One Million Random Twenty-Four Puzzle Instances in the STM metric

I have solved sub-optimally 1,000,000 random instances of 5x5 sliding tile puzzle in STM metric (single-tile moves). The actual running time was about 18,5 hours. The minimum, maximum and average solution length were 73, 171 and 124.48 moves respectively. About 52% of 1,000,000 solutions were in range [118; 132]. There were only 32 instances with (suboptimal) solution length less than 81 (range [73; 80]). Only one instance was solved in 171 moves.

The suboptimal solver (kumi na tano 3.10 in batch mode) uses four phases as on the diagram below.

1 1 1 1 1
2 3 3 3 3
2 3 4 4 4
2 3 4 4 4
2 3 4 4 x

Along with this scheme, mirror reflection through main diagonal was also used. The program was allowed only to optimal solutions on each phase (the "slackness" value was limited to 0).

The header of the report is given below. The full report from batch solver can be downloaded from (7z archive) or (zip archive). The archive contains two text files: report.txt is the report, and instances.txt is just list of all solved configurations without any additional information. The archive expands to about 200 MB.

Puzzle:               5 x 5
Move metric:          STM

Start search at:      off
Stop search at:       off
Start with slackness: off
Stop at slackness:    1
Time limit:           off
Right turns only:     off

Instances Solved:     1000000
Total Time:           67102.171 s
Average Time:         67.102 ms
Min. Length:          73
Max. Length:          171
Average Length:       124.4809
Total rNodes:         1505742903
Average rNodes:       1505.7429

    length          count
        73              2
        74              4
        75              2
        76              4
        77              4
        78              5
        79              7
        80              4
        81             17
        82             24
        83             26
        84             46
        85             66
        86             96
        87             97
        88            154
        89            173
        90            304
        91            331
        92            515
        93            530
        94            745
        95            873
        96           1196
        97           1428
        98           1926
        99           2260
       100           2882
       101           3367
       102           4293
       103           4814
       104           5996
       105           6722
       106           8557
       107           9025
       108          11264
       109          11948
       110          14706
       111          15629
       112          18661
       113          19246
       114          23049
       115          23429
       116          27506
       117          27353
       118          31613
       119          30715
       120          35137
       121          33700
       122          37859
       123          35612
       124          39417
       125          36343
       126          39202
       127          35806
       128          38200
       129          33875
       130          35289
       131          31161
       132          31747
       133          27451
       134          27206
       135          23205
       136          22558
       137          18707
       138          17872
       139          14648
       140          13744
       141          10780
       142           9897
       143           7697
       144           6765
       145           5214
       146           4616
       147           3453
       148           2849
       149           2078
       150           1777
       151           1167
       152            956
       153            661
       154            522
       155            373
       156            298
       157            166
       158            141
       159             65
       160             61
       161             48
       162             23
       163             20
       164              4
       165              5
       166              6
       167              2
       168              2
       171              1

I have attempted to run the same batch in MTM metric; however, the number of alternative optimal solutions for each phase in this metric is significantly larger, and each instance requires 20 seconds in average to finish search with slackness = 0 (compared to 67 milliseconds in STM metric). So I've solved only 100 random instances in MTM metric with the same settings (searching only for optimal solutions for each phase). Results are given below.

Puzzle:               5 x 5
Move metric:          MTM

Start search at:      off
Stop search at:       off
Start with slackness: off
Stop at slackness:    1
Time limit:           off
Right turns only:     off

Instances Solved:     100
Total Time:           2001.022 s
Average Time:         20.010 s
Min. Length:          49
Max. Length:          72
Average Length:       64.3000
Total rNodes:         808429478
Average rNodes:       8084294.7800

    length          count
        49              1
        57              5
        58              6
        59              3
        60              2
        61              8
        62             11
        63              6
        64              7
        65             12
        66              7
        67              7
        68              8
        69              6
        70              1
        71              4
        72              6

Goal configuration: Blank Last 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 0

