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I was thinking of creating this very thing on several occasions being in an elevator. The logic of elevators is very intriguing and more complicated than people

by voldemort1968 5y ago

I was thinking of creating this very thing on several occasions being in an elevator. The logic of elevators is very intriguing and more complicated than people realize.

7373737373 5y ago
I'm not sure if this is true. I think all elevators I've encountered followed the elevator/SCAN algorithm: > the elevator continues to travel in its current direction (up or down) until empty, stopping only to let individuals off or to pick up new individuals heading in the same direction. with the elevator staying on its last location if there are no new requests and there being no buffering time after a request, first come first served https://en.wikipedia.org/wiki/Elevator_algorithm https://en.wikipedia.org/wiki/Elevator_algorithm
- dialogbox 5y ago
  That is true only for the single elevator system. If there are multiple elevators, the system could be extremely complicated.
- falldmg 5y ago
  Have you ever seen elevators where you select a floor from the outside and it gets assigned to one of multiple elevators? Those seem like they might be doing something more sophisticated.
  - disposedtrolley 5y ago
    I used to have those elevators where I worked and everybody hated them. I think the algorithm was tuned for efficiency, so you’d be waiting for an elevator for minutes as it tries to batch everyone up, while a dozen other elevators sit idle. This was made worse through the need to specify the number of people who are travelling to a specific floor so the algorithm can allocate enough space in each elevator. Large groups often ignored this so you’d often find that an elevator you’ve waited minutes for is full, and start the dance all over again. https://en.wikipedia.org/wiki/Destination_dispatch https://en.wikipedia.org/wiki/Destination_dispatch
    - bombcar 5y ago
      This is the problem - if the system goes beyond “what floor should I idle at” and “do I idle door open” people get mad at it because of apparent unfairness and inefficiency even if it is actually more efficient overall. Same thing happens with traffic lights.
      - jchw 5y ago
        This got downvoted, but I’m pretty sure it is objectively correct. I feel like the same sentiment occurs with one queue vs multiple queues.
        bombcar 5y ago
        Continued small motion in a long single queue feels “fairer” than multiple queues - and may actually be. But I also know most people prefer a driving trip where they’re continually moving rather than one where they’re basically stopped - even if the second is shorter in time. “Apparent fairness” is an important design criteria for dealing with the public. Even if the system is actually incredibly unfair.
- nextlevelwizard 5y ago
  This works if you have only a single elevator, but if you have a group of elevators that work together and serve same set of floors you can start optimizing the trips for example journey time vs wait time.

I was thinking of creating this very thing on several occasions being in an elevator. The logic of elevators is very intriguing and more complicated than people realize.

7373737373 5y ago

I'm not sure if this is true. I think all elevators I've encountered followed the elevator/SCAN algorithm: > the elevator continues to travel in its current direction (up or down) until empty, stopping only to let individuals off or to pick up new individuals heading in the same direction. with the elevator staying on its last location if there are no new requests and there being no buffering time after a request, first come first served https://en.wikipedia.org/wiki/Elevator_algorithm https://en.wikipedia.org/wiki/Elevator_algorithm

dialogbox 5y ago
That is true only for the single elevator system. If there are multiple elevators, the system could be extremely complicated.
falldmg 5y ago
Have you ever seen elevators where you select a floor from the outside and it gets assigned to one of multiple elevators? Those seem like they might be doing something more sophisticated.
- disposedtrolley 5y ago
  I used to have those elevators where I worked and everybody hated them. I think the algorithm was tuned for efficiency, so you’d be waiting for an elevator for minutes as it tries to batch everyone up, while a dozen other elevators sit idle. This was made worse through the need to specify the number of people who are travelling to a specific floor so the algorithm can allocate enough space in each elevator. Large groups often ignored this so you’d often find that an elevator you’ve waited minutes for is full, and start the dance all over again. https://en.wikipedia.org/wiki/Destination_dispatch https://en.wikipedia.org/wiki/Destination_dispatch
  - bombcar 5y ago
    This is the problem - if the system goes beyond “what floor should I idle at” and “do I idle door open” people get mad at it because of apparent unfairness and inefficiency even if it is actually more efficient overall. Same thing happens with traffic lights.
    - jchw 5y ago
      This got downvoted, but I’m pretty sure it is objectively correct. I feel like the same sentiment occurs with one queue vs multiple queues.
      - bombcar 5y ago
        Continued small motion in a long single queue feels “fairer” than multiple queues - and may actually be. But I also know most people prefer a driving trip where they’re continually moving rather than one where they’re basically stopped - even if the second is shorter in time. “Apparent fairness” is an important design criteria for dealing with the public. Even if the system is actually incredibly unfair.
nextlevelwizard 5y ago
This works if you have only a single elevator, but if you have a group of elevators that work together and serve same set of floors you can start optimizing the trips for example journey time vs wait time.