
Rybka disqualified and banned from World Computer Chess Championships - fogus
http://www.chessvibes.com/reports/rybka-disqualified-and-banned-from-world-computer-chess-championships/
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sireat
I haven't followed computer chess for a few years, so wasn't aware there was
such a growing controversy, especially considering how dominant Rybka has
been(or was).

Maybe someone who is more familiar with the case can explain what happened to
warrant such an action?

Crafy(free/open source though not GPL) by
<http://en.wikipedia.org/wiki/Robert_Hyatt> has been one of the cornerstones
in computer chess.

I am sure most aspiring computer chess programmers have looked at its source
and techniques.

Fruit I also believe was open source(not sure what licence).

Now, both Crafty and Fruit are very strong GM level programs on a modern
computer but are far from being the best. In fact, I(a lowly FM) routinely was
able to find flaws in their algorithms (especially Crafty) and draw or win
games using standard tricks(closed openings, passive no obvious weakness
openings, etc.).

Rybka is pretty much immune to such anti computer chess shenigans. It has a
much better "knowledge" of human chess somewhat explained by fact that Rajlich
is an IM.

In fact, Rybka stood heads and shoulders above all the other contenders for a
while.

~~~
nas
There have been rumblings for years, at least since Strelka came out. I happen
to think the GPLed code of Fruit was the best thing to happen to computer
chess for a long while (thank you to Fabian). IMHO, cloning is not a bad thing
since allows incremental improvement by multiple authors. Cloning without
respecting the license of the source, however, it not okay and it seems clear
now that's what Rajlich did.

~~~
sireat
Thank you for the explanation!

I took the time to read the official report on Rybka Investigation and Summary
of Findings for the ICGA
[http://www.chessvibes.com/plaatjes/rybkaevidence/RybkaInvest...](http://www.chessvibes.com/plaatjes/rybkaevidence/RybkaInvestigation.pdf)

For those interested in the issue, I recommend you read the report, as well.

Some real heavies weight in on the issue including Ken Thompson. All are in
agreement that early versions of Rybka show disturbing similarities to Crafty
and then Fruit(this is when the big jump in rating performance was made).

Rajlich has continued to claim that his code is all original which is highly
doubtful.

To me the real damning evidence was by Hyatt, which showed that the early
version of Rybka has whole bunch of useless code from Crafty, which Hyatt had
used:

"Summary: Pre-Rybka 1.6.1 contains much identical code to Crafty, even
including large blocks of code with obsolete code inside them, and code that
performs tests that make no sense today (code that was left in Crafty by
accident, by Robert Hyatt, also shows up in Rybka 1.6.1)."

Off course, most of the code must be gone by the later versions, but it is
seriously in such a bad taste to be so disrespectful to other programmers.

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wccrawford
I haven't seen the evidence, but it seems to me to accuse him of code theft
because the moves end up being the same seems a bit much.

Did he refuse to show his source code?

Also, claiming that he knew he was in the wrong because he denies being in the
wrong is too much, too. He's more guilty because he claims to be innocent?
Jeez.

Also, demanding the trophies and prize money back is fine, but if they take
him to court over them, that's going too far. He might very well not have the
money any more. That it took them 6 years to figure out he was cheating says
it wasn't very obvious, to me. And now they claim that there is overwhelming
evidence.

I dunno, something smells fishy to me. I'd certainly want more proof than 'it
does the same moves'.

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mike-cardwell
"demands that he returns the trophies and prize money of the World Computer
Chess Championships in 2007, 2008, 2009 and 2010."

What if he just says "no". Is there anything legally compelling him to comply?

~~~
oinksoft
If they have a good case for plaigarism, I'm sure they could successfully sue
him for that money, and then some.

~~~
gwern
But will they? It looks very bad and lawsuits cost a lot of money.

~~~
oinksoft
I don't think it looks bad; it helps to maintain the integrity of the
tournament, encouraging fair contestants.

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docgnome
I'm a little confused about what he's been accused of here. Are they saying he
cut and pasted code from other chess bots? Or that he examined other chess
bots and used the ideas they implemented? Or...? What exactly do they mean by
plagiarism?

~~~
Isofarro
The attached document indicates that Rybka contains the exact logic that is
supposedly uniquely implemented in either Crafty or Fruit. These are not
standard algorithms, and the likelihood of a closed implementation of a chess
engine exactly matching the logic of an open sourced version on a number of
unusual algorithms cannot be down to pure coincidence.

I guess the developer behind Rybka studied the code behind both Crafty and
Fruit, and elected to use pieces of code from them, but didn't
acknowledge/give credit for those pieces of code.

One of the example pieces of code is a hack to avoid enpassant specifically in
a King and pawn versus a King and pawn endgame - something rather unusual
considering the same issue occurs if either/both sides have more than 1 pawn.
Fruit's approach was just to treat the KPvKP, and so to did Rybkas.

Again, the algorithms documeted were based around unique approaches to
evaluating various facets of evaluating the score of a position, not something
as simple as "can the White king castle in this position". So they don't make
a massive difference in playing strength, which suggests more strongly that
there's been some uncredited copying going on.

Rybka has been the strongest rated chess engine for a few years now. Granted
that the developer has found definite improvements over the other chess
engines out there. But, for the purposes of World Computer Chess Champion, the
developer must own the program he runs (or document/credit the sections of the
code he doesn't own)

Definitely have a look through the evidence. It's quite surprising how
detailed it is. Comparing Crafty/Fruit source code to a decompiled Rybka
codebase and looking at specific unusual engine-specific edge-cases and
exceptions.

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ltamake
Let this be a lesson, kids: cheaters never win.

~~~
perlgeek
While I'd love it if it were true, that's not a valid conclusion. How many
cases of winning cheaters are out there that never got caught?

Only "cheaters that get caught never win" would be true, but that's kinda
obvious.

~~~
ltamake
I know. I meant it somewhat ironically. ;P

