[WCA Regulations 2014] Scramble Filtering (new poll)

[Stefan]

It is not as simple as doubling the twist metric table because (x,y) is counted as 1 if one of them is zero and 2 otherwise. So the table would have to be computed from scratch, and from what I've heard, generating the original table took a year (in 2005).

But we can use it for a bound. Ten moves counting all U/D/R-turns corresponds to at most five R-turns, right? So only states reachable with at most five R-turns are filtered out, so at most 1 out of 130316 states.

Also, computers today are much more powerful than in 2005, and if you just want to know the percentage of states filtered out, you don't need the full distribution table.

I'm probably not understanding this problem correctly, but why do 2x2, pyraminx, square-1, and skewb have such a high filter as compared to 3x3. Actually, my real question is why doesn't 3x3 have a higher filter? Isn't the purpose to not let extremely easy (2 moves away) cases happen? Why is 3x3 allowed 2 moves, but other puzzles are not?

I believe 2x2, pyraminx, skewb and square-1 get special treatment because there, "too short" solutions have a non-negligible chance of actually happening.

 

[Stefan]

Same thing for Skewb: 2.2% is too high. If what Sarah said is right, 6 moves (0.04%) would be much better.

You don't jump between 2.2% and 0.04% with one move. That's a factor of 55. Not even the 7x7x7 has that many possibilities for one move. I notified them.

 

[DavidCip86]

It doesn't. It says "at least two moves to solve". Reason is above.

Yeah, but I dont think a scramble could be that lucky on big puzzles

 

[Kirjava]

Yeah, but I dont think a scramble could be that lucky on big puzzles

You're wrong.

 

[ottozing]

errrm, odder's WR pyra single is 6 moves...I don't think I should have to be less lucky than him to get a WR.

I was thinking the exact same thing when I heard about the 7 move limit.... So many weird regulations and stuff this year. Not sure how I feel about them.

 

[Robert-Y]

Scramble filtering wont prevent all bad scrambles. Extremely easy scrambles, which do not violate the scramble filtering regulations, may still occur. You could still potentially get an F2L skip for 3x3x3, for example.

Is anyone going to suggest filtering scrambles in which at least two thirds of the puzzle has been solved?
If so, what about one third of the puzzle? Is it okay to have a first layer skip? No?
What about just a cross skip?

Where does it end?

 

[Stefan]

I don't understand how people seem to think that 2 moves is silly and compromises the integrity of the event, but 4 moves is suddenly respectable.

Let me try to help you understand then, at least my personal reasoning, as I happen to think that.

Zero moves is solved, not scrambled. One move is still considered solved by WCA (with +2), and one or two moves also just feels "not scrambled" to me. Even non-cubers can solve that easily. And wouldn't give it to us when asked to scramble. Plus, if I remember correctly, for 2x2 a two moves scramble has already been thrown out a while back, so there's precedent for not considering it scrambled (enough) and forbidding it. Now at this point, the question for me already isn't anymore whether to draw a line. Ruling some states out but others not, I now have to draw a line somewhere, and the question only is where. Three moves still seem doable for non-cubers (they can easily reduce it to two moves), but four moves finally feel like it's (somewhat) scrambled. Also, for 2x2 (which I guess you meant, as you said four moves) we have already used a four moves scramble, so there's precedent for considering it scrambled (enough) and allowing it.

Maybe now you or one of the others who think we shouldn't even filter the solved position can enlighten me about that, cause that's something I don't understand. Do you consider a solved cube scrambled? Or do you think we don't need to scramble?

If a random state was one move away would you want somebody who has no idea how to cube get the WR just because they could see one move in advance or would you give it to the people who actually know how to cube?

If a person has no idea how to cube, they wouldn't be trying to compete and would never see the scramble in the first place.

Almost true (I believe I heard of at least one such person competing), but change Meth's remark to say "somebody who's a beginner/intermediate at Skewb" and it becomes realistic. What's your answer then?

 

[Julian]

I don't agree that how we've handled scrambles in the past should set a precedent. If skewb were to be introduced with a minimum scramble length of 9, and then we realized that was stupid, I don't think we should be stuck and never be allowed to lower the minimum. Rather, those cubers who competed under scramble filtering and had a low-move scramble removed were just unlucky that the WCA was handling things this way at that time (similar to cubers competing under the Rubik's-brand-only rule).

