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 Post subject: The «hardest position» (according to http://cube20.org/)
PostPosted: Sun Jan 16, 2011 9:00 am 
Quote:
http://cube20.org/
The hardest position for our programs.
Hello, twisty puzzles legends, utillising the scramble for the «hardest
position», let us have a look at a sample solve illustrating the classic

block building technique and inserting algorithm(s)
to cancel moves. In particular, we will see the optimisation of a first
«fewest moves» solution by moving the three-corner-cycle from the
end of the solution to the beginning (second solution) or by insertion
at a suitable position (third solution) in order to cancel some moves.
Quote:
http://cube20.org/
The following position was the hardest for our programs to solve:

Image
scramble
F U' F2 D' B U R' F' L D' R' U' L U B' D2 R' F U2 D2
Image

first solution (block building)
block 2*2*2: F B L2 D L' U' R2 B R' D (=10)
block 2*2*3: B2 L' B2 L (+4 =14)
plus 1*2*2: B' R' B R' (+4 =18)
block 2*3*3: U R U' R' (+4 =22)
3*3*3: . F' U2 F' D' F U2 F' D F2 . U2 (+9+1 =32)
32 moves (40q, 32f, 32s) in <35 minutes
ImageImage


second solution (based on first)
3-corner-cycle: . F' U2 F' D' F U2 F' D (F2... . (=9)
block 2*2*2: ...F) B L2 D L' U' R2 B R' D (-1+10 =18)
block 2*2*3: B2 L' B2 L (+4 =22)
plus 1*2*2: B' R' B R' (+4 =26)
block 2*3*3: U R U' R' (+4 =30)
3*3*3: U2 (+1 =31)
31 moves (38q, 31f, 30s) in <40 minutes
Image :solved: Image


third solution (also based on first)
block 2*2*2: F B L2 D L' U' R2 B R' D (=10)
block 2*2*3: B2 L' B2 L (+4 =14)
3-corner-cycle: . R' F R B' R' F' (R B) . (+8-2 =20)
plus 1*2*2: (B' R') B R' (-2+4 =22)
block 2*3*3: U R U' R' (+4 =26)
3*3*3: U2 (+1 =27)
27 moves (32q, 27f, 25s) in <55 minutes
ImageImage

And now, for your viewing pleasure, check out the following animations.

ImageImageImage


Image :scrambled:
computer-generated solutions by
http://software.rubikscube.info/JACube/JACube31c.zip
java -cp ACube3.jar ACube af
...
-UF -UR -UB -UL -DF -DR -DB -DL -BR -BL -FR -FL +UBL +ULF +UFR +URB -DLB -DBR -DRF -DFL
...
depth 12...
...
L U' B R2 D R' F L U' L2 B' L' . U2 F2 D' L2 B2 R2 B2 U L2 D2 F2 (34q, 23f, 23s)
...
23 moves in <1 minute
...
depth 14...
...
L D2 F' U L' B R' F' U' B2 L' U2 D F . R2 U F2 U B2 R2 D B2 (30q, 22f, 22s)
L B' U' F L D R B U' L U D' F2 R' . D F2 L2 D' R2 F2 L2 U (28q, 22f, 22s)
L B' U' F L D R B U' L E R2 B' . D R2 F2 D' B2 R2 F2 U (28q, 22f, 21s)
...
22 moves in <5 minutes
...
depth 15...
...
L B2 U F R2 D L R2 B L2 R F D L2 F' . L2 F2 U' F2 L2 U (30q, 21f, 21s)
...
21 moves in <55 minutes
...
depth ??...
...
20 moves in ?? hours


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 Post subject: Re: The «hardest position» (according to http://cube20.org/)
PostPosted: Sun Jan 16, 2011 9:47 am 
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Joined: Tue Mar 10, 2009 7:06 pm
Location: Nowhere in particular.
Just tried it with Fridrich, and it actually flowed quite nicely. Easy cross, easy pairs, edge orientation already done...

Hmm, I'm going to have to keep trying this one. :P

_________________
~Kapusta

PB: At home (In Competition)
2x2 1.xx (2.88)
3x3 11.xx (15.81)
4x4 1:18.26 (1:24.63)
5x5 (3:00.02)
6x6 4:26.05 (6:34.68)
7x7 6:38.74 (9:48.81)
OH (35.63)

Current Goals:
7x7 sub 6:30
4x4 sub 1:10


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 Post subject: Re: The «hardest position» (according to http://cube20.org/)
PostPosted: Sun Jan 16, 2011 11:45 am 
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Joined: Wed Oct 01, 2008 2:39 pm
Location: Marquette, MI, USA
I think one of the reasons this is so difficult is the fact there are no "good" edges when doing the first cross. they all require multiple moves no matter what ones you choose.


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 Post subject: Re: The «hardest position» (according to http://cube20.org/)
PostPosted: Sun Jan 16, 2011 12:09 pm 
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Joined: Thu Sep 24, 2009 12:21 pm
Location: Chichester, England
Easy solve. I got 13.34 seconds on it. I scrambled with yellow on top, and each of the edges on the white side were perfect. Each one put the next one into the correct position, and then after that all you had to do was a U move.

_________________
3x3x3 single: 5.73 seconds.
3x3x3 average of five: 8.92 seconds.
3x3x3 average of twelve: 9.77 seconds.

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 Post subject: Re: The «hardest position» (according to http://cube20.org/)
PostPosted: Sun Jan 16, 2011 4:44 pm 
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Joined: Wed May 13, 2009 4:58 pm
Location: Vancouver, Washington
Saying it's hard for the computer is not even close to the same thing as saying it's hard for people. It's a completely meaningless statistic imo. The programmers could switch the order that it tries difference faces and then all of the sudden, this could be an easy cube and some other random cube would be the hardest.

It kind of makes me mad that they even mention that that cube is the "harderst" because it's really not.

_________________
Real name: Landon Kryger


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