WGM Yelena Dembo banned for cheating, threatens to sue!

To my considerable surprise, Greek WGM Yelena Dembo has been banned for engine use by Chess.com, according to reports:

http://www.chessninja.com/boards/ubbthreads.php?ubb=showflat&Number=156963

That same report also claims Dembo has threatened legal action unless the reason for her exit is changed

Kind of old news. I heard she matched up with Rybka like %95 of the time.

Yes, I see that now - end of September. Topical in the light of recent threads here though.

It's nothing new.
A couple of FM's have also gone, including
http://www.chess.com/members/view/Nosferatu
aka
Stefan Docx
aka
User 282210

Originally posted by atticus2
To my considerable surprise, Greek WGM Yelena Dembo has been banned for engine use by Chess.com, according to reports:

http://www.chessninja.com/boards/ubbthreads.php?ubb=showflat&Number=156963

That same report also claims Dembo has threatened legal action unless the reason for her exit is changed

My wife likes reality shows.

I'd like to see one where these people are in a house online with no engine to help them make their moves.

Just a strip computer board to toy with, but no engine access and see if they still match Fritz or Rybka at 90% plus.

They should also be given plenty of liquor, babes and studs and go clubbing... that's fun too.

P-

Thanks for the article, wasn't old news to me.

I couldn't find it initially but here's a good link: http://lousyatchess.blogspot.com/search?q=yelena+dembo

Deep Rybka 3 x64 Hash:256 Time:30s Depth:12-20ply
AMD Phenom x 4 2.30Ghz 4GB DDR2 RAM

Results for non-theory moves:

YelenaDembo (Games: 20)
Top 1 Match: 530/723 ( 73.3% )
Top 2 Match: 638/723 ( 88.2% )
Top 3 Match: 676/723 ( 93.5% )
Top 4 Match: 698/723 ( 96.5% )

Here are previously banned FM Stefan Docx's submitted results in comparison:

Houdini 1.03a x64 4_CPU Hash:256 Time:30s Depth:12-20ply
AMD Phenom x 4 2.30Ghz 4GB DDR2 RAM

Nosferatu (Games: 20)
Top 1 Match: 537/801 ( 67.0% )
Top 2 Match: 680/801 ( 84.9% )
Top 3 Match: 735/801 ( 91.8% )
Top 4 Match: 770/801 ( 96.1% )

It should be noted that this analysis was merely passed to chess.com staff & flagged for their attention.
How they proceed & what further checks they do in such cases are not disclosed.

Originally posted by Zygalski
Deep Rybka 3 x64 Hash:256 Time:30s Depth:12-20ply
AMD Phenom x 4 2.30Ghz 4GB DDR2 RAM

Results for non-theory moves:

YelenaDembo (Games: 20)
Top 1 Match: 530/723 ( 73.3% )
Top 2 Match: 638/723 ( 88.2% )
Top 3 Match: 676/723 ( 93.5% )
Top 4 Match: 698/723 ( 96.5% )

Here are previously banned FM Stefan Docx's submitted results in comparison:

...[text shortened]... eir attention.
How they proceed & what further checks they do in such cases are not disclosed.

Wow, when people said that she matched 90%+, I didn't realize that they were talking about being in the top four best moves.

Depending on the openings and positions, I think it could be hard for a titled player to AVOID hitting one of the top four moves on a consistent basis.

I'm a hack, and even I can come up with a series of candidate moves that overlap Rybka- my problem is differentiating the best from the 5th best, or the degree of differentiation among those moves- by that I mean situations where the best move for white is +0.75 and the fourth move is +0.10, and situations where the best move is +0.75 and the fourth move is -0.40 or worse.

In closed or semi-closed positions I sometimes match up well with a whole series of moves, as there are limited options in terms of pawn breaks or piece placements. I very often don't play the best one, but I am pretty good about playing the most thematic move.

I also miss often, and that's when I lose.

In open positions I am all over the map- especially when I play the King's Gambit, where the computer postgame pretty much makes fun of me.

My rambling point is that I am not as sure about passing my own judgment on her, and I would like to hear her case.