Looking at the long-term, we can't never change the way things are because of a ruling at one competition, it's simply unfortunate to cubers at that competition. Following this reasoning, I think that neither the case of throwing out a 2-move scramble nor the case of allowing a 4-move scramble for 2x2 set a precedent. I'm in favour of allowing all non-solved states to appear (where 1 move off is solved). This seems to be the most non-arbitrary course of action.

 

[Julian]

Some thoughts here. I agree with zero filtering beyond removing 1-move scrambles for many of the reasons already outlined in this thread.

 

[Sa967St]

Scramble filtering wont prevent all bad scrambles. Extremely easy scrambles, which do not violate the scramble filtering regulations, may still occur. You could still potentially get an F2L skip for 3x3x3, for example.

Is anyone going to suggest filtering scrambles in which at least two thirds of the puzzle has been solved?
If so, what about one third of the puzzle? Is it okay to have a first layer skip? No?
What about just a cross skip?

Where does it end?

Very short scrambles on certain puzzles require hardly any skill to get a fast time whereas partially-solved scrambles at least require skill and some knowledge to get a relatively fast time.

Hypothetically, if a 2x2x2 scramble had a layer solved and the last layer required the maximal number of moves, the faster and more skilled 2x2x2 solvers should get better times on it than new and less experienced cubers would. On the other hand, if a 2x2x2 scramble were 3 moves long, any cuber, no matter how experienced, can get a ridiculous time.

I don't think we should worry about filtering beyond move count for this reason. The reason we should have filtering in the first place is for fair sportsmanship. Do we really want the 2x2x2 WR single holder to be the person who is lucky enough to get a 2-move scramble? There needs to be some extent of skill involved. For those who say luck is part of the game, I agree since it's inevitable, but we should do what we can to avoid situations where WRs are solely determined by luck. Getting easy but not necessary short scrambles are part of the game.

I think the issue is how to fairly decide filtering limits. It's unfortunate that some of the current WR singles had scrambles that aren't defined by the current limits (how did the 6-move pyraminx scramble happen anyway?).

 

[uberCuber]

Almost true (I believe I heard of at least one such person competing), but change Meth's remark to say "somebody who's a beginner/intermediate at Skewb" and it becomes realistic. What's your answer then?

I gave my answer two posts below the one you quoted.

Presumably such a person would not be able to start a stackmat timer, perform a move on their cube, and stop the timer in a faster time than every fast-ish cuber in the round. And if they did manage to, then good for them. Luck is inherent to cubing.

 

[Stefan]

Some thoughts here. I agree with zero filtering for many of the reasons already outlined in this thread.

I'm confused. Here you're for "zero filtering", but in the your post you link to in this same post, you're "in favour of allowing all non-solved states to appear (where 1 move off is solved)"...

 

[Julian]

Hypothetically, if a 2x2x2 scramble had a layer solved and the last layer required the maximal number of moves, the faster and more skilled 2x2x2 solvers should get better times on it than new and less experienced cubers would. On the other hand, if a 2x2x2 scramble were 3 moves long, any cuber, no matter how experienced, can get a ridiculous time.

I could do a 0.7x J-perm when I was an 18ish second solver. I think I would have just as much of a shot at getting a better time on that scramble than a top-tier 2x2er as if it was a 3-move scramble.

I don't think we should worry about filtering beyond move count for this reason. The reason we should have filtering in the first place is for fair sportsmanship. Do we really want the 2x2x2 WR single holder to be the person who is lucky enough to get a 2-move scramble?

This is essentially what exists currently, top 3 2x2 single results.

There needs to be some extent of skill involved. For those who say luck is part of the game, I agree since it's inevitable, but we should do what we can to avoid situations where WRs are solely determined by luck. Getting easy but not necessary short scrambles are part of the game.

I agree with the last line. But why are short scrambles not also part of the game?

EDIT:

I'm confused. Here you're for "zero filtering", but in the your post you link to in this same post, you're "in favour of allowing all non-solved states to appear (where 1 move off is solved)"...

Apologies, I'm in favour of filtering out only solved states. Editing.

 

[Stefan]

First of all: you know perfectly well that the chances of this are smaller than that I win the lottery 10 times on a day without rain in the Netherlands.

I don't know your lottery and rain, but I doubt this. We've just seen bad WRs being set (at that first skewb competition) and if you insist on the "50 seconds" cuber, we've had that as well (one such cuber was the best at that competition). All it would take is a combination of these two and a one-move scramble. This certainly seems way more likely than your lottery+rain scenario.

