I clicked on the video without looking at the channel name or views. The quality of the video was so good that I thought it must've had millions of views. Amazing job!
Crazy how many little design decisions we overlook every day, I have used elevators for almost all my life but ive never once thought to think that their might be more behind the scenes to improve our experience
I've actually coded up an elevator algorithm before, and it was a huge pain in the ass. The calling algorithm is definitely one of those non-trivial things that no one ever really stops to think about or appreciate
Oh I've thought about it a lot whenever I wait for an elevator in my office, I wonder what's the algorithm behind it. It fascinates me that how they work.
For some odd reason, I've devoted an unreasonable amount of passive headspace to what it would take to write a complete elevator algorithm, including how to handle people pressing floors while it's moving, and accounting for private floors. So I was tickled to see this explanation. Thanks!
When I was a teenager first learning how to program (in actionscript!), I once had the idea to code up an elevator algorithm. I glad I never got around to it, because it seems way too complicated for 13 year old me 😂
Those elevators look dangerous. Stand in the wrong place on a floor and an elevator could pass through the ceiling and flatten you! Joking aside, this is a great video. Loving the channel. 😀
I have always thought that elevators have one of the most insane design features, in that they ask you whether you want to go up or down It sounds obvious, but that's the kind of stuff every programmer *wishes* they could add, just stopping the user and saying "hey, so how do you actually want this to work?", and elevators just did it and it became standard and no one questions it now. Incredible
One really neat system I've seen is to select your destination floor before you get into the elevator car. A screen tells you which elevator to enter and takes you to the floor. At first, this system had no buttons inside the elevator, but they eventually retrofitted them probably because it's confusing for anyone not used to it. This system allowed the computer to more effectively schedule the cars.
Never seen it, but it was exactly my thought. Algorithm could be improved if the elevator would know the destination before arriving on a floor. However, people are already confused by the two buttons (up and down) as they tend to press both of them, hoping the elevator would arrive faster
One needs to optimize an algorithm for max wait time. How long can you stretch wait times, how slow can you make it move , so that a maximum of 10% od people use the stairs
I stayed in a hotel in Sunny Beach - Bulgaria a couple years ago. There was only one elevator and it was SO slow, the first time I got on it, I wanted to leave before we reached the first floor. It was a shock, nobody expects an elevator to be that slow. At first we thought it was faulty, but it wasn't. We started laughing at the absurd slowness of the elevator. Only used it a couple of times going up, never when going down :D I could easily walk upstairs at the same speed as the elevator, and if I hurried just a little bit, I was faster than it.
@@erayk96 opposite of my previous work there was one similarly slow. it even had the feature that when you pressed 6 it also triggered 4. the people who worked in the top floor "loved" it
An elevator that goes back and forth between floors, intentionally avoiding everyone’s destination, and keeps picking up confused passengers would do the job
The elevator in the building I used to live in had you input your destination on a screen which would assign you an elevator and call it, it could then group passengers for the same floor together, or the same range of floors, and it knew how many passengers were assigned to each elevator and when it was at capacity. Very clever system.
Every passenger has to punch in his floor at the lobby, and watch for elevator assignment. Everyone, yes. And one must go down to the lobby, reach the console, do the same, in order to go to another floor.
i recently encountered such a system in a hospital with something like 15+ floors and 10+ elevators. each(!) floor had a panel where everybody(!) needed to select his destination, then got an elevator assigned on a screen display by elevator number with a little diagram where that is. after entering that elevator, you wouldn't have to select the floor again (there even were no buttons besides overwrites for stop/emergencycall and the doors), and you magically would quickly (with no interference by "button pushers", and mostly together with only few other people/transports that had the same source and destination) be brought to the correct destination.
Let's say you had friends over, and all 3 of you leave your apartment for drinks at a bar. What happens then? Do you input how many people are waiting for the same destination, or does each person have to input the same destination again and again? Or is it just simply it cannot correctly know how many passengers are assigned to that elevator in that case?
@@erayk96 there are multiple screens on each floor and it takes about 1 second to enter the destination so you either A. Hit floor 1 three times or B. Hit it once and hope the elevator doesn't get overcrowded
There used to be a 4 storey building at 1014 Homer St in Vancouver that had a slow elevator that went to the floors in the order they were selected, so if you wanted floor 4 & the riders entering selected 3, then 2 & then you press 4, it went literally 3, 2, 4. So savvy riders would block newbies from pressing anything until a discussion of floor preferences was completed, then floors would be selected for greater efficiency. Needless to say, the stairs were well used.
Fascinating. I never had to face the elevator problem, but more than a decade ago I started writing systems who are able to learn and adapt their behavior; it's funny how 2 days in they are still "stupid" and predictable, but how their decisions puzzle me after just a month. Or how two identical systems behave differently depending upon the environment they are placed in. Thanks for this video, you've got yourself a new subscriber :)
I was asking myself this question for a long time and I love this video handled it. key points : In the single lift case - going to the nearest waiting person may mean a far user has to wait for ever - not a viable solution. - there is a solution that eventually serves every user (all the way up then down then again). - that solution can be slightly improve by not going all the way if there is no one waiting. In the multiple lifts case - it's dump if 2 lifts just follow each others. Hence lifts should specialise. - the best algo depends on the building characteristic and what we are trying to minimise. - the best algos can be find with reinforcement learning.
How would I manage elevators? I would maximize travel speed as much as possible. You would enter on the ground floor, and after a brief pause, you would be slammed into the ground as the elevator begins accelerating upwards at 2.5 Gees. Then, after the elevator overshoots the requested floor, it would accelerate downwards slightly faster than 1 Gee, meaning that you would be in free fall for a second or two. Once the destination has been reached, the doors will remain open for exactly 400 milliseconds to give you a chance to exit. After the doors close, the elevator would briefly visit the basement for cleaning before returning to the ground floor to pick up more passengers.