Of course, a cheat-busting guru is probably going to tell me that this is a sign that I don't really know squat about the subject, and they will be right!

Originally posted by Paul Leggett
Wow, when people said that she matched 90%+, I didn't realize that they were talking about being in the [b]top four best moves.

Depending on the openings and positions, I think it could be hard for a titled player to AVOID hitting one of the top four moves on a consistent basis.

I'm a hack, and even I can come up with a series of candidate mov t this is a sign that I don't really know squat about the subject, and they will be right![/b]

Well, if someone is matching a 3200 Elo rated engine to such a great extent in many games over time, you'd expect their rating to reflect that.

Many pre computer era CC World Championship finalists & OTB Super GM's have been tested in the same way & their match rates for 400+ non-database moves without fail fall below
Top 1 Match: 65%
Top 2 Match: 80%
Top 3 Match: 90%

Maybe Dembo plays a natural engine-like game in her OTB, well this was tested in the same way too:

"I picked the last 20 games >= 35 moves from chessgames.com. All against high-rated opposition (lowest ELO in the set is 2222, highest is 2655)"
The results of the analysis were:
Dembo OTB games:

Stockfish 1.8, 512MB hash, min/max ply=12/30, 40s/ply, 2GHz Core Duo:
{ Yelena Dembo (Games: 20) }
{ Top 1 Match: 422/929 ( 45.4% )
{ Top 2 Match: 615/929 ( 66.2% )
{ Top 3 Match: 717/929 ( 77.2% )
{ Top 4 Match: 777/929 ( 83.6% )

These are rather mundane figures suggest Dembo's unassisted style isn't particularly engine-like at all.
Of course the match rates will likely be a little higher in CC as opposed to OTB, but this just shows how much she matched in those OTB & that is all. The low match rates, especially 45% for top 1 match, may come as a surprise to you, Paul, seeing as they are from an International Master.

By the way, Yelena was moving on a daily basis in the chess.com games & had about 15 in progress when her account was closed.
Her record before that was
P=155
W=140
D=15
L=0
and she was #21 highest rated on site & climbing.

Originally posted by atticus2
To my considerable surprise, Greek WGM Yelena Dembo has been banned for engine use by Chess.com, according to reports:

http://www.chessninja.com/boards/ubbthreads.php?ubb=showflat&Number=156963

That same report also claims Dembo has threatened legal action unless the reason for her exit is changed

Myabe she will resume playing here User 349307

Originally posted by Zygalski
Well, if someone is matching a 3200 Elo rated engine to such a great extent in many games over time, you'd expect their rating to reflect that.

Many pre computer era CC World Championship finalists & OTB Super GM's have been tested in the same way & their match rates for 400+ non-database moves without fail fall below
Top 1 Match: 65%
Top 2 Matc ...[text shortened]... efore that was
P=155
W=140
D=15
L=0
and she was #21 highest rated on site & climbing.

The 45% doesn't surprise me at all, as not even engines play the same moves- my point is that once you start talking about to 3 or 4 matches (in the opinion of an engine, using human programming), the choice of reasonable moves starts getting thin, and her 83% matchp OTB is what I would expect. Matches with #1 move choices make me suspicious, but "top 4" matches much less so.

As for the ratings reflecting anything, that difference between "best" and "fourth best" can be huge at times. The engine gets its 3200 elo for playing its best move each time, but the rating would not be that high if it mixed in its second, third, and fourth choices in games.

In fact, it probably has its rating because its opponents mistakenly choose those second, third, or fourth best moves, and that's where the performance gap lies.

Thanks for investing so much time on this- it is certainly an education!

