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How to snapshot an ABM

This topic describes how to save, load, resume, and inspect a saved snapshot of an ABM model simulation. See lm.abm.snapshot for full reference information.

Save a snapshot

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import laser.measles as lm

params1 = lm.ABMParams(num_ticks=3650, seed=42, start_time="2000-01")
model1 = lm.ABMModel(scenario, params1)
model1.components = [lm.VitalDynamicsProcess, lm.InfectionProcess]
model1.run()

lm.save_snapshot(model1, "checkpoint.h5")

save_snapshot prints a summary:

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Squashing 12,483 recovered agents
Snapshot saved → checkpoint.h5
  t_snap=3650  snap_date=2009-12-28  people.count=486,712
  cbr_per_1000=32.0
  Resume with: params.start_time='2009-12'

Load and resume a snapshot

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params2 = lm.ABMParams(num_ticks=1825, seed=42, start_time="2009-12")
model2 = lm.load_snapshot("checkpoint.h5", params2,
                           components=[lm.VitalDynamicsProcess, lm.InfectionProcess])
model2.run()

load_snapshot prints a complementary summary:

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Loaded snapshot from checkpoint.h5
  snap_date=2009-12-28  t_snap=3650
  people.count=486,712  capacity=537,040
  params.start_time=2009-12  num_ticks=1825

Use the classmethod alias

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model2 = lm.ABMModel.from_snapshot("checkpoint.h5", params2,
                                    components=[lm.VitalDynamicsProcess, lm.InfectionProcess])

Inspect a snapshot file

Snapshots are standard HDF5 files (.h5), readable by any HDF5-compatible tool. Because snapshots are plain HDF5, you can inspect them with standard tools:

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import h5py

with h5py.File("checkpoint.h5", "r") as f:
    print("snap_date:", f["snap_date"][()].decode())
    print("t_snap:   ", int(f["t_snap"][()]))
    print("people.count:", int(f["people/count"][()]))
    print("patch_states shape:", f["patch_states"].shape)
    print("keys:", list(f.keys()))

Or from the shell:

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h5ls -r checkpoint.h5