Queue_N_Priority

Full Library / Resource / Event Queue /Queue_N_Priority
Block Name: Queue_N_Priority

Code File Location: VisualSim/actor/lib/Queue_N_Priority

Note: If you have purchased the Smart_Resource package, use the Smart_Resource block and not this one.

Block Overview

o Define multiple Ingress or Egress ports using a single block.

o This block differs from the Queue_N in that the queue is reordered based on the priority of the transactions.

o Create a FIFO or LIFO with multiple concurrent queues

o Define a temporary memory location to store requests or transactions from different sources or for different destinations in separate queues.

o Create rudimentary cache with equal sized data access (Read or Write). Consider each FIFO/LIFO in the Queue_N to define a single block of cache.

Description

The following is a block diagram that illustrates the operation of the Queue_N_Priority block.

Queue_N_Pri

This block defines multiple queues of equal length operating as independent queues. Each queue orders the incoming data structures from highest to the lowest priority. When a transaction arrives on the input port, the transaction is assigned to a particular queue based on the queue_number_input port value. This block queues the incoming transaction or token in a FIFO or LIFO order. When the block receives a value on the pop_input port, it sends the head of the Queue on the output port. The queue_number_input port specifies the target queue to be output. If the value on the pop_input port is an integer, it sends the data structure in the specific numbered location of the queue on the output port. To queue a transaction and to pop a queue, the queue_number_input port value is required.

Higher the number signifies higher the priority. In order for the data token or data structure to be queued, the 'queue_input', priority_input and 'queue_number_input' must be available. If the queue is full, then the incoming Data Structure or token is sent to the reject_output port (Queue_Reject_Mechanism->Incoming Token) or the lowest priority among the incoming token + the queued tokens (Queue_Reject_Mechanism->Lower Priority). If there are multiple tokens with the same priority, the last arriving is discarded.

To illustrate the usage, look at the Examples in the BDE.

Using All Queues

Using Copy, Set and Length

Viewing Rejected/Dropped Data Structure

Generating Statistics

Statistic Name	Value	Explanation	Mathematical Equation	Type
Number_Entered	100	Number of transactions entering the queue.	-	int
Number_Exited	25	Number of transactions that left the queue.	-	int
Number_Rejected	10	Number of transactions rejected and output to reject port.	-	int
Queue_Number	1	Queue Number. Queue number start at 1.	-	int
Occupancy_Min	4.0	Minimum queue size during the simulation.	// Obtain Min for X, where X0 = Double.MAX_VALUE if (Xn < Xn – 1) Xmin = Xn	double
Occupancy_Mean	8.0	Mean/Average queue size during the simulation.	// Obtain Mean for X Xµ = (1 / n) * (X1 + X2 + … + Xn)	double
Occupancy_StDev	3.0	Standard Deviation from the Mean queue size during the simulation.	// Obtain Standard Deviation for X Xσ = Math.sqrt ((1 / n) * ((X1 - Xµ)2 + (X2 - Xµ)2 + … + (Xn - Xµ)2)) STDEV_90_PCT = 1.6448530004790 STDEV_95_PCT = 1.9599610823207 STDEV_99_PCT = 2.5758345145732	double
Occupancy_Max	25.0	Maximum queue size consumed during the simulation.	// Obtain Max for X, where X0 = Double.MIN_VALUE if (Xn > Xn – 1) Xmax = Xn	double
Total_Delay_Min	1.3	In seconds. Least time through the queue among all transactions.	// Obtain Min for X, where X0 = Double.MAX_VALUE if (Xn < Xn – 1) Xmin = Xn	double
Total_Delay_Mean	1.3	In seconds. Mean/Average time through the queue among all transactions.	// Obtain Mean for X Xµ = (1 / n) * (X1 + X2 + … + Xn)	double
Total_Delay_StDev	1.3	In seconds. Standard Deviation from the Mean time through the queue among all transactions.	// Obtain Standard Deviation for X Xσ = Math.sqrt ((1 / n) * ((X1 - Xµ)2 + (X2 - Xµ)2 + … + (Xn - Xµ)2)) STDEV_90_PCT = 1.6448530004790 STDEV_95_PCT = 1.9599610823207 STDEV_99_PCT = 2.5758345145732	double
Total_Delay_Max	1.3	In seconds. Maximum time through the queue among all transactions.	// Obtain Max for X, where X0 = Double.MIN_VALUE if (Xn > Xn – 1) Xmax = Xn	double
Utilization_Pct_Mean	0.0	Not Used for Queues. Will default to 0.0.

Where n is the number of samples and X is occupancy or delay.

