Is Maverick a Clone?

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Let me state unequivocally, Maverick is not a clone!

There have always been problems with clones and computer chess. The first one I recall was Quickstep.  This was a program competing in the 1989 World Computer Chess Championship in Portorož.  After a couple of rounds it was discovered to be a clone of Richard Lang’s Mephisto Almeria program. It was scandalous at the time.  Thankfully there was little cloning activity after this for about ten years. Then Crafty had a few clones (e.g. Bionic Impakt).  But when Fruit burst onto the scene it became a big problem. This then lead to the Rybka controversy (which I’m not doing to get into).

The computer chess community has developed a test to quickly identify clones.  This work was pioneered by Adam Hair.  You can read about it here – A Pairwise Comparison of Chess Engine Move Selections. I must say I was a little skeptical about the test. I wondered if a basic engine with piece-square-tables, mobility and passed-pawn code would choose similar moves even if they weren’t at all related.  Adam was kind enough to put Maverick through his test – here are the results:

------ Maverick 0.5 x64 (No Popcount) (time: 100 ms scale: 1.0) ------
45.50 Fruit 2.1 (time: 100 ms scale: 1.0)
45.24 Movei00_8_438 (time: 100 ms scale: 1.0)
44.74 SmarThink 1.20 (time: 100 ms scale: 1.0)
44.72 Strelka 2.0 B x64 (time: 100 ms scale: 1.0)
44.50 Fruit 2.2.1 (time: 100 ms scale: 1.0)
44.32 Doch64 09.980 JA (time: 100 ms scale: 1.0)
44.19 Loop 2007 32-Bit (time: 100 ms scale: 1.0)
44.17 Strelka 1.8 UCI (time: 100 ms scale: 1.0)
43.99 Toga II 1.0 (time: 100 ms scale: 1.0)
43.72 Nemo SP64n 1.0.1 Beta (time: 100 ms scale: 1.0)
43.38 Rybka 1.0 Beta 32-bit (time: 100 ms scale: 1.0)
43.26 Daydreamer 1.75 JA (time: 100 ms scale: 1.0)
43.17 Twisted Logic 20090922 (time: 100 ms scale: 1.0)
42.94 Nebula 2.0 (time: 100 ms scale: 1.0)
42.91 RedQueen 1.1.4 (time: 100 ms scale: 1.0)
42.66 Cyrano 0.6b17 JA (time: 100 ms scale: 1.0)
42.61 Hamsters 0.7.1 (time: 100 ms scale: 1.0)
42.60 Naum 4.2 (time: 100 ms scale: 1.0)
42.33 Murka 3 x64 UCI (time: 100 ms scale: 1.0)
42.32 spark-1.0 (time: 100 ms scale: 1.0)
42.26 Octochess revision 5190 (time: 100 ms scale: 1.0)
41.81 DiscoCheck 4.3 JA (time: 100 ms scale: 1.0)
41.77 Bobcat 3.25 (time: 100 ms scale: 1.0)
41.67 cheng3 1.07 (time: 100 ms scale: 1.0)
41.58 Gandalf 6.0 (time: 100 ms scale: 1.0)
41.37 Glass 2.0 PERSONALITY (time: 100 ms scale: 1.0)
41.28 RobboLite 0.085d3 x64 (time: 100 ms scale: 1.0)
41.22 Spike 1.4 (time: 100 ms scale: 1.0)
41.04 Houdini x64 1_CPU (time: 100 ms scale: 1.0)
40.93 Houdini 3 x64 (time: 100 ms scale: 1.0)
40.79 Gaviota v0.86 (time: 100 ms scale: 1.0)
40.75 Ruffian 2.1.0 (time: 100 ms scale: 1.0)
40.71 Stockfish 4 64 (time: 100 ms scale: 1.0)
40.70 Godel 2.3.7 (time: 100 ms scale: 1.0)
40.62 Pawny 1.0.x64 (time: 100 ms scale: 1.0)
40.59 Shredder 11 UCI (time: 100 ms scale: 1.0)
40.37 MinkoChess 1.3 x64 (time: 100 ms scale: 1.0)
40.36 Gaviota v0.87-a8 (time: 100 ms scale: 1.0)
40.24 Komodo CCT 64-bit (time: 100 ms scale: 1.0)
40.19 iCE 1.0 v1619 x64 (time: 100 ms scale: 1.0)
40.13 Arasan 16.1 (time: 100 ms scale: 1.0)
40.03 Alfil 13.1 x64 MT (time: 100 ms scale: 1.0)
40.01 GNU Chess 5.50-64 (time: 100 ms scale: 1.0)
39.92 Hannibal 1.3x64 (time: 100 ms scale: 1.0)
39.84 Tornado 4.88 x64 (time: 100 ms scale: 1.0)
39.78 Komodo 5.1 64-bit (time: 100 ms scale: 1.0)
39.66 Atlas 3.50 x64 (time: 100 ms scale: 1.0)
39.16 SlowChess 2.96 (time: 100 ms scale: 1.0)
38.84 Gull 2.2 x64 (time: 100 ms scale: 1.0)
38.54 Quazar 0.4 x64 (time: 100 ms scale: 1.0)
35.63 Texel 1.02 64-bit (time: 100 ms scale: 1.0)
34.33 Deep Sjeng WC2008 x64 (time: 100 ms scale: 1.0)

A score of >55 starts to get suspicious, while greater than 60 is highly likely to be a derivative work. As you can see all of Maverick’s scores are in the 40s! So it passed the test.

Some people seemed to think it was odd I asked about Maverick’s similarity to other engines. It was just simple curiosity. I know Maverick isn’t a clone. Having gone through the similarity test I now have more confidence in the similarity test.

Thanks again Adam for taking the time to test Maverick!