Aggression Test

[chesskobra]

The reason is, the EAS Tool looks for less material, a missing queen, but later the win for this color. But the 2 conditions (less material, a missing queen) must be true for 8 plies in a row. In this rare case here, the queen is recaptured after 9 plies...
In most cases, the 8-ply interval works fine. If I would increase it to 10 or 12, a lot of sacs would be missed by the EAS Tool.
So 8 plies work best, but there is no perfect world... If you parse games only by their moves with pgn-extract, without any evaluation by an engine (that makes the EAS Tool so brutally fast), there can be mismatches finding sacs. I am not able to avoid this completely, sorry.

Yep.

If have to see the perfection definition is a sac, anyone?

I have been thinking about exactly this problem (and especially the issue pointed out by Stefan) last couple of days. I think to improve the sac discovery, using the current implementation of pgn-extract, will be complicated. We will have to implement something like what they call 'technical analysis' in the finance world, where they (mostly amateurs) consider various patterns in ups and downs of a stock value for making buy or sell decisions. Although, technical analysis is considered pseudo-science in finance, it could be useful in chess to an extent. But beyond searching for sacs, it will be pseudo-science in chess as well.

[chrisw]

[pgn][Event "?"]
[Site "?"]
[Date "2024.04.02"]
[Round "105"]
[White "Rebel-xyz"]
[Black "Clover-5.0"]
[Result "1-0"]
[ECO "D31"]
[Opening "QGD"]
[Variation "3.Nc3"]
[TimeControl "40/10"]
[Termination "adjudication"]
[PlyCount "204"]

1. d4 d5 2. c4 e6 3. Nc3 Bb4 4. Qc2 Nf6 5. cxd5 exd5 6. Bg5 c5 7. dxc5 h6
8. Bh4 Nc6 9. e3 Be6 10. Bb5 O-O 11. Ne2 Bxc5 12. O-O Bd6 13. h3 Qe7 14.
Rad1 Rfd8 15. f4 Bc5 16. Rf3 a6 17. Bxc6 bxc6 18. Ng3 Bd7 19. Nh5 Bxe3+ 20.
Kh1 Ba7 21. Nxf6+ gxf6 22. Rg3+ Kh8 23. Qe2 Bc5 24. Re1 Qxe2 25. Bxf6+ Kh7
26. Rg7+ Kh8 27. Rxf7+ Kg8 28. Rg7+ Kf8 29. Nxe2 Ra7 30. Rh7 Re8 31. Be5
Rb7 32. Rxh6 Be3 33. Rf6+ Kg8 34. Nc1 d4 35. Nd3 Rb5 36. Rg6+ Kf8 37. a4
Rd5 38. g4 Kf7 39. Rf6+ Kg8 40. Kh2 a5 41. b3 c5 42. Kg3 Re6 43. h4 Rxf6
44. Bxf6 Bc8 45. Be7 Rd7 46. Bxc5 Rc7 47. Rd1 Bb7 48. b4 axb4 49. Bxb4 Rc2
50. f5 Kf7 51. g5 Rg2+ 52. Kh3 Bxg5 53. Ne1 Rg1 54. hxg5 Rxg5 55. Rc1 Bd5
56. Rc7+ Kg8 57. f6 Rf5 58. Rg7+ Kh8 59. Rd7 Be6 60. Rd8+ Kh7 61. Kg3 Rxf6
62. a5 Ba2 63. Nf3 Kg6 64. Nxd4 Bc4 65. Rc8 Bd5 66. Rc5 Bh1 67. Rb5 Be4 68.
Re5 Bh1 69. Re1 Bd5 70. Kg4 Bb7 71. Re8 Bd5 72. Rd8 Bc4 73. Rc8 Bd3 74. Rc3
Ba6 75. Kg3 Bb7 76. Rc1 Ba8 77. Rc7 Bh1 78. Rd7 Ba8 79. Bd2 Be4 80. Re7 Ba8
81. Bf4 Bd5 82. Re5 Bh1 83. Rb5 Kf7 84. Rh5 Ba8 85. Rc5 Rg6+ 86. Kf2 Ke7
87. Rc7+ Kd8 88. Ke3 Bg2 89. Be5 Bd5 90. Rc5 Bb7 91. Kf4 Ba6 92. Ke4 Bc8
93. Rb5 Ba6 94. Rb8+ Kd7 95. Kd5 Rh6 96. Rg8 Rh7 97. Rg6 Bd3 98. Rb6 Ke8
99. Rb8+ Kd7 100. Nb3 Ke7 101. Nc5 Kf7 102. Nxd3 Kg6 1-0
[/pgn]

