Page 695 - ExtendSim User Guide
P. 695

Analysis 669
Optimization
(called decision variables) so the equation can reference them. In some cases the required variable will be a dialog parameter and in others it will need to be calculated based on a dialog parameter.
An Optimizer block’s access to model variables is accomplished by either using the Clone Layer tool to drag clones of the desired dialog variables onto the block’s icon (clone dropping), or shift-clicking the variable and selecting Add to Optimizer.
Either operation adds information about the variable to the Variables table. It also enables the Optimizer block to remotely read and change the value of that variable in the model, so that it can explore possible solutions.
Using the variables nomenclature from the form for the equation (MaxProfit = $2.50*#sold - #deliveries*($1000 + #drinks*$1.00) - time empty * $100), the steps are:
# sold
The total number of sales for the day is an output variable calculated by the model; it is directly available in a block’s dialog.
Open the Holding Tank block labeled “Total sales”.
Using the Clone Layer tool, drag the Current level parameter value (but not its label) onto
the closed Optimizer block.
When the Optimizer block’s icon is highlighted, release the mouse.
This puts the variable into the first row of the Optimizer’s Variables table. Close the Holding Tank’s dialog.
☞ The Optimizer block will highlight when a cloned variable can be dropped onto it. Starting with the first row, each cloned item is automatically placed into successive rows of the Vari- ables table.
# deliveries
Unlike the other required variables for this example, the number of deliveries is not directly available as a dialog item. However, that value can be calculated using the frequency of deliv- eries, as you will see on page 670.
To get the repeat delivery time, open the Lookup Table block labeled “Filler truck”. From the Table tab, use the Clone Layer tool to drag the parameter value (but not its label or
checkbox) for the Repeat table every field onto the closed Optimizer block.
#drinks
The decision variable for the number of drinks per tank is also located in the Lookup Table block labeled “Filler truck”.
Clone the data table from the Lookup Table block’s Table tab and drag it to the closed Opti- mizer block.
Close the Lookup Table’s dialog time empty
The model calculates the amount of time that the drink tank is empty; this is an output variable. Open the Holding Tank block labeled “Empty time”.
Clone the parameter value for Current level onto the closed Optimizer block.
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