Jokes aside, the actual driving of the elevator is important for time saving. Bigger lifts actually now use fast accelerating motors, and very quick de accelerations. But it comes at a cost! As reliability should not be compromised, but still need greater efficiency. So the approach on how the elevator knows when to slow down, when to fully apply the breaks, when to open doors, all when keeping in mind other safetys is a bit complicated. But it can be done. And seeing those machines do their job fast is beautiful. Search for the video "Awesome Efficient Kone M series" by Beno
Just to throw another wrinkle into the algorithm, check out double-deck elevators. They service two adjacent floors at the same time. The reason is to reduce the floor space for elevator shafts as you can service (in theory) twice as many people using the same elevators. At the start of the day you go to the basement of the building if your destination is an even-numbered floor, and to the ground floor if your destination is an odd-numbered floor. If you are in the even level, and someone in the odd level pressed floor 7 but nobody requested floor 6 then the elevator would stop to service the other level but your doors would remain closed - a bit disconcerting the first time you take it. They do support exceptions like someone wanting to travel from floor 5 to floor 8, but if you enter from the ground level you cannot press floor 8.
Great vid, one solution i have to minimize most wait times is a timed system where a floor's importance to be served is exponentially calculated (for example timeWaited^1.5), where the elevator usually goes to near floors first (by multiplying nearby floor's importance by a higher number the closer it is, like current*3, off by one*2.5, etc), but eventually far floors would get higher priority. Nonetheless this is a problem that has no single truly correct solution, a lot is based on context (an optimal hospital elevator needs to prioritize based on the patient's condition, probably including an elevator stationed on the intake floor to provide critical patients service as quick as possible; an optimal buisness elevator might prioritze based on approximate rank of the person badging into the system, wasting as little of the CEO's time as possible but letting managers and employees wait a little) - however, these require more logic/devices integrated into the circuit (for the hospital a nurse has to badge in and rank their patient's criticality 1-10, for example)
Very interesting that this got recommended to me. Since august, I’ve been living in a dorm at college. My dorm has 2 elevators in it and since I’ve never used an elevator this often, I started to think about it. For the last semester and a half, I’ve been thinking about this “elevator algorithm” and TH-cam just seemed to read my mind lol
This problem sounds a lot like an scheduler from an operative system having to choose which process gets the CPU and when. In this sense I think that that the "Highest response ratio next" algorithm (HRRN) might be a good attempt at solving the problem
This video unlocked childhood memories of some game that looked a lot like the presentation, and you have to think about the elevator systems like this to ever have an efficient building.
I was in a hotel once where you had to pres the "going up" button even when going down, if you pressed the "going down" button you would end up with an overcrowded elevator every time
Great video. I was thinking about this yesterday. Didn’t say anything to anyone about it, didn’t search anything on my phone or laptop. Just wondering in my head. And then this popped up in my feed the next day. Crazy.
Now image all that (except the neural network stuff) with relays... Oh wait, it's how they used to be! Since the 1910's! And in the 1950's with vacuum tubes (and later with discrete transistors) they also managed to account for the cab load / time inside cab factor. Awesome machines. Fascinating to watch it working. It's noisy too haha
Thx. Early 80's got group assignment ( whole class in Computer Science ) to come up with such a Algorithem . I couldn´t do well, finding it difficult to make flow chart fulfilling our aim. I learned however to Appreciate This and other ROBATICs as such, made by Human ingenuity, hard work & endurance on their way to " Goal-Achievements ".Cheers🍻
I used to live in a 21 storey apartment block with two lifts. Both lists serviced the ground floor, 1st floor and 21st floor (it's in London so the 1st floor is up 1 level from the ground). Lift 1 serviced all the remaining odd numbered floors and lift 2 the even numbered floors. From any level above the ground floor you could only call a lift to go down so if you wanted to go from the 3rd floor to the 6th floor you would have to go to the ground level first unless you are lucky enough that somebody was already going up and the lift happened to stop on your floor. If a lift hadn't been used for a while, it would go to the 10th or 11th floor to wait for the next resident calling it. While this seems a really strange way to work, it was actually quite efficient and when the lift engineers changed the programming, people generally had to wait longer for the lift to reach them. I could never quite work out why this was 🤔
I kept thinking about this and discussed with my friend and he kept giving overly simple answers, but I kept asking deeper questions, like when he said "a queue" I said does each elevator have one, is there one global queue, what happens when there are more people waiting than elevators, can you avoid starvation, what is "optimal", speed, time in elevator, average wait time, mean or median wait time, longest wait time, etc.
Wow! I am feeling weirdly proud of myself for realizing it was Brian talking just one minute in! How nice it is that we meet again in a random video dear sir! Nice channel! Lots of love from edx cs!
I am a delivery driver that goes to 60+ buildings per day. Have tried many different elevators so naturally I've started to wonder about just this. Great video!
Wow, kinda glad this showed up in my feed while working on an elevator for a mall. As a programer programing a virtual environment resources aren't something to care about so you can simply put more of what i call "elevator complex" with a simple algorithm that just takes one person and simply taking them to their desired spot. The machine learning system sound very interesting but i feel that's too complex for my level.
Worth noting that one reason for the complexity is that users can input requests at random. A more efficient system from the elevator's perspective, but less convenient from the users' perspective, would be to have everyone input their requests to be serviced at once, so the elevator(s) can decide optimal routing before they ever start moving. I run into issues like this at my job quite frequently. I might design something to be optimal from my point of view, only to have end users, testers, or designers come to me with a request to design things from a different perspective. It's inconvenient for me, but creates interesting challenges for making things more user-friendly.
