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. Items

3.1. Import block

3.1.1. generates arrivals

3.1.2. specify arrival pattern

3.1.3. specify amount per arrival

3.1.4. alternative would be Generator block

3.2. Input Data block

3.2.1. changing arrival rate based on exponential distribution

3.3. Program block

3.3.1. schedule specific arrivals at specific times

3.4. Attributes

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

3.4.2. carry through entire process

3.5. Prioritizing items

3.5.1. Stack block choose type of stack

3.5.2. other methods?

3.6. Repository block

3.6.1. holding area (think inbox)

3.6.2. can start with some items

3.6.3. assign attribute and priority as they leave

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

3.6.5. items leave FIFO

3.7. Export block

3.8. Operations block

3.8.1. simulates an activity

3.8.2. delays item passing through

3.8.3. delay time constant unless Input Random Number is attached

3.9. Transaction block

3.9.1. alternative to Operations for modeling parallel servers

3.9.2. also used to model multiple simultaneous activities

4. Processing Time

5. Resources

5.1. Labor Pool block

5.1.1. defines attributes of resource including availability and usage

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

6. Cycle Time Analysis

6.1. Timer block

7. Special Blocks

7.1. Executive

7.1.1. must farthest to the left

7.1.2. required for all simulations

7.1.3. controls timing and passing of events

7.2. Input Random Number block

7.2.1. from Generic lib

7.2.2. uses probability distributions

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

8. Activity blocks

8.1. Transaction block

8.1.1. allow for parallel processing

8.2. Activity Multiple block

8.2.1. allow for parallel processing

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

9. Models share certain concepts

9.1. Selection of time units

9.2. Length of a run

9.3. Number of runs

9.4. Model verification

9.5. Model validation

10. Queuing

10.1. blocks

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

10.2. reneging option

10.2.1. leaves the queue because wait is too long

10.2.2. set in Queue tab of Stack block

10.2.3. adjust time with R connector

10.3. balking

10.3.1. never enters queue because line too long

10.3.2. Decision block used to model balking

10.4. blocking

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

10.5. priority queues

10.5.1. attributes tab of Input block - set priority

10.5.2. use Select DE Output block

11. Routing

11.1. Decision block

11.1.1. yes/no or binary paths

11.2. Decision(5) block

11.2.1. up to five paths

11.3. Select DE (discrete event) block

11.3.1. use for probabilistic section of paths

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

11.4. Merge block

11.4.1. combine up to three streams into one

11.4.2. doesn't process or hold; just combine

12. Batching

12.1. Operation block

12.2. Batch block

12.2.1. batch up to three items into a single output

12.3. Unbatch block

12.3.1. separate up to three item

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

12.3.3. when batch/unbatch, check Preserve Uniqueness

13. Measures

13.1. wait time

13.1.1. queue modeling blocks

13.2. utilization

13.2.1. resource blocks

13.3. Count Items block

13.3.1. number of items that route through a certain path

13.4. various statistics blocks

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

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

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

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

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

13.4.6. 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

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

13.4.8. Activity Stats

13.5. Plotters

13.5.1. 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

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