[Help Thread] FMC Discussion

[nigtv]

y should slice moves considered as 2 moves? Its just 1 move...
i know u are going to tell me its because I rotate the centers or sth. like that, but imagine i use a LED cube or solve at my computer - theres no sence y it should be considered to be 2 moves...

Speedsolving wiki. Now

It is important to note that in HTM a slice move actually counts as two turns, since the centers are assumed to be fixed.

http://www.speedsolving.com/wiki/index.php/Htm

STM is a very popular metric for those who use methods with many slice turns (such as Roux) although the official Fewest Moves event uses HTM.

http://www.speedsolving.com/wiki/index.php/STM

That 'centers assumed to be fixed' thing makes the most sense to me.

Also, im working on the current FMC scramble (270, I believe), will get back to ya.

 

[jms_gears1]

why should centers assumed to be fixed?
maybe im missing something but shouldnt slice moves count as only one...

 

[jms_gears1]

im confused with pre-moves,
are they moves you apply before the scramble?
if so then when you solve it wouldnt you have to undo them and it wouldnt be solved?
also is their any kind of tutorial that would help me?

im extremely new to FMC so any help would be appreciated thanks : D

 

[Mike Hughey]

why should centers assumed to be fixed?
maybe im missing something but shouldnt slice moves count as only one...

This is the convention. It is true that there are arguments that can be made for other conventions, but honestly the current convention works okay, and if we changed the convention, it would invalidate the old results. So I suggest you simply get used to the convention, since that's the way it works in competitions.

im confused with pre-moves,
are they moves you apply before the scramble?
if so then when you solve it wouldnt you have to undo them and it wouldnt be solved?
also is their any kind of tutorial that would help me?

im extremely new to FMC so any help would be appreciated thanks : D

A good place to start would be this thread. (Moderators, I suggest we sticky the thread - I'm surprised it's not already.) An example of premoves is given on the second page with a bit of explanation.

 

[stiwi griffin]

why should centers assumed to be fixed?
maybe im missing something but shouldnt slice moves count as only one...

This is the convention. It is true that there are arguments that can be made for other conventions, but honestly the current convention works okay, and if we changed the convention, it would invalidate the old results. So I suggest you simply get used to the convention, since that's the way it works in competitions.

it is not a convection, a slice movement ( M' ), which counts as 2 moves, is equivalent to ( R L' X ), which also counts as 2 moves.

 

[TMOY]

This is the convention. It is true that there are arguments that can be made for other conventions, but honestly the current convention works okay, and if we changed the convention, it would invalidate the old results.

Switching to STM would not invalidate the old results, it would only make them easier to beat. In partiular it would give people a better chance to break that insane 22-move WR without relying on a LL skip or a similarly lucky solve.

 

[Mike Hughey]

why should centers assumed to be fixed?
maybe im missing something but shouldnt slice moves count as only one...

This is the convention. It is true that there are arguments that can be made for other conventions, but honestly the current convention works okay, and if we changed the convention, it would invalidate the old results. So I suggest you simply get used to the convention, since that's the way it works in competitions.

it is not a convection, a slice movement ( M' ), which counts as 2 moves, is equivalent to ( R L' X ), which also counts as 2 moves.

I'm sorry - my post was terribly unclear. I meant that it is the convention to count a slice move as 2 moves, as you stated. Sorry for my unclear post.

 

[jms_gears1]

why should centers assumed to be fixed?
maybe im missing something but shouldnt slice moves count as only one...

This is the convention. It is true that there are arguments that can be made for other conventions, but honestly the current convention works okay, and if we changed the convention, it would invalidate the old results. So I suggest you simply get used to the convention, since that's the way it works in competitions.
...

Sorry i meant to ask what the arguement for this convention was just curious.

im confused with pre-moves,
are they moves you apply before the scramble?
if so then when you solve it wouldnt you have to undo them and it wouldnt be solved?
also is their any kind of tutorial that would help me?

im extremely new to FMC so any help would be appreciated thanks : D

A good place to start would be this thread. (Moderators, I suggest we sticky the thread - I'm surprised it's not already.) An example of premoves is given on the second page with a bit of explanation.[/QUOTE]

thanks, ive seen this thread before i dont know why i didnt go back and read it....

i agree that it should be stickied

 

[stiwi griffin]

why should centers assumed to be fixed?
maybe im missing something but shouldnt slice moves count as only one...

