Inconsistency between PGN data and the data on the site.

[salvador-dali]

Here is an example from lichess_db_standard_rated_2015-03.pgn.

One of the PGNs I am getting from this file looks in the following way:

[Event "Rated Classical game"]
[Site "https://lichess.org/cclZlRwO"]
[Date "????.??.??"]
[Round "?"]
[White "gunsti"]
[Black "azuaga"]
[Result "1/2-1/2"]
[UTCDate "2015.03.05"]
[UTCTime "23:09:12"]
[WhiteElo "1572"]
[BlackElo "1631"]
[WhiteRatingDiff "+2"]
[BlackRatingDiff "-2"]
[ECO "B30"]
[Opening "Sicilian Defense: Nyezhmetdinov-Rossolimo Attack"]
[TimeControl "360+10"]
[Termination "Normal"]

1. e4 { [%eval 0.17] } 1... c5 { [%eval 0.27] } 2. Nf3 { [%eval 0.27] } 2... Nc6 { [%eval 0.32] } 3. Bb5 { [%eval 0.45] } 3... e6 { [%eval 0.39] } 4. Nc3 { [%eval 0.26] } 4... a6 { [%eval 0.48] } 5. Bxc6 { [%eval 0.42] } 5... bxc6 { [%eval 0.41] } 6. e5 { [%eval 0.41] } 6... g6 $4 { [%eval #3] } 7. d4 $4 { [%eval 0.55] } 7... cxd4 { [%eval 0.74] } 8. Qxd4 { [%eval 0.7] } 8... Bg7 { [%eval 0.84] } 9. O-O { [%eval 0.63] } 9... Qc7 $2 { [%eval 2.18] } 10. Bf4 $2 { [%eval 0.62] } 10... Ne7 $6 { [%eval 1.38] } 11. Rad1 $6 { [%eval 0.48] } 11... Nd5 $6 { [%eval 1.32] } 12. Nxd5 $2 { [%eval 0.15] } 12... cxd5 { [%eval 0.26] } 13. c3 { [%eval 0.2] } 13... Rb8 { [%eval 0.24] } 14. b4 { [%eval 0.09] } 14... a5 { [%eval 0.32] } 15. a3 { [%eval 0.0] } 15... O-O { [%eval 0.33] } 16. Rfe1 { [%eval 0.0] } 16... Ba6 { [%eval 0.22] } 17. Qe3 { [%eval 0.0] } 17... Rbc8 { [%eval 0.13] } 18. Rc1 { [%eval 0.2] } 18... axb4 { [%eval 0.57] } 19. axb4 $6 { [%eval 0.03] } 19... Qc4 { [%eval 0.15] } 20. Bh6 { [%eval 0.08] } 20... Qd3 { [%eval 0.36] } 21. Qg5 $2 { [%eval -0.69] } 21... Qf5 $6 { [%eval 0.29] } 22. Qh4 { [%eval 0.36] } 22... Rc4 $6 { [%eval 1.15] } 23. Nd4 { [%eval 1.12] } 23... Qh5 { [%eval 1.08] } 24. Qxh5 { [%eval 1.18] } 24... gxh5 { [%eval 1.17] } 25. Bxg7 { [%eval 1.06] } 25... Kxg7 { [%eval 1.12] } 26. Re3 $6 { [%eval 0.17] } 26... Kh8 $2 { [%eval 1.73] } 27. Rh3 $6 { [%eval 0.93] } 27... Rfc8 { [%eval 0.74] } 28. Ne2 $2 { [%eval -2.1] } 28... Re4 { [%eval -1.77] } 29. Ng3 { [%eval -1.83] } 29... Rxe5 $2 { [%eval -0.25] } 30. Nxh5 { [%eval -0.26] } 30... Re4 $2 { [%eval 1.91] } 31. Nf6 { [%eval 1.91] } 31... Kg7 { [%eval 1.98] } 32. Nxe4 { [%eval 1.96] } 32... dxe4 { [%eval 1.86] } 33. Re3 $6 { [%eval 1.32] } 33... d5 { [%eval 1.43] } 34. Ra1 $2 { [%eval 0.0] } 34... Bc4 $2 { [%eval 1.34] } 35. h4 { [%eval 1.11] } 35... Bd3 { [%eval 1.18] } 36. Ra3 { [%eval 1.15] } 36... Kg6 { [%eval 1.25] } 37. g3 { [%eval 1.06] } 37... Kh5 { [%eval 1.5] } 38. Kh2 { [%eval 1.06] } 38... Kg6 { [%eval 1.13] } 39. Re1 { [%eval 1.36] } 39... Kf6 { [%eval 1.5] } 40. Kh3 { [%eval 1.39] } 40... Rg8 { [%eval 1.48] } 41. Rb3 { [%eval 1.41] } 41... Bb5 { [%eval 1.51] } 42. Rg1 { [%eval 1.08] } 42... h5 { [%eval 1.34] } 43. g4 $6 { [%eval 0.81] } 43... hxg4+ { [%eval 0.87] } 44. Rxg4 { [%eval 0.8] } 44... Rh8 { [%eval 1.07] } 45. Kg3 { [%eval 0.93] } 45... Ke5 { [%eval 1.18] } 46. Rg5+ { [%eval 1.09] } 46... f5 { [%eval 1.29] } 47. h5 { [%eval 1.36] } 47... Be2 { [%eval 1.6] } 48. Kh4 { [%eval 1.43] } 48... Bb5 { [%eval 1.63] } 49. Rg6 { [%eval 1.27] } 49... Kf4 { [%eval 1.25] } 50. Rxe6 $6 { [%eval 0.47] } 50... Be2 $6 { [%eval 1.07] } 51. Kh3 $4 { [%eval #-3] } 51... Rxh5+ { [%eval #-2] } 52. Kg2 { [%eval #-2] } 52... Rg5+ $6 { [%eval #-4] } 53. Kh2 { [%eval #-4] } 53... Rh5+ { [%eval #-3] } 54. Kg2 { [%eval #-2] } 54... Rg5+ $4 { [%eval -6.61] } 55. Kh2 $4 { [%eval #-6] } 55... Rh5+ $4 { [%eval 0.0] } 56. Kg2 { [%eval #-2] } 1/2-1/2

And the corresponding game from lichess: https://lichess.org/cclZlRwO

Notice that the PGN claims that evaluation of move 6 is mate in 3: 6... g6 $4 { [%eval #3] }. One the other hand the data on lichess looks just fine. There are other less noticeable differences. Like the first move is evaluated as 0.17 in PGN and as 0 on the site (almost every move has differences which can't be due to the rounding errors.

Any idea why this is happening?

[niklasf]

There was a bug when the game was first analysed. When it was reported here I let Stockfish redo the analysis, so now it's fixed on the site but not in the dumps that were done before.

[ornicar]

i'm going to re-export this month.

[salvador-dali]

Understood. In this case I can give you a few other examples where the engine found a mate in a position with no mate.

• https://lichess.org/fie4LKuG#20
• https://lichess.org/ca9HD1Xg#9

If it possible, can you please bump the thread when the files are regenerated?

Thank you very much for a fast explanation of this bug

[ornicar]

I suggest you just ignore these games. Better yet, use more recent exports, where analysis will be more accurate.