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guusrs

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I find the first approach works best as it allows me to write down all possible commutators while working trough my solution.
I will only execute the (best) commutator after checking the full skeleton, never during.

For identifying the best commutators I only glance at the start and end move, if it doesn't cancel anything I move further trough the skeleton.
(I do write down the very first 8-mover even if it does not cancel, just in case there is nothing better.)

I never really execute any insertion. I only investigate, write down and continue for searching an even better insertion.
 

guusrs

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Which competition? Information available in the WCA site? I'd like to go if possible! :)

Ha, ha,
That competition exists for 3 years now.... in Erik's head.
But I really hope he's going to organize that comp some time.

Do you already know were Twente is located?
It's the area were Erik and I grew up (with 25 years in between)
 

okayama

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Ha, ha,
That competition exists for 3 years now.... in Erik's head.
But I really hope he's going to organize that comp some time.

Do you already know were Twente is located?
It's the area were Erik and I grew up (with 25 years in between)
I see. :eek: When it becomes reality I want to participate it!
I didn't know the place, and I want to see Erik's and your hometown. :)
 
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kinch2002

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I can try to explain some logic behind using premoves while solving with the normal scramble only.

Imagine you've made a pseudo F2L (so that, say, you need to do R2 to put some of those pieces in the 'correct' place) Then you might carry on solving the LL. And then right at the end you would do R2 and everything would be solved. You can do this of course, but it's really difficult to, for example, see what LL case you have, because not all the pieces are of one colour etc. So to help you do this, you can do a premove, and then the F2L will actually look correct and you can do some nice LL stuff. Of course when you come to write down your solution at the end, you need to add the premove to the end of your solution - remember I said that you would 'do an R2 and everything would be solved'.
 

okayama

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thank you for answer... I often get confused about premoves... because I don't really get the logic behind them at all...

Scramble + Solution can be considered as a loop.

Suppose that

Scramble: A B C D
Solution: p q r s

then the sequence A B C D p q r s doesn't anything to the cube.
And, as an important thing, the sequence
s (A B C D p q r s) s' = s A B C D p q r
doesn't anything to the cube. If you connect the head and tail, and consider
it as a loop, A B C D p q r s and s A B C D p q r are the same.
Similarly, the following sequences

  • s A B C D p q r
  • r s A B C D p q
  • q r s A B C D p
  • ...
  • B C D p q r s A
don't anything to the cube, because these are the same loop if you connect the head and tail.
And for example, the first one can be considered as

Premove: s
Scramble: A B C D
Solution: p q r

This is why premove works.

See also my example solve.
The logic is explained at the end.
 
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Kryptonite

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Jul 16, 2010
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Why do the things you've done forward appear in the inverse and vice versa? Also, since at least some of the pieces are predictable, is there a way to predict the entire cube layout before you NISS?

Just realized the answers to both my questions. Since the Scramble + Solution in Progress are a cycle we can express them in cycle notation. And any piece that ends up where it started is its own cycle (X), which is just the identity permutation. The Inverse of the Scramble + Solution in Progress is simply the inverse of the forward cycle, so identities stay identities, which explains why solved pieces stay solved. Also, this means we can predict how the inverse of any move set will look without turning any faces or even knowing the move set.

For example (ignoring orientation for simplicity), if you have a 2x2x3 solved, made up of the pieces 6, 7, 14, 15, 17, 18, 19, you might have a cycle that looks like
(154238)(9 12 10 20 13 16 11)(6)(7)(14)(15)(17)(18)(19)

Which simplifies to
(154238)(9 12 10 20 13 16 11)

And the inverse would be
(11 16 13 20 10 12 9)(832451)

So technically you could use your infinite stickers to paste on the NISS effects... but it might be faster just to do the moves.
 
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Cubenovice

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35-move linear FMC: D' R' U' F2 U F' D B2 R F2 D L' F' B2 U' D F D' U R B D2 R L D'

R' B U B' U'
D B' D2 B2 D2 B'
D' F D F' D L D L'
D2 F D F2 R F R'
B R F' R' B' R F R' D

A very nice solve but something tells me this was not specifically intended as a fewest moves attempt ;)
Then you would have made a completely different start with all those blocks.
 

Cubenovice

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Learned something new about premoves today:
Premoves can lower the optimal movecount for a specific block :)
I thought they would typically cancel out...

On the weekly 46 scramble my 2x2x3 block incl its 2 premoves is 1 HTM shorter than all possible optimal 2x2x3 blocks on the normal scramble :)

Before someone disagrees after seeing my solution: I inserted one move for better continuation; making the block no longer optimal.
 

Zane_C

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My FMC solution for Weekly comp 46: :)

FMC = 28 HTM
Solution: R' D' B' U' L D2 R2 D B' D2 B F' L D' L' F' R F2 R2 D R2 U' R2 D' R2 U R' F = 28 HTM

2x2x2: R' D' B' U' L
2x2x3: D2 R2 D B' D2 B
F2L-1: F' L D' L'
Finish F2L: F' R F2 R'
LL: R' D R2 U' R2 D' R2 U R' F

Comment: Too easy, lucky actually.
My intention was to use OLL/PLL for the backup solution, then the skip turned it into a good final solution. Thus, I found this in about 10 minutes.
 

Kryptonite

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Jul 16, 2010
Messages
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Learned something new about premoves today:
Premoves can lower the optimal movecount for a specific block :)
I thought they would typically cancel out...

On the weekly 46 scramble my 2x2x3 block incl its 2 premoves is 1 HTM shorter than all possible optimal 2x2x3 blocks on the normal scramble :)

Interesting, I always assumed that premoves/NISS could yield more and better options.

Though interestingly enough...
if you started on the inverse scramble, there are 5 ways you could get to a 2x2x3 in one fewer move than the optimal going forward (8 vs 9). But then, I suppose that could be considered eight premoves... :)
 
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