@Stefan, I came across this game labelled as queen sacrifice, 24.Re1 Qxe2 25.Bxf6 but it really isn't, see 29.Nxe2

The reason is, the EAS Tool looks for less material, a missing queen, but later the win for this color. But the 2 conditions (less material, a missing queen) must be true for 8 plies in a row. In this rare case here, the queen is recaptured after 9 plies...
In most cases, the 8-ply interval works fine. If I would increase it to 10 or 12, a lot of sacs would be missed by the EAS Tool.
So 8 plies work best, but there is no perfect world... If you parse games only by their moves with pgn-extract, without any evaluation by an engine (that makes the EAS Tool so brutally fast), there can be mismatches finding sacs. I am not able to avoid this completely, sorry.

Yep.

If have to see the perfection definition is a sac, anyone?

Yup, detection is using the PV.
1. PV[0] can be any move except a capture.
2. PV[1] is a capture by the opponent that reduces raw material balance below zero.
3. The capture piece at 2 has not been recaptured by PV[end] and raw material balance is still below zero.
4. Score (which equals static eval at PV[end]) is above zero and not reached mate.

In other words the (PV, score) shows positive even though the material balance is still negative. The engine didn’t just sacrifice because it has tactics that recover, it must have sacrificed because it has positional knowledge that compensates for the material sacrificed. As far as I can tell, no aggressiveness algorithm has been put forward which uses this test. Aggression algorithms that do not use this test will contain many false positives because they are detecting tactical sacrifices. The faster/deeper the engine the more the false positives, therefore the latest SF will show the highest false results.

[Werewolf]

What is aggressive chess? Counting sacrifices is just one metric, somewhat meaningless in my opinion.

Yes I agree. This may be the reason, perhaps, I'm getting very different results to Mr. Pohl.

I'm defining it as a propensity to attack the enemy king.

Where are these different results? What was measured? And how?

(And by the way: My EAS-Tool does much, much more, than just counting sacs...)

OK noted about your EAS tool. I'm not criticising it, but I do get different results.

It'll take me another month to build up the data but I'm testing engines with around 1000 Elo difference in strength, where resignation is not allowed, based on this logic:

1) Where massive Elo difference exists the stronger side can usually exert its will without much resistance
2) Checkmate terminates a game immediately
3) Therefore, an engine with a tendency to attack the enemy king by flinging pieces at it will likely have shorter games on average than a grinder.

The EAS Tool measures short wins and the overall length of all won games of an engine, too.
https://www.sp-cc.de/files/eas_scoring_explanation.txt

Point 1 is missing though.

[chesskobra]

I would like to see evidence that an engine playing against stronger engines demonstrates the same aggressiveness as when playing against weaker engines, as measured by the EAS tool.

Also, why not use a very simple metric like number of points earned per 100 moves? This will incentivise short wins. For example, if your engine wins a game in 50 moves, draws another in 50 moves, its score is 1.5, which is better than an engine grinding 2 wins in 200 moves. Maybe some variation of this, since an engine winning a game in 100 moves gets 1 point, and another engine winning one game in 50 and losing 1 in 50 also gets a score of 1. It depends on how you want to assign weights. But such a metric will be much easier to calculate and will be quite informative at the same time.

[pohl4711]

I would like to see evidence that an engine playing against stronger engines demonstrates the same aggressiveness as when playing against weaker engines, as measured by the EAS tool.

Here:
https://www.sp-cc.de/experiments.htm

[pohl4711]

What is aggressive chess? Counting sacrifices is just one metric, somewhat meaningless in my opinion.

Yes I agree. This may be the reason, perhaps, I'm getting very different results to Mr. Pohl.

I'm defining it as a propensity to attack the enemy king.

Where are these different results? What was measured? And how?

(And by the way: My EAS-Tool does much, much more, than just counting sacs...)

OK noted about your EAS tool. I'm not criticising it, but I do get different results.

It'll take me another month to build up the data but I'm testing engines with around 1000 Elo difference in strength, where resignation is not allowed, based on this logic:

1) Where massive Elo difference exists the stronger side can usually exert its will without much resistance
2) Checkmate terminates a game immediately
3) Therefore, an engine with a tendency to attack the enemy king by flinging pieces at it will likely have shorter games on average than a grinder.

The EAS Tool measures short wins and the overall length of all won games of an engine, too.
https://www.sp-cc.de/files/eas_scoring_explanation.txt

Point 1 is missing though.

Just depends on you, which games you give to the EAS Tool. Play a lot of enginegames with huge Elo differences of the engines and give these games to the EAS Tool. Point 1 no longer missing.