Simulation-UniversityofHawaiiatHilo模拟-夏威夷大学希洛.ppt

1、Operations Management,Module F Simulation, 2006 Prentice Hall, Inc.,PowerPoint presentation to accompany Heizer/Render Principles of Operations Management, 6e Operations Management, 8e,What is Simulation?,An attempt to duplicate the features, appearance, and characteristics of a real system To imita

2、te a real-world situation mathematically To study its properties and operating characteristics To draw conclusions and make action decisions based on the results of the simulation,Simulation Applications,Table F.1,Probability of Demand,Table F.2,Assignment of Random Numbers,Table F.3,Table of Random

3、 Numbers,Table F.4,Simulation Example 1,Select random numbers from Table F.3,Simulation Example 1,Advantages of Simulation,Relatively straightforward and flexible Can be used to analyze large and complex real-world situations that cannot be solved by conventional models Real-world complications can

4、be included that most OM models cannot permit “Time compression” is possible,Advantages of Simulation,Allows “what-if” types of questions Does not interfere with real-world systems Can study the interactive effects of individual components or variables in order to determine which ones are important,

5、Disadvantages of Simulation,Can be very expensive and may take months to develop It is a trial-and-error approach that may produce different solutions in repeated runs Managers must generate all of the conditions and constraints for solutions they want to examine Each simulation model is unique,Queu

6、ing Simulation,Overnight barge arrival rates,Table F.5,Queuing Simulation,Queuing Simulation,Inventory Simulation,Table F.8,Daily demand for Ace Drill,Inventory Simulation,Table F.9,Reorder lead time,Inventory Simulation,Begin each simulation day by checking to see if ordered inventory has arrived.

7、If if has, increase current inventory by the quantity ordered. Generate daily demand using probability distribution and random numbers. Compute ending inventory. If on-hand is insufficient to meet demand, satisfy as much as possible and note lost sales. Determine whether the days ending inventory ha

8、s reached the reorder point. If it has, and there are no outstanding orders, place an order. Choose lead time using probability distribution and random numbers.,Inventory Simulation,Table F.10,Order quantity = 10 units Reorder point = 5 units,Inventory Simulation,Inventory Simulation,Daily order cos

9、t=(cost of placing 1 order) x (number of orders placed per day) =$10 per order x .3 order per day = $3,Daily holding cost=(cost of holding 1 unit for 1 day) x (average ending inventory) =50 per unit per day x 4.1 units per day =$2.05,Daily stockout cost=(cost per lost sale) x (average number of lost

10、 sales per day) =$8 per lost sale x .2 lost sales per day =$1.60,Total daily inventory cost=Daily order cost + Daily holding cost + Daily stockout cost =$6.65,Using Software in Simulation,Computers are critical in simulating complex tasks General-purpose languages - BASIC, C+ Special-purpose simulation languages - GPSS, SIMSCRIPT Require less programming time for large simulations Usually more efficient and easier to check for errors Random-number generators are built in,Using Software in Simulation,Commercial simulation programs are available for many appl