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Subject: Re: What constitutes a clone?

Author: Daniel Shawul

Date: 20:51:46 02/16/05

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On February 16, 2005 at 10:46:39, Robert Hyatt wrote:

I don't have your search or your eval.
Why don't you check my source code and post here.
Is that too much to ask??

>On February 15, 2005 at 18:38:43, John Merlino wrote:
>
>>I'm not trying to start a brutally long thread here, but I'm just curious about
>>how people feel about a particularly touchy subject -- clones. What, in your
>>mind, would lead you to the conclusion that an engine is a clone?
>>
>>Let's forget trying to find ways to PROVE that a clone is a clone; I'm just
>>trying to define one. For the sake of argument, assume that the author of this
>>engine in question tells you exactly what he did and did not do, and you must
>>decide whether to call it a clone or not.
>>
>>Here are some hypothetical questions to start the debate:
>>
>>If the author took Crafty and completely rewrote the evaluation code and nothing
>>else, would it be a clone?
>>
>>How about if the author rewrote the evaluation code and search algorithm only,
>>but left the hashing code, et. al.?
>>
>>How about if the author rewrote everything EXCEPT for the evaluation?
>>
>>How about if the author rewrote everything EXCEPT for Crafty's evaluation of
>>passed pawns?
>>
>>I think you can see where I'm driving. Obviously, many engine authors have
>>studied Crafty and other engines whose authors have graciously provided their
>>source code. But, for an engine to not be considered a clone, does it have to be
>>absolutely 100% the work of the author? (Forget about Nalimov's EGTB probing
>>code and any other code that can be used with permission).
>>
>>Many thanks in advance for your thoughts,
>>
>>jm (who's just preparing for any eventuality during his upcoming stint as
>>moderator :-)
>
>
>Here is my thinking.
>
>1.  The things that give a program its "personality" are the evaluation and the
>search itself.  The search defines the program's tactical ability, the
>evaluation defines the programs non-tactical chess playing ability.  Copying
>either/both should not be allowed.
>
>2.  Other parts such as the opening book are probably OK.  For example how many
>are using a GUI that handles the book outside of the engine?  That seems
>difficult to stop.  Of course a "shared opening book" is a no-no, since that is
>another part of a program that defines its playing skill level.
>
>If there is something that produces a single correct answer, such as "what is
>the set of moves for this position?" or "what is the updated chess position
>after making or unmaking this move?" or "what is the expected (SEE) win/loss for
>capturing on this square?" or "is the king in check?" then there is little
>reason to worry about those parts being copied, because copied or written from
>scratch, they by necessity produce exactly the same answer.  But the eval and
>search don't have that characteristic.



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