Regions (6):
 A  fixed tiles: { }, current tiles: { 1 2 3 4 5 }
 B  fixed tiles: { 1 2 3 4 5 }, current tiles: { 6 11 16 21 }
 C  fixed tiles: { }, current tiles: { 1 6 11 16 21 }
 D  fixed tiles: { 1 6 11 16 21 }, current tiles: { 2 3 4 5 }
 E  fixed tiles: { 1 2 3 4 5 6 11 16 21 }, current tiles: { 7 8 9 10 12 17 22 }
 F  fixed tiles: { 1 2 3 4 5 6 7 8 9 10 11 12 16 17 21 22 }, current tiles: { 13 14 15 18 19 23 }

Chains (2):
   [A,B,E,F]    45
   [C,D,E,F]    55

    #                                                           Instance  Length   Time, ms     rNodes      Chain
                                                                                  
    1   17 10 16 4 7 14 19 1 20 5 24 8 6 22 21 9 13 3 18 12 15 23 2 11 0      68      15625    2364109  [A,B,E,F]
    2   19 5 4 20 9 22 14 21 17 6 10 24 1 3 12 8 16 11 2 13 0 23 15 7 18      66       4516     329536  [C,D,E,F]
    3   9 14 2 6 22 4 13 18 7 16 20 5 10 8 24 23 17 21 12 0 11 19 1 15 3      72      10890    3288922  [C,D,E,F]
    4   23 16 5 3 12 6 18 7 24 10 19 17 9 20 8 0 1 13 15 4 21 22 14 2 11      63      81734   30454580  [C,D,E,F]
    5   1 6 14 12 15 24 22 13 16 7 0 8 19 18 20 2 3 23 11 10 17 21 4 9 5      66       2344     862938  [A,B,E,F]
    6   17 23 12 14 22 10 2 19 15 7 18 4 6 3 21 1 13 16 20 0 8 5 11 9 24      64      10547    3321975  [A,B,E,F]
    7   5 20 10 17 7 6 11 13 12 8 9 4 3 2 16 24 21 15 22 19 0 1 14 23 18      64      63281   25227109  [A,B,E,F]
    8   18 0 5 13 15 17 24 21 9 19 11 22 6 7 14 2 8 16 12 4 23 10 20 3 1      68       4266    1942328  [C,D,E,F]
    9   20 12 8 23 16 6 7 14 19 2 0 18 21 17 13 22 10 1 3 11 24 9 5 4 15      65       4844    1301122  [A,B,E,F]
   10   22 16 14 21 19 20 2 17 5 3 4 13 12 18 15 10 11 0 9 23 8 6 24 1 7      72       2265     264099  [C,D,E,F]
   11   5 10 13 0 3 17 9 4 6 8 18 7 2 19 15 20 14 12 21 23 11 16 22 1 24      57      50484   20508436  [C,D,E,F]
   12   15 23 7 2 4 17 24 5 16 0 19 10 8 13 14 9 12 11 1 3 22 6 20 21 18      65      16422    4338673  [A,B,E,F]
   13   7 16 21 19 9 4 13 5 6 8 10 24 14 20 23 17 3 2 0 18 12 1 11 15 22      61       1453     543453  [A,B,E,F]
   14   14 8 11 7 17 1 23 13 15 0 12 16 22 6 10 18 4 21 3 19 9 5 2 24 20      58      67641   20815945  [C,D,E,F]
   15   17 2 0 24 18 12 23 5 3 13 15 22 14 6 7 4 21 1 19 20 8 10 16 11 9      62       3390     579982  [C,D,E,F]
   16   18 11 23 1 5 16 17 2 0 4 20 3 12 10 9 22 24 6 14 15 21 19 13 8 7      49        422      85282  [A,B,E,F]
   17   2 0 11 16 9 19 23 10 8 4 5 12 15 20 13 18 21 6 3 14 7 22 24 1 17      66       4547    1215456  [A,B,E,F]
   18   21 24 8 20 14 11 12 10 0 22 2 6 7 5 23 9 4 19 3 13 18 15 16 17 1      67       4953    1086766  [A,B,E,F]
   19   6 17 0 4 7 13 22 14 16 23 19 2 1 5 20 21 24 3 10 12 11 8 9 18 15      58      10937    4702300  [A,B,E,F]
   20   4 3 14 2 11 12 20 21 15 17 16 13 5 22 18 8 6 10 9 7 19 0 1 24 23      68        484      78615  [A,B,E,F]
   21   21 19 17 15 24 13 11 3 4 20 0 10 6 7 12 5 14 16 9 1 18 23 2 22 8      64      61734   28688899  [A,B,E,F]
