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The largest sofa you can move around a corner
- gnabgib 2y agoDiscussion (131 points, 73 days ago, 36 comments) https://news.ycombinator.com/item?id=42300382 https://news.ycombinator.com/item?id=42300382
- alejohausner 2y agoIt just occurred to me that the optimal sofa looks rather uncomfortable. There’s this narrow bit in the middle, which has very little room to sit on. You can’t lie down on it and take nap.
- dmurray 2y agoIf you assume it's the size of a reasonable hallway, I think there's enough room for an average person to lie down on either of the halves. At least if the back isn't too thick.
- riffraff 2y agoI never knew this was a real thing math people studied! I wonder if Douglas Adams knew about it when he wrote about the sofa stuck in the staircase in Dirk Gently's Holistic Detective Agency, or if it's a coincidence.
- adsteel_ 2y agoThere was even a computer program in that book that was constantly rotating the sofa, trying to find a way for it to come out. If Adams didn't know about this, he certainly had a sixth sense.
- petersumskas 2y agoI love the punchline: the computer eventually worked out that the sofa could never have gotten into that spot in the first place. Adams always brought me joy!
- WesolyKubeczek 2y agoThe origin story of the sofa is exactly this: furniture items in the St. John's College got trapped upstairs, and if you assume all other things being equal, they couldn't get there in the first place. The reason was that the furniture was brought upstairs for the staircase remodeling, and the new staircase made it impossible to move it back.
- normie3000 2y agoPerhaps life imitating art?
- taurknaut 2y agohttps://en.wikipedia.org/wiki/Moving_sofa_problem https://en.wikipedia.org/wiki/Moving_sofa_problem
- petersumskas 2y agoI skimmed the article hoping for a reference to Adams or Dirk Gently.
- dcminter 2y agoI believe Douglas based it on something that happened to him - though take with a pinch of salt as I can't recall where I read this. I can believe it though as I had the same thing happen to me - I believe in my case the building had settled (it was always very wonky) and the sofa had sagged taking the result beyond the very narrow threshold that had let me get it in in the first place. A friend helped me saw it in half in the end after I dissuaded him from chucking it out the window; I was on the 8th floor and there were cars parked below so it would have been risky at best. I'd always assumed the Dirk Gently story had inspired the maths problem, but I see from the Wikipedia article that it first arose in 1966 - so TIL.
- lb1lf 2y agoRecycled anecdote from an earlier time this was discussed on HN: While a student, I looked after the apartment of a friend of mine, who was overseas. When he moved there, we were _just_ able to eke his sofa around the last corner from the stairwell and through the door to his apartment. Just. After much cursing and several failed attempts. So, what does a good (cough) friend do while the owner is overseas? Get some hardwood mouldings/trimmings/whatever you call those long, thin pieces of wood typically put where wall transitions to ceiling or floor and nail them to the exterior doorframes, making both door openings perhaps 3/8" or so narrower, paint them in the color of the doorframe, sit back and wait. Then, years later, as he is about to leave town, moving company comes along and everything runs smoothly until one item remains. The sofa. Obviously, it got in - so it'll (as obviously) come out. Only it doesn't. We (everybody except the owner and the moving guys were in on the joke) managed to keep a straight face for several minutes. The moving guys even laughed as they (eventually) left, mollified by a bottle filled with a Scottish export product which we'd kept on hand to ensure no feelings were hurt afterwards.
- DiggyJohnson 2y agoI have made significant life decisions based primarily on not wanting to move a sofa out of a space I moved it into.
- jjice 2y agoI'm the same way. A friend of mine bought a new couch because she wanted a change of pace, so I came over to help her. I have no idea how that couch got in. I ended up literally sawing it in half (it was an old, beat down couch) to be able to remove it. Needless to say, that reinforced by Ikea furniture only mindset until I know I'm not moving for a decade.
- lostlogin 2y agoHave you checked that some arsehole didn’t narrow the doorframe?
