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List of Special Elevator Modes

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Re: List of Special Elevator Modes

#161

Post by grishka »

svat wrote: post #86

Donald Knuth's The Art of Computer Programming has, in its first volume, a lengthy section on simulating an elevator. It is a single regular elevator (nothing "special" going on as in the post here), but even so, as he tries to make things precise, you realize how much detail is involved, and get some appreciation for the task of programming. It occupies about 15 pages (plus several pages of exercises and solutions).…

Hm. I've always thought that the algorithm of operation of a single elevator is fairly simple? While passing each floor, if a button of that floor was pressed (is lit up), or if the button of the direction it's going on that floor is pressed, then stop. If the elevator is not in use and someone presses any call button, go to that floor. That's mostly it. At least that's how I have that algorithm in my head.

Now, if there are multiple elevators but a single set of up/down buttons for them on each floor, that's where things get really complex really fast.

Re: List of Special Elevator Modes

#162

Post by saila »

grishka wrote: post #161
svat wrote: post #86

Donald Knuth's The Art of Computer Programming has, in its first volume, a lengthy section on simulating an elevator. It is a single regular elevator (nothing "special" going on as in the post here), but even so, as he tries to make things precise, you realize how much detail is involved, and get some appreciation for the task of programming. It occupies about 15 pages (plus several pages of exercises and solutions).…

Hm. I've always thought that the algorithm of operation of a single elevator is fairly simple? While passing each floor, if a button of that floor was pressed (is lit up), or if the button of the direction it's going on that floor is pressed, then stop. If the elevator is not in use and someone presses any call button, go to that floor. That's mostly it. At least that's how I have that algorithm in my head. Now, if t…

What if you have, say, a 7 story building and someone on each floor presses the call button at around the same time? Do you send the elevator to each floor based on the time the button was pressed, or do you maybe go to the top floor and pick everyone up on the way down, or do something else? The algorithm probably also needs to consider max weight/occupancy. I think even for a single elevator it's quite complex, assuming you want operation to be both fair and efficient.

Re: List of Special Elevator Modes

#163

Post by grishka »

saila wrote: post #162
grishka wrote: post #161

Earlier quoted context omitted.

Hm. I've always thought that the algorithm of operation of a single elevator is fairly simple? While passing each floor, if a button of that floor was pressed (is lit up), or if the button of the direction it's going on that floor is pressed, then stop. If the elevator is not in use and someone presses any call button, go to that floor. That's mostly it. At least that's how I have that algorithm in my head. Now, if t…

What if you have, say, a 7 story building and someone on each floor presses the call button at around the same time? Do you send the elevator to each floor based on the time the button was pressed, or do you maybe go to the top floor and pick everyone up on the way down, or do something else? The algorithm probably also needs to consider max weight/occupancy. I think even for a single elevator it's quite complex, ass…

I'd assume that it would first go to the floor where the button was pressed first, and subsequently collect everyone in the direction it'll go from there. Because that's actually what I feel some elevators are doing because you wait for one for ages. Some certainly do work like that, but newer ones are probably indeed smarter.

Then there's the curiously simple system that you'd find in Soviet buildings, the kind built out of prefab concrete panels. The elevator doesn't allow to be called while it's in use, period. The call buttons on all floors light up while it's in use, and you have to wait for the light to go out before the button would do anything. The buttons inside also only work with doors open (I think?) and you could only press one at a time. The controller for these is most probably made out of relays or something similar.

Re: List of Special Elevator Modes

#164

Post by vintermann »

ALMOST HUMAN

    The thinking elevator,
    so the makers proudly say,
    will optimize its program
    in an almost human way.
    And truly, the resemblance
    is uncomfortably strong:
    it isn't merely thinking,
    it is even thinking wrong.
(Piet Hein, 1973)

Re: List of Special Elevator Modes

#165

Post by Animats »

hawk_ wrote: post #6

my personal favorite is the Sabbath mode https://elevation.fandom.com/wiki/Sabbath_service_(SHO) not to pick on a specific belief system, but it's quite interesting the lengths people go to follow the letter but not the spirit of things.