This is the convention. It is true that there are arguments that can be made for other conventions, but honestly the current convention works okay, and if we changed the convention, it would invalidate the old results. So I suggest you simply get used to the convention, since that's the way it works in competitions.

it is not a convection, a slice movement ( M' ), which counts as 2 moves, is equivalent to ( R L' X ), which also counts as 2 moves.

I'm sorry - my post was terribly unclear. I meant that it is the convention to count a slice move as 2 moves, as you stated. Sorry for my unclear post.

no problem MIke

 

[nigtv]

im confused with pre-moves,
are they moves you apply before the scramble?
if so then when you solve it wouldnt you have to undo them and it wouldnt be solved?

Looking through that first post in the link he gave you, I don't think he talks about pre-moves specifically (not in the first post, I believe other people cover it later in the thread). I'm pretty new with FMC also, but AFAIK a pre-move is a move that is more abstract, which you apply before the 'start' of your solve to influence the position of things at some point later in the solve.

I'm not really sure if that's the same pre-move everyone else talking about. I've seen them mentioned a few times recently in this thread, in association with inverse scrambles, for example;

my solve: D' B' U B2 D' L F2 L' D R U2 R U2 B' R' U2 RU' R B' R' F2 U' L B' (25)
explanation:
inverse scramble: nice start: B L' U F2 (4)
apply on normal sramble: [pre-moves F2 U' L B'] nice continuation: D' B' U B2 R2
apply on inverse scramble: [pre-moves R2 B2 U' B D]: B L' U F2 (4+[5])
then continuation on inverse scramble was easy:
F2L: R B R' U R' U2 R B (12+[5])
LL: U2 R' U2 R' D' L F2 L' D R2 (22+[5])
pre-move correction: R2 B2 U' B D, 2 moves cancel (25)

in this post by guusrs. I've never really gotten used to inverse scrambles, and I'm still working on figuring out exactly how to use them correctly, so I don't know if this is what people are referring to either, although it seems more likely that this is what people are referring to.

I guess it's also possible that those two uses of the term aren't mutually exclusive? Maybe an FMC veteran can clear up the confusion.

 

[Mike Hughey]

Generally, you use premoves to modify a scramble so you can solve it more easily. The most common approach for this is to solve a "pseudo-block" of some sort, where for instance you might put in a corner-edge pair of the wrong color into a 2x2x2 or 2x2x3 block. Then you find the moves necessary to put that corner-edge pair (or whatever) into it's proper location in the solved cube. If you then apply those moves to the solved cube prior to applying the scramble, you'll find that the pseudo-block becomes an actual block. Then you can add those moves to the end of your final solution and it will be solved.

Guus's solution you mention is using "NISS" - his "normal-inverse-scramble-switch" method, where you solve part of the cube with the normal scramble, then when you get stuck, you switch to the inverse scramble and use it, then when you get stuck again, you switch back to the normal scramble, and so on. I love NISS - it's really fun to do! Anyway, when you switch from normal to inverse scrambles, the moves you used at the beginning of the normal scramble solve become premoves to the inverse scramble (and vice-versa). It takes trying it to see how it really works, and it's really quite ingenious.

The best way to understand these is to look at some of the solves that others have done (like the ones in the weekly competitions) and understand how they work. Examples are much more useful than descriptions - this isn't a particularly good description, but maybe it gives you an idea of what's going on.

 

[nigtv]

If you then apply those moves to the solved cube prior to applying the scramble, you'll find that the pseudo-block becomes an actual block.

this isn't a particularly good description, but maybe it gives you an idea of what's going on.

That actually makes a pretty good amount of sense. I never really understood why the inverse scramble thing was so popular and seemed to yield good results. I think I'll play around with this a little and try to get my head around it, maybe I'll be able to come across some kind of example or something and see if I'm actually doing it right.

 

[trying-to-speedcube...]