Well, let's post here some of the great games Yelena Dembo played on chess.com. In my humble opinion these games prove that Yelena apparently plays more engine-like than any other CC or OTB player in the history. There is a but here: she only plays like that online. OTB her style is different. While online she can easily exploit the slightest inaccuracy of a few centipawns with a forced tactical sequence of 20 moves, exactly as Rybka would have done it, OTB she makes many tactical mistakes. Maybe she is shy and feels uncomfortable to play in public 🙂

http://www.chess.com/echess/game.html?id=31283361
http://www.chess.com/echess/game.html?id=31428905
http://www.chess.com/echess/game.html?id=30677309
http://www.chess.com/echess/game.html?id=30417704
http://www.chess.com/echess/game.html?id=6811582
http://www.chess.com/echess/game.html?id=6569548
http://www.chess.com/echess/game.html?id=6569547
http://www.chess.com/echess/game.html?id=6443299
http://www.chess.com/echess/game.html?id=6529799
http://www.chess.com/echess/game.html?id=6457417

Originally posted by cotoi
Well, let's post here some of the great games Yelena Dembo played on chess.com. In my humble opinion these games prove that Yelena apparently plays more engine-like than any other CC or OTB player in the history. There is a but here: she only plays like that online. OTB her style is different. While online she can easily exploit the slightest inaccuracy of a f ...[text shortened]... p://www.chess.com/echess/game.html?id=6529799
http://www.chess.com/echess/game.html?id=6457417

String 'em up.

Here's Yelena's final gift to chess.com.
Her last win, which didn't form part of the analysis sent to staff.
The output log for analysis gives move played, then top 4 engine choices under analysis parameters given above the pgn in the order move/score/depth at which score attained. The played move is shown in bold.

http://www.chess.com/echess/game.html?id=30386348

4 x AMD Phenom 2.30 GHz 4GB RAM
Analysis Deep Rybka 3 x64 Hash:640 Time:60s Depth: Max 20 ply

[Event "Let's Play!"]
[Site "Chess.com"]
[Date "2010.02.01"]
[White "BoboXXL"]
[Black "YelenaDembo"]
[Result "0-1"]
[WhiteElo "2608"]
[BlackElo "2541"]

{ Book Moves: }

1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Na5 6. Bb5+ c6 7. dxc6 bxc6 8. Bd3 h6
9. Ne4 Nd5 10. 0-0

{ Analyzed: }

10... Nf4 { Nf4 27 14 : Be7 38 13 : g6 52 13 : Qc7 53 13 }

11. Be2 { Be2 39 15 : Re1 27 15 : Nbc3 23 14 : Qf3 13 14 }
11... Be7 { Be7 39 14 : Qb6 56 14 : f5 71 14 : Bb4 63 13 }

12. d3 { d3 43 14 : Bf3 43 14 : Nbc3 30 14 : a3 30 14 }
12... Rb8 { 0-0 47 14 : Qc7 44 13 : Rb8 46 13 : Qb6 56 13 }

13. Re1 { Bf3 50 13 : Nbd2 47 13 : a3 46 13 : Bg4 41 13 }
13... 0-0 { 0-0 51 13 : Qc7 58 13 : Ne6 72 13 : Nxe2+ 72 13 }

14. a3 { Bf3 51 13 : Nbd2 51 13 : Nbc3 42 13 : Bf1 39 13 }
14... c5 { c5 37 13 : Be6 42 13 : Qc7 43 13 : Nxe2+ 44 13 }

15. Bf3 { Bf3 40 14 : Bf1 27 14 : Nbd2 28 13 : Bxf4 19 13 }
15... Qc7 { Be6 45 14 : Qc7 54 14 : Ne6 63 13 : Nc6 63 13 }

16. b3 { Nec3 56 14 : Bxf4 36 14 : Nbc3 34 14 : b3 28 14 }
16... Rd8 { Be6 29 14 : Rd8 32 14 : Nc6 40 14 : Re8 59 13 }

17. Nec3 { Bxf4 35 14 : Nbc3 35 14 : Nec3 28 14 : Bd2 13 14 }
17... Be6 { Be6 19 14 : Bf6 61 14 : Nxd3 60 13 : Bg5 63 13 }

18. Bxf4 { Nd2 29 13 : Bxf4 19 13 : Bg4 0 13 : Ra2 -14 13 }
18... exf4 { exf4 19 14 : Nc6 365 14 : f6 346 13 : Bd6 359 13 }

