Queue Equation: Ranking & Resources

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wilsonli
Posts: 2
Joined: Mon Apr 24, 2017 6:16 pm
First Name: Wilson
Last Name: Lin

Queue Equation: Ranking & Resources

Post by wilsonli » Wed May 31, 2017 3:49 pm

Several questions regarding the functionality of Queue Equation:

1. If we rank a particular item as the highest, but its advanced resource requirements aren't met yet, would the item necessarily be released?
2. How is the "when downstream block tries to pull an item" control for calculating item rankings done?
3. Does the AR allocate requirement output variable, when set to TRUE, enforce the resource requirement for the item?

petert
Posts: 12
Joined: Tue Nov 18, 2008 7:42 pm
First Name: Peter
Last Name: Tag

Re: Queue Equation: Ranking & Resources

Post by petert » Thu Jun 08, 2017 10:28 am

Answers to your questions:

1. If we rank a particular item as the highest, but its advanced resource requirements aren't met yet, would the item necessarily be released?

If you are releasing the highest ranked item, it will be released regardless of the resource requirement being satisfied. If you want to prevent an item from being released if its resource requirement is not satisfied, set the rank value of the item to BLANK if the required resources are not available.

2. How is the "when downstream block tries to pull an item" control for calculating item rankings done?

Whenever a downstream residence block has an opportunity to hold new inbound items, it will try to PULL items from upstream residence blocks. If the "When downsstream block tries to pull an item" is checked, each downstream pull request will trigger a calculation cycle in an Queue Equation block. Based on how you are controlling the release of items in your Queue Equation blocks, this may result in unnecessary calculation cycles, i.e., they will not make a difference in the flow of items out of the Queue Equation block. Thus, the option exists to ignore downstream PULL requests to reduce model run-time. Controlling when the Queue Equation block calculates can become very important when the queue lengths become large in Queue Equation blocks. Many modelers choose to carefully control calculation cycle triggers in their Queue Equation blocks to reduce computational overhead and model run-time.

3. Does the AR allocate requirement output variable, when set to TRUE, enforce the resource requirement for the item?

Yes. The AR requirement output variable executes AND allocates resources to the item. The "AR requirement is avail" input variable is only a QUERY to determine IF the requirement can be satisfied for the item

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