I assumed elevator algorithms would be simple clicking into the video, but oh was I wrong! Great video, who would have thought there would be so much complexity in something seemingly mundane
Would just say move to earliest press of the button after last passenger gets off then after collecting this passenger collect any people moving in same direction. If earliest press is top or bottom floor also take and deliver people on the way to them. Any passenger pressing opposite direction of current travel (would only get in if pressing wrong call button) will be delivered last, also taking people who go the same direction with. This would be somewhat of a tradeoff between wait time and Efficiency.
At my university they have installed very intelligent elevators. So the building has a total of 15 floors and about 12'000 students every day. So this building has got 4 sets of 3 elevators each. If you get to the elevator instead of pressing "up" or "down" you actually chose which floor you want to get to. Now a screen instantly tells you which of the three elevators you should take. The computer consideres how many people are waiting, how many people want to get from which floor to which, which elevator is nearby, how many people are in the elevator and so on. You rarely have to wait longer than 2minutes for an elevator and aren't in it longer than a minute or so. And I think that is pretty impressing considering the size of the building (one floor is as high as 2-3 floors in a normal house) and the amount of students who have to use it at the same time (everyone changes rooms within the same short time period).
What are these elevators? I guess they are mostly for business buildings and such, where people actually have a need for travelling up. In most of our houses we have just one button, supposedly because it rarely has sense for anyone to go to the upper floors, it's just to go to the first one
In many buildings, there is now a new technique being employed for elevators, where the passenger waiting doesn't just press the button for up or down, but, inputs their destination floor. Now the elevators not only know where there are waiting passengers, but, also where they intend to go. The elevator bank then tells the passenger which elevator car is coming for their destination, and when the door opens, it displays all the floors that that car is going to. Every time I get to a building with this system, I'm wondering how the elevators are optimized.
Does optimizing for minimal waiting time really leave people stuck? Eternal waiting doesn‘t seem that minimal to me. Maybe the described approach was wrong, but the goal is still valid
That frustration when I get to wait for the elevator on 4th floor and it completely ignores my request, heading up and down on below floors, just to eventually switch direction and pass through to the 7th and finally down again. Now I know exactly why it happens 😅
An interesting idea would be for the passenger to input the floor they are going to at the point they are summoning the elevator from. This way the computer would know the desired destination of those wishing to use it before sending the elevator. This might result in a more optimal route calculation.
How about keeping track of all the variables such as waiting time and energy usage, and create a function to convert the current planned route (with all the nuances like speeding up and slowing down) to relevant variables (a prediction of waiting times), then create a score that optimize whatever variable you want to optimize, then constantly re-calculating estimated score based on the sequence of planned stops and updated variables, and adjusting the planned stops in real time, as much as is physically possible? Or maybe that is what they are already doing?
That is exactly how it works. The AI decides the path, and the humans give it a score based on whatever they are trying to optimize. The AI will then learn to optimize for the best score.
During covid, my local hospital only allowed 4 people on an elevator at a time. This didn't really impact me that much since I usually just travelled between G and 2 for my infusions so I'd just take thr stairs. But if I have a specialist appt I have to go up to level 9, so when I got sick of waiting one busy afternoon, I decided to take the stairs since 2 floors wasn't too bad... well after the 4th or 5th floor I regretted it and felt bad for being unfit... until I found out a week later that I was having a flareup 😅 so I don't mind waiting now haha.
As a passenger, I prefer the simple elevator algorithm. If it doesn't suffice build more elevators. If it serves too many floors split it into two. If it's a mess change the architecture. The worst feeling is to see the elevator come in the right direction then go past you.
One logic that should definitely be implemented into elevator algorithm is the carrying weight. If an elevator full of passengers is approaching its max capacity, then it should stop stopping at every floor attempting to pick up more passengers, especially when assuming most people are likely headed for the lobby / a popular floor.
there was one bank of elevators i encountered where it seemed like pressing the button a bunch of times in a row made a previously dormant elevator wake up and come get us. but idk, i didn't have time to experiment or find the people who designed it.
My late grandma's home was in a 24-floor building. There are two elevators next to each other, and when no one calls an elevator, it tends to keep one at 1F and the other at 12F. When we call the elevator from 16F, this somehow often happens: - The 1F elevator moves first. IDK why, but my guess is a bug makes the 12F elevator open its door before it goes up, and elevator recognizes that the 12F elevator is now unavailable due to the open door, thus moving the 1F elevator up. - The 12F elevator finally closes its door on its own - at this point, the other elevator is at 8F - With both elevators finally both available and the 12F one being closer, the 12F one now starts moving up towards 16F, and the other one just awkwardly makes a stop at 8F.
I always wondered why there aren't buttons on each floor for what floor you want. Then it highlighting which floor requests go to which shaft, which seems like it would be more optimal.
In college we all had to get up to the 7th floor for our math and science,the hairdressers only needed to go to 2nd or 3rd and would hog the elevators and try to play the "girls first"card. We got fed up with this. All the geeks therefore would go up ONE flight of stairs and ONE geek would stay in the elevator and stop it reaching the ground floor since he would always take it down to 2nd and press for up. We NEVER touched the 2nd elevator. So it took the faculty a whole term to notice. Thus we were never late and tired from an unnecessary climb through the entire stairwell. . When they picked up on the reason,the faculty caved to the hairdressers need to not climb stairs in heels,naturally. Cue the mysterious elevator breakdown,which could not possibly be due to anything we did. (👞Any body know the word you get from a french wooden shoe,that was coined during the industrial revolution?)
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These elevators should have weight measure systems too, like, if the weight of the elevator is at 80% or above the limit, it should skip requests of other floors. And in public place like hospitals where a lot of people do not know well how the elevator function, the go down/up should be made clear so that people won't accidentally go in wrong direction elevators.