19. Bg4 { Nd2 19 14 : Bg4 10 14 : Qe2 -9 14 : h3 -25 14 }
19... Bxg4 { Bxg4 10 14 : Bc8 61 14 : Nxb3 85 14 : Nc6 76 13 }

20. Qxg4 { Qxg4 10 14 : f3 -384 14 : Qc1 -383 13 : Qd2 -383 13 }
20... Bf6 { Bf6 10 14 : Nc6 23 14 : g6 57 14 : Bg5 59 14 }

21. Ra2 { Ra2 8 14 : Qe2 -18 13 : Qf5 -19 13 : Qf3 -26 13 }
21... c4 { c4 0 14 : Be5 14 14 : Nc6 23 14 : g6 28 13 }

22. Ne4 { dxc4 0 15 : Ne4 0 14 : bxc4 -6 14 : b4 -69 14 }
22... Be5 { Be5 0 14 : Bd4 85 14 : Rb6 105 13 : cxb3 105 13 }

23. b4 { dxc4 0 14 : b4 -11 14 : bxc4 -27 14 : c3 -78 13 }
23... cxd3 { cxd3 -11 13 : Nb7 32 13 : Nc6 60 13 : f3 93 13 }

24. cxd3 { Nbd2 -7 14 : cxd3 -28 13 : Nc5 -70 13 : c3 -78 13 }
24... Nb3 { Nb3 -28 13 : Nc6 15 13 : Nb7 38 13 : Qb7 106 13 }

25. Qd1 { Qd1 -28 13 : Qf3 -63 13 : Qf5 -71 13 : h3 -73 13 }
25... Nd4 { Nd4 -28 14 : f3 131 13 : Na5 177 13 : Na1 205 13 }

26. Nbd2 { Nbd2 -31 14 : Ned2 -30 13 : Nc5 -47 13 : Qc1 -56 13 }
26... a5 { a5 -31 14 : f6 0 14 : Re8 5 13 : Rd5 5 13 }

27. Nc5 { Qh5 -31 13 : Qb1 -34 13 : Qa4 -41 13 : Nb3 -42 13 }
27... Ra8 { Ra8 -46 14 : f6 0 14 : Rbc8 16 13 : axb4 21 13 }

28. Nc4 { Nc4 -46 13 : Qb1 -53 13 : Ncb3 -69 13 : Na4 -78 13 }
28... Bf6 { Bf6 -46 13 : Bd6 -41 13 : Re8 -21 13 : f6 -8 13 }

29. Ne4 { Rb2 -56 13 : Ne4 -58 13 : Qb1 -74 13 : Nb3 -82 13 }
29... axb4 { axb4 -57 14 : Ra6 27 14 : Be7 39 13 : Bh4 42 13 }

30. Nxf6+ { Nxf6+ -58 14 : Qb1 -96 13 : a4 -111 13 : Rb2 -122 13 }
30... gxf6 { gxf6 -64 16 : Kh8 152 15 : Kf8 157 15 }

31. Qh5 { Qh5 -64 13 : Qd2 -64 13 : f3 -73 13 : Qg4+ -76 13 }
31... Re8 { Re8 -74 14 : Kg7 -64 13 : b3 -57 13 : Kh7 -49 13 }

32. Rxe8+ { Rf1 -75 14 : Rb1 -78 14 : Rea1 -76 13 : Rd1 -76 13 }
32... Rxe8 { Rxe8 -80 5 : Kh7 #3 4 : Kg7 #3 4 }

33. h3 { Ra1 -83 13 : h3 -83 13 : Qd1 -171 13 : f3 -237 13 }
33... b3 { b3 -115 14 : f3 -68 13 : Re1+ -67 13 : Qe7 0 13 }

34. Rb2 { Rb2 -99 14 : Ra1 -115 13 : Qg4+ -396 13 : Rd2 -481 13 }
34... Kg7 { Kg7 -99 14 : Re6 -84 14 : Kh7 -69 14 : f3 -69 14 }

35. Qd5 { Qg4+ -121 14 : Qd1 -197 14 : Qa5 -172 13 : Rb1 -180 13 }
35... Re1+ { Re1+ -373 14 : f3 -231 13 : Qa7 -85 13 : Rd8 -66 13 }

