A Historic Day for the World of Competitive Rubik’s Cube Solving | Hacker News Reader

A Historic Day for the World of Competitive Rubik’s Cube Solving

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59 pointsohjeez39 comments

I assume the time depends very much on the initial state.

I wonder how they set the initial state. I think it's fairly easy to calculate the minimum number of moves required to solve from a given state, so you'd think they would control for this.

Most states can be solved in around 21 moves by the best computer algorithms, but the fastest humans usually solve it in significantly more.

The initial state is a random computer generated scramble. It's easy to calculate if you have a computer but it isn't easy when you have to do it in your head.

It is, in fact, not easy at all to calculate that.

https://en.wikipedia.org/wiki/God%27s_algorithm

(There isn't as much info as there should be on that Wikipedia page but it was an open area of research for decades.)

Isn't it though? I thought the hard part was proving the minimum number of moves that can solve all possible initial states. Korf's algorithm and several subsequent improvements seem to be able to find the minimum number of moves to solve any given initial state.

A yes. You are correct.

Finding minimum # of moves from a single state = not so hard.

Finding the worst possible state (the state where the minimum # of moves is a maximum) = pretty hard, though now solved.

There are standard randomized scrambles generated for competitions. Most competitions use some subset of 12 solves and take the average, although this appears to be the single solve record.

Agreed. More interesting is the variant where people try to solve a cube in as few moves as possible.

Speedcuber here: each competitor starts with the same initial state for each solve in their best of X. Yes, there is some luck involved but it's distributed equally.

Per competition though, not across competitions, which is relevant WRT world records.

Yes - the fact that the record was broken twice in this one competition suggests that its particular initial state should be analyzed for solvability before we assume that we have entered 'a new chapter for speedcubing.'

The two records were actually on different scrambles (i.e. different initial states).

It's one thing if there was a particular scramble that everyone was solving faster than usual, but that wasn't the case here.

Well, yeah. You can't account for everything. Traditional sports don't consider elevation, air quality, wind, etc.

To an extent. Road race world records are only valid if they fall within certain limits of elevation change. You can run slightly downhill, but can't descend 500 meters. Ditto for tailwinds, I believe.

Wind speed is accounted for in athletics. Records won't get validated if there is a strong tail wind.

This seems to be the only somewhat common variable.

They do consider wind. Too much tail wind can invalidate a world record.

https://en.wikipedia.org/wiki/Wind_assistance

That's one factor in one sport.

Does anyone disregard a track world record because the weather was pleasant that day, and the previous recordholder did it on a hot, humid one? Does anyone argue Barry Bonds' home run title should be disregarded because of the thin air at his away games in Denver?

Take away wind assistance, and Bucky Dent loses his place in history. Take away a pebble in the grass and the Red Sox win the 1986 World Series. Add some rain to give pitchers an extra day of rest, and all sorts of baseball history gets upended.

Is there the scramble/analysis of the 4.90s solve somewhere? Looks to me like a nice fast cross, standard F2L, standard OLL, and then a clean PLL skip?

edit: found something on page 16 of a thread: https://www.speedsolving.com/forum/showthread.php?55952-WR-L...

looks like the last move was an OLL(CP) alg (https://www.speedsolving.com/wiki/index.php/OLLCP), not just standard OLL, making the last layer skip 6x (?) more likely at the cost of remembering a few hundred more algs.

Sort of, technically, no state needs more than 20 moves to be solved (but finding that optimal solution is kinda hard for humans). So while luck can play a part (i.e.: you may get a configuration that only requires three moves), it's much more a matter of skill to find those 15, 20, 23 moves.

http://www.cube20.org/ https://www.youtube.com/watch?v=yF2J39Xny4Q

The strategies humans use to solve it are not nearly so optimal in terms of number of moves. More like 50-100 for a typical solve.

There is a point at which the elites of any activity become so proficient that meaningful differences between them disappear. Competitions are then won based on factors seemingly outside the nature of the activity. These rubik solvers seem to be at a point.

Looking at the comments on this thread few talk of the actual solving. Most are concerned with the circumstances of the competition, I think because most here realize the differences between competitors are so slight that one must look to the competition rather than the competitive act to determine validity.

So I offer this alternative:https://www.youtube.com/watch?v=B5Zi054Fa5k

By increasing the underlying difficulty of the task to the point that even the elites make many mistakes during competition, the focus returns to the underlying skill.

And:https://www.youtube.com/watch?v=hOilnrGrKsY

Few comments are about the solving because few commenters are actually cubers.

If you look at discussions of this on actual cubing forums, then you'll see that the differences between competitors are actually significant.

Edit: As a direct example of competitors making mistakes, Etter's 4.9s solve could actually have been trivially improved if he had done a U instead of U' U' U' on the 2nd pair.

Rubik's cube always gets me thinking about group theory. Eg. http://www.gap-system.org/Doc/Examples/rubik.html

Relevant TED Ed video: https://youtu.be/FW2Hvs5WaRY

The human reaction time is about 0.1 seconds. They shouldn't use a manual chronometer to measure these results 4.9+/-0.1 is the difference between a world record and a good score.

I believe WCA officially uses StackMats for the timing. Timer starts when you lift your hands from the touch pads and stops when you return them to the pads.

This isn't perfect either but it doesn't rely on someone else's reaction time.

Correct.

The guy with the stopwatch isn't the official timer. He's just duplicating the job for fun / backup.

This happened with the 2x2 cube too, 3 world records in the same competition: https://www.worldcubeassociation.org/results/events.php?even... (Trentin Open 2011)

The scramble was too easy, required only 4 moves.

WRs of people solving Rubik's cubes with their feet is a thing these days. These seem much more skill based.

https://youtu.be/DDWdSWfUAeo

It looks like he picks it up and examines it for a while, then puts it down. The timed solving starts only when he picks it up again -- is this correct? Is there a time limit to the examination stage?

15 seconds

The video embeds on this story say they're stopped because I have Do Not Track set on my browser. They imply that if I do watch the videos, it's my own damn fault if I get tracked. So thanks for reminding me to never visit medium.com, I guess.

The videos are on youtube. If you visit youtube you WILL get tracked

The video embeds are YouTube videos in iframes. Medium is showing that warning in accord with their Do Not Track policy:

https://medium.com/policy/how-we-handle-do-not-track-request...

So you can blame Google / YouTube for their tracking, or blame the content creator for inserting the YouTube videos into their piece. Medium is just the messenger here.

This refers to the hosting site (YouTube), not medium.com. They are advising you that whilst they are observing the policy, YouTube is not.

See https://medium.com/policy/how-we-handle-do-not-track-request...

Hmm? This is Medium doing a reasonable thing.

They comply with Do Not Track, but people can embed videos on sites that do not comply. Here they do a reasonable thing, and show a message to people with "Do Not Track" enabled, letting them know that they can still click through and see the video, but the site they are directing you towards might track you.

Medium is just a blog hosting platform, as far as I know they don't control the content that gets posted. What would you prefer they do; not allow embedding YouTube videos? Not warn you that the linked content tracks you?

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