One interesting aspect of these algorithms and whichever performance metric chosen, is the (presumably declining) marginal return as more optimizations are added.
thats why you have *2 buttons* for up and down before entering. if you press the button for down but the elevator goes up, he ignores you. problem: if you press both, you can end up in a wrong direction floor first, and even worse: sometimes he stops, in your floor again and no one is there, because you pressed it 2x. trick is: if you see it bypasses you, you can start walking :D
@@gregoryford2532 yes, youre right, thats what i say. but some people press both buttons - OR: there is just 1 button and the elevator react as if you pressed the wrong because he didnt know which direction you wanna go (bec of just 1 button)
In my building you have to indicate on a screen which stairs you are going before entering the elevator, and then the screen tell you to take a particular elevator, for exemple the C one among 8 of them. It can be a next video 🤷
I've always kinda assumed that elevators just followed a first come-first served algorithm (whoever presses the button first gets serviced first). Never really thought about actually optimizing the experience.
I feel somewhat qualified to answer this question. I’m going to assume this is a large storey building with a big bank of lifts. If a user presses for a call, the computer sends either the nearest idle lift to the user, or if a lift is approaching in that direction, stops that lift. If no lifts are going in the users requested direction, the computer will send the nearest idle lift, when available. If all lifts are idle for about 30 seconds, the computer will send one of the lifts down to the “lobby”. And if you have an even bigger building, destination dispatch. It groups calls based on final destination, meaning any lift can run a stopper service, and any lift can run express.
surely algorithms change based on the information available to it? It makes a difference whether the 'call button' is just that, whether it indicates up or down, or whether the passenger selects their exact destination floor before ever entering the elevator.
This works based on the fact that people know which button to press when calling the elevator lol. If you go up, press the up button, if you go down, press the down button. If you think this is obvious and everyone knows it, I have seen lots of times people pressing the button based on where the elevator is, and not where they are going. The elevator goddam knows where it is and where it needs to go, it needs to know where YOU are going, to plan accordingly.
Wait wait wait... There are people who don't know how elevator call buttons work???????????? I have had days where I have lost some faith in my fellow man... But they all pale in comparison to today.
@@TheEvox81 Actually no-one nowhere teaches that. I don't even think it is written somewhere in the elevator instructions plackard. I had to rely on my common sense to understand the "two-button per floor" elevators when those started to appear in my life instead of the "single-button per floor" ones.
Elevators would be more efficient if they were better informed by floor request buttons instead of the simple up/down call buttons. Especially in larger buildings, it seems the benefits would outweigh the minimal expense.
0:47 woww, so, these are the (umh, can't recall the name..) disk lookup/servicing algorithms from "operating system" right? the scan, c-scan, look, c-look, FIFO, ... (oh god, i don't even remember names of the algos 😓) and problem mentioned is formally called "starvation". awesome. interesting. intriguing. and these visuals are making me want to try implementing these algos in scratch language as i want to visually live these algorithms.
The elevator algorithm works well in theory. In practice no one seems to know what the up or down arrows do, or they assume it's to call the elevator up or down to their floor. It annoys me to no end every day and no-one bothers to learn what the button intended uses are.
There's still a faster way for the elevators to operate, queue the calls with timestamps and go to the first in the queue, picking up any others that were queue'd along the way, whatever direction it had to go to get to the 1st in queue it will then prioritise that direction before going to the next in queue, dropping off any that needed to go further down that direction along the way
i actually visited a very very tall building afew years ago... anyways, they had 4 elevator, 2 of them resposible for the first half of the floors, and the second 2 basically speeding through the first half and serving only the other half...
I clicked on the video without looking at the channel name or views. The quality of the video was so good that I thought it must've had millions of views. Amazing job!
Really!!
Commendable 👍👍
the effort put it in deserves credit !
Oh my sorry there was a giant monkey outside
Good vid but get a new mic and record with sound damping
Except the sound quality is shit
Crazy how many little design decisions we overlook every day, I have used elevators for almost all my life but ive never once thought to think that their might be more behind the scenes to improve our experience
Only shows how many things we all overlook everyday- and how we take some things for granted heh-
@@Kris4Infinity for sure
Most of us don't even realise how much its going on inside our body unless you are a doctor😂
@@rishabhanand5563 that was a good one
I've thought about it since I was a kid lol. Some of us are curious I guess.
I've actually coded up an elevator algorithm before, and it was a huge pain in the ass. The calling algorithm is definitely one of those non-trivial things that no one ever really stops to think about or appreciate
I tried implementing it in a game using basic logic gates, following a circuitry which was used by lifts back in the 60's.
Oh I've thought about it a lot whenever I wait for an elevator in my office, I wonder what's the algorithm behind it. It fascinates me that how they work.
Can u predict algorithm behavior based on reinforcement learning? Kindly?
I am a beginner programmer and thought about this problem. Understood it was way beyond my level and gave up.
For some odd reason, I've devoted an unreasonable amount of passive headspace to what it would take to write a complete elevator algorithm, including how to handle people pressing floors while it's moving, and accounting for private floors. So I was tickled to see this explanation. Thanks!
@@tylisirn omg. Thank you. This hol...I mean game, was made for me.
@@tylisirn wow this is very interesting
@@tylisirn Thanks man, that’s fun!
When I was a teenager first learning how to program (in actionscript!), I once had the idea to code up an elevator algorithm. I glad I never got around to it, because it seems way too complicated for 13 year old me 😂
@@tylisirn I KNEW THIS HAD TO EXIST (or I might have made it). The Internet has delivered again in the form of yt commentsssss
Those elevators look dangerous. Stand in the wrong place on a floor and an elevator could pass through the ceiling and flatten you!
