Full Library / Resource / Quantity-based / Resource_QS_Allocate_Priority

Block Name: Resource_QS_Allocate_Priority

• A polymorphic quantity-shared resource for N-identical resources, which enqueues input tokens in either a FIFO, or LIFO, order depending on the "Queuing_Discipline" parameter attribute. This block supports blocking and non-blocking model through the "Queueing Displine" parameter.  In non_blocking mode, the DS is released from the queue as soon as the quantity is allocated, while the blocking mode does not release the DS until the resources has been released at the Resource_QS_Free.  Every incoming Data Structure requests for certain quantity of resources.  If the requested units are available, they are immediately allocated and the Data Structure is placed in the queue or released (depending on blocking or non-blocking). A copy of the Data Structure is sent out on the 'ds_output' port.  When the token on the 'ds_output' port is sent to the Resource_QS_Free block input, the units are put back into the resource pool.  The associated Data Structure in the Queue, if blocking, is now destroyed.
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• Unlike the Queue blocks, no pop is required to remove the Data Structure in the queue and place it on the output port.  The QS block delays (blocking-mode) each token until the granted quantity has been released using the Resource_QS_Free block.  Each of the N dimensions operate as independent Queue + Server.  The 'priority_input' is used to determine the order of the data tokens in the queue and for the reject mechanism.  The priority is utilized in two modes- first to order the elements in the queue and second to determine the token to be rejected when the queue overflows.  
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• This block has five input ports:

• The ds_input port for the incoming data tokens, the quantity_request (must be a positive integer) port for the requested units, the dimension_input (first queue starts at 1) port for dimension of the internal server and the priority_input (must be a positive integer) port for priority of the incoming transaction are all required for each incoming token.
• The stats_input port to trigger the current updated statistics (-1 == reset, 0-N == summary statistics for the respective server, 'Number_of_Dimensions' + 1 value == summary statistics for all the servers) on the stats_output port. 

• The Use Model for the Resource_QS_Allocate Block is to model resource unit requests to a limited capacity ('Resource_Capacity'). One might model a multi communication channel, or memory capacity with this block. If current capacity is not available, then based on 'Queue_Reject_Mechanism' ('Incoming_DS_Rejected' or 'Lowest_Priority_DS_Rejected'), one request will be rejected. Once, a number of units have been granted, then an ObjectToken is sent out the 'ds_output' port (to be processed and delayed).

• Note

• If the user has multiple dimensions, then it is best if the enqueued data structures contains a field with the dimension number for further processing.  Statistics are generated using the getBlockStatus("QS Name","stats") or the ResourceStatistics block.
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• Data Structure of the Statistics Output:

• See Also:
• QueueItem
• QS_Resource
• Resource_QS_Allocate

ds_input

public TypedIOPort ds_input

• Input port.  This is used for data tokens entering QS Queue.  In order for the data token or data structure to enter the queue properly, the 'ds_input', 'dimension_input', 'quantity_request' and 'priority_input' must also be entered at the same time, else port data could be overwritten.  This port can be of any type.
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quantity_request

public TypedIOPort quantity_request

• Input port for resource units requested for the incoming token.  This number is dependent on the 'Resource_Capacity' parameter. If available, then process else enqueue request.  The token is rejected if 'Max_Queue_Occupancy' parameter is exceeded.  In order for the data token or data structure to enter the queue properly, the 'ds_input', 'dimension_input', 'quantity_request' and 'priority_input' must also be entered at the same time, else port data could be overwritten.  This is of type integer.

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priority_input

public TypedIOPort priority_input

• Input port for specifying the priority of data tokens entering resource.  In order for the data token or data structure to enter the queue properly, the 'ds_input', 'dimension_input', 'quantity_request' and 'priority_input' must also be entered at the same time, else port data could be overwritten.  This is of type Integer.

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dimension_input

public TypedIOPort dimension_input

• Input port for specifying the priority of data tokens entering resource.  This is the queue number and the first queue is the number 1.  In order for the data token or data structure to enter the queue properly, the 'ds_input', 'dimension_input', priority_input, and 'quantity_request' must also be entered at the same time, else port data could be overwritten.  This is of type Integer.

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stats_input

public TypedIOPort stats_input

• Input port. that clears statistics (-1) for all dimensions, or an individual dimensions (>= -2), or getting statistics (0 to n) on stats_output. If 'stats_input' is '-2', then dimensions (2) will be reset. This approach cannot reset dimensions(0), or dimensions(1) using this method. If the 'stats_input' is '0' or greater, then the statistics for this queue number will be obtained. If the input value equals 'Number_of_Dimensions' parameter setting, then the statistics for all the FCFS dimenions will be generated in one request. The type is integer.
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ds_output

public TypedIOPort ds_output

• Output port sending processed data token (numerical) or composite data structure (StringToken), based on Resource_QS_Free receiving the 'ds_free_output'.  The ordering in the queue is based on the 'priority_input'. This takes the type of the ds_input and removes the incoming Data Structure from the resource.

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reject_output

public TypedIOPort reject_output

• Output port sends the incoming data structure when the 'Max_Queue_Occupancy' parameter has been exceeded. Type of incoming data structure.

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stats_output

public TypedIOPort stats_output

• Output port sending FCFS Queue statistics based on the trigger at the stats_input port. The type is string.

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Block_Name

public Parameter Block_Name

• Parameter.  A unique over all other Resource and Architecture blocks in the model. The type is string.

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Resource_Capacity

public Parameter Initial_Resource_Capacity

• Parameter.  This specifies the number of units of resource that the block contains at start-up. The type is integer.

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Number_of_Dimensions

public Parameter Number_of_Dimensions

• Parameter.  This specifies the number of resource dimensions, or resource queues to create for this block. The type is integer.

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Blocking_Mechanism

public StringAttribute Blocking_Mechanism

• Queue attribute to determine the blocking mechanism. The model can either "Wait_for_Resource", "Seize_Available_Units" or "Exit_Without_Resource_Units". The default is "Wait_for_Resource.

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Max_Queue_Occupancy

public StringAttribute Max_Queue_Occupancy

• This parameter is the maximum number of tokens or data structures that can be in the queue at any instanceof time. All items exceeding this time will be send to the reject_output port. The type is integer.
  

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Queueing_Disipline

public StringAttribute Queueing_Disipline

• QS Queuing type attribute, either "FIFO," or "LIFO." The default is "FIFO."  This is the ordering of the tokens in the queue, either First-In, First-Out or Last-In, Last-Out.

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Addressing_Mode

public StringAttribute Addressing_Mode

• Queue type attribute, either "Indexed_First_Fit," "Indexed_Best_Fit" or "Non_Indexed" (default). "Indexed_First_Fit" looks for the first fit of available resource IDs, which may not be the best use of the resource IDs, yet runs faster than the "Indexed_Best_Fit" mode. Indexed addresses might be used to model memory availability, for example.

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