   22   1 5 24 4 14 22 6 16 2 3 0 17 19 9 10 18 11 15 23 7 13 21 8 20 12      57        266      19261  [C,D,E,F]
   23   24 14 0 12 6 3 4 1 19 17 23 16 2 15 11 18 10 20 5 9 22 21 13 8 7      63       3453     736051  [C,D,E,F]
   24   23 21 10 3 24 4 0 5 11 18 9 22 14 13 6 1 19 16 12 17 7 15 20 8 2      69      14469    2403736  [C,D,E,F]
   25   11 18 9 12 1 20 4 17 10 5 13 8 0 6 19 21 14 2 15 16 22 24 7 3 23      59       5500    1645635  [C,D,E,F]
   26   2 10 21 13 12 11 17 4 1 23 14 16 18 19 8 24 3 0 5 15 6 9 7 22 20      61       1782     837255  [C,D,E,F]
   27   16 6 10 2 21 23 15 20 17 0 24 7 1 4 19 13 9 5 11 12 8 18 3 22 14      61      36156   16022992  [A,B,E,F]
   28   19 9 15 0 22 6 21 16 14 18 12 1 4 17 3 13 10 23 7 11 24 2 20 5 8      66        469     204538  [C,D,E,F]
   29   0 7 8 2 22 12 20 23 5 16 3 15 17 6 10 19 13 21 9 18 1 14 4 11 24      66      11546    4913908  [C,D,E,F]
   30   13 11 3 14 22 24 19 8 17 21 1 4 9 0 15 18 6 7 12 16 10 2 5 23 20      62      17687    8755985  [A,B,E,F]
   31   9 5 24 19 2 13 18 10 6 14 12 22 23 4 7 0 16 21 3 8 11 20 1 15 17      63      14625    5705597  [C,D,E,F]
   32   17 6 21 16 1 5 18 19 4 15 2 14 12 23 7 8 10 3 9 11 0 22 13 24 20      62      60906   24395670  [A,B,E,F]
   33   7 16 17 6 18 14 21 20 11 0 24 10 12 23 4 9 3 8 5 15 19 2 1 22 13      65      63313   24722577  [C,D,E,F]
   34   7 8 0 23 21 15 20 22 3 6 2 19 24 10 14 16 17 11 18 9 5 1 4 13 12      66     274625  111291709  [C,D,E,F]
   35   8 11 24 6 1 10 14 13 15 19 5 0 7 18 16 9 22 23 2 20 17 12 21 3 4      64       8735    3240705  [A,B,E,F]
   36   9 3 23 13 21 18 1 19 14 4 8 20 22 5 15 6 24 10 11 7 12 2 0 17 16      61       3500    1131400  [A,B,E,F]
   37   5 16 15 2 21 19 17 22 6 8 4 13 1 23 7 18 24 10 9 20 11 12 0 3 14      65      60016   26948453  [C,D,E,F]
   38   1 20 18 7 24 16 10 9 3 2 21 11 5 12 0 19 4 13 6 14 17 23 8 22 15      57       2391     789338  [C,D,E,F]
   39   9 17 13 6 19 8 15 16 21 14 23 5 11 7 22 18 2 0 4 24 3 10 1 12 20      61       2235     978543  [A,B,E,F]
   40   15 1 3 20 21 7 18 6 5 0 24 17 9 11 10 13 23 12 19 8 4 16 2 14 22      67      12672    5648079  [C,D,E,F]
   41   2 1 8 23 21 4 5 11 6 18 17 22 12 14 0 16 19 7 3 15 13 9 24 20 10      62       5391    1979476  [A,B,E,F]
   42   20 2 24 19 18 5 6 0 3 23 4 8 9 11 7 22 10 15 12 13 14 1 17 21 16      58       7062    2267176  [C,D,E,F]
   43   7 11 1 6 16 14 23 0 18 21 5 4 15 24 22 10 9 19 17 20 2 13 3 8 12      71      66031   34794500  [C,D,E,F]
   44   15 9 20 10 18 22 17 5 8 7 11 0 3 4 23 24 13 12 6 2 14 21 1 16 19      65       5750     989661  [A,B,E,F]
   45   17 23 2 14 12 4 6 11 0 20 9 21 15 10 16 5 19 18 13 24 8 3 22 1 7      65       8781    4018920  [C,D,E,F]
   46   24 9 22 3 8 18 11 19 21 2 5 6 15 7 1 0 10 16 17 12 4 23 20 13 14      71      19578    7299144  [A,B,E,F]
   47   11 10 4 14 0 18 20 21 2 23 12 5 8 9 13 3 24 15 19 7 6 1 22 17 16      67       1187     139938  [A,B,E,F]