Oh, the workarounds. See KosherSwitch.[1]

[1] http://www.kosherswitch.com

Re: List of Special Elevator Modes

#166

Post by Animats »

SilverRed wrote: post #150
dinkleberg wrote: post #8

Maybe this is common knowledge, but I never knew people used fandom for topics like this. I’m amazed that it had 800+ articles and over 1000 videos on a wiki dedicated to elevators.

I was impressed and disappointed at the same time. I wanted to find a page explaining the safeties and failure modes of elevators but I didn't find anything.

Here's a simple explanation of elevator overspeed safeties.[1]

[1] https://youtu.be/UgEL6aeGUrQ

Re: List of Special Elevator Modes

#167

Post by TeMPOraL »

flycaliguy wrote: post #120
grensley wrote: post #99

My favorite interview question is "how do elevators work"? 0. If they immediately blurt out something like "I know how elevators work", probably don't hire them. 1. You can find out what areas they're most interested in. Do they jump straight to the physical mechanics? The programming? The UI? The abstraction that they're solving a problem? 2. Eventually, they reach a point where they just have to say "I don't know".…

I did a design interview which involved drawing up an elevator control panel for an apartment building with 1000 floors. Me, trying to leverage my sense of humour I guess (oops) designed a system in which the presumed wealthiest users at the top were instantly recognized with a face scan and never had to see a panel of buttons. The rest were forced to use a basic number pad. Needless to say I didn’t get the job. Does…

Your idea reminds me of a recent novella by Cory Doctorow, Unauthorized Bread. In there, there was an apartment tower with an elevator that had separate doors for poor and rich people (with the two groups living on different floors), and the poor people couldn't call the elevator when it was in use by the rich.

Re: List of Special Elevator Modes

#168

Post by TeMPOraL »

iaw wrote: post #132
svat wrote: post #86

Donald Knuth's The Art of Computer Programming has, in its first volume, a lengthy section on simulating an elevator. It is a single regular elevator (nothing "special" going on as in the post here), but even so, as he tries to make things precise, you realize how much detail is involved, and get some appreciation for the task of programming. It occupies about 15 pages (plus several pages of exercises and solutions).…

> We often fail to realize how little we know about a thing until we attempt to simulate it on a computer. I'll often write out with pen and paper of how I think the flow of a model will go, it's always fascinating how much that diagram changes once I actually build the model. There are both drastic simplifications and increases in nuance based on experience with the system being modeled and where divergences occur.

Same here. And this also works for existing code. When I start diagramming some complex bit of flow, I'm often surprised by how little I actually understood it. I think translating to a different medium of expression forces you to actually read the code, instead of just skimming it and thinking you understand it.

Re: List of Special Elevator Modes

#169

Post by ben_bai »

pram wrote: post #136
svat wrote: post #86

Donald Knuth's The Art of Computer Programming has, in its first volume, a lengthy section on simulating an elevator. It is a single regular elevator (nothing "special" going on as in the post here), but even so, as he tries to make things precise, you realize how much detail is involved, and get some appreciation for the task of programming. It occupies about 15 pages (plus several pages of exercises and solutions).…

If you love elevators try out SimTower, it's all about micromanaging them!

SimTower started as elevator simulator, and was then turned into a game.

Also, this is a great talk if you want to know more about elevators: https://www.youtube.com/watch?v=ZUvGfuLlZus

Re: List of Special Elevator Modes

#170

Post by varjag »

grishka wrote: post #163
saila wrote: post #162

Earlier quoted context omitted.

What if you have, say, a 7 story building and someone on each floor presses the call button at around the same time? Do you send the elevator to each floor based on the time the button was pressed, or do you maybe go to the top floor and pick everyone up on the way down, or do something else? The algorithm probably also needs to consider max weight/occupancy. I think even for a single elevator it's quite complex, ass…

I'd assume that it would first go to the floor where the button was pressed first, and subsequently collect everyone in the direction it'll go from there. Because that's actually what I feel some elevators are doing because you wait for one for ages. Some certainly do work like that, but newer ones are probably indeed smarter. Then there's the curiously simple system that you'd find in Soviet buildings, the kind buil…

Elevators in former Soviet Union (even those installed long after its disintegration) are quite dumb compared to Western and SE Asia installations in tall buildings.
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