The Beer Game in Stella

The Beer Game model built in Stella Architect, loaded from its XMILE file and run on both engines.

Keywords

system dynamics, xmile, stella, bptk, bptk-py, python, business simulation, beer game, beer distribution game

The Beer Game in Stella

The Beer Game model of Understanding the Beer Game also exists as a Stella Architect model: beer_game.stmx, in the XMILE format. BPTK-Py compiles it into an SD DSL model and runs it like any other.

The scenario file

A scenario file beside the page names the XMILE file as source and the file the compiled model is written to as model. Its scenarios set the policy switches of the model; the typical game is the base case:

{
  "smBeergameSD": {
    "source": "simulation_models/beer_game.stmx",
    "model": "simulation_models/beer_game",
    "base_constants": {
      "policySettings.steadyStateOn": 0,
      "policySettings.sophisticatedOrderDecisionOn": 0,
      "policySettings.weightingOpenOrders": 0,
      "policySettings.weightingBackorder": 1,
      "policySettings.stockAdjustmentTime": 1
    },
    "scenarios": {
      "typical": {},
      "ignoreBackorders": {
        "constants": {"policySettings.sophisticatedOrderDecisionOn": 1}
      }
    }
  }
}

When bptk reads it, the model is compiled - and compiled again whenever the .stmx changes. XMILE Step by Step explains the details.

Running it

The typical game, with the whiplash that Understanding the Beer Game explains - the same orders as the SD DSL version of the model gives:

from BPTK_Py import bptk

bptk = bptk()
bptk.plot_scenarios(
    scenario_managers=["smBeergameSD"],
    kind="area",
    scenarios=["typical"],
    title="Order Behaviour in a Typical Game",
    x_label="Weeks",
    y_label="Beer Ordered",
    equations=[
        "brewery.actualProduction",
        "distributor.actualOrder",
        "wholesaler.actualOrder",
        "retailer.actualOrder",
        "retailer.incomingOrder",
    ],
    series_names={
        "smBeergameSD_typical_brewery.actualProduction": "Brewery",
        "smBeergameSD_typical_distributor.actualOrder": "Distributor",
        "smBeergameSD_typical_wholesaler.actualOrder": "Wholesaler",
        "smBeergameSD_typical_retailer.actualOrder": "Retailer",
        "smBeergameSD_typical_retailer.incomingOrder": "Consumer",
    },
    format="axes",
)