Skip to content

Latest commit

 

History

History
311 lines (248 loc) · 12.3 KB

documentation.md

File metadata and controls

311 lines (248 loc) · 12.3 KB

========================= Description of the stages

Stage 1

Goal:

  • Orient the corner cubies.
  • Put the u- and d-layer edges into those two layers. (A d-layer edge may be in u layer, and a u-layer edge may be in the d layer.)

Turns allowed:

U, U', U2, u, u', u2, D, D', D2, d, d', d2,
L, L', L2, l, l', l2, R, R', R2, r, r', r2,
F, F', F2, f, f', f2, B, B', B2, b, b', b2

One-time whole cube rotations allowed: 120-degree turns (either direction) about the UFL-DBR axis.

There are 3 possibilities for each corner orientation and 8 corners so 3^8 possibilities. However, when setting the orientation of 7 corners, the 8th is fixed so only 3^7 = 2,187 cases.

For the edges, we have to record the position of 8 edges among 24 slots, so C^24_8 = 735,471 cases. This coordinate is reduced by symmetry. There are 48 symmetries, which let to only 15582 cases.

The overall space of this stage is 2,187 x 15,582 = 34,077,834.

Stage 2

Goal:

  • Put front and back centers onto the front and back faces into one of the twelve configurations that can be solved using only half-turn moves.
  • Arrange u- and d-layer edges within the u- and d-layers so that they will be in one of the 96 configurations that can be solved using only half-turn moves.

Turns allowed:

U, U', U2, u, u', u2, D, D', D2, d, d', d2,
       L2, l, l', l2,        R2, r, r', r2,
       F2, f, f', f2,        B2, b, b', b2

One-time whole cube rotations allowed: 90-degree turn about U-D axis.

As for edges of stage 1, there are C^24_8 = 735,471 cases for storing the position of the 8 F/B centers, and we also need to keep track of which center are F and which are B, requiring another C^8_4 = 70, so a total of 735,471 x 70 = 51,482,970. However, we don't need to track the exactly colour of those centers, but only if two centers are from the same or different colours. This reduce by a factor of two, giving 735,471 x 35 = 25,741,485. This (large) coordinate is reduced by symmetry (16 symmetries), giving 1,612,515 unique coordinates.

For the edges, the total number of permutations is 8! = 40,320 and there are 96 configurations that are considered solved (square group), so the coordinate is 40,320/96 = 420.

The overall space of this stage is 1,612,515 x 420 = 677,256,300

Stage 3

Goal:

  • Put centers for left and right faces into the left and right faces so that they are in one of the 12 configurations that can be solved using only half-turn moves. This leaves the centers for the U and D faces arbitrarily arranged in the U and D faces.
  • Put top and bottom layer edges into positions such that the U or D facelet is facing either up or down. Also, put these edges into an even permutation.

Turns allowed:

U, U', U2,        u2, D, D', D2,        d2,
       L2,        l2,        R2,        r2,
       F2, f, f', f2,        B2, b, b', b2

For centers, this is the same as for stage 2, except that now there are only 16 remaining slots for one center, as F and B faces are filled during stage 2. Using the same principle, the center coordinate is C^16_8 x C^8_4 = 12,870 x 35 = 450,450. Using symmetry reduction (8 in this stage), we only need to store 56,980 positions.

For edges, we need to put half of the edges in half of the positions, so C^16_8 = 12,870 cases. The even permutation required gives a extra factor of 2.

The overall space of this stage is 56,980 x 12,870 x 2 = 1,466,665,200.

Stage 4

Goal:

  • Put corners into one of the 96 configurations that can be solved using only half-turn moves.
  • Put U and D centers into one of the 12 configurations that can be solved using only half-turn moves.
  • Put all U- and D-layer edges into a configuration that can be solved using only half-turn moves. This consists of 96 possible configurations for the l- and r-layer edges, and 96 for the f- and b-layer edges.

Turns allowed:

U, U',U2, u2, D, D', D2, d2,
      L2, l2,        R2, r2,
      F2, f2,        B2, b2

The corner coordinate is exactly like the edge coordinate from stage 2, which gives 420 cases.

The remaining centers are already in the right faces, so we only need to put them in the right order: C^8_4 = 70. Using the same trick as for stage 2 and 3, we only need to keep 35 cases.

The edges are as the corners, except that there are two groups of edges so 420 x 420 = 176,400. In fact, only half of the cases happen, because of the parity condition from stage 3, so 88,200 real cases. We are doing the symmetry reduction on this coordinate (16 symmetries), which leave only 5,968 cases.

The overall size is 420 x 35 x 5,968 = 87,729,600

Stage 5

Goal:

  • Put all cubies into their solved position.

Turns allowed:

U2, u2, D2, d2,
L2, l2, R2, r2,
F2, f2, B2, b2

There are 96 positions for corners.

Edges are like 3 independent groups of corners, so 96 x 96 x 96 = 884,736 positions. We are doing a symmetry reduction, and we use a trick to get as much as 192 different symmetries, so that this coordinate has only 7,444 positions. In addition to the usual 48 symmetries of the cube, we add 4 cube rotations (generated by x2 and y2) because the cube can be in four different solved positions. This allows us to reduce this coordinate by a factor of 48 x 4 = 192.

For centers, each pairs of opposite centers have 12 different configurations, so 121212 = 1,728 positions.

