g-dog wrote on 09/20/10 at 19:42:18:


Pretty close?  100% certain?  This is a statistical problem, you understand?  So what is the model, what are the statistics, and what is the degree of confidence with which your conclusion about Dembo was obtained?  If you don't understand the relevance of this information you have no business drawing definite conclusions that could have consequences for IM Dembo outside chess.com.

E.g., I suggest you produce a random set of 2,000 sets of games of persons rated in 
Dembo's class and who play on chesspub, not necessarily all games in a given 20-game set played by the same player, and see what percent of the 2,000 trigger your +5% criterion.

What exactly are your "thresholds?"  Means, percentiles of given distributions, what?

Also there is something funny about your sample including ICCF games, since ICCF games are played with full-blown computer assistance with a fairly high degree of probability.  You seem to be saying that Dembo is relying on an engine even more than people who rely upon engines?!

Would you care to state the exact engine and think time that you're using to establish a set of machine preferences?  Any experience using other engines?

g-dog wrote on 09/20/10 at 19:42:18:
That's not sufficient. Even a patzer in my range has some database-data going beyond CB-products. I use CA and books. Some CBM stuff goes beyond the database from CB. Why would anyone buy the magazine if not. etc, etc.

This is one of my games just running on chess.com:
1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Nc3 dxc4 5.a4 Bf5 6.Ne5 Nbd7 7.Nxc4 Nb6 8.Ne5 a5 9.f3 Nfd7 10.e4 Nxe5 11.dxe5 Qxd1+ 12.Kxd1 Be6 13.Kc2 Bc4 14.Be3 Bxf1 15.Rhxf1 Nc4 16.Bd4 e6 17.b3 O-O-O 18.Rfd1 Rxd4 19.Rxd4 Ne3+ 20.Kb2 Nxg2 21.Rad1 Be7 22.Ne2 g5 23.Rd7 Re8 24.R7d3 Nh4 25.f4 Ng6 

I followed the Vigus book and CA11. 

Where does Megabase end? How many black moves aren't in the range of first four engine moves? (I hope none btw.)

Under the arguments of the side pro chess.com in this topic I must hope to be detected as a cheater in lots of phases of the game. What a weird situation!

The methods used by chess.com staff to determine engine-using cheaters isn't known. They may well have a Top 3 matching kind of analysis going on, and then something else too. They also have an IM who leads their detection efforts; he may eyeball games for non-human seeming moves.

The Dembo analysis results you see come from members of chess.com, not staff. 

I was one of those who ran her games using Batch Analyzer (BA), the same software RHP games mods use for their cheat detection. The results of her 20-game batch exceeded the human thresholds+5% that I have derived after analyzing in total >13000 moves from WC otb matches, a few modern super GM tournament performances, and importantly, the top finishers in the 5th-11th ICCF WC Finals (>7700 moves)

For all benchmark games and all games of any suspected player, the same hardware, software, and BA settings are used.

All benchmark games have their database moves screened out from analysis using MegaBase 2010 and MegaCorr 4, with the DBs being rolled back to the time of the benchmark games.

My human thresholds based on the benchmark games are 61/78/85%. Add 5% to account for error and 66/83/90%=blatant engine use.

Her results:

{ YelenaDembo (Games: 20) }
{ Top 1 Match: 493/694 ( 71.0% )  
{ Top 2 Match: 609/694 ( 87.8% )  
{ Top 3 Match: 644/694 ( 92.8% ) 
{ Top 4 Match: 660/694 ( 95.1% ) 

Database moves were determined using MegaBase 2010 and MegaCorr 4 and screened out from analysis.

3 other BA users had the same results with the same games using varying engines and hardware. She exceeded the heritage human thresholds +5% of 65/80/90% in all cases.

The games were the 18 most recent vs. 2200+ opposition, plus 2 more most recent vs near 2200 to reach the 20 game batch size.

Insofar as engine use can be determined by a Top 3 analysis, she has been caught.

She apparently used engines freely during her games. She's a cheater and I wouldn't dare bet against it.

Is she 100% guilty? I wouldn't say that, but we are pretty close in my opinion.

There are, after all, other ways the data can be held up to the light.

Schaakhamster wrote on 09/20/10 at 20:33:18:


It's not odd at all to express oneself in such a way, to express a degree of confidence.

They do that in civil court cases by reaching a preponderance of evidence. Sometimes expressed as 50.1%.

Nowadays I just don't have time to invest in RHP with ICCF games and my book going on. Perhaps when I finish the book I can go back. But that's the short answer.

g-dog wrote on 09/20/10 at 19:42:18:


So you determine guilty in percentages? Odd... . 

I think chess.com dropped the ball on this one...

Is she 100% guilty? I wouldn't say that, but we are pretty close in my opinion.

[...]I take exception when secret methods are employed to label people "known cheaters."  It's the labeling much more than the banning that bothers me.  Who gives a frig who is banned from some bullshit chess site?  But when they post a list of people and say these are "known cheaters," that goes too far.[...]