[HN Gopher] Speedsolving Rubik's Cube: 8355 Method
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Speedsolving Rubik's Cube: 8355 Method
Author : Tomte
Score : 115 points
Date : 2022-05-01 12:13 UTC (1 days ago)
(HTM) web link (www.speedsolving.com)
(TXT) w3m dump (www.speedsolving.com)
| noman-land wrote:
| I would just like to point out that Sexy Move is an actually used
| piece of cuber terminology.
|
| https://www.speedsolving.com/wiki/index.php/Sexy_Move
| mauro3 wrote:
| This YT-video explains the 8355 method really well
| https://youtu.be/zB8cKBYNTps . It's how I learned it. They call
| the sexy-move the fishing-move.
| Waterluvian wrote:
| Is there hypothetically a single algorithm I can just repeat
| indefinitely and eventually get a solved cube?
|
| I'm guessing no: you need conditional branches otherwise your
| single algorithm would just end up back where you started?
| tzs wrote:
| You definitely need conditional branches. Without conditional
| branches you would be limited to fixed sequences of cube moves.
|
| Fixed sequences of cube moves are reversible and they are
| deterministic.
|
| It follows that for any given fixed sequence S there is exactly
| one starting configuration C such that applying S to C results
| in a solved cube.
| dunkadunka wrote:
| There is the up-up-down-down method that basically uses only
| one algo over and over but you still have to rotate the cube
| after each up-up-down-down before applying the next up-up-down-
| down.
|
| I am sure that is not quite what you meant, but this is what is
| referred to as the 'using only one algo to solve the rubiks
| cube' this also only works (AFAIR) for 3x3x3
|
| https://www.youtube.com/watch?v=n7irFvVkLpk
|
| Twistypuzzling produces great Youtube videos for all types of
| twisty puzzles.
| myaccount80 wrote:
| It's called Devil's algorithm but I believe it is not know yet
| whether it exists or not
|
| https://getgocube.com/play/devils-number/
| hvdijk wrote:
| It has to exist: it's a mindbogglingly large but finite
| number of possible permutations, and to go from any one
| permutation to any other takes a finite number of moves.
| Therefore, if you can enumerate all possible permutations in
| some way, any arbitrary way will do, you have _a_ Devil 's
| algorithm by going through them in that order. The question
| is not whether a Devil's algorithm exists but what the
| shortest one is.
| owalt wrote:
| Worth noting that the Devil's algorithm is not a sequence
| of turns you repeat over and over, but one that takes you
| through every possible cube state. You "abort" it partway
| through when you reach your desired state.
| hvdijk wrote:
| It is both: it is a sequence of turns that if you repeat
| them over and over, will take you through every possible
| cube state. But it is possible that the shortest such
| sequence is trillions of moves long.
| vikingerik wrote:
| There are 43 quintillion cube states, so "trillions" is
| understating by at least a factor of 10^6.
|
| I'm not sure if the 43 quintillion are reachable in a
| loop of that many moves, or if you need to backtrack
| through some states to reach others and thus need more
| moves than that.
| 988747 wrote:
| Somewhat related: I was playing with cube recently, and,
| starting with solved state, I started doing sequence of two
| moves that came to my mind: rotate right side down, then the
| bottom, clockwise. After maybe a 100-150 repetitions (I did
| not count, just did the moves mindlessly for couple minutes)
| I went back to solved state. I wonder if there are more such
| sequences, and how long it takes to go back to original
| state. The obvious difference from Devil's algorithm was that
| the 2x2 sub-cube remained untouched the whole time, only the
| edges were messed up.
| zeroonetwothree wrote:
| Because there are only finitely many states, repeating one
| move will inevitably get you back to where you started
| from.
|
| Also check out Lagrange's theorem in group theory
| lupire wrote:
| _Every_ sequence behaves this way (For all sequences S,
| there exists n_S such that S ^ n_S equals S^0, the starting
| state.) Proving this is an introductory problem in Rubik 's
| theory. Try it!
