Simulation An Inventory Simulation
Example Daily demand for refrigerators at Hotpoint City has a probability distribution Lead time is not fixed but has a probability distribution Customers who arrive and find Hotpoint out of stock will shop elsewhere and Hotpoint will lose the sale These conditions do not meet the restrictions of inventory models developed earlierThese conditions do not meet the restrictions of inventory models developed earlier
Simulation Approach Simulation cannot determine the best inventory policy But it can compare policies Compare the following: –Reordering 10 when supply reaches 6 or less –Reordering 12 when supply reaches 3 or less
Hotpoint Input Data Current inventory = 10 Holding costs: $2/refrigerator/day Order costs: $50 per order Shortage costs: $30 per occurrence (sale is lost) Demand/dayLead Time Demand/day Prob Lead Time Prob days day days days
RANDOM NUMBER MAPPINGS DAILY DEMAND DAILY DEMAND -- Use column PROB RN LEAD TIME (DAYS) LEAD TIME (DAYS) -- Use column PROB RN
SIMULATION OF Q*= 10; r* = 6 COSTS DAY BI RN DEM EI LOST ORDER RN LT ORD HOLD SHORT YES YES YES Based on this one 10-day simulation average daily cost = $26.20.
SIMULATION OF Q*= 12; r* = 3 COSTS DAY BI RN DEM EI LOST ORDER RN LT ORD HOLD SHORT YES YES Based on this one 10-day simulation average daily cost = $ THE OTHER POLICY APPEARS BETTER!
Review Simulation of Inventory Models -- Comparing 2 Possible Policies For Each -- Estimate System Parameters Using Pseudorandom Numbers Simulate Cost Replicate Experiment or Longer Simulation for better results