Resource Types#

UPSTAGE comes with new resource types in addition to the SimPy resources:

The self-monitoring stores are discussed in the simulation data section. They enable recording of data within the store or container over time, with an optional input for a function to evaluate when recording on the items in the stores.

ContinuousContainer#

This container accepts gets and puts that act continuously, requiring both a rate and time to get or pull at that rate:

tank = UP.ContinuousContainer(env, capacity=10, init=0)
tank.put(rate=3.0, time=2.5)
env.run(until=3.0)
print(tank.level)
>>> 7.5

The gets and puts can be done simultaneously, and the container will determine the current level when asked for it. The container will also, by default, raise errors when it has reach capacity or when it is empty.

SortedFilterStore#

This store behaves similar to the SimPy FilterStore, except that it also accepts a function that prioritizes the items in the store.

with UP.EnvironmentContext() as env:
    shelf = UP.SortedFilterStore(env)
    # pre-load items
    shelf.items.extend([(1, "a"), (2, "b"), (1, "b"), (1, "B")])

    def _proc() -> tuple[float, str]:
        ans = yield shelf.get(
            filter=lambda x: x[1] == x[1].lower(),
            sorter=lambda x: (x[1], -x[0]),
            reverse=True,
        )
        return ans

    p = env.process(_proc())
    env.run()
    print(p.value)
    >>> (1, 'b')

In the above, we filter items to have lower-case letters. Then we sort by ascending alphabetical and descending numerical. Note the use of reverse=True and the -x[0] to do this. That gives us the tie-breaker between (1, "a") and (1, "b") that ignores (1, "B").

ReserveContainer#

The reserve container is not a true Container, in that it doesn’t hold on queues. It is used to hold first-come reservations for something numeric. Those requests can be timed out, and then checked on later by the requestor. This is useful if you want to reserve access to a limited resource, but don’t want or need to hold in a line to do so.

The public methods on the ReserveContainer are:

reserve(requestor, quantity, expiration=None): Hold an amount
cancel_request(requestor): Cancel a hold
take(requestor): Get the amount held - or fail if request expired
put(amount, capacity_increase=False): Put something in the container, optionally increasing capacity.

The workflow with this resource is to resever, take, then put back when done - if the resource represented isn’t consumable.