| kuboble wrote:
| Cube state is basically a permutation of pieces and any
| algorithm applied to the cube is a cycle applied to the
| permutation.
|
| You can't solve any state of a cube with one algorithm the same
| way as you can't sort any array with a single cycle.
| thenoblesunfish wrote:
| If by "algorithm" you mean a fixed sequence of moves, then the
| (rusty math alert) I'd think the answer is "no", because then
| that algorithm would be an element of the Rubik's cube group,
| which you could apply compose repeatedly with any other element
| to get the identity. This would imply that the Rubik's cube
| group is cyclic, and I don't think it is (because it's non-
| Abelian).
| voldacar wrote:
| Correct, the Rubik's cube group is neither cyclic nor
| abelian. It is generated by 6 elements, which correspond to
| quarter turns of each of the 6 faces.
| thenoblesunfish wrote:
| I got a 5x5 cube a while ago and was reading about how to solve
| it, and came across a nice, concise description of how one might
| invent moves which can be combined into algorithms which let you
| make incremental progress on a cube. I can't find it again, now!
|
| Some of it was along the lines of (1) Figure out how to do
| something A to a single layer (while messing up the rest of the
| cube). (2) Observe that if you do A, then rotate the layer R,
| then undo A (A'), you have an operation B = A R A' which does
| something to only one layer of the cube. I assume that most moves
| in most common algorithms can be expressed in terms of a couple
| of fundamental techniques like this (probably using the words
| "commutator" and "conjugate"). Does someone have a link or
| reference that gives you the general meta-technique (even if it
| involves incompletely-specified things like "figure out an
| interesting sequence of moves in terms of their effect on a
| single layer")?
|
| I'm interested in this because I'm not really interested in
| learning (again) and forgetting (again) any particular existing
| method for solving the cube, but it would be fun to be able to
| fiddle around with it in a less-than-random way and eventually
| arrive at a method, based on some higher-level principles.
| vvatermelone wrote:
| https://youtu.be/54SGrZbLcoE
|
| Not sure if this is exactly what you're looking for, but but it
| was pretty much the basis for my interest in "big" cubes a few
| years back.
| macrolocal wrote:
| Typically, you can use commutators (and the derived series) to
| solve these sorts of puzzles.
| zwegner wrote:
| There's a method entirely based on group theory, a version of
| the original computer algorithm created to solve the cube (the
| Thistlewaite algorithm) simplified for use by a human [1]. It
| iteratively solves the cube into simpler groups that need a
| smaller moveset to solve (the last step uses only half turns on
| each face, no quarter turns). It requires only a bit of
| memorization, and you can understand exactly how the algorithm
| works. It's not a great speedsolving method, but you can get
| relatively fast with it: in [2] there's a solve below 30
| seconds.
|
| [1]
| https://www.ryanheise.com/cube/human_thistlethwaite_algorith...
| [2] https://www.youtube.com/watch?v=GmjYWYDPhiM
| thechao wrote:
| I spent a disenjoyable 45 minutes one afternoon trying to learn
| the basics of solving; somehow, I could never get the cube
| "solved". Eventually, I discivered my daughter had rearranged a
| few of the stickers, resulting in an unsolvable cube.
| falcrist wrote:
| There's actually a parity to the positions of the pieces that
| most people don't seem to know about. If you flip an edge or
| twist a corner, the whole cube becomes unsolvable.
|
| You can also make it unsolvable by swapping stickers because
| each piece is unique. There is only one red/white/blue corner
| and only one green/yellow edge. Assuming standard color
| arrangement, there is no piece with both yellow and white, or
| both blue and green, or both red and orange.