Joking aside, this is a great video. Loving the channel. 😀
heres your fear coming true
TRIGGER WARNING!
th-cam.com/video/7wdPgZAR5lg/w-d-xo.html
😀
😀
I thought same
I have always thought that elevators have one of the most insane design features, in that they ask you whether you want to go up or down
It sounds obvious, but that's the kind of stuff every programmer *wishes* they could add, just stopping the user and saying "hey, so how do you actually want this to work?", and elevators just did it and it became standard and no one questions it now. Incredible
but I have the feeling many people even dont get this and push whatever button or both, to make the elevator appear faster :D
One really neat system I've seen is to select your destination floor before you get into the elevator car. A screen tells you which elevator to enter and takes you to the floor. At first, this system had no buttons inside the elevator, but they eventually retrofitted them probably because it's confusing for anyone not used to it. This system allowed the computer to more effectively schedule the cars.
It's called Destination Dispatch
Never seen it, but it was exactly my thought. Algorithm could be improved if the elevator would know the destination before arriving on a floor. However, people are already confused by the two buttons (up and down) as they tend to press both of them, hoping the elevator would arrive faster
I’ve been used this kind of elevator in certain hotels, and boy it was confusing as first, but so effective
One needs to optimize an algorithm for max wait time. How long can you stretch wait times, how slow can you make it move , so that a maximum of 10% od people use the stairs
I stayed in a hotel in Sunny Beach - Bulgaria a couple years ago. There was only one elevator and it was SO slow, the first time I got on it, I wanted to leave before we reached the first floor. It was a shock, nobody expects an elevator to be that slow. At first we thought it was faulty, but it wasn't. We started laughing at the absurd slowness of the elevator. Only used it a couple of times going up, never when going down :D I could easily walk upstairs at the same speed as the elevator, and if I hurried just a little bit, I was faster than it.
@@erayk96 opposite of my previous work there was one similarly slow. it even had the feature that when you pressed 6 it also triggered 4. the people who worked in the top floor "loved" it
Nothing gets your heart rate up like an elevator that’s not working properly, whether you get on it or take the stairs.
@@2fortsmostwanted poetic
An elevator that goes back and forth between floors, intentionally avoiding everyone’s destination, and keeps picking up confused passengers would do the job
The elevator in the building I used to live in had you input your destination on a screen which would assign you an elevator and call it, it could then group passengers for the same floor together, or the same range of floors, and it knew how many passengers were assigned to each elevator and when it was at capacity. Very clever system.
Every passenger has to punch in his floor at the lobby, and watch for elevator assignment. Everyone, yes. And one must go down to the lobby, reach the console, do the same, in order to go to another floor.
i recently encountered such a system in a hospital with something like 15+ floors and 10+ elevators.
each(!) floor had a panel where everybody(!) needed to select his destination, then got an elevator assigned on a screen display by elevator number with a little diagram where that is. after entering that elevator, you wouldn't have to select the floor again (there even were no buttons besides overwrites for stop/emergencycall and the doors), and you magically would quickly (with no interference by "button pushers", and mostly together with only few other people/transports that had the same source and destination) be brought to the correct destination.
Let's say you had friends over, and all 3 of you leave your apartment for drinks at a bar. What happens then? Do you input how many people are waiting for the same destination, or does each person have to input the same destination again and again? Or is it just simply it cannot correctly know how many passengers are assigned to that elevator in that case?
@@erayk96 there are multiple screens on each floor and it takes about 1 second to enter the destination so you either A. Hit floor 1 three times or B. Hit it once and hope the elevator doesn't get overcrowded
@@EoRdE6 Well, that makes sense. For some reason I thought the input process would be longer than a regular elevator :D Thanks!
There used to be a 4 storey building at 1014 Homer St in Vancouver that had a slow elevator that went to the floors in the order they were selected, so if you wanted floor 4 & the riders entering selected 3, then 2 & then you press 4, it went literally 3, 2, 4. So savvy riders would block newbies from pressing anything until a discussion of floor preferences was completed, then floors would be selected for greater efficiency. Needless to say, the stairs were well used.
This video is incredible! The explanations were clear and concise and the animation was simple and helpful. Bravo!
man i've been thinking about this for a while, how elevators decide on what floor to go to. it's super cool to find a video that explains it so well.
Fascinating. I never had to face the elevator problem, but more than a decade ago I started writing systems who are able to learn and adapt their behavior; it's funny how 2 days in they are still "stupid" and predictable, but how their decisions puzzle me after just a month. Or how two identical systems behave differently depending upon the environment they are placed in. Thanks for this video, you've got yourself a new subscriber :)
I was asking myself this question for a long time and I love this video handled it.
key points :
In the single lift case
- going to the nearest waiting person may mean a far user has to wait for ever - not a viable solution.
- there is a solution that eventually serves every user (all the way up then down then again).
- that solution can be slightly improve by not going all the way if there is no one waiting.
In the multiple lifts case
- it's dump if 2 lifts just follow each others. Hence lifts should specialise.
- the best algo depends on the building characteristic and what we are trying to minimise.
- the best algos can be find with reinforcement learning.
How would I manage elevators?
I would maximize travel speed as much as possible. You would enter on the ground floor, and after a brief pause, you would be slammed into the ground as the elevator begins accelerating upwards at 2.5 Gees. Then, after the elevator overshoots the requested floor, it would accelerate downwards slightly faster than 1 Gee, meaning that you would be in free fall for a second or two. Once the destination has been reached, the doors will remain open for exactly 400 milliseconds to give you a chance to exit. After the doors close, the elevator would briefly visit the basement for cleaning before returning to the ground floor to pick up more passengers.
perfect approach, if i ever make building with elevators, i will use this
Sounds like the elevator from "Who framed Roger Rabbit"
Jokes aside, the actual driving of the elevator is important for time saving. Bigger lifts actually now use fast accelerating motors, and very quick de accelerations. But it comes at a cost! As reliability should not be compromised, but still need greater efficiency. So the approach on how the elevator knows when to slow down, when to fully apply the breaks, when to open doors, all when keeping in mind other safetys is a bit complicated. But it can be done. And seeing those machines do their job fast is beautiful. Search for the video "Awesome Efficient Kone M series" by Beno
Just to throw another wrinkle into the algorithm, check out double-deck elevators. They service two adjacent floors at the same time. The reason is to reduce the floor space for elevator shafts as you can service (in theory) twice as many people using the same elevators. At the start of the day you go to the basement of the building if your destination is an even-numbered floor, and to the ground floor if your destination is an odd-numbered floor. If you are in the even level, and someone in the odd level pressed floor 7 but nobody requested floor 6 then the elevator would stop to service the other level but your doors would remain closed - a bit disconcerting the first time you take it. They do support exceptions like someone wanting to travel from floor 5 to floor 8, but if you enter from the ground level you cannot press floor 8.