- el_benhameen 2y ago
- ghaff 2y agoI'm actually looking forward to doing this with a bed. My prior bed was something I assembled (which I could do gain). Wondering what will work if I want to get a better, e.g. non-IKEA, platform bed. (The mattress will be memory foam so presumably not a problem.)
- hinkley 2y agoOne of the earliest tricks I learned with couches is that if it’s shorter than the ceiling then the arms and back form this U. Sofas used to be great because they were also shorter than the height of a door frame. Now everything is oversized and you need a 10-15% bigger apartment just to have one of each thing your grandparents had. With the right design sometimes this still plays out on the diagonal.
- aqueueaqueue 2y agoI have a huge sofa. It comes in sections that you can disconnect and is very easy to move.
- marssaxman 2y agoYou yourself are probably 10-15% bigger than your grandparents were, since average height has increased 4 inches over the last 150 years.
- hinkley 2y agoI’m the “runt” of the litter. I’m maybe 5% taller and my uncles and cousins got the rest. But it’s the depth as much as the length. I get that a table has to be a couple inches wider so people don’t bump knees but your thigh bone only grows at a quarter to a third of your overall height increase, right? Couches are just oversized. They’re uncomfortable to get out of if you’re not careful when shopping.
- DiggyJohnson 2y agoAm I being pedantic for pointing out that that is 3x the normal two generations separating grand parents and grand kids and a height difference of only 6 percent? The only major difference since our grandparents is average weight and expectations of comfort. Correlated but not synonymous.
- hinkley 2y agoI think if you’re a GenX or a Millenial the height thing relative to the grandparents is mostly true. And if you’re complaining about how tiny grandpa’s house was compared to today, you’re probably outing yourself as being born in the last century. So it’s a relatively safe bet GP made.
- Invictus0 2y agoSerious request: can someone please solve this for moving furniture around in 3D? Let me take an AR scan of a flight of steps with a corner and another scan of a couch, and tell me if it's possible to do the move.
- dgfitz 2y agoLooked over every comment hoping to find this. Kind of negates the whole article, and it should.
- Sharlin 2y agoIt does not negate the article in any way. This was a mathematical thought experiment and an optimization problem, not about real furniture in real corridors.
- lostlogin 2y agoIt comes down to millimetres and I just wouldn’t trust an AR scan.
- simondanerd 2y agoIt always does. Always. Never a spare inch when moving a couch.
- 2y ago
- illusive4080 2y agoBack in my first house, we upgraded our bed and triedto move the old bed into the basement. We had a very small hallway with a door leading ti the basement. The mattress fit, of course, because it flexes. The frame fit because I could disassemble it. The box frame, made of iron and wood slats, could not fit. That day, I cut all the wood slats in half, bent the metal, and got that box spring downstairs. Then I but bracing brackets on the slats and unbent the metal. A few years later, we did the same process over again when moving.
- gigel82 2y agoPivot! Pivot! PIVOT!
- sandworm101 2y agoWhich brings up a good point. This is only about 2d sofas. That episode involved a real world 3d sofa, a much more challenging problem.
- iscrewyou 2y ago3d sofa that had to go up the stairs that bent. Not just a simple hallway.
- esafak 2y agohttps://theonion.com/report-uttering-phrase-easy-does-it-prevents-78-of-1819579893/ https://theonion.com/report-uttering-phrase-easy-does-it-pre...
- thom 2y agoTo me… To you…
- deadbabe 2y agoClassic example of engineers and mathematicians overthinking something where a mover will just tell you to stand the sofa up on its side.
- deleted 2y ago[deleted]
- tecleandor 2y agoUnless it's a 2D mover (because this is a 2D sofa).
- aqueueaqueue 2y agoLol this has nothing to do with sofas or real life. It is a fun toy problem to flex some math muscle on.
- joeross 2y agoReplace sofa with refrigerator and somewhere a Siracusa will get its wings.
- throwaway519 2y agoMade the sofa modular. Duh!
- aqueueaqueue 2y agoNow do it in 3d Then do it in 4d Then 24d Then if you dare, 17d.
