Lower bound for Megaminx in htm and qtm

Discussion in 'Puzzle Theory' started by Herbert Kociemba, Mar 1, 2012.

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  1. Herbert Kociemba

    Herbert Kociemba Member

    138
    3
    Nov 29, 2008
    I analyzed the number of generic move sequences to get lower bounds for God's number of Megaminx, taking into account the commutativity of moves. There are a lot of commutating moves because of the many disjoint faces of Megaminx. In htm, I found a lower bound of 45 moves and in qtm a lower bound of 55 moves.

    I posted the details here:

    http://cubezzz.dyndns.org/drupal/?q=node/view/328
     
  2. qqwref

    qqwref Member

    7,822
    5
    Dec 18, 2007
    a <script> tag near you
    WCA:
    2006GOTT01
    YouTube:
    qqwref2
    I made a somewhat similar recursion a while back and ended up with, I think, 43 moves for the Megaminx. I'm not sure exactly where our techniques differ, but I do like this technique in general, as you can get some pretty nice results without a huge amount of work.
     
  3. Herbert Kociemba

    Herbert Kociemba Member

    138
    3
    Nov 29, 2008
    I assume, the techniques differ somehow, because the difference between 43 und 45 means that you have more than 1000 times the number of move sequences with 45 moves.
    I would be really pleased, if
    1. Someone could double check, that there are 25 unordered pairs of faces (X,Y), which have no pieces in common and either X or Y (or both) have pieces in common with some arbitrary different fixed face,e.g. U.
    2. The same for 15 unordered triples (X,Y,Z), which have no pieces in common and either X or Y or Z have pieces in common with another different face, for example the U face.
    3. Compute the true number of positions of Megaminx out to some depth in htm and qtm to check if the numbers are the same for the first ??? depths. This depends on the length of the shortest nontrivial identity. Btw, What is the shortest nontrivial identity on Megaminx?
     
    Last edited: Mar 1, 2012
  4. Lucas Garron

    Lucas Garron Super-Duper Moderator Staff Member

    At most 10 moves. FRU'R'U2F'L'ULU2' works on Megaminx.
     
  5. TMOY

    TMOY Member

    1,802
    0
    Jun 29, 2008
    WCA:
    2008COUR01
    The niklas done the wrong way (L' U R U' L U R' U') is a 8-move identity.
     

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