I don’t know how this channel does not have more views, such a great content. Please don’t stop. Keep doing your great work
Amazing content on interesting subjects that I don't see anyone else covering. Great job!
Great vid, one solution i have to minimize most wait times is a timed system where a floor's importance to be served is exponentially calculated (for example timeWaited^1.5), where the elevator usually goes to near floors first (by multiplying nearby floor's importance by a higher number the closer it is, like current*3, off by one*2.5, etc), but eventually far floors would get higher priority. Nonetheless this is a problem that has no single truly correct solution, a lot is based on context (an optimal hospital elevator needs to prioritize based on the patient's condition, probably including an elevator stationed on the intake floor to provide critical patients service as quick as possible; an optimal buisness elevator might prioritze based on approximate rank of the person badging into the system, wasting as little of the CEO's time as possible but letting managers and employees wait a little) - however, these require more logic/devices integrated into the circuit (for the hospital a nurse has to badge in and rank their patient's criticality 1-10, for example)
Very interesting that this got recommended to me. Since august, I’ve been living in a dorm at college. My dorm has 2 elevators in it and since I’ve never used an elevator this often, I started to think about it. For the last semester and a half, I’ve been thinking about this “elevator algorithm” and TH-cam just seemed to read my mind lol
A great day is when a video pops up on my recommended that teaches me something I never thought about before. Great video
This problem sounds a lot like an scheduler from an operative system having to choose which process gets the CPU and when. In this sense I think that that the "Highest response ratio next" algorithm (HRRN) might be a good attempt at solving the problem
This video unlocked childhood memories of some game that looked a lot like the presentation, and you have to think about the elevator systems like this to ever have an efficient building.
I was in a hotel once where you had to pres the "going up" button even when going down, if you pressed the "going down" button you would end up with an overcrowded elevator every time
I love how this made me interested in learning the algorithm behind the elevator.
Great video. I was thinking about this yesterday. Didn’t say anything to anyone about it, didn’t search anything on my phone or laptop. Just wondering in my head. And then this popped up in my feed the next day. Crazy.
Great Video! cute animation, nice explanation! Thanks for the video.
Now image all that (except the neural network stuff) with relays... Oh wait, it's how they used to be! Since the 1910's! And in the 1950's with vacuum tubes (and later with discrete transistors) they also managed to account for the cab load / time inside cab factor.
Awesome machines. Fascinating to watch it working. It's noisy too haha
Awesome explanation, informative and helpful 👍 Do more videos on algorithms
Great quality, I appreciate a lot !!
Looks simple, it gave overview of design and working model . Thanks to you.
Thx. Early 80's got group assignment ( whole class in Computer Science ) to come up with such a Algorithem . I couldn´t do well, finding it difficult to make flow chart fulfilling our aim. I learned however to Appreciate This and other ROBATICs as such, made by Human ingenuity, hard work & endurance on their way to " Goal-Achievements ".Cheers🍻
I used to live in a 21 storey apartment block with two lifts. Both lists serviced the ground floor, 1st floor and 21st floor (it's in London so the 1st floor is up 1 level from the ground). Lift 1 serviced all the remaining odd numbered floors and lift 2 the even numbered floors. From any level above the ground floor you could only call a lift to go down so if you wanted to go from the 3rd floor to the 6th floor you would have to go to the ground level first unless you are lucky enough that somebody was already going up and the lift happened to stop on your floor. If a lift hadn't been used for a while, it would go to the 10th or 11th floor to wait for the next resident calling it.
While this seems a really strange way to work, it was actually quite efficient and when the lift engineers changed the programming, people generally had to wait longer for the lift to reach them. I could never quite work out why this was 🤔
Lovely video! Way higher quality than I expected clicking onto it
I kept thinking about this and discussed with my friend and he kept giving overly simple answers, but I kept asking deeper questions, like when he said "a queue" I said does each elevator have one, is there one global queue, what happens when there are more people waiting than elevators, can you avoid starvation, what is "optimal", speed, time in elevator, average wait time, mean or median wait time, longest wait time, etc.
Great video! I was just thinking about this problem while waiting for an elevator
it's fascinating how some simple things actually take a lot of effort and time to actually implement properly
Great video.
One thing I'd add to elevators if I could, would be to enable them to display the amount of wait time to passengers waiting for one.
Amazing channel with a truly gifted creator! Bravo, monsieur! ❤🎉😊
Wow! I am feeling weirdly proud of myself for realizing it was Brian talking just one minute in! How nice it is that we meet again in a random video dear sir! Nice channel! Lots of love from edx cs!
I am a delivery driver that goes to 60+ buildings per day. Have tried many different elevators so naturally I've started to wonder about just this. Great video!
This was surprisingly interesting
"How would you manage an elevator sytem?"
Me, an engineering student studying automation: *panicked noises*
Wow, kinda glad this showed up in my feed while working on an elevator for a mall.
As a programer programing a virtual environment resources aren't something to care about so you can simply put more of what i call "elevator complex" with a simple algorithm that just takes one person and simply taking them to their desired spot.
The machine learning system sound very interesting but i feel that's too complex for my level.