| icambron wrote:
| A friend of mine got into a Rubik's Cube in college. As a
| prank, we swapped the stickers on his cube and were amazed
| when he noticed it in a few seconds and correctly
| identified what was swapped. Familiarity with the
| invariants
| frob wrote:
| The guy I learned to speedcube from was so good that we
| would secretly flip a corner or edge on his cube, challenge
| him to a race, and he would solve it to the point where
| only one piece was flipped, curse at us, fix it himself,
| and still beat us all by at least 10 seconds.
| falcrist wrote:
| Depending on his method, he probably saw the problem
| immediately when he got to the last layer.
| celias wrote:
| Are you thinking of the Mathologer video "A simple trick to
| design your own solutions for Rubik's cubes"
|
| https://www.youtube.com/watch?v=-NL76uQOpI0
| rprenger wrote:
| Here's the resource I've used that I've liked best. It's more
| the math, but thinking this way helped me with other puzzles:
| https://math.berkeley.edu/~hutching/rubik.pdf
| 1maginary wrote:
| The Heise method might be a great fit for you. Unlike most
| methods, it requires no memorization. And, unlike most methods
| that require no algs, it can be quite fast. AND it forces you
| to learn about how the cube actually works and to think in
| commutators and conjugates:
| https://www.ryanheise.com/cube/heise_method.html
| yesenadam wrote:
| Thanks, that's a nice site, and a method I feel like I could
| actually learn. But saying "it requires no memorization"
| seems a bit of a stretch!
| 1maginary wrote:
| Do you mean the short-term memory needed to apply the
| commutators or the conjugates? Otherwise you only really
| need to "memorize" the steps of the method.
|
| I learned this method around 10 years ago, and I can still
| solve the cube without applying any memorized algorithms
| because of it. It really is the only fun way for me to
| solve the cube after all this time.
| habibur wrote:
| This. I used to forget the algos whenever I didn't touch
| the cube for 6 months. Then learnt Ryan's method. Picked
| up the cube 4 months later and found I can still solve
| it.
| reedf1 wrote:
| Wow this looks cool, I learned CFOP as a teenager and from
| showing it to people the number of algos (150-200+) is definitely
| the barrier for entry for most.
|
| Solving a cube with 3 algos means most people can probably learn
| in an hour or two.
| ibraheemdev wrote:
| You can follow 2-look OLL/PLL with just a handful of
| algorithms.
| fouronnes3 wrote:
| Choosing a speedcubing method is an interesting algorithm design
| challenge. It's basically a tradeoff between speed and how many
| subalgorithms sequences you need to learn by heart. On the
| simplicity extremum there's the corner-3-cycle method, where you
| can solve it using zero hard coded sequence (pure reasoning). On
| the speed extremum, there's Fridrich or ZZ, which most top level
| speedcubers use but they require memorizing hundreds of
| sequences.
| charcircuit wrote:
| There is also a difference between knowing a sequence and being
| able to maintain it and keep execution fast. Two fast ones can
| be faster than one slow one.
| progbits wrote:
| Are there statistics on how many moves people used for record
| runs? I've only seen them measure the time but from the video
| recording you could probably get a rough count of moves too.
|
| I would love to see the trend lines for those. Are the world
| records getting faster due to quicker execution of same number
| of moves, or using fewer moves thanks to better algorithms?
| kuboble wrote:
| There are two main 3x3x3 speedsolving methods. Cfop and roux.
| 90% of world class solvers use cfop which has significantly
| higher move count (55 vs 45). The cfop method has
| characteristics which make it considerably more finger
| friendly, allows for less regrips and makes look ahead easier
| which makes up for the extra 10 moves.
|
| The world record progression is mostly due to top solvers
| being able to turn faster with fewer pauses.
|
| E.g. the fastest cuber ever Max Park averages less than 6
| seconds but his solves are not more sophisticated than those
| averaging 10s.
| chrisdhal wrote:
| I chose Roux specifically so I didn't _have_ to learn a
| bunch of algorithms. You do obviously have to know a few,
| but you get to a couple points and while you can use a
| specific algorithm, you can also basically do the same
| thing X number of times and it works out and gets you to
| the next step.
