectionProcess

params2 = lm.CompartmentalParams(num_ticks=365, seed=42, start_time="2001-01")
model2 = load_snapshot(
    "checkpoint.h5", params2, components=[InfectionProcess]
)
model2.run()
```

`laser.measles.compartmental.snapshot.save_snapshot(model, path, verbose=True)`

Save compartmental model patch state to an HDF5 snapshot file.

Call this after CompartmentalModel.run() to persist the full patch SEIR state. The resulting HDF5 file can be resumed with load_snapshot to continue the simulation from exactly where it left off.

Parameters:

Name	Type	Description	Default
`model`	`CompartmentalModel`	A fully-run (or mid-run) `CompartmentalModel` instance.	required
`path`	`str \| Path`	Destination HDF5 file path (created or overwritten).	required
`verbose`	`bool`	Print a progress summary.	`True`

Example:

```python
import laser.measles as lm
from laser.measles.compartmental import save_snapshot
from laser.measles.compartmental.components import (
    InfectionSeedingProcess,
    InfectionProcess,
)

params = lm.CompartmentalParams(num_ticks=365, seed=42, start_time="2000-01")
model = lm.CompartmentalModel(scenario, params)
model.components = [InfectionSeedingProcess, InfectionProcess]
model.run()

save_snapshot(model, "checkpoint.h5")
```