## Optimal solutions to the Eliac puzzle

Submitted by Ben Whitmore on Sat, 05/18/2019 - 16:13.The Eliac is a complex deep-cut 2-gen circle puzzle:

The left circle rotates in increments of 90 degrees and the right circle rotates only by 180 degrees. There is a simulator of the puzzle here.

Using ksolve++ I made an optimal solver modified it slightly to turn it into a coset solver. The subgroup I used for the coset solver is the subgroup of positions where the 18 small triangles, 10 diamonds, and 2 squares are solved. There are 1600300800 arrangements of those 30 pieces and each coset has 3024000 solvable positions. Unfortunately since the puzzle is 2-gen, there isn't a good way to select a subgroup generated by a subset of the generators of the whole puzzle, which (as far as I can tell) is what is required in order to make the "pre-pass" trick work for sub-optimally solving cosets very quickly. So each coset needs to be solved optimally using a pure DFS, which takes quite a long time (about 1.5 hours on my laptop). Notice that the puzzle has a horizontal reflection symmetry so we only need to solve one coset in each symmetry class.

The left circle rotates in increments of 90 degrees and the right circle rotates only by 180 degrees. There is a simulator of the puzzle here.

Using ksolve++ I made an optimal solver modified it slightly to turn it into a coset solver. The subgroup I used for the coset solver is the subgroup of positions where the 18 small triangles, 10 diamonds, and 2 squares are solved. There are 1600300800 arrangements of those 30 pieces and each coset has 3024000 solvable positions. Unfortunately since the puzzle is 2-gen, there isn't a good way to select a subgroup generated by a subset of the generators of the whole puzzle, which (as far as I can tell) is what is required in order to make the "pre-pass" trick work for sub-optimally solving cosets very quickly. So each coset needs to be solved optimally using a pure DFS, which takes quite a long time (about 1.5 hours on my laptop). Notice that the puzzle has a horizontal reflection symmetry so we only need to solve one coset in each symmetry class.

## Remember to use http://forum.cubeman.org

Submitted by cubex on Sun, 05/12/2019 - 19:56.Hi folks,

This is a notice that http://cubezzz.dyndns.org/drupal will probably stop working tomorrow. Please use http://forum.cubeman.org instead.

The similar http://cubezzz.duckdns.org/drupal should also work.

More news to come soon.

This is a notice that http://cubezzz.dyndns.org/drupal will probably stop working tomorrow. Please use http://forum.cubeman.org instead.

The similar http://cubezzz.duckdns.org/drupal should also work.

More news to come soon.

## {4,3,3} 3 symmetry

Submitted by Jakub Stepo on Sun, 02/24/2019 - 06:09.Hello, I am new to this forum and this is my first post. I know that maybe its content will seem trivial to some of you, but I am afraid that I am not so well versed in mathematics and programming, so I try to do at least something within my limited capabilities (I am 15.34 at the moment).

Based on Dan Hoey’s calculations, I was able to calculate the number of essentially different positions up to symmetry of the four-dimensional analogue of the Rubik’s cube. However, it is quite probable that I have made some mistakes, as I have done it only by hand. Nevertheless, from the patterns observed I was able to make some interesting generalizations, presented later in this post.

Based on Dan Hoey’s calculations, I was able to calculate the number of essentially different positions up to symmetry of the four-dimensional analogue of the Rubik’s cube. However, it is quite probable that I have made some mistakes, as I have done it only by hand. Nevertheless, from the patterns observed I was able to make some interesting generalizations, presented later in this post.

## The 2018 Computer Fewest Moves Challenge is Underway

Submitted by NoLongerUnsolve... on Thu, 10/18/2018 - 06:53.For the first time, the FMC will have solvers in the "NxNxN" category for up to 9x9x9 competing to solve 10 random scrambles in as few moves as possible. Also of note: There are now four solvers in the 5x5x5 section.

For those who are interested, visit:

http://cubesolvingprograms.freeforums.net/

For those who are interested, visit:

http://cubesolvingprograms.freeforums.net/

## Lower bound for the diameter of the 3-gen subgroup <U,F,R>

Submitted by Ben Whitmore on Sun, 09/02/2018 - 22:00.What are the known bounds for the diameter of this subgroup? This thread gives a lower bound of 26 QTM but doesn't discuss HTM. I seem to recall a lower bound of 20 HTM from somewhere, but no upper bound. However, I recently found a position that requires 21 HTM:

U R F2 R U2 F2 U' F' R U F U R' F R2 U F R U2 R F'Is this the first one known? Out of all 186624 positions with all pieces correctly permuted, this position and the inverse are the only ones requiring 21. Here's the full distribution:

Depth Positions

» 13 comments | read more

## 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.Hello everybody :)

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.

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.I optimally solved three million positions in four distinct metrics.

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

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

» 7 comments | read more

## Presentation for the Mathieu Group M24 from dedge superflip

Submitted by Paul Timmons on Fri, 04/20/2018 - 20:58.Following on from a highly symmetric presentation I supplied for the miniature Rubiks cube group
Presentation for the 2x2x2 Rubiks cube group
I investigated whether the Mathieu Group M24 could be similarily presented taking full advantage of the
plentiful symmetry inherent in the Rubiks Revenge cube (4x4x4). The answer was indeed yes - here is the presentation I found - again on three involutions:

**< 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.Write the puzzle as the group <R,F,U,D> where R and F are 180 degree moves. We use a two-phase algorithm to first reduce the state of the puzzle to the subgroup <R3,F3,U,D>, and then finish the solve in the second phase. The subgroup <R3,F3,U,D> is the group of all positions where all of the gears are oriented, because R3 is the same as R' except the gear orientation remains unchanged.

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:

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.