Scramble: L2 R2 F2 U B2 D2 L2 F2 D' L2 D F D B2 D2 U' B' L2 R' F' R'
Solution: B' R2 F' R B2 R' F R B2 R L' B L B L' B' L B L U M U' L' U M' F' U2 F R' L2 U' B' U R2
Explanation:
Start on inverse scramble.
Triple x-cross: R2 U' B U L2 R F' U2 F U' .
Last slot: B' L' B L B' L' B' L
COLL: R' B2 R' F' R B2 R' F R2 B
Insert at .: U M U' L U M' U' L', 2 moves cancel.

Magical start with a terrible ending, resulting in a normal solve. Can anybody find a good continuation for this start?

 

[guusrs]

Scramble: L2 R2 F2 U B2 D2 L2 F2 D' L2 D F D B2 D2 U' B' L2 R' F' R'
Solution: B' R2 F' R B2 R' F R B2 R L' B L B L' B' L B L U M U' L' U M' F' U2 F R' L2 U' B' U R2
Explanation:
Start on inverse scramble.
Triple x-cross: R2 U' B U L2 R F' U2 F U' .
Last slot: B' L' B L B' L' B' L
COLL: R' B2 R' F' R B2 R' F R2 B
Insert at .: U M U' L U M' U' L', 2 moves cancel.

Magical start with a terrible ending, resulting in a normal solve. Can anybody find a good continuation for this start?

Maarten,

Did you try B' L' B' L B after Triple-X cross?
which gives a nice 15 move edge frame
Then double corner insertion?
Should definitely become sub 30!

Gus

 

[cuBerBruce]

Scramble: L2 R2 F2 U B2 D2 L2 F2 D' L2 D F D B2 D2 U' B' L2 R' F' R'
Solution: B' R2 F' R B2 R' F R B2 R L' B L B L' B' L B L U M U' L' U M' F' U2 F R' L2 U' B' U R2
Explanation:
Start on inverse scramble.
Triple x-cross: R2 U' B U L2 R F' U2 F U' .
Last slot: B' L' B L B' L' B' L
COLL: R' B2 R' F' R B2 R' F R2 B
Insert at .: U M U' L U M' U' L', 2 moves cancel.

Magical start with a terrible ending, resulting in a normal solve. Can anybody find a good continuation for this start?

Maarten,

Did you try B' L' B' L B after Triple-X cross?
which gives a nice 15 move edge frame
Then double corner insertion?
Should definitely become sub 30!

Gus

I solved the last 5 edges keyhole-style and got the same sequence as Gus: B' L' B' L B.

This leaves 4 corners to solve. This can lead to a 30-move "linear" solution.

3X Cross: R2 U' B U L2 R F' U2 F U' (10)
Edges (also 1 LL corner): B' L' B' L B (15)
Corner 3-cycle to solve 1 corner: (B2 D' F2 D)2 (23-1 = 22)
Corner 3-cycle to solve last 3 corners: D' (U' L' U R2 U' L U R2) D (32-2 = 30)

Using two 3-cycle insertions for the last 4 corners, I got the move count down to 26.

First, I found an insertion for the "flexible" case of solving 1 corner, while moving the twisted corner. That leaves an ordinary corner 3-cycle for the 2nd insertion.

3X Cross: R2 U' B U L2 R F' . U2 F U' (10)
Edges (also 1 LL corner): B' L' B' L B (15)
Flexible insertion (at "."): F D' F' U' F D F' .. U (23-3 = 20)
2nd insertion (at ".."): R U' L U R' U' L' U (28-2 = 26)

(Note that the 2nd insertion has a U cancelling with a U' since the first insertion combined a U with a U2 to net a U'.)

I note that flexible insertions such as the one here seem to me to be very time-consuming to search for thoroughly because there are 4 possible 3-cycles to consider at each move in the skeleton (and each of those involve one piece in which the orientation doesn't matter). The nice thing is that there are many more opportunities for getting a high cancellation. Only getting 3 moves cancelling was somewhat disappointing. (It's quite possible I missed something, however.)