I gave my answer two posts below the one you quoted.

Oops, apparently I managed to skip those two posts. It's 7:42am, I should go to bed.

 

[Stefan]

Apologies, I'm in favour of filtering out only solved states. Editing.

Ok, thanks. Now you just need to change your vote accordingly as well

 

[Sa967St]

I don't think we should worry about filtering beyond move count for this reason. The reason we should have filtering in the first place is for fair sportsmanship. Do we really want the 2x2x2 WR single holder to be the person who is lucky enough to get a 2-move scramble?

This is essentially what exists currently, top 3 2x2 single results.

Those three cubers at least had enough skill to see the full 4-move solution and were able to execute it relatively quickly. If it were a 2 move scramble, it could have been almost anyone's game.

FYI, I'm okay with the 2x2x2 scramble filtering limit as 4 moves -- I think it's a reasonable and explainable cut-off. I completely agree with Stefan's post on why.

There needs to be some extent of skill involved. For those who say luck is part of the game, I agree since it's inevitable, but we should do what we can to avoid situations where WRs are solely determined by luck. Getting easy but not necessary short scrambles are part of the game.

I agree with the last line. But why are short scrambles not also part of the game?

"Short" as in ones that are filtered with the current limits.

 

[Julian]

Ok, thanks. Now you just need to change your vote accordingly as well

Well, that might be a bit misleading, especially to someone who hasn't read discussion regarding 1-move scrambles. But I'm fine if someone wants to change my vote to option 2.

Those three cubers at least had enough skill to see the full 4-move solution and was able to execute it relatively quickly. If it were a 2 move scramble, it could have been anyone's game.

I agree somewhat. Most cubers would be able to see an optimal solution for a 2-move scramble. Less cubers would be to see an optimal solution for a 3-move scramble (scramble: R' U' F2. Especially if the cuber wants to solve on white, they would need to do at least some tracing to determine there is a 3-move solution). And still less for a 4-move scramble, etc. It's very subjective for us to just choose a number that feels mixed enough to be the minimum. I think we shouldn't be arbitrary.

Also for skewb, because the puzzle is deep-cut and the pieces move in a way many are not used to, a decent number of cubers would find 3 or even 2 moves to be non-obvious. Enough, at least, to make them think twice about one-looking.

 

[Sa967St]

It's very subjective for us to just choose a number that feels mixed enough to be the minimum. I think we shouldn't be arbitrary.

Arbitrary decisions are nothing new, and it's natural to not want/like them, but without a reasonable limit, WR singles would just go out to people who get the shortest scrambles ever generated (I know this is a bit of an exaggeration -- but regardless they would go out to those who have a certain relatively low amount of skill and get super lucky with a very short scramble). Deciding filtering limits based on what feels right is indeed arbitrary to a high extent, but out of sportsmanship I believe the filtering limit should not simply be >1 (i.e. ≥2).

 

[qqwref]

We're definitely going to have arbitrary limits, but if we do filter things beyond 1 move, I'd like to at least have consistent reasoning across puzzles, as opposed to arguments about whether an N-move scramble feels easy or can be solved by a non-cuber or whatever. One possible way is as follows:
- Choose a constant k, much less than 1.
- For a given puzzle, let P be the number of positions.
- Let n be the greatest integer so that the number of positions solvable in at most n moves is no greater than kP.
- If computationally feasible, forbid any positions that are solvable in at most n moves.

For instance, if we let k = 1/1000, we forbid the following: 2x2x2 positions solvable in <=4 moves; Pyraminx positions solvable in <=3 moves (or <=5 moves if you include tips); Skewb positions solvable in <=4 moves; Square-1 positions solvable in <=6 twists; 3x3x3 positions solvable in <=14 moves. Unless I made a mistake, of course.

 

[Erik]

and one or two moves also just feels "not scrambled" to me. Even non-cubers can solve that easily. And wouldn't give it to us when asked to scramble.

2 points:

- it doesnt matter how you feel about a scramble. A scramble is no more than a random position of a cube in my opinion. This is the point where a lot of us just have a different opinion. Imho: If you dont like the fact that one of the random positions is 1 move (which is only considered solved because of our regs) then why bother with a sport-hobby-etc of where luck is a clear possible factor. A factor which, is already filtered by averages of 5.

- yes lets use non-cubers insight in cubes to determine what is a scramble or not...