Computer Chess Club Archives




Subject: Re: guilty until probed the opposite

Author: Thomas Mayer

Date: 17:09:18 05/28/05

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Hi Cesar,

I may start with Rule Nr. 2 of the ICGA for computer chess world championships:

"Each program must be the original work of the entering developers. Programming
teams whose code is derived from or including game-playing code written by
others must name all other authors, or the source of such code, in their
application details. Programs which are discovered to be close derivatives of
others (e.g., by playing nearly all moves the same), may be declared invalid by
the Tournament Director after seeking expert advice. For this purpose a listing
of all game-related code running on the system must be available on demand to
the Tournament Director."

Think about the spirit in this. Therefor copying just a small part of another
engine is simply cloning. I think if someone wants to start with an open source
project he may contact the author and work together with him. But claiming
afterwards something as own work after copying parts of another engine can not
be accepted.

Let's get back to Fafis. Well, you are right, it's not finally conclusive, all
the observations. If I would see ONE of those observations when comparing
engines I would get maybe suspicious, but I would not yet think that there is
really something fishy.
The problem is: There are so MANY indications. All known engines which have so
many similarities with Crafty ARE in fact Crafty clones. (Christopher mentioned
El Chinito and LaPetite) I am quite sure that at court the jury would say guilty
now. BUT - and that is the big BUT - there is still a chance for the other suide
to show evidences that there is no Crafty in Fafis. How ? Well, at court they
would show their source to the jury. Or to an independant expert. (Dann Corbit
is mentioned quite often when it is about such things, he might have seen more
chess-software source codes than anyone else in the world... :) So far we only
saw a very old source code even in another programming language. That might make
some even more suspicious. No good step of the defending site, IMHO.

> - The strings "captured a king" and "feature rejected by xboard" are not a
> good evidence.

in itself of course not. (But it seems that they are VERY seldom in chess
engines) - but they are another piece in the hole puzzle.

> - The code needed to generate moves, parse FEN it's a little part of a chess
> program, you can't say it's a clone based on that little parts.

I think sharing this parts is already cloning. Because it's not only about
generating move, we talk here also about move ordering etc. -> Also the move
generator uses kind of a data structur. I think the data structur in itself is
one of the most complicate thing in chess engines.

> - The virus thing can happen to all we engine authors, we are confident in
> our antivirus, but virus are first then antivirus, and some virus simply
> desactivate the antivirus. I think some pleople here just closing their
> mind, i can imagine a loot of ways the virus can get into the exe  (worm
> mutation, worm modification, bad information from antivirus companies). You
> can suspect that Rafael append the worm himself, but you can't be for sure.

Well, I hope you are right here, I think the same. It's quite possible that the
virus was attached to the exe just before he encrypt it which makes sense to me.
To append himself a virus would be - well - stupid.

> i can imagine it's not dificult to find similar behaviors on some aspects on
> very diferent engines.

well, they have clearly shown that the number of similar behavior is outstanding
and only known clones of Crafty have the same number of similarities.

> - How many % of code make an engine a clone?
> - How many lines of code make an engine a clone?
> - How many % of fafis it's crafty code?
> - then how do you know it's a clone?
> - suposing you got conclusive evidence tell that Move generator and FEN
> parser it's crafty code? how mutch % of the code it is?

I think the first paragraph in this posting answers this.

Greets, Thomas

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