Worth noting that one reason for the complexity is that users can input requests at random. A more efficient system from the elevator's perspective, but less convenient from the users' perspective, would be to have everyone input their requests to be serviced at once, so the elevator(s) can decide optimal routing before they ever start moving.
I run into issues like this at my job quite frequently. I might design something to be optimal from my point of view, only to have end users, testers, or designers come to me with a request to design things from a different perspective. It's inconvenient for me, but creates interesting challenges for making things more user-friendly.
I assumed elevator algorithms would be simple clicking into the video, but oh was I wrong! Great video, who would have thought there would be so much complexity in something seemingly mundane
That moment when you are given an assignment and TH-cam provides you the solution immediately
A trully wonderfull video, i wish ir had better audio cuality
I was literally thinking about how this could be solved with a priority queue when you mentioned the similarity.
Would just say move to earliest press of the button after last passenger gets off then after collecting this passenger collect any people moving in same direction. If earliest press is top or bottom floor also take and deliver people on the way to them. Any passenger pressing opposite direction of current travel (would only get in if pressing wrong call button) will be delivered last, also taking people who go the same direction with. This would be somewhat of a tradeoff between wait time and Efficiency.
This is so cool and something I would’ve never even thought about. Thanks!
At my university they have installed very intelligent elevators. So the building has a total of 15 floors and about 12'000 students every day. So this building has got 4 sets of 3 elevators each. If you get to the elevator instead of pressing "up" or "down" you actually chose which floor you want to get to. Now a screen instantly tells you which of the three elevators you should take.
The computer consideres how many people are waiting, how many people want to get from which floor to which, which elevator is nearby, how many people are in the elevator and so on.
You rarely have to wait longer than 2minutes for an elevator and aren't in it longer than a minute or so. And I think that is pretty impressing considering the size of the building (one floor is as high as 2-3 floors in a normal house) and the amount of students who have to use it at the same time (everyone changes rooms within the same short time period).
TYJ, I’ve had this question for years!
What are these elevators? I guess they are mostly for business buildings and such, where people actually have a need for travelling up. In most of our houses we have just one button, supposedly because it rarely has sense for anyone to go to the upper floors, it's just to go to the first one
In many buildings, there is now a new technique being employed for elevators, where the passenger waiting doesn't just press the button for up or down, but, inputs their destination floor. Now the elevators not only know where there are waiting passengers, but, also where they intend to go. The elevator bank then tells the passenger which elevator car is coming for their destination, and when the door opens, it displays all the floors that that car is going to.
Every time I get to a building with this system, I'm wondering how the elevators are optimized.
Does optimizing for minimal waiting time really leave people stuck? Eternal waiting doesn‘t seem that minimal to me. Maybe the described approach was wrong, but the goal is still valid
"The Science Behind Elevator Algorithms" seems more appropriate, since there is a lot more to elevator science. (Think about mechanics for example.)
That frustration when I get to wait for the elevator on 4th floor and it completely ignores my request, heading up and down on below floors, just to eventually switch direction and pass through to the 7th and finally down again. Now I know exactly why it happens 😅
An interesting idea would be for the passenger to input the floor they are going to at the point they are summoning the elevator from. This way the computer would know the desired destination of those wishing to use it before sending the elevator. This might result in a more optimal route calculation.
How about keeping track of all the variables such as waiting time and energy usage, and create a function to convert the current planned route (with all the nuances like speeding up and slowing down) to relevant variables (a prediction of waiting times), then create a score that optimize whatever variable you want to optimize, then constantly re-calculating estimated score based on the sequence of planned stops and updated variables, and adjusting the planned stops in real time, as much as is physically possible?
Or maybe that is what they are already doing?
That is exactly how it works. The AI decides the path, and the humans give it a score based on whatever they are trying to optimize. The AI will then learn to optimize for the best score.
The ideas behind the video are interesting, as we should think about how we optimize daily tasks, rather adding more sub-tasks
this channel is so underated wtf
Thank you to all the engineers who create such self learning machines, algorithms etc. Unknown people who we never know about. O.O
and yet they still cant figure out how to put some good music in them
Hahaha!
During covid, my local hospital only allowed 4 people on an elevator at a time. This didn't really impact me that much since I usually just travelled between G and 2 for my infusions so I'd just take thr stairs. But if I have a specialist appt I have to go up to level 9, so when I got sick of waiting one busy afternoon, I decided to take the stairs since 2 floors wasn't too bad... well after the 4th or 5th floor I regretted it and felt bad for being unfit... until I found out a week later that I was having a flareup 😅 so I don't mind waiting now haha.
As a passenger, I prefer the simple elevator algorithm.
If it doesn't suffice build more elevators.
If it serves too many floors split it into two.
If it's a mess change the architecture.
The worst feeling is to see the elevator come in the right direction then go past you.
One logic that should definitely be implemented into elevator algorithm is the carrying weight. If an elevator full of passengers is approaching its max capacity, then it should stop stopping at every floor attempting to pick up more passengers, especially when assuming most people are likely headed for the lobby / a popular floor.
there was one bank of elevators i encountered where it seemed like pressing the button a bunch of times in a row made a previously dormant elevator wake up and come get us. but idk, i didn't have time to experiment or find the people who designed it.
My late grandma's home was in a 24-floor building. There are two elevators next to each other, and when no one calls an elevator, it tends to keep one at 1F and the other at 12F. When we call the elevator from 16F, this somehow often happens:
- The 1F elevator moves first. IDK why, but my guess is a bug makes the 12F elevator open its door before it goes up, and elevator recognizes that the 12F elevator is now unavailable due to the open door, thus moving the 1F elevator up.
- The 12F elevator finally closes its door on its own - at this point, the other elevator is at 8F
- With both elevators finally both available and the 12F one being closer, the 12F one now starts moving up towards 16F, and the other one just awkwardly makes a stop at 8F.