- ziofill 2y agoSomehow it doesn’t sit well with me the fact that it’s still quite a complicated shape. I accept that it’s the best one, but I would have expected a simpler shape to be the solution.
- thom 2y agoA bit like the three body problem, I guess. The problem seems simple because it’s just four walls, but think how complicated the constraints are once you have an arbitrary shaped sofa: you shave a tiny bit off one corner, and now you can translate the sofa in one axis a little bit or rotate it a little bit. But all the other points in the sofa are potentially limiting that movement, in complex ways because they might be curved. You get stuck, so you shave a tiny bit off somewhere else and suddenly all the constraints have changed again depending on the cut you made. The optimal shape is rather elegant, I think, because it’s basically the half-donut shape you’d expect but with some very limited perturbations that gain a tiny bit of area during key transitions.
- sushid 2y agoThat has got to be the worst possible navbar imaginable.
- msravi 2y ago> and that the equations that defined Gerver’s sofa also satisfied those conditions. > showing that Gerver’s sofa was the biggest possible shape that could move through the hallway without getting stuck at its corner But there could be other shapes that also satisfy these conditions and could also have the biggest possible shape, correct?
- mmooss 2y agoWhen someone discovered a new tiling (tesselating?) shape, people made tiles in that shape. Where can I buy this sofa?
- Tade0 2y agoI was meaning to get one - if only for the novelty, but no luck so far. It appears that manufacturers favour modular over optimal furniture. Also any deviation from a cuboid quickly becomes expensive.
- ks2048 2y agoHere's a rendering. Would be very cool to have. https://www.mdpi.com/symmetry/symmetry-14-01409/article_deploy/html/images/symmetry-14-01409-g007.png https://www.mdpi.com/symmetry/symmetry-14-01409/article_depl...
- TheSpiceIsLife 2y agoWe can measure the angular velocity of mental objects, and it appears to increase linearly with the degree of rotation relative to a reference. See Shepard, R. N., & Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, 171(3972), 701–703. https://psycnet.apa.org/record/1971-28060-001 https://psycnet.apa.org/record/1971-28060-001
- gamedever 2y agomay favorite sofa was from Ikea. It disassembled easily. some slots and big bolts took the sides off. then some other big bolts separated the seat from the back. the legs twisted off. now you could carry the two biggest parts, the back and the seat, long and vertical
- switch007 2y agoUnfortunately IKEA sofas are total trash these days Even the beloved Ektorp has had multiple rounds of bean counters ruin it
- motorest 2y agoFrom the article: > But that was an impossible task: There’s no one formula that can give the area for every kind of shape. (Think about how you use different functions to find the areas of circles versus triangles.)But that was an impossible task: There’s no one formula that can give the area for every kind of shape. (Think about how you use different functions to find the areas of circles versus triangles.) I don't get it. Am I missing something obvious? I mean, if you have a shape then you can calculate it's area with Green's theorem. https://en.wikipedia.org/wiki/Green%27s_theorem https://en.wikipedia.org/wiki/Green%27s_theorem If your shape is parameterized then so is your area definition. What's the problem?
- mr_mitm 2y agoThe problem is not to find the area, but to find a parameterization of all possible shapes that fit, ideally a differentiable one so you can simply compute some derivatives to find the maximum.
- gneray 2y agoPIVOT
- rishikeshs 2y agoReminds me of 'Pivot' from friends.
- amai 2y agoThe solution for our real 3d-space looks probably a lot different: https://mathoverflow.net/questions/246914/sofa-in-a-snaky-3d-corridor https://mathoverflow.net/questions/246914/sofa-in-a-snaky-3d...
- dragant 2y agoAnd this is why modular sofas are so popular now. Whether it be lovesac or another company, sofas these days are coming in multiple boxes and making you do all the work unless you get costco white glove delivery service ;)
- deleted 2y ago[deleted]
- celias 2y agoUp and Atom has a 2023 youtube video about the moving sofa problem https://www.youtube.com/watch?v=bUNl_jJMTOw https://www.youtube.com/watch?v=bUNl_jJMTOw