The overall size is 967,4441,728 = 1,234,870,272

============== Cube structure

Edges

There are 24 "edge" cubies, numbered 0 to 23. The home positions of these cubies are labeled in the diagram below. Each edge cubie has two exposed faces, so there are two faces labelled with each number.

            -------------
            |    5  1   |
            |12   U   10|
            | 8       14|
            |    0  4   |
-------------------------------------------------
|   12  8   |    0  4   |   14 10   |    1  5   |
|22   L   16|16   F   21|21   R   19|19   B   22|
|18       20|20       17|17       23|23       18|
|    9 13   |    6  2   |   11 15   |    7  3   |
-------------------------------------------------
            |    6  2   |
            |13   D   11|
            | 9       15|
            |    3  7   |
            -------------

Corners

There are 8 "corner" cubies, numbered 0 to 7. The home positions of these cubies are labeled in the diagram below. Each corner cubie has three exposed faces, so there are three faces labelled with each number. Asterisks mark the primary facelet position. Orientation will be the number of clockwise rotations the primary facelet is from the primary facelet position where it is located.

           +----------+
           |*5*    *1*|
           |    U     |
           |*0*    *4*|
+----------+----------+----------+----------+
| 5      0 | 0      4 | 4      1 | 1      5 |
|     L    |    F     |    R     |    B     |
| 3      6 | 6      2 | 2      7 | 7      3 |
+----------+----------+----------+----------+
           |*6*    *2*|
           |    D     |
           |*3*    *7*|
           +----------+

Centers

There are 24 "center" cubies. They are numbered 0 to 23 as shown.

            -------------
            |           |
            |    3  1   |
            |    0  2   |
            |           |
-------------------------------------------------
|           |           |           |           |
|   10  8   |   16 19   |   14 12   |   21 22   |
|    9 11   |   18 17   |   13 15   |   23 20   |
|           |           |           |           |
-------------------------------------------------
            |           |
            |    6  4   |
            |    5  7   |
            |           |
            -------------

=============== Distance tables

Stage 1 - 48 symmetries

                Slice turns
          ------------------------
distance  positions         unique
--------  ---------         ------
   0              3              1
   1              6              1
   2            144              4
   3          2,796             66
   4         48,324          1,033
   5        745,302         15,620
   6     10,030,470        209,273
   7    103,416,912      2,155,397
   8    575,138,592     11,984,424
   9    826,559,202     17,222,730
  10     92,489,544      1,927,399
  11         43,782            916
      -------------    -----------
      1,608,475,077     33,516,864

Stage 2 - 16 symmetries

                Slice turns
          ------------------------
distance  positions         unique
--------  ---------         ------
   0             12              6
   1             36              8
   2            684             54
   3          9,254            661
   4        103,998          6,785
   5      1,149,674         73,297
   6     11,929,486        750,382
   7     92,729,838      5,803,099
   8    447,778,202     27,991,967
   9  1,247,722,776     77,990,037
  10  1,930,825,644    120,695,743
  11  2,215,400,576    138,498,874
  12  2,607,462,418    163,000,022
  13  1,828,141,454    114,282,664
  14    426,682,056     26,675,281
  15      1,487,536         93,585
  16             56              5
       ------------  -------------
     10,811,423,700    675,862,470

Stage 3 - 8 symmetries

                 Slice turns
           ------------------------
distance   positions         unique
--------   ---------         ------
   0               6              6
   1              12              4
   2             150             28
   3           1,556            230
   4          16,310          2,185
   5         169,240         21,630
   6       1,717,460        216,142
   7      16,888,105      2,115,779
   8     155,841,738     19,496,147
   9   1,219,752,205    152,510,075
  10   5,364,611,902    670,664,810
  11   4,687,652,572    586,031,875
  12     147,926,722     18,500,776
  13           5,021            732
  14               1              1
      --------------  -------------
      11,594,583,000  1,466,665,200

Stage 4 - 16 symmetries

                 Slice turns
           ------------------------
distance   positions         unique
--------   ---------         ------
   0               6              4
   1              12              3
   2             102             12
   3             640             56
   4           3,774            285
   5          20,482          1,475
   6         113,908          7,655
   7         629,922         40,711
   8       3,456,044        219,404
   9      17,629,510      1,110,842
  10      76,036,148      4,774,517
  11     233,265,250     14,621,516
  12     379,795,898     23,799,062
  13     369,324,336     23,143,536
  14     193,668,736     12,142,383
  15      22,539,628      1,420,768
  16          55,572          3,983
  17              32              8
       -------------    -----------
       1,296,540,000     81,286,220

Stage 5 ("Squares Coset") - 192 symmetries

                 Slice turns
           --------------------------
distance    positions          unique
--------    ---------          ------
   0                4               1
   1               48               2
   2              420               7
   3            3,456              36
   4           27,168             228
   5          203,752           1,429
   6        1,451,996           9,127
   7        9,527,856          55,967
   8       56,528,036         320,517
   9      295,097,696       1,636,219
  10    1,306,291,304       7,145,262
  11    4,761,203,264      25,797,686
  12   13,820,728,272      74,257,367
  13   29,956,341,744     159,930,965
  14   43,427,866,752     231,079,243
  15   36,297,535,208     193,022,572
  16   14,711,566,720      78,368,608
  17    2,063,584,704      11,055,492
  18       59,082,112         320,252
  19           45,056             244
      ---------------   -------------
      146,767,085,568     783,001,224