Takes in items and holds them until they are requested by other blocks in the model. The stack holds items on a First-In-First-Out (FIFO), Last-In-Last-Out (LIFO), or Priority basis, as specified in the dialog. This block also provides the capability of setting the priority for each item that passes through.
If the stack receives an item with a Value greater than 1 (for example, as set by the Import block), the stack treats the item as a number of items which will exit the stack one at a time. For example, an item with a Value of 4 becomes 4 items in the stack.
Dialog Choices
Arrivals/Departures: Displays the number of items that have entered and left the stack.
Ave. length: Average number in the queue. This is a time-weighted average.
Ave. wait: Average time an item spends in this block.
FIFO queue: Specifies the stack as a FIFO ( First-In-First-Out) queue.
LIFO queue: Specifies the stack as a LIFO (Last-In-Last-Out) queue.
Maximum items allowed: Determines the maximum number of items that can be held in the stack.
Max. length: Longest length of the queue during this simulation run.
Max. wait: Longest wait in the queue during this simulation run.
Priority queue: Specifies the stack as a priority queue. The highest priority item in the block is released first; if all items have the same priority, items are released on a FIFO basis. The lower the number (including negative numbers), the higher the priority.
Stop simulation if stack overflows: If selected, the simulation stops if the number of items in the block reaches the maximum specified. When this happens, a message is displayed and the simulation will stop. If this choice is not selected and the number of items reaches the maximum specified, subsequent items will be prevented from entering the block until the number in the stack goes below the maximum number. Note that if the stack overflows and it is directly preceded by an Import block, items generated by the Import block may be lost to the model.
Utilization: The percentage of time the block held items over the course of the simulation run. The total time that items were in the block is used in the calculation, including the time items were blocked from leaving because the next block could not pull them in.
Connectors
The item input takes in the items to be queued.
The item output is the queued items released one at a time.
P: Input used to set the priority of an item entering the queue. This is only valid and only used when the stack is defined as a Priority queue.
L: Current length of the stack (how many items are in the stack).
W: Amount of time an exiting item spent in the stack.
Animation:
The Stack block uses green circles to show items entering and exiting and displays the number of items in the stack.
