ExtendSim Models

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ExtendSim Models by Mind Map: ExtendSim Models

1. Model Building Steps

1.1. Determine goals

1.2. Understand process to be modeled

1.3. Draw a block diagram of process

1.4. Specifiy parameter values

1.5. Define logic of model and connections

1.6. Validate the model

1.7. Add data collection and graphical analysis

1.8. Analyze output and draw conclusions

2. Block types

2.1. model activities

2.2. model resources

2.3. model routing

2.4. collect data

2.5. calculate stats

2.6. display output

3. Models share certain concepts

3.1. Selection of time units

3.2. Length of a run

3.3. Number of runs

3.4. Model verification

3.5. Model validation

4. Items

4.1. Import block

4.1.1. generates arrivals

4.1.2. specify arrival pattern

4.1.3. specify amount per arrival

4.1.4. alternative would be Generator block

4.2. Input Data block

4.2.1. changing arrival rate based on exponential distribution

4.3. Program block

4.3.1. schedule specific arrivals at specific times

4.4. Attributes

4.4.1. set via Input block easiest Operation block Repository block Labor Pool block Program block Set Attribute blocks

4.4.2. carry through entire process

4.5. Prioritizing items

4.5.1. Stack block choose type of stack

4.5.2. other methods?

4.6. Repository block

4.6.1. holding area (think inbox)

4.6.2. can start with some items

4.6.3. assign attribute and priority as they leave

4.6.4. can't measure wait time; use Stack block instead

4.6.5. items leave FIFO

4.7. Export block

4.8. Operations block

4.8.1. simulates an activity

4.8.2. delays item passing through

4.8.3. delay time constant unless Input Random Number is attached

4.9. Transaction block

4.9.1. alternative to Operations for modeling parallel servers

4.9.2. also used to model multiple simultaneous activities

5. Queuing

5.1. blocks

5.1.1. Stack block like Repository but with Q stats and custom routing

5.2. reneging option

5.2.1. leaves the queue because wait is too long

5.2.2. set in Queue tab of Stack block

5.2.3. adjust time with R connector

5.3. balking

5.3.1. never enters queue because line too long

5.3.2. Decision block used to model balking

5.4. blocking

5.4.1. item finished but can't move forward; held in queue

5.5. priority queues

5.5.1. attributes tab of Input block - set priority

5.5.2. use Select DE Output block

6. Routing

6.1. Decision block

6.1.1. yes/no or binary paths

6.2. Decision(5) block

6.2.1. up to five paths

6.3. Select DE (discrete event) block

6.3.1. use for probabilistic section of paths

6.3.2. check Do Not Use Connector and select Route Items by Probability

6.4. Merge block

6.4.1. combine up to three streams into one

6.4.2. doesn't process or hold; just combine

7. Processing Time

8. Batching

8.1. Operation block

8.2. Batch block

8.2.1. batch up to three items into a single output

8.3. Unbatch block

8.3.1. separate up to three item

8.3.2. used to separate resource from the item so item can go forward and resource back to pool

8.3.3. when batch/unbatch, check Preserve Uniqueness

9. Resources

9.1. Labor Pool block

9.1.1. defines attributes of resource including availability and usage

9.1.2. use to determine staffing needs based on performance measures such as queue length, waiting time, resource utilization

10. Cycle Time Analysis

10.1. Timer block

11. Measures

11.1. wait time

11.1.1. queue modeling blocks

11.2. utilization

11.2.1. resource blocks

11.3. Count Items block

11.3.1. number of items that route through a certain path

11.4. various statistics blocks

11.4.1. don't need to be connected; just present

11.4.2. collect data from blocks that have a delay or processing time (Operation, Stack, etc.)

11.4.3. Queue Stats block from DE lib ave queue length, max Q length, ave wait, max wait time

11.4.4. Resource Stats block from DE lib collects from resource-type blocks like Repository, Labor Pool resource utilization

11.4.5. Costs Stats block from DE lib info on costing blocks like Operations cost per item, cost per unit of time, total cost

11.4.6. Cost by Item block from DE lib cost info for every block that passes through the block (must be connected) cost of each item connectors average cost current cost total cost

11.4.7. Mean & Variance block calcs average and std dev for the simulation connect to plotter to see ave over time

11.4.8. Activity Stats

11.5. Plotters

11.5.1. Plotter, DE block four inputs on discrete events value time value (when it happened) use Show Instantaneous Length option if connected to L on Stack

11.5.2. Histogram connect L from Stack Length column is length of queue adjust bins; often 6

12. Special Blocks

12.1. Executive

12.1.1. must farthest to the left

12.1.2. required for all simulations

12.1.3. controls timing and passing of events

12.2. Input Random Number block

12.2.1. from Generic lib

12.2.2. uses probability distributions

12.2.3. connect to D input on Operations block (delay)

13. Activity blocks

13.1. Transaction block

13.1.1. allow for parallel processing

13.2. Activity Multiple block

13.2.1. allow for parallel processing

13.3. used to model transportation activities like mailing, emailing, faxing docs