   48   3 23 9 2 10 18 12 14 15 8 17 19 0 1 22 5 13 24 11 20 6 4 21 16 7      63       5578    2752704  [C,D,E,F]
   49   1 20 12 5 6 23 2 9 22 7 11 17 18 0 19 8 4 16 3 21 24 10 13 15 14      61       1860     438761  [C,D,E,F]
   50   4 0 21 13 14 8 19 11 9 7 1 6 2 16 23 15 12 3 20 24 10 18 22 17 5      62      20719    9676830  [C,D,E,F]
   51   10 4 23 3 1 8 0 16 7 9 21 11 18 22 17 2 13 24 14 5 6 12 19 15 20      62       2344     993458  [C,D,E,F]
   52   15 18 11 0 13 14 23 1 2 19 7 3 12 4 5 8 16 21 20 24 17 6 22 10 9      59       2047     607672  [A,B,E,F]
   53   15 9 24 6 21 5 8 13 17 12 22 14 19 18 16 20 3 10 0 1 4 2 23 7 11      69     126422   61608710  [A,B,E,F]
   54   19 5 23 10 0 17 8 9 18 4 6 2 1 22 7 21 11 16 12 24 3 13 20 14 15      57       1328     199642  [C,D,E,F]
   55   3 2 1 23 17 9 19 8 6 12 5 0 13 22 24 18 7 11 10 20 15 21 4 16 14      66       7047    1471169  [A,B,E,F]
   56   7 16 3 4 0 12 8 18 6 19 23 21 1 13 2 10 9 17 20 15 24 11 22 5 14      62        297      51387  [C,D,E,F]
   57   1 20 3 2 8 15 13 12 21 22 5 23 19 10 11 0 24 9 7 16 4 17 18 6 14      68       7656    3334984  [A,B,E,F]
   58   1 5 24 23 13 18 9 8 17 14 16 11 2 6 15 20 10 22 7 3 21 4 12 0 19      58        218      23925  [C,D,E,F]
   59   4 13 20 21 16 10 15 6 23 1 2 19 14 12 11 3 22 7 17 24 9 5 0 8 18      65      38860    9974118  [C,D,E,F]
   60   22 4 24 16 13 12 2 1 18 3 5 10 11 15 23 14 6 8 19 0 20 7 17 9 21      68       1375     143252  [A,B,E,F]
   61   13 9 5 8 7 18 14 15 17 20 3 1 16 19 21 2 6 23 22 10 11 24 4 0 12      61       2672    1006829  [C,D,E,F]
   62   3 24 21 19 15 22 0 14 11 10 5 1 13 9 16 6 17 23 8 2 4 12 20 7 18      68       2765     977561  [C,D,E,F]
   63   8 22 0 24 23 20 10 17 1 6 11 21 9 5 14 4 7 15 12 16 2 13 18 3 19      70       7485    1241101  [A,B,E,F]
   64   21 5 24 12 2 22 14 3 6 15 16 11 9 4 10 8 18 20 23 1 17 13 19 7 0      64       4188     523962  [C,D,E,F]
   65   17 4 1 18 11 16 9 21 7 24 3 15 2 8 14 19 12 6 23 0 20 10 13 22 5      62       5547    1796898  [A,B,E,F]
   66   20 4 23 15 12 21 24 7 8 18 2 1 22 6 19 5 14 0 3 9 10 16 17 13 11      69      15094    1793012  [C,D,E,F]
   67   23 15 14 12 1 3 8 11 22 24 6 21 10 4 9 2 17 7 5 0 19 20 13 16 18      64       9062    1430957  [C,D,E,F]
   68   7 6 17 4 9 0 21 2 12 20 10 1 15 8 3 11 13 23 16 14 18 5 24 22 19      58        734      73969  [A,B,E,F]
   69   10 16 4 15 18 0 6 11 22 24 8 3 1 13 9 17 7 19 12 14 21 5 23 20 2      65        922     100400  [C,D,E,F]
   70   10 19 18 0 6 5 3 17 2 13 9 22 21 11 16 24 23 1 15 8 20 4 12 7 14      68       1094     244580  [C,D,E,F]
   71   17 22 15 21 0 8 9 6 4 5 16 1 11 19 2 12 7 23 20 10 24 18 14 13 3      58      54766   26183863  [C,D,E,F]
   72   5 7 6 11 14 17 3 1 24 0 4 9 2 23 13 22 16 21 15 12 18 20 10 19 8      59       2562    1011956  [A,B,E,F]
   73   7 16 5 21 10 1 12 9 15 24 8 14 23 19 18 13 2 6 3 0 20 17 22 4 11      60      20875    7108795  [A,B,E,F]
   74   13 7 19 24 4 23 15 18 22 5 21 16 3 14 11 1 17 10 2 9 0 6 8 12 20      65       1469     319130  [A,B,E,F]
