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Stockfish Glitch

FEN - 8/6pk/6p1/6P1/5q1p/1B6/P7/6QK b - - 43 80

Stockfish reads this position as equal but after making the suggested move it changes drastically. Black to move.

Within a second of loading up stockfish the reading was +3.4, after a minute at 7 cores, it was at +9.6. Making the recommended move reset it to +4, after which it slowly climbed back up again

With 1 cpu enabled, it said +2.3 within a small fraction of a second

This is very odd. Yesterday it had a different reading. And I tried here on lichess and on Scid. And going through the game it still happens.

Here's the PGN

1.e4 e5 2.Nf3 Nc6 3.g3 Nf6 4.d3 d5 5.exd5 Nxd5 6.Bg2 Bc5 7.O-O Bg4 8.Re1 O-O 9.h3 Bh5 10.g4 Bg6 11.Nxe5 Nxe5 12.Rxe5 c6 13.Nd2 Bxf2+ 14.Kxf2 Qf6+ 15.Nf3 Nb6 16.Kg1 Nd7 17.Re1 Rad8 18.d4 Qd6 19.c3 a5 20.Nh4 b5 21.Nxg6 fxg6 22.Rf1 b4 23.Bd2 bxc3 24.bxc3 Nb6 25.Qb3+ Kh8 26.Qxb6 Qg3 27.Qxc6 Qd3 28.Rad1 Rxf1+ 29.Bxf1 Qg3+ 30.Qg2 Qb8 31.Bc4 h5 32.g5 a4 33.Rf1 Qc7 34.Bb5 Qa5 35.c4 Qb6 36.Bc3 a3 37.Kh1 Qd6 38.d5 Qe7 39.h4 Qe3 40.Bb4 Qd4 41.Be1 Ra8 42.Bf2 Qb2 43.Bc5 Qc3 44.d6 Rc8 45.d7 Rd8 46.Bb6 Rxd7 47.Bxd7 Qxc4 48.Kg1 Qxh4 49.Be6 Qb4 50.Bd8 Qd4+ 51.Kh1 Qxd8 52.Bb3 Qd3 53.Rf8+ Kh7 54.Ra8 Qe3 55.Rxa3 Qc1+ 56.Kh2 Qxa3 57.Kg1 Qc5+ 58.Kh1 h4 59.Kh2 Qe5+ 60.Kh1 Qe1+ 61.Qg1 Qe4+ 62.Kh2 Qf4+ 63.Kh1 Qe4+ 64.Qg2 Qe1+ 65.Kh2 Qe5+ 66.Kg1 Qe1+ 67.Qf1 Qg3+ 68.Qg2 Qe3+ 69.Kh1 Qe1+ 70.Kh2 Qe5+ 71.Kh1 Qe1+ 72.Qg1 Qe5 73.Qg4 Qe1+ 74.Kh2 Qf2+ 75.Kh3 Qf1+ 76.Kh2 Qf2+ 77.Kh1 Qf1+ 78.Qg1 Qf3+ 79.Kh2 Qf4+ 80.Kh1 Qf3+ 81.Qg2 Qe3 82.Bd5 Qe1+ 83.Kh2 Qe5+ 84.Kh3 Qe3+ 85.Bf3 Qe6+ 86.Qg4 Qxg4+ 87.Bxg4 Kg8 88.Kxh4 Kf7 89.a4 Ke7 90.a5 Kd8 91.a6 Kc7 92.Be2 Kb6 93.Kg3 Kc5 94.Kf4 Kd5 95.a7 Kd6 96.a8=Q 1-0

In the game, certain positions have already been reached twice before, which means that if they are reached again, the game ends in a draw. Black can only force a draw because he can make a position appear on the board that has already been reached twice. If you look back in the game, you'll see that the position which is reached after 80. .. Qe4+ has already appeared twice, and so black can claim a draw after playing it, making it the best move.

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