|
| CFOP is definitely more finger friendly (no middle layer
| changes), but I think Roux has fewer regrips, at least at
| non-speedcube levels (maybe I'm wrong, but I never change
| the orientation). Roux is also considered more "intuitive",
| there are points where you can look at the cube and (after
| a while) just see what needs to be done.
|
| I don't do it for speed, so I haven't bothered learning all
| the algorithms. I'm "fast enough", but I probably only do
| 10ish solves a day, and Roux makes it really easy to
| remember the 3-4 algorithms needed to solve that. It still
| amazes people when you can do it, and even taking 90
| seconds to do it, but with hardly any pauses, still makes
| people think you're a wizard or something.
| phkahler wrote:
| >> It still amazes people when you can do it, and even
| taking 90 seconds to do it, but with hardly any pauses,
| still makes people think you're a wizard or something.
|
| I find this to be quite true. I learned a fairly slow
| method back in the 80's and can't remember all of the
| details so I have to figure it out. I don't run across a
| cube more than say once a year, so it may take 2-3
| minutes to solve it. But part of the time I'm doing
| memorized sequences which allow looking up at a person
| while solving. You have a little conversation while doing
| it, and at the end you just put it down like it's not a
| big deal. The person looks at you not quite sure if
| there's any significance to what just happened and then
| you move on as if you were timing your nails or
| something. It's just a fun little thing to do from time
| to time.
| loloquwowndueo wrote:
| Zz is also not unpopular and is " focused both on low move
| count and high turning speed".
| https://www.speedsolving.com/wiki/index.php/ZZ_method
| nsilvestri wrote:
| ZZ is actually rather unpopular and seems to have
| decisively lost its spot as a top tier method a few years
| back. The tradeoffs vs CFOP are generally not considered
| worthwhile, because an entirely rotationless solve
| doesn't make up for a dramatically more complex EOLine
| and harder xcross. Only ZBLL exists as the extant
| remnants of ZZ.
| simonsaysso wrote:
| Q: Wasn't ZZ an attempt to avoid the crazy ZBF2L
| algorithms and came after ZB? People understood the value
| of ZBLL (hell, even I wrote out all the speed-oriented
| algorithms for it) but everyone doubted the viability of
| ZBF2L, so they tried to find other ways of orienting
| edges. Or was ZZ around before and people just realized
| they could apply ZBLL to it?
| reedf1 wrote:
| At a high enough level it becomes a numbers game. In CFOP you
| will occasionally skip whole sequences due to a favourable
| permutation, a lot of high level cubing is just solving
| enough cubes that you get these rare and extremely fast
| permutations in a competition setting.
| falcrist wrote:
| Particularly good solvers are able to see potential skips
| or favorable arrangements and alter their solve to "force"
| a particular arrangement in a later stage.
|
| Preserving an F2L pair during the cross, or choosing a
| better OLL algorithm during F2L.
|
| It's pretty neat to watch breakdowns of solves.
| SnooSux wrote:
| Most records have "reconstructed solutions", where people
| recreate the solution from start to end. You could get the
| number of moves that way, though I couldn't find a dataset of
| them.
|
| > Are the world records getting faster due to quicker
| execution of same number of moves, or using fewer moves
| thanks to better algorithms?
|
| My novice understanding is that it's the former. The
| algorithms haven't changed very much in the past 20 years or
| so, maybe a few variations that are more ergonomic. After
| learning all the algs, it's a matter of improving look-ahead
| (making sure you know what alg to perform next while your
| current is wrapping up) and otherwise increasing your turns
| per second (TPS).
|
| The records dropped quite drastically a few years back, which
| is likely coming from advancements in cubing hardware. Adding
| magnets to prevent overshoot while turning helped people
| speed up quite a bit.
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