Supply chain

2 of the bundled models. The numbers are from a run made when this page was generated: see how.

(s, S) inventory with backorders

(s, S) inventory control with a replenishment lead time and backorders. Stock is a LEVEL; customers are entities that draw from it through a TRANSFER block and WAIT when it is short -- the backorder. A falling threshold at s fires the reorder signal that releases the purchasing agent. Base unit days.

naga run inventory_sS

flowchart LR
    b0["demand (CREATE)"]
    b1["take_stock (TRANSFER)"]
    b2["sold (RECORD)"]
    b3["leave (DISPOSE)"]
    b4["agent (CREATE)"]
    b5["wait_reorder (HOLD)"]
    b6["order_placed (RECORD)"]
    b7["order_charge (RECORD)"]
    b8["lead_time (DELAY)"]
    b9["receive (TRANSFER)"]
    b0 --> b1
    b1 --> b2
    b2 --> b3
    b4 --> b5
    b5 --> b6
    b6 --> b7
    b8 --> b9
    b9 --> b5
    b7 --> b8

1 replication, seed 0:

KPI	Mean	95% half-width
system/Total Entities Completed	137
system/Avg Throughput Time	0
user/units_sold	685
user/orders_placed	10
level/Stock/Average	49.7
system/Total Cost	350

Two-echelon supply chain (library assets)

A two-echelon supply chain built entirely from the Supply chain and inventory library: customers draw from a store on an (s, S) policy with lost sales, the store's replenishment orders are demand at a central warehouse that backorders, and the central warehouse buys from a capacitated supplier. Each echelon's lead time is the next one's queueing outcome, not a number. Base unit days.

naga run supply_chain_library --replications 3

flowchart LR
    b0["customer_demand_1 (SUBMODEL)"]
    b1["warehouse_s_s_r_q_1 (SUBMODEL)"]
    b2["warehouse_s_s_r_q_2 (SUBMODEL)"]
    b3["supplier_1 (SUBMODEL)"]
    b4["dispose_1 (DISPOSE)"]
    b5["dispose_2 (DISPOSE)"]
    b6["delay_1 (DELAY)"]
    b0 --> b1
    b1 --> b4
    b1 --> b5
    b1 --> b2
    b2 --> b6
    b6 --> b1
    b2 --> b5
    b2 --> b3
    b3 --> b2

3 replications, seed 0:

KPI	Mean	95% half-width
system/Total Entities Completed	697	94
system/Avg Throughput Time	0	0
system/Avg Queue Length	1.75	0.039
system/Avg Resource Usage %	2.3	1
user/warehouse_s_s_r_q_1/Scm fill rate	0.981	0.014
user/warehouse_s_s_r_q_1/Scm units served	2,390	410
user/warehouse_s_s_r_q_1/Scm units lost	57.3	37
level/warehouse_s_s_r_q_1/Scm Stock/Average	31.1	1.6
level/warehouse_s_s_r_q_1/Scm On order/Average	7.94	1.4
level/warehouse_s_s_r_q_2/Scm Stock/Average	160	3.6
system/Total Cost	426	15