What is wrong with so many engine on this position?

[consen]

[Event "Chess24"]
[Site "Chess24"]
[Date "2014.??.??"]
[Round "?"]
[White "DELOIRE"]
[Black "Ted Summers"]
[Result "0-1"]
[ECO "B21"]
[WhiteElo "1809"]
[BlackElo "1740"]
[PlyCount "80"]
[EventDate "2014.??.??"]

1. e4 c5 2. d4 cxd4 3. c3 d3 4. Bxd3 g6 5. Bc4 Bg7 6. Nf3 d6 7. h3 Qc7 8. Qe2
a6 9. Bf4 Nd7 10. Nbd2 Ngf6 11. g4 b5 12. Bb3 O-O 13. Rg1 Bb7 14. h4 e5 15. Be3
d5 16. exd5 Nxd5 17. O-O-O N7b6 18. h5 Rac8 19. Kb1 a5 20. hxg6 hxg6 21. Nh4 a4
22. Bc2 Qxc3 23. Ne4 Qxc2+ 24. Qxc2 Rxc2 25. Kxc2 Nxe3+ 26. fxe3 Bxe4+ 27. Kd2
Nc4+ 28. Ke2 Nxb2 29. Rd7 Bc6 30. Rc7 Be4 31. Rc5 Rd8 32. Rxb5 Nc4 33. Nf3 Bd3+
34. Kf2 e4 35. Nd4 Bxd4 36. exd4 Rxd4 37. Rb8+ Kg7 38. Rh1 e3+ 39. Kf3 Be4+ 40.
Kf4 Bxh1+ 0-1

On the move 31. the most of chess engine show fault points.

They all show Rd7 with 0 points. If we do this move, chess engine show minus 6 point. And if I go back to 31 move, again chess engine show 0 point.

Some program like Houdini have not this fault and show 31. Nf3 with minus 6 points.

The engine which have this fault is:
Crafty
Chess Tiger 2007
Deep Fritz 14 and 11. (Not Fritz 13)
Deep Junior Yokohama
Deep Rybka 4.1
Fruit 2.2.1
Glarung 1.2.1
Komodo 6 + 7a + 8 + TCEC (But not Komodo 64)
The King 3.33
All version of Stockfish

The version that show the correct result is:

Houdini 3 Pro + 4 Pro
Bouquet
Critter 1.6a
Deep Fritz 13
DeepSaros
IvanHoe 9.87b
Komodo 64
Zappa Mecoco II

Can any of you explain for me what this is?

[flok]

[Event "Chess24"]
[Site "Chess24"]
[Date "2014.??.??"]
[Round "?"]
[White "DELOIRE"]
[Black "Ted Summers"]
[Result "0-1"]
[ECO "B21"]
[WhiteElo "1809"]
[BlackElo "1740"]
[PlyCount "80"]
[EventDate "2014.??.??"]

1. e4 c5 2. d4 cxd4 3. c3 d3 4. Bxd3 g6 5. Bc4 Bg7 6. Nf3 d6 7. h3 Qc7 8. Qe2
a6 9. Bf4 Nd7 10. Nbd2 Ngf6 11. g4 b5 12. Bb3 O-O 13. Rg1 Bb7 14. h4 e5 15. Be3
d5 16. exd5 Nxd5 17. O-O-O N7b6 18. h5 Rac8 19. Kb1 a5 20. hxg6 hxg6 21. Nh4 a4
22. Bc2 Qxc3 23. Ne4 Qxc2+ 24. Qxc2 Rxc2 25. Kxc2 Nxe3+ 26. fxe3 Bxe4+ 27. Kd2
Nc4+ 28. Ke2 Nxb2 29. Rd7 Bc6 30. Rc7 Be4 31. Rc5 Rd8 32. Rxb5 Nc4 33. Nf3 Bd3+
34. Kf2 e4 35. Nd4 Bxd4 36. exd4 Rxd4 37. Rb8+ Kg7 38. Rh1 e3+ 39. Kf3 Be4+ 40.
Kf4 Bxh1+ 0-1

On the move 31. the most of chess engine show fault points.

They all show Rd7 with 0 points. If we do this move, chess engine show minus 6 point. And if I go back to 31 move, again chess engine show 0 point.

Some program like Houdini have not this fault and show 31. Nf3 with minus 6 points.

The engine which have this fault is:
Crafty
Chess Tiger 2007
Deep Fritz 14 and 11. (Not Fritz 13)
Deep Junior Yokohama
Deep Rybka 4.1
Fruit 2.2.1
Glarung 1.2.1
Komodo 6 + 7a + 8 + TCEC (But not Komodo 64)
The King 3.33
All version of Stockfish

The version that show the correct result is:

Houdini 3 Pro + 4 Pro
Bouquet
Critter 1.6a
Deep Fritz 13
DeepSaros
IvanHoe 9.87b
Komodo 64
Zappa Mecoco II

Can any of you explain for me what this is?

Do you have a fen string for that position?

[consen]

5rk1/2R2pb1/6p1/1p2p3/p3b1PN/4P3/Pn2K3/6R1 w - - 0 1


1. = (0.00): 31.Rd7

[Dirt]

They all show Rd7 with 0 points. If we do this move, chess engine show minus 6 point. And if I go back to 31 move, again chess engine show 0 point.

Rd7 is a repetition of moves. If black continues to do the same as before it will be a draw. Some engines always assume that once a repetition has been made, the same choice will always be made in the future.

This rarely causes any problems except for the strange draw score that people see.

[flok]

On the move 31. the most of chess engine show fault points. They all show Rd7 with 0 points. If we do this move, chess engine show minus 6 point. And if I go back to 31 move, again chess engine show 0 point.

I let QueenBee run in monte-carlo mode for 5 minutes on it and:

info string 2137410 playouts
info string chosen with 106360 hits
info string moves looked at: 108630660
info score cp -56
bestmove b2b3

(insiders may recognize this as uci protocol output)

The score (-56) can be compared with +/- -6 on regular searchers (it does extra evaluations required for the MC search).

[syzygy]

They all show Rd7 with 0 points. If we do this move, chess engine show minus 6 point. And if I go back to 31 move, again chess engine show 0 point.

Rd7 is a repetition of moves. If black continues to do the same as before it will be a draw. Some engines always assume that once a repetition has been made, the same choice will always be made in the future.

This rarely causes any problems except for the strange draw score that people see.

See also here.