如何不占用不需要的资源单元？

Question

I'm simulating an unloading process of a ship. The complete unloading of the ship can be perfectly done with only two resources making round trips (load, move to destination, unload, go back to loading) and the ship would never be idle waiting for trucks to load.

I need to demonstrate that if I increase the number of resource units (trucks) to 3, the third one will never be seized because it's not needed, the problem is that the seize block seizes all units evenly, so at the end, all units end up with a utilization percentage greater than 0.

How can I configure the seize block to only use the needed resources and leave the “excess” units with utilization of zero?

(The real model by default will have many resources available, and ships could need more than two trucks. What I want with this is to determine the best amount of resources needed).

Thank you.

Answer 1

In the ResourcePool there is an options Customize request choice which when set to True will allow Request choice condition function to be created. There it is possible to make sure that the resources taken first are the ones with utilisation > 0. If your assumption is correct then the 3rd truck will never be taken.

Answer 2

you just need to run two experiments. One with 2 trucks and another with three. Then compare them in terms of ship waiting time and truck pool utilization.

Answer 3

I solved the question in a very easy way:

In the Seize block use the option "Customize Resource Choice" with "Resource selection" equal to "Units with top rating" and "Unit rating" = unit.getUtilization().

In the way, Anylogic sorts the idle resources by utilization rating and chooses the most utilized resource, this means that unneeded resources will never be seized.