36. Kh2 { Kh2 -495 16 }
36... f3+ { f3+ -495 15 : Qa7 -46 15 : Nc2 0 15 : Ne2 20 14 }

37. g3 { Nd6 -494 3 : Qd6 -950 2 : Ne5 -1000 3 : Qd6 -#7 3 }
37... Qc8 { Qc8 -495 15 : Qa7 -97 15 : Nc2 0 14 : Ne6 6 14 }

38. Qh5 { g4 -289 12 : Qh5 -464 12 : Qxf7+ -1765 12 : Rb1 -3448 12 }
38... f5 { f5 -471 13 : Rf1 -349 13 : Qe6 -119 13 : Re2 -111 13 }

39. Qh4 { Rxb3 -471 12 : Qh4 -486 12 : Nd6 -519 12 : a4 -1008 12 }
39... Qc5 { Ne2 -632 13 : Qc5 -501 13 : Qd7 -118 12 : f4 -111 12 }

40. Qf4 { Qf4 -501 12 : Qh5 -1338 12 : Qd8 -1546 12 : g4 -1937 12 }
40... Re2 { Re2 -501 12 : Nc2 -229 12 : Kg6 -134 12 : Kh7 -130 12 }

41. Rd2 { Qc1 -655 12 : Rd2 -711 12 : g4 -913 11 : h4 -968 11 }
41... b2 { b2 -742 12 : Kh7 -200 12 : Kg8 -200 12 : f6 -174 12 }

42. Rxb2 { Rxb2 -501 11 : Nxb2 -721 11 : Nd6 -#14 11 : Ne5 -#14 11 }
42... Nc2 { Nc2 -1004 13 : Qa7 0 13 : Kg6 0 13 : Kh7 0 13 }

43. d4 { d4 -987 12 : Qxf3 -1078 11 : Ne3 -1231 11 : Qe5+ -2972 11 }
43... Qxc4 { Qxc4 -1007 13 : Nxd4 -444 13 : Rxf2+ -323 13 : Qxd4 0 13 }

44. Qxf3 { Qxf3 -501 8 : g4 -1047 8 : Rb1 -1563 8 : Rxc2 -#13 8 }
44... Nxd4 { Nxd4 -985 13 : Re1 -249 13 : Qe6 -203 13 : Kg6 -165 13 }

45. Qb7 { Qb7 -965 10 : Qxe2 -988 10 : Qe3 -1715 10 : Qf4 -#19 10 }
45... Re1 { Re1 -984 12 : Re4 -578 12 : Nf3+ -525 12 : Re6 -523 12 }

46. Rd2 { h4 -1015 12 : Rb3 -1019 12 : Rb1 -1866 12 : Rd2 -2560 12 }
46... Qf1 { Qf1 -#17 13 : Nc6 -917 13 : Qc3 -631 13 : h5 -627 13 }

47. h4 { h4 -509 2 : Qxf7+ -#3 2 : Qg2 -#3 2 : Rxd4 -#2 2 }
47... Qg1+ { Qg1+ -#16 14 : Re4 -795 14 : Kg6 -389 13 : h5 -373 13 }

48. Kh3 { Kh3 -#16 11 }
48... Re4 { Re4 -#15 13 : Qf1+ -644 13 : Re7 -375 13 : Re6 -375 13 }

49. Qxe4 { f4 -723 4 : Qxe4 -991 4 : Qb1 -1885 4 : Qxf7+ -#7 4 }
49... fxe4 { fxe4 -#14 15 : Qf1+ 330 14 : Ne6 409 14 : Kg6 472 14 }


0-1

{ Game Summary }

{ White: BoboXXL }
{ Top 1 Match: 19/39 ( 48.7% )
{ Top 2 Match: 30/39 ( 76.9% )
{ Top 3 Match: 31/39 ( 79.5% )
{ Top 4 Match: 33/39 ( 84.6% )

{ Black: YelenaDembo }
{ Top 1 Match: 36/40 ( 90.0% )
{ Top 2 Match: 39/40 ( 97.5% )
{ Top 3 Match: 40/40 ( 100.0% )
{ Top 4 Match: 40/40 ( 100.0% )