   75   20 3 0 15 23 1 12 13 5 10 8 22 21 6 11 2 7 14 24 17 9 16 18 19 4      61       3704    1241366  [A,B,E,F]
   76   7 21 24 8 9 16 10 6 11 23 2 0 15 12 17 3 4 22 1 5 20 19 18 13 14      68       1579     223532  [C,D,E,F]
   77   18 20 19 10 12 23 8 11 24 5 0 16 17 4 15 22 2 9 6 13 7 21 14 3 1      69       3079     625239  [C,D,E,F]
   78   23 15 14 6 4 20 17 19 10 21 2 24 22 0 1 13 18 16 11 9 8 7 3 5 12      72      14765    5273099  [A,B,E,F]
   79   10 3 12 23 22 16 0 5 4 17 7 19 8 13 21 6 15 2 11 9 20 14 18 1 24      65       9313    3075238  [C,D,E,F]
   80   9 2 20 17 18 15 11 23 6 7 12 4 14 24 19 13 21 8 16 1 10 3 5 22 0      67      42469   19436832  [C,D,E,F]
   81   3 17 12 7 21 18 10 20 13 15 6 22 19 0 4 9 16 1 8 23 11 2 5 24 14      63      96750   46267106  [A,B,E,F]
   82   8 17 14 6 15 5 18 21 2 9 13 11 1 12 23 3 22 20 7 16 24 19 4 10 0      64      35344   15834118  [C,D,E,F]
   83   6 14 23 15 16 24 7 19 10 20 18 3 4 0 2 13 9 12 21 5 1 22 8 11 17      72       2657     967913  [C,D,E,F]
   84   0 3 10 1 24 22 14 21 5 18 6 20 11 9 17 4 19 15 23 12 8 13 16 7 2      62      42031   13467875  [A,B,E,F]
   85   23 4 24 1 18 7 11 2 12 14 13 5 10 17 6 20 16 15 19 8 0 21 22 3 9      65       4797     919814  [A,B,E,F]
   86   9 8 13 0 23 18 5 7 3 19 20 6 16 21 15 17 2 22 4 10 1 14 24 11 12      67       4782     491437  [A,B,E,F]
   87   11 4 12 15 9 24 18 19 22 16 20 7 17 6 8 10 0 3 13 2 14 23 5 21 1      72       3828    1162876  [A,B,E,F]
   88   24 9 10 17 3 14 18 22 13 12 16 0 21 11 2 20 4 15 6 5 23 7 1 19 8      62       2656     416363  [C,D,E,F]
   89   12 16 11 1 5 20 22 8 9 6 17 7 0 15 4 19 14 3 24 10 23 13 21 2 18      57       1562     387487  [A,B,E,F]
   90   7 15 24 16 6 13 21 3 19 12 0 23 9 20 11 10 4 8 14 17 22 1 5 2 18      69     139735   73969673  [A,B,E,F]
   91   16 13 6 17 2 3 1 9 7 15 14 20 21 22 24 0 8 18 10 11 5 23 19 4 12      63       1828     554163  [C,D,E,F]
   92   22 20 9 24 16 13 19 2 10 3 18 17 15 0 6 4 23 1 21 8 7 11 14 12 5      71       7703    2504389  [C,D,E,F]
   93   21 7 15 9 13 22 24 23 1 19 6 3 8 10 16 5 2 14 20 4 17 12 0 11 18      69       1516     338280  [C,D,E,F]
   94   21 1 9 11 10 0 23 13 22 4 12 14 2 8 7 18 15 24 6 20 19 16 5 17 3      60        672     289571  [C,D,E,F]
   95   22 14 16 6 13 2 24 15 20 21 1 10 23 17 7 3 0 11 18 19 12 4 5 8 9      72      20672    8466378  [C,D,E,F]
   96   15 13 16 4 7 9 11 24 21 2 23 8 20 5 14 22 1 17 18 6 0 3 19 12 10      71       2578     430369  [C,D,E,F]
   97   21 14 18 2 17 10 9 16 3 7 19 0 12 11 4 1 22 20 23 13 5 6 15 8 24      67      48063   21236300  [C,D,E,F]
   98   15 6 4 21 20 0 7 24 12 3 17 11 2 13 9 16 1 5 14 18 10 23 22 8 19      67       7110    1641391  [A,B,E,F]
   99   16 1 24 12 23 4 8 14 7 19 22 20 6 13 5 0 18 3 2 11 10 21 15 9 17      65       7875    1442361  [C,D,E,F]
  100   20 18 19 15 5 3 13 12 24 11 14 0 4 6 16 2 1 22 10 8 17 21 23 7 9      62      18063    8795911  [A,B,E,F]