Parameter	Explanation	Type	Example
Max_Queue_Length	This is the maximum number of tokens or data structures that can be in the queue at any instance of time. This length is the same for each queue. All items above this limit will be send to the reject_output port.	Integer	30
Number_of_Queues	This specifies the number of queues in this block.	Integer	1
Initial_Queue_State	Queue initial state attribute. This setting is used whenever the queue is empty and the first token arrives. The default is 'First_Token_Flow_Through'. If 'First_Token_Flow_Through' then the first data token or data structure will flow through the queue. If 'First_Token_Enqueue', then one must provide 'pop_queue_input' to obtain the first data token or data structure.	-	First_Token_Flow_Through
Queue_Reject_Mechanism	Queue reject attribute, either 'Incoming_Token_Rejected' (default), or 'Lowest_Priority_Token_Rejected'. If 'Incoming_Token_Rejected' is selected and the designated queue is full, then the incoming data structure is sent to the 'reject_queue_output' port. If 'Lowest_Priority_Token_Rejected' attribute is selected, and the queue is full, then the lowest priority queue element among all the elements of the queue and the incoming token will be sent to the 'reject_queue_output'.	-	Incoming_Token_Rejected
Queue_Type	Queue type attribute, either 'Queue_FIFO', or 'Queue_LIFO'. The default is 'Queue_FIFO'. FIFO means first-in-first-out, whereas LIFO means last-in-last-out. This pertains to the ordering of the incoming Data Structure in the queue.	-	FIFO

Port	Explanation
queue_input	Input port for data tokens (numerical values) or data structures entering the queue. This input must arrive with a queue_number_input that contains the queue number to assign the incoming token or data structure.
priority_input	This is the priority of the incoming data tokens (numerical values) or data structures. This port must receive an integer. Every time a data structure enters the queue, the particular queue will be reordered based on the priority of the new data structure. If the queue is full, the Queue_Reject_Mechanism will determine the data structure to be rejected.
queue_number_input	This is an input port that is a required to assign to a particular queue and pop from a queue. This port contains the queue number. A value is required on this port for both the queue_input and pop_queue_input.
pop_queue_input	This port initiates the queue to send an item out of the queue. This must arrive with a queue_number_input that contains the queue number to pop the token or data structure. This input can either be an integer or any data type. If it is a non-integer data type then the head of the queue is sent to the pop_queue_output port. If the value is an integer, then the input number is the token location to be sent out. A '0' on the 'pop_queue_input' will send the head (front) of the FIFO queue to the 'pop_queue_output'. If the input on the 'pop_queue_input' is '1', then the second element of the queue will be sent to the 'pop_queue_output'.
set_queue_input	The incoming integer token specifies the position in the queue to overwrite with the new incoming Data Structure. In order for the data token or data structure to enter the queue properly, the 'queue_input', priority_input and 'queue_number_input' must also be entered at the same time.
copy_queue_n_input	This input specifies the index location of a token in the queue that must be placed on the 'Copy_queue_n_output" port. This must arrive with a queue_number_input that contains the queue number. The items in the queue are not disturbed, thereby preserving the queue order. This is used to trigger an algorithm like a arbiter to act on the incoming request. This copied data structure can be a request for service or access.
stats_input	This port is triggered to output accumulated statistics for this block. If the stats_input is a positive queue number, ranging from 1 to Number_of_Queues, the current statistics for that queue is placed on the stats_output. If the stats_input is a negative queue number, ranging from -1 to -(Number_of_queues), the current statistics are reset for the particular queue. When the statistics are reset, the Number_in_Queue is equal to the current queue length. If a value of {Number_of_Queues + 1} is sent in, then the statistics for all the servers are sent to the stats_output. A single queue statistics is output as a data structure while the statistics for all the queue is output as a array of data structures, where each data structure corresponds to one of the queue statistics. Similarly, if the negative of the {Number_of_Dimensions + 1} is sent, the statistics are reset for all the Servers.
pop_queue_output	The pop data structure or token is placed on this port and the token is removed from the queue.
reject_queue_output	The incoming token is sent to this output when the selected queue is full. The type is based on the input token type.
copy_queue_n_output	This outputs the current token or Data Structure in the index location specified by the integer on the 'copy_queue_n_input' port and in the queue specified in 'queue_number_input' port. The data structure is not removed from the queue.
queue_length_output	This provides the length of the queue each time a token is received on either the input_queue, pop_queue_input or copy_queue_n_input ports. Note: The queue length output is for the queue matching the 'queue_number_input' port value when the token is received.
stats_output	Output port receiving queue statistics as a data structure. A single queue statistics is output as a data structure while the statistics for all the queue is output as a array of data structures, where each data structure corresponds to one of the queue statistics. See top for details on the fields of this Data Structure.

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