I always wondered why there aren't buttons on each floor for what floor you want. Then it highlighting which floor requests go to which shaft, which seems like it would be more optimal.
In college we all had to get up to the 7th floor for our math and science,the hairdressers only needed to go to 2nd or 3rd and would hog the elevators and try to play the "girls first"card.
We got fed up with this.
All the geeks therefore would go up ONE flight of stairs and ONE geek would stay in the elevator and stop it reaching the ground floor since he would always take it down to 2nd and press for up.
We NEVER touched the 2nd elevator.
So it took the faculty a whole term to notice.
Thus we were never late and tired from an unnecessary climb through the entire stairwell.
.
When they picked up on the reason,the faculty caved to the hairdressers need to not climb stairs in heels,naturally.
Cue the mysterious elevator breakdown,which could not possibly be due to anything we did.
(👞Any body know the word you get from a french wooden shoe,that was coined during the industrial revolution?)
These elevators should have weight measure systems too, like, if the weight of the elevator is at 80% or above the limit, it should skip requests of other floors. And in public place like hospitals where a lot of people do not know well how the elevator function, the go down/up should be made clear so that people won't accidentally go in wrong direction elevators.
One interesting aspect of these algorithms and whichever performance metric chosen, is the (presumably declining) marginal return as more optimizations are added.
Please make more videos these are great
I believe Image Processing is a much needed feature too
thats why you have *2 buttons* for up and down before entering.
if you press the button for down but the elevator goes up, he ignores you.
problem: if you press both, you can end up in a wrong direction floor first, and even worse: sometimes he stops, in your floor again and no one is there, because you pressed it 2x.
trick is: if you see it bypasses you, you can start walking :D
@@gregoryford2532 yes, youre right, thats what i say. but some people press both buttons - OR: there is just 1 button and the elevator react as if you pressed the wrong because he didnt know which direction you wanna go (bec of just 1 button)
In my building you have to indicate on a screen which stairs you are going before entering the elevator, and then the screen tell you to take a particular elevator, for exemple the C one among 8 of them.
It can be a next video 🤷
I love learning about elevators
I swear to GOD you did videos for Harvard's CS50 edX course. Good work btw
Ah, I was right. Followed the link in your bio. The satisfaction is strong in this one.
thank you for the video
I've always kinda assumed that elevators just followed a first come-first served algorithm (whoever presses the button first gets serviced first). Never really thought about actually optimizing the experience.
A fun and interesting video!
realistically you want to keep track of which floors are used in which patterns and when and make a pattern or algorithm based on the data
I feel somewhat qualified to answer this question. I’m going to assume this is a large storey building with a big bank of lifts. If a user presses for a call, the computer sends either the nearest idle lift to the user, or if a lift is approaching in that direction, stops that lift. If no lifts are going in the users requested direction, the computer will send the nearest idle lift, when available. If all lifts are idle for about 30 seconds, the computer will send one of the lifts down to the “lobby”.
And if you have an even bigger building, destination dispatch. It groups calls based on final destination, meaning any lift can run a stopper service, and any lift can run express.
surely algorithms change based on the information available to it? It makes a difference whether the 'call button' is just that, whether it indicates up or down, or whether the passenger selects their exact destination floor before ever entering the elevator.
That was perfect video
Fantastic video your doing well for your sub count
Great video!
when do you 'breakout' and take the STAIRS?
This works based on the fact that people know which button to press when calling the elevator lol. If you go up, press the up button, if you go down, press the down button. If you think this is obvious and everyone knows it, I have seen lots of times people pressing the button based on where the elevator is, and not where they are going. The elevator goddam knows where it is and where it needs to go, it needs to know where YOU are going, to plan accordingly.
Underrated comment.
Wait wait wait... There are people who don't know how elevator call buttons work???????????? I have had days where I have lost some faith in my fellow man... But they all pale in comparison to today.
@@TheEvox81 Actually no-one nowhere teaches that. I don't even think it is written somewhere in the elevator instructions plackard. I had to rely on my common sense to understand the "two-button per floor" elevators when those started to appear in my life instead of the "single-button per floor" ones.
Amazing video, thank you
I heard his sound and was like "The CS50 guy?"
and then I clicked on channel , read brian yu and immediately subbed🎉
Elevators would be more efficient if they were better informed by floor request buttons instead of the simple up/down call buttons. Especially in larger buildings, it seems the benefits would outweigh the minimal expense.
They’re talking about A.I. and machine learning at the end!
0:47 woww, so, these are the (umh, can't recall the name..) disk lookup/servicing algorithms from "operating system" right? the scan, c-scan, look, c-look, FIFO, ... (oh god, i don't even remember names of the algos 😓) and problem mentioned is formally called "starvation".
awesome. interesting. intriguing.
and these visuals are making me want to try implementing these algos in scratch language as i want to visually live these algorithms.
1:43 yeah, here :)
3:36 > _"can try one scheduling algorithm"_
yeahh, got it. "disk scheduling algo" - but yeah, just "scheduling algo" seems better/more general term
The elevator algorithm works well in theory. In practice no one seems to know what the up or down arrows do, or they assume it's to call the elevator up or down to their floor.
It annoys me to no end every day and no-one bothers to learn what the button intended uses are.
Would the feedback be how often a person repeatedly pushed the button (indicating that he feels that he is waiting too long)?
There's still a faster way for the elevators to operate, queue the calls with timestamps and go to the first in the queue, picking up any others that were queue'd along the way, whatever direction it had to go to get to the 1st in queue it will then prioritise that direction before going to the next in queue, dropping off any that needed to go further down that direction along the way
Is there an algorithm behind the "close door" button? Or did the ADA rip it's electronics out?
i actually visited a very very tall building afew years ago... anyways, they had 4 elevator, 2 of them resposible for the first half of the floors, and the second 2 basically speeding through the first half and serving only the other half...