 

[Stini]

Here is my 28-move solution from the Benelux Open:

Scramble: F2 U2 B2 R' U2 B' L' R2 U2 R2 D2 U B2 F D' L2 R F'
(Inverse scramble: F R' L2 D F' B2 U' D2 R2 U2 R2 L B U2 R B2 U2 F2)

Solution: R L2 B2 L' B' L2 U' L' U2 B' U' L2 B2 D B D L' D L2 B' R B2 R B2 R' F U F2

I used the inverse scramble with R' pre-move:

2x2x3 (without last move): F2 U' F' R B2 R' B2 R'

Some block building: B L2 D' L D' B' D' B2

Finish with a setup to short LL-alg: L2 U B U2 L U L2 B L B2 L2

Finally a decent solution in a competition!

(btw I just realized how I could have done 26 haha, do the finishing moves like L2 B2 D B D2 R D R2 B R L2 and it cancels with the pre-move)

 

[Stini]

I forgot to send my classic format solve for Per's weekly FMC contest #285 so here it is:

Scramble: D L2 R U2 L2 R2 D' F2 L2 R' F' R2 L D L F R D' R U2 R2 D L U B' D2 U2 B' R' L2

Solution: L' D' U2 F' D2 F U2 F' D2 R F2 U' B' z2 U L F' L2 U R U' R' U' L U2 F U' F' U2 (28 HTM)

2x2x3: L' D'. F' R F2 U' B' z2 (same as my 1h solution)
F2L minus slot: U L F' L2 U R U' R' U' L
Leave 3 corners: U2 F U' F' U2

Insert U2 F' D2 F U2 F' D2 F at the dot to cancel 2 moves.

Only one move shorter than my 1h solution, but it's only because the insertion cancelled 4 moves. I like how I build the top 1x2x2 during F2L, also I'm really satisfied that I found a 7-move 2x2x3, which actually turned out to be the only optimal solution.

 

[Jude]

Bristol 2010 FMC scramble: D2 L U2 F2 L D' R2 B' D R2 B U' F' L2 R' D2 F L'

I'd be interested to see what solutions people come up with

My solution:

Spoiler

Double X-Cross: U2 R D' B U L R B2 L B' (10, 10)
3rd Pair: U B U B' R U R' . (7, 17)
4th Pair: U' R' U R U' B U B' (8, 25)

3 cycle, insert at .: R U' R U R U R U' R' U' R2

Final Solution: U2 R D' B U L R B2 L B' U B U B' R2 U R U R U' R' U' R2 U' R' U R U' B U B' (31)

 

[Stini]

Bristol 2010 FMC scramble: D2 L U2 F2 L D' R2 B' D R2 B U' F' L2 R' D2 F L'

Solution: L' F' L2 D2 F D' B' U' F' U B L' F' L F L' F' L D U2 L2 U R U' L2 U D' L2 B (29)

From the inverse scramble you can find this 2x2x2-block: B' L2 D R' U, then I put that inversed as pre-moves for the normal scramble and a couple of extra moves.

So pre-moves for the normal scramble: L D U' R D' L2 B

2x2x3+EO: L' F' L2 D2 F D'
F2L minus slot: B' U' F' U B L'
Leave 3 corners: F' L F L' F'
Undo pre-moves: L D U'. R D' L2 B

Insert U' L2 U R U' L2 U R' at the dot to cancel 3 moves.

 

[kinch2002]

Bristol 2010 FMC scramble: D2 L U2 F2 L D' R2 B' D R2 B U' F' L2 R' D2 F L'

Here's my solution. I was doing well until I couldn't find a good LL. Shame. Well done on the NR Jude though!

Solution: F2 R B R' F2 R B2 R' F U' F2 B' R B' D' R' D B2 F' R F R' D R F D' F' D F D F' D' R' D B' D' (36)

Normal Scramble
Premove B' (to randomly move a block in F2L - helped with the 4th pair)
2x2x2: R .B' R' F U' F2 (6)
F2L-1: B' R B' D' R' D B2 F' R F R' (11)
Switch to inverse
4th pair: D B D' R D R' (6-1=5)
OLL+AUF: R F D' F' D' F D F' R' D' (10-1=9)
3 corner insertion at . R' F2 R B R' F2 R B' cancels 3 moves

So it was 22 move F2L but couldn't find anything better for LL. Anyone see anything good to with my LL?