[Help Thread] FMC Discussion

Cubenovice said:
Nice one!
Click to expand...
Thanks. :)

Zane_C said:
FMC = 39 HTM
Scramble: D2 R' F R2 D2 U' F' U R2 B2 F2 D2 B' L' U' F2 R U2
.........

2x2x2: R' U2 D R F' R2
........
Click to expand...
irontwig said:
You just start using pseudo block, Zane
(D) B2 L2 D2
After your 2x2x2 looks promising.
Click to expand...
I must ask about premoves. I know what they are, but don't know how to find them.
How is it known that a D premove will set up a good block? All I know is yellow pieces will be permuted differently.
 
It's the other way around; you find the premoves after the you find the block(s). The premoves are the moves that you would do to bring all pieces into the correct places.

Example:
Scramble: R2 B D B2 D U B F2 R' B L2 U' F2 B R D2 B' R2 D B2 D2 B' U D' L R' B' D' B2 L2 (FMC 361)

F2 L2 F2 L' B2 D' R D R (After L2 the pieces in the left square is solved, so premove is L2) (My start)
U' F2 L' R D2 L' U2 L2 B2 D U' (Both roux blocks need to be turned counter clockwise to be solved so premoves are U' D') (Mirek's start)

hth
 
Zane_C said:
I must ask about premoves. I know what they are, but don't know how to find them.
How is it known that a D premove will set up a good block? All I know is yellow pieces will be permuted differently.
Click to expand...

Good premoves can realistically be found at any time, though they are most commonly used to fix a psuedo block, and there are a couple ways to do it. If you decide to start and solve on the inverse scramble, you are essentially only using premoves. And when you use NISS you are creating premoves any time you switch to the inverse.

Like you said the yellow pieces are permuted differently, this is what allows you to visualize the effects of a premove without switching your cube to the inverse. The premove D will essentially rotate the yellow pieces, as if they were all on the same face, and premove X rotates the pieces that are the same color as the center face you are turning. So D moves the Yellow-Red edge to where the Yellow-Blue edge is and so forth. It's sort of like a fourth dimensional move, because it's a move you want now, but actually happens to the scramble later.

Edit: My solution from FMC 371 is actually a pretty good example of using pre-moves. I found all four of these without switching the cube to the inverse.

Solution: F2 U' B2 R U2 B U B2 U B2 U' R2 B2 R F R' B2 R F' U2 R B' R2 F2 R2 B' (26 moves)

Here is the order I actually found/used the first 8 moves [for premoves]
[B'] [R2] F2 [F2] U' B2 R [R2]
 
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Kryptonite said:
Good premoves can realistically be found at any time, though they are most commonly used to fix a psuedo block, and there are a couple ways to do it. If you decide to start and solve on the inverse scramble, you are essentially only using premoves. And when you use NISS you are creating premoves any time you switch to the inverse.

Like you said the yellow pieces are permuted differently, this is what allows you to visualize the effects of a premove without switching your cube to the inverse. The premove D will essentially rotate the yellow pieces, as if they were all on the same face, and premove X rotates the pieces that are the same color as the center face you are turning. So D moves the Yellow-Red edge to where the Yellow-Blue edge is and so forth. It's sort of like a fourth dimensional move, because it's a move you want now, but actually happens to the scramble later.

Edit: My solution from FMC 371 is actually a pretty good example of using pre-moves. I found all four of these without switching the cube to the inverse.

Solution: F2 U' B2 R U2 B U B2 U B2 U' R2 B2 R F R' B2 R F' U2 R B' R2 F2 R2 B' (26 moves)

Here is the order I actually found/used the first 8 moves [for premoves]
[B'] [R2] F2 [F2] U' B2 R [R2]
Click to expand...

That was a great solution for a hard scramble. You beated everyone.
It also proves that a range of pre-moves can sometimes (!) be found without the inverse scramble.
 
Thanks! I was pretty excited, new PB. Still got pretty lucky in a few places, so I'm yet to really keep up with you guys :)
 
okayama said:
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 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.
Click to expand...

