## Mad Octahedron

Submitted by B MacKenzie on Thu, 06/21/2018 - 09:47.I have written a computer simulation of the octahedral twisty puzzle. It is available as freeware on the Apple App Store:

Mad Octahedron## Future URL recommendation for the forum

Submitted by cubex on Tue, 05/08/2018 - 14:21.In the future I think it would be a good idea if we all used URLs of the form:

http://forum.cubeman.org/?q=node/view/563#comment

rather than

http://cubezzz.dyndns.org/?q=node/view/563#comment

dyndns.org has raised their prices every year and I'm considering

dropping their service. Unfortunately if we do that a lot of old URLs will stop

working, so I'm open to any clever ideas on what is the best way to deal with

this problem. I'm committed to keeping the maxhost.org and

cubeman.org domain names working for the long term, but

I'm very unhappy with dyndns.

## Three Million Positions in Four Metrics

Submitted by rokicki on Mon, 04/23/2018 - 10:52.These positions are distinct from the three million positions I ran

some years back. Random numbers were generated with the Mersenne

Twister algorithm. The four metrics I ran were quarter-turn metric,

half-turn metric, slice-turn metric, and axial-turn metric (equivalent

to the robot-turn or simultaneous-turn metric on the 3x3 cube).

The generators for each metric are strict super- or sub-sets of the

generators for the other metrics. The quarter-turn metric has 12

generators, the half-turn metric has 18 generators, the slice-turn

## Presentation for the Mathieu Group M24 from dedge superflip

Submitted by Paul Timmons on Fri, 04/20/2018 - 20:58.

**< a,b,c | a ^{2} = b^{2} = c^{2} = 1,
**

** (ab) ^{6} = [(bc)^{6}] = [(ca)^{6}] = 1,
**

** bacabacacabacababacabac = 1,
**

** (ababacbc) ^{3} = 1,
**

** bababcbcbcbabab = cacabacacabacac** >

## Gear cube extreme can be solved in 25 moves

Submitted by Ben Whitmore on Thu, 02/15/2018 - 23:07.The first phase is easy to compute. There are only 3^8 = 6561 positions because each gear has only 3 different orientations, despite having 6 teeth.

Phase 1 distribution:

Depth New Total 0 1 1 1 4 5 2 8 13 3 78 91 4 102 193 5 1064 1257 6 920 2177 7 3576 5753 8 592 6345 9 216 6561 10 0 6561The second phase is harder. The number of positions is 24*8!^2/2 = 19,508,428,800, since it turns out that the permutation of the 3 unfixed edges on the E slice is completely determined by the permutation of the centres. This phase was solved with a BFS and took around 7 and a half hours to complete.

## Kilominx can be solved in 34 moves

Submitted by Ben Whitmore on Sun, 02/11/2018 - 12:58.The ⟨U,R,F⟩ subgroup, while much smaller than G_0, is still pretty large, having 36 billion states. It's small enough that a full breadth-first search can be done if symmetry+antisymmetry reduction is used, but I will leave this for another time.

## 5x5 sliding puzzle can be solved in 205 moves

Submitted by Ben Whitmore on Fri, 01/26/2018 - 17:46.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24We can solve the puzzle in three steps. First solve 1,2,3,4,5,6,7, then solve 8,9,10,11,12,16,17,21,22, and finally solve the 8 puzzle in the bottom right corner. Step 1 requires 91 moves:

depth new total 0 18 18 1 6 24 2 13 37 3 27 64 4 54 118 5 117 235 6 231 466 7 443 909

## God's algorithm for the <2R, U> subset of the 4x4 cube

Submitted by Ben Whitmore on Wed, 01/24/2018 - 22:00.Depth New Total 0 1 1 1 6 7 2 18 25 3 54 79 4 162 241 5 486 727 6 1457 2184 7 4360 6544

## Do we have a 3x3x3 optimal solver for stm metric?

Submitted by cubex on Thu, 08/10/2017 - 06:46.Also is it true we don't know if using slice turns plus face turns could reduce God's Number from 20 to less than 20?

## More details about my new program

Submitted by Jerry Bryan on Thu, 06/08/2017 - 14:55.
**Introduction**

On 02/23/2016, I posted a message about a new program I had developed that had succeeded in enumerating the complete search space for the edges only group. It was not a new result because Tom Rokicki had solved the same problem back in 2004, but it was important to me because the problem served as a testbed for some new ideas I was developing to attack the problem of the full cube. I am now in the process of adapting the new program to include both edges and corners. In this message, I will include some additional detail about my new program that was not included in the first message.