# Proposal: Subobtimal FMC scrambles



## EMI (Aug 15, 2014)

The idea is to use random state scrambles, but make them lenght 20 (or longer, if necessery?) every time. In my opinion the competitor shouldn't know an upper bound for the length of an optimal solution.
For example, the third scramble at Euro was only 16 moves. So without even looking at the result of the scramble, you know it is an "easy scramble".
To be more concrete: Let's assume there is a 13 move scramble. 13 move optimal solutions are not impossible to find. 1) This kind of gives you an advantage, as you know there is such a short solution, and might adapt your strategy. 2) It also gives you a disadvantage, as you might even find the inverse scramble as a solution - but cannor use it.
BTW, suboptimal scrambles are already used for 2x2, although the competitors don't even see the scrambles.

This was just a few thoughts I had after FMC at Euros. Opinions?


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## Julian (Aug 15, 2014)

I agree.


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## porkynator (Aug 15, 2014)

I have no opinion about this, but I have to point out that too long scrambles make it harder to use techniques like inverse scramble or NISS and might be a big disadvantage for people who tend to solve & re-scramble a lot during solves.
So, your proposal to make all scrambles 20 moves long is fine, but making them longer wouldn't be good.


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## slinky773 (Aug 15, 2014)

porkynator said:


> I have no opinion about this, but I have to point out that too long scrambles make it harder to use techniques like inverse scramble or NISS and might be a big disadvantage for people who tend to solve & re-scramble a lot during solves.
> So, your proposal to make all scrambles 20 moves long is fine, but making them longer wouldn't be good.



Are you saying that the scramble length makes it harder to use those techniques because it takes longer to use the scramble on a cube? Because if so, I would agree that this would be a disadvantage, but we would have to weigh that con against the pro that we would no longer have problems with using the inverse scramble and other such problems, and I think that both of us would agree that the pro outweighs the con there.

Then again, I'm not a FMCer either (yet), but I would think that the advantage is huge over that disadvantage of having to perform more moves. Using the example of Euro 2014, if the scramble was 22 moves instead of 16, that increase in moves may be nontrivial, but it's still better than the possibility of finding the inverse scramble as the solution, or something similar to what Julian had.


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## porkynator (Aug 15, 2014)

slinky773 said:


> Are you saying that the scramble length makes it harder to use those techniques because it takes longer to use the scramble on a cube?


Yes, this is the reason.


> Because if so, I would agree that this would be a disadvantage, but we would have to weigh that con against the pro that we would no longer have problems with using the inverse scramble and other such problems, and I think that both of us would agree that the pro outweighs the con there.


I'm not sure; IMO, for example, 27 HTM scrambles are long enough to be a disadvantage, but short enough to be a good solve if reversed.

I think that the idea of making all scrambles the same length to make it impossible to know whether a scramble is good or not is nice, but I'm not sure making them longer than 20 moves might solve (or prevent) any problem.


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## Laura O (Aug 15, 2014)

porkynator said:


> I think that the idea of making all scrambles the same length to make it impossible to know whether a scramble is good or not is nice, but I'm not sure making them longer than 20 moves might solve (or prevent) any problem.



I am actually unsure if the length of a scramble makes it good or not in terms of FMC.
There are probably other factors that influence that more, like the length of 2x2x2/2x2x3 blocks, oriented/solved edges, etc. (depending on the "method" used).


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## Noahaha (Aug 15, 2014)

I think that 20 moves every time makes the most sense.


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## Hypocrism (Aug 15, 2014)

Assumes every scramble is soluble in 20 moves, I don't think that's been proven yet?

EDIT: _exactly_ 20 moves


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## qqwref (Aug 15, 2014)

20 moves every time would be good. I agree with porkynator that more moves is generally bad (a while ago I went to a comp where they had like 30-40 move scrambles and it was kind of annoying) but 20 is pretty short and at the same time doesn't reveal info about how easy the scramble is.


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## okayama (Aug 16, 2014)

I agree. My opinion was already posted here.


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## Lucas Garron (Aug 17, 2014)

We already use suboptimal scrambles. 

I think a minimum of 20 moves for every FMC scramble is fine. We already do that for e.g. 2x2x2 and Pyraminx speedsolve events.

If you want Jeremy to act on this, you should make sure to post an issue on GitHub or send an email to the mailing list for the scramble program.


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## Cubenovice (Aug 17, 2014)

Another vote for using 20 HTM as a standard


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## guysensei1 (Aug 17, 2014)

Cubenovice said:


> Another vote for using 20 HTM as a standard



Can all states on a cube be expressed as exactly 20 HTM?


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## cubernya (Aug 17, 2014)

guysensei1 said:


> Can all states on a cube be expressed as exactly 20 HTM?



I would assume so, but we don't know this for sure. If it couldn't, I doubt anyone would have a problem going to the next lowest available length.


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## Musicalboy2 (Aug 17, 2014)

theZcuber said:


> guysensei1 said:
> 
> 
> > Can all states on a cube be expressed as exactly 20 HTM?
> ...



Technically yes, if you end a scramble in, say, R2 R' (yes, this is kind of silly, but it's still 20 HTM)


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## cubernya (Aug 17, 2014)

Musicalboy2 said:


> Technically yes, if you end a scramble in, say, R2 R' (yes, this is kind of silly, but it's still 20 HTM)



That's not what I meant. If 20 doesn't exist, use 21 if you can. Do not go lower, since that defeats the purpose.


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## bobthegiraffemonkey (Aug 18, 2014)

Seems like a good idea, but what if 20 is possible but not always practical? There may be a slightly larger solution length for which solutions of that length are easily and quickly found for most or all positions. For example, it may be easy to get solutions of length 22 for most random positions, which is still fairly short.


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## AvGalen (Aug 24, 2014)

I support making it 21, but wouldn't mind just 20. This is a great, simple proposal


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