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Resources and Containers

Standard SimPy objects are static. Dynamic DES wraps SimPy objects so their capacity follows the registry in real time.

1. Discrete Resources (DynamicResource)

DynamicResource is built from a SimPy PriorityStore request queue and a Container token pool, and represents discrete assets that process individual tasks (e.g. machines, bays, or operators).

Shrinking Safety Guarantee

When capacity increases, tokens are immediately added to the pool. When capacity shrinks (e.g., from 5 to 2 due to an unexpected machine breakdown): * If 4 machines are currently processing tasks, Dynamic DES will not terminate active processes. * The resource enters a temporary "over-capacity" state where it waits for tasks to finish. * As tasks complete and release their tokens, DynamicResource intercepts and discards them until the capacity level naturally drops to the targeted limit (2).

2. Continuous Containers (DynamicContainer)

DynamicContainer wraps a SimPy Container and represents continuous quantities (e.g. fuel tank levels, conveyor queues, or concept drift/physical wear).

  • Capacity: The physical size limit of the tank or container. It follows the registry.
  • Level: The current fluid level or quantity of material. It changes only through put and get.

3. Dynamic Stores (DynamicStore)

DynamicStore wraps a SimPy Store, or a PriorityStore when priorities are needed, and represents item-based collections (e.g. warehouses, buffer areas, or order books).

Creating Them

SimulationContext.run() creates a DynamicResource for every add_resource. It does not create containers or stores: add_container registers the capacity paths only. A process that needs a container builds it from the registered paths. DynamicContainer and DynamicStore are imported from dynamic_des, like DynamicResource. Stores have no builder method; register them with SimParameter(stores=...) on the low-level API.

from dynamic_des import DynamicContainer, SimulationContext

# Declare resources and containers in SimulationContext
app = (
    SimulationContext(sim_id="Line_A")
    .add_resource("lathe", current_cap=2, max_cap=5)
    .add_container("fuel_tank", current_cap=100.0, max_cap=500.0)
)

def refuel(context):
    # The container reads its capacity from Line_A.containers.fuel_tank
    tank = DynamicContainer(context.env, "Line_A", "fuel_tank", init=50.0)
    while True:
        yield context.env.timeout(10.0)
        yield tank.put(25.0)
        context.publish("fuel_tank.level", tank.level)

app.add_process(refuel)