Resource States

In the tutorial for the first simulation, there was this example of a resource state:

class CheckoutLane(UP.Actor):
    customer_queue = UP.ResourceState[SIM.Store]()

with UP.EnvironmentContext() as env:
    lane = CheckoutLane(
        name="FirstLane",
        customer_queue={
            "kind": UP.SelfMonitoringStore,
            "capacity":10,
        }
    )

The obvious question is, why? The following works just fine:

import upstage.api as UP
import simpy as SIM

class CheckoutLane(UP.Actor):
    customer_queue = UP.State[SIM.Store]()


with UP.EnvironmentContext() as env:
    queue_store = UP.SelfMonitoringStore(env, capacity=10)
    lane = CheckoutLane(
        name="FirstLane",
        customer_queue=queue_store,
    )

    def proc():
        yield lane.customer_queue.put("thing")

    env.process(proc())
    env.run()
    print(lane.customer_queue.items)
>>> ["thing"]

There are several reasons for doing this:

1. To make cloning an Actor for rehearsal more aware and intelligent about stores and containers as states

2. Simplifies actor instantiation. Instead of having to build a store on your own for each actor, the states accept simpler data types and handle the environment for you.

3. Better default behavior instead of needing a partial or a lambda function in the factory.

4. Default expectations, such as being frozen.

5. State does not understanding recording of entries or counts in stores or containers.

In practice, the second and last reasons are the most compelling in our experience.

Instantiation Arguments

The input an Actor needs to receive for a ResourceState is a dictionary of:

• ‘kind’: The class of the store or container, which is optional if you provided a default.

• ‘capacity’: A numeric capacity of the store or container.

• ‘init’: For containers only, an optional starting amount.

• key:value pairs for any other input expected as a keyword argument by the store or container class.

If you want to pre-load a store with items, it’s recommended to run a process to yield them. That way you get all the recording you want, if you have it enabled.

The alternative is to do the trick of the_actor.some_store.items.extend(list_of_your_items), but that won’t get the recording to work. You could, in a pinch, run the_actor.some_store._record("hand-record").