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'.
Click to expand...

thank you I think I finally reached the concept... I'll try some solves and I'll see your example later... thank you very much!
 
So, I've got a question. The WCA rules state that competitors can have unlimited stickers. Given this, would a cube with magnetic tiles be acceptable? I can't see it providing any significant advantage over having unlimited stickers other than providing more convenient adhesive.
 
Kryptonite said:
So, I've got a question. The WCA rules state that competitors can have unlimited stickers. Given this, would a cube with magnetic tiles be acceptable? I can't see it providing any significant advantage over having unlimited stickers other than providing more convenient adhesive.
Click to expand...
The WCA rules are quite vague on what's allowed. I've seen people use cubes with stickers removed, and someone using a 7x7x7 cube as one of his extra cubes. Arguably these could be viewed as violations of the rules as stated. For example, I believe 3x3x3's are not allowed for 2x2x2 speedsolve, so by the same logic, 7x7x7's would seem to illegal for 3x3x3 fewest moves, since the rules for fewest moves doesn't seem to have any special rules saying otherwise. Perhaps you should raise the question on the WCA forum.
 
Now that UK Open is over, I can start on my next project, which is a Fewest Moves Tutorial. I know what you're probably thinking - how can you teach FMC in a video?! Well I'm not overly concerned about that, because although I think written tutorials work better for FMC, I know that a lot of people would rather just sit back and watch a video instead. There's a constant stream of people who want to know how to FMC and ask about inverse/pseudo/NISS etc so I think it's time there's a series of videos to link people to. I've had some initial thoughts about it and this I what I've come up with:

1. Basic overview: Includes some important rules, some of the methods that are used, and a few general tips
2. Starting a solve and finding continuations
3. Finishing a solve: Insertions (corners inc. 4 and 5 corners left, and edges too), and other LL stuff
4. Pseudo blocks and using the inverse scramble (including NISS ofc)

What I'd really appreciate now is if people could give me some feedback on what they think should be included, because I'm bound to miss something important out!
Or just tell me if you you think it's a terrible idea/I'm the wrong person for the job!
 
I think you should try to keep it simple:
- typical blockbuilding starts
- insertions of single moves into those blocks to check for better continuation
- the simple way to 5 corners left: F2L-1 + LL edges
- show how you find premoves via pseudo blocks.
- if people go for a finished F2L:
- - - - when inserting the last pair: try different ways of inserting to see if you get lucky
- - - - try multiple OLL and their mirrors to see if you get lucky
- simple edge and corner cycle insertions (would not include all the info that was posted over the last week on the finding the 5-cycles in a single pass of the sekelton)

For NISS I'd stick to a "plain" inverse scramble or perhaps max one switch.
Keep "switching back and forth" for a possible later video as it will confuse the hell out of people :)

For methods: refer to some good tutorials (heise, petrus) and offcourse AVG write up on FMC .
 
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does someone used the Heise method after F2L-1? there are three approaches:

-solve all 5 edges (leaving 5 corners)
-making two pairs + solve edges (leaving 3 corners)
-make one pair and solve edges while solving the second pair (? too hard XD)

I'm focusing on second step but I usually do easly the two pairs but then for solving all but 3 corners I need often to do a pairs comm and it's cool (XD) but are too many moves... (at least 8 for comm + 8 for insertion of the last 3C) do you have any example solve with this method?
 
I think all of these are used or at least tested at the F2L-1 stage.
Since I am very bad at the pair (s) approach I typically try to keep a short F2L-1 and go for the “leaving 5 corners”
I will offcourse try some variations to see if I can fluke my way into leaving just 3 corners.

If I can’t find 3 corners is still prefer L4C over L5C as I feel this increases chances of finding cancellations as the 1st commutator only needs to solve one corner.
This makes for many possible commutators and if you can link one to a conjugate in the skeleton you’re in for a cancel-fest.

For example solves I think Okayama is your man; he uses pair comm more often than the other regular FMC solvers.

There is also a speedsolving thread on the 2 pair approach with examples on forming the pair and some full solves from there.

BTW: does anyone know where Armin and Johannes went? They both seem very knowledgable.
 
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