I've solved 10 instances from Korf and Taylor paper 'Finding Optimal Solutions to the Twenty-Four Puzzle' (1996). Search settings were the same; only optimal solutions in each phase were considered. The results are given below along with optimal solution lengths from the mentioned paper.

------------------------------------------------------------------------------------
Instance                                                          Solved in  Optimal
------------------------------------------------------------------------------------
17 1 20 9 16 2 22 19 14 5 15 21 0 3 24 23 18 13 12 7 10 8 6 4 11        124      100
14 5 9 2 18 8 23 19 12 17 15 0 10 20 4 6 11 21 1 7 24 3 16 22 13        119       95
7 13 11 22 12 20 1 18 21 5 0 8 14 24 19 9 4 17 16 10 23 15 3 2 6        126      108
18 14 0 9 8 3 7 19 2 15 5 12 1 13 24 23 4 21 10 20 16 22 11 6 17        120       98
2 0 10 19 1 4 16 3 15 20 22 9 6 18 5 13 12 21 8 17 23 11 24 7 14        125      101
16 5 1 12 6 24 17 9 2 22 4 10 13 18 19 20 0 23 7 21 15 11 8 3 14        114       96
21 22 15 9 24 12 16 23 2 8 5 18 17 7 10 14 13 4 0 6 20 11 3 1 19        128      104
6 0 24 14 8 5 21 19 9 17 16 20 10 13 2 15 11 22 1 3 7 23 4 18 12        115       97
3 2 17 0 14 18 22 19 15 20 9 7 10 21 16 6 24 23 8 5 1 4 11 12 13        129      113
23 14 0 24 17 9 20 21 2 18 10 13 22 1 3 11 4 16 6 5 7 12 8 15 19        138      114
------------------------------------------------------------------------------------

- Bulat