Page 172 - ExtendSim User Guide
P. 172

146 Queueing
Sorting items using the Queue Equation block
Once each item has been assigned a ranking, the items are released from the queue according to the ranking rule selected in the Options tab’s Release popup; the ranking rules are listed on page 147. The block's internal data structure keeps track of the ranking assigned to each item.
☞ Giving an item a Blank ranking makes it an ineligible candidate for leaving the queue for that particular query cycle
Variables
The Queue Equation block has several types of input and output variables. The tables below (input variables and output variables) describe the common set of variables shared by all equa- tion-based blocks. The following variables are unique to the Queue Equation block.
To modify the number of rows used in the variable tables:
• Changethenumberofrowsinthetablebyclickingthegreen+/-resizebuttoninthetable’s bottom right corner and entering the number of rows desired.
• Delete rows by first selecting the rows you wish to delete, clicking the green +/- resize but- ton, and then selecting the option to "delete selected rows."
• Duplicate any rows by first selecting the row you wish to duplicate, clicking the green +/- resize button, and then selecting the option to "copy selected row."
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Input variables
Input Variable QEQ arrival time
QEQ FIFO position
QEQ current best item rank
QEQ attrib last item to exit
QEQ num items in queue QEQ static calc cycle init
QEQ static item value
AR requirement is avail AR num requirements avail
Uses
The time the item arrived to the queue
The item’s first-in, first-out (FIFO) position in the queue
The best (highest or lowest) item rank result for the current calculation cycle
Provides the chosen attribute value of the last item to exit the block
The number of items currently in the queue
A static variable that gets initialized to its starting value at the beginning of every calculation cycle. Changes to this variable remain fixed (static) across equation calculations.
A static variable used to temporarily store information on items during their stay in the queue.
This boolean variable is True if an advanced resource (AR) requirement is available for the current item. See note below.
Provides the number of advanced resource (AR) requirements available for the current item. See note below.
☞ The AR variables are only shown in the Queue Equation block if Enable Advanced Resources (AR) is checked in the block’s Options tab and the model contains a Resource Manager block (Item library of ExtendSim AT and ExtendSim Suite).
Discrete Event


































































































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