Stockfish test position (& possible eval bug)

[carldaman]

[D]r1bqk1nr/1p2b1pp/p1np4/4p3/2P1Pp2/N1NB4/PP3PPP/R1BQK2R w KQkq - 0 10

In this position, Stockfish4 (and the latest updates), tends to play the baffling 10.Qh5+ [not every single time], and after the obvious 10..g6, it will play 11.Qd1, thus losing 2 tempos for no good reason. Black can follow up with Nf6, and eventually mobilize a pawn storm on the K-side (if capable of it, of course).

I've done some re-tracing, and this tendency to favor the tempo-losing Qh5 began with version 2.3 and has been around ever since.

The position occurs after these moves:
[pgn]
1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nb5 d6 6. c4 Be7 7. N1c3 a6 8. Na3 f5 9. Bd3 f4
[/pgn]

Sometimes a more sensible move than 10.Qh5 will be played, such as the theoretical 10.Nc2 or O-O, but Qh5 is played at least 50% in my long time control tests on my i3 Win7 x64 machine.

Overall, I'm inclined to believe that something like this could be fixed without otherwise weakening the engine elsewhere, since the maneuver Qd1-h5-d1 has no redeeming features -- it just throws away valuable opening tempos and should leave the initiative in the hands of Black, if good play is assumed. Fixing what lies at the bottom of this should further improve the engine's play and analysis capabilities.

Regards,
CL

[JManion]

I am not noticing this behavior. I tested SF 4.

Almost instantly I get 0-0 D=15 .08

As I was typing this I get Nc2 D=25 .18

[JManion]

Came back and now its 0-0 D=33 .26

[Lyudmil Tsvetkov]

Hi Carl.

I did not go deep enough into the position, so I do not know if Qh5 is good or bad, but I think that the logic behind such a seemingly strange move might be as follows: when Qh5 and g6 are played, as pawns do not go back, the engine would consider that, when the black king castles short (a very probable option), the king on g8 would be worse covered by the pawn on g6 than a pawn still on g7, as in this case the king will have a pawn less immediately adjacent, and this is an important pawn. Pawns do not go back

The position is still somewhat open, so g6 might be a good move, but might also be a weakness, I did not go deep enough and am undecided.

I have also been frequently 'baffled' by similar engine moves in the past, they sometime prove to have some logic behind, though.

[zullil]

I am not noticing this behavior. I tested SF 4.

Almost instantly I get 0-0 D=15 .08

As I was typing this I get Nc2 D=25 .18

Not seeing this either, also with Stockfish 4. Here's the search log created by the engine---no GUI or book involved. (As the engine was searching, Qh5 appeared as about the tenth best move in the ordered move list.)

Code: Select all

Searching: r1bqk1nr/1p2b1pp/p1np4/4p3/2P1Pp2/N1NB4/PP3PPP/R1BQK2R w KQkq - 0 10
infinite: 0 ponder: 0 time: 0 increment: 0 moves to go: 0
 1   +0.65   00:00     198  O-O Nf6 
 2   +0.97   00:00     560  O-O Nf6 Nd5 
 3   +0.46   00:00    1778  O-O Nf6 Nd5 O-O Bd2 
 4   +0.12   00:00    2588  O-O Nf6 Nd5 O-O Bd2 Bd7 
 5   +0.28   00:00    4246  Nd5 Nf6 Nxe7 Qxe7 O-O O-O Bd2 
 6   -0.04   00:00    8388  Nd5 Nf6 O-O O-O Bd2 Be6 Nxe7+ Qxe7 f3 
 7   +0.08   00:00   16091  Nd5 Nf6 O-O O-O Bd2 Bd7 Nc2 Rc8 Ncb4 Nxb4 Nxe7+ Qxe7 
                            Bxb4 
 8   +0.16   00:00   31060  Nd5 Nf6 O-O O-O Bd2 Kh8 Re1 Bd7 Qb3 Nxd5 cxd5 
 9   +0.14   00:00   72691  Nd5 Nf6 O-O O-O Bd2 Kh8 Bc3 Bd7 Nxe7 Qxe7 f3 Qd8 Qb3 
                            b6 
10   +0.14   00:00  100493  Nd5 Nf6 O-O O-O Bd2 Kh8 Bc3 Bd7 Nxe7 Qxe7 f3 Qd8 Qb3 
                            b6 
11   +0.14   00:00  122101  Nd5 Nf6 O-O O-O Bd2 Kh8 Bc3 Bd7 Nxe7 Qxe7 f3 Qd8 Qb3 
                            b6 
12   +0.26   00:00  313421  Nd5 Nf6 O-O O-O Bd2 Rb8 Bc3 Bd7 Nxe7+ Qxe7 f3 Qe6 
                            Nc2 Rbc8 b3 b6 
13   +0.14   00:01  972331  Nd5 Nf6 O-O O-O Bd2 Be6 Bc3 Rc8 Nc2 Nd7 Ncb4 Nc5 
                            Nxe7+ Qxe7 Nd5 Bxd5 exd5 Nxd3 Qxd3 
14   +0.10   00:01   1131K  Nd5 Nf6 O-O O-O Bd2 Be6 Bc3 Rc8 f3 Nd7 Nxe7+ Nxe7 
                            Be2 Qc7 Kh1 Nc6 b4 Bf7 
15   +0.16   00:01   1295K  Nd5 Nf6 O-O O-O Bd2 Be6 Bc3 Rc8 f3 Nd7 Nxe7+ Nxe7 
                            Be2 Qc7 Kh1 Nc6 b4 Bf7 Rc1 Nf6 b5 
16   +0.16   00:01   2633K  Nd5 Nf6 O-O O-O Bd2 Be6 Bc3 Nd7 Be2 Rc8 Bf3 Bg5 Rc1 
                            Ne7 Bg4 Bxg4 Qxg4 Nxd5 Qe6+ Kh8 cxd5 
17   +0.16   00:01   2728K  Nd5 Nf6 O-O O-O Bd2 Be6 Bc3 Nd7 Be2 Rc8 Bf3 Bg5 Rc1 
                            Ne7 Bg4 Bxg4 Qxg4 Nxd5 Qe6+ Kh8 cxd5 
18   +0.10   00:02   4723K  Nd5 Nf6 O-O O-O Nxe7+ Qxe7 Bd2 Be6 b3 Rac8 Bc3 Qc7 
                            Nc2 Qb6 Qd2 Bg4 h3 Bh5 Nb4 Nxb4 Bxb4 
19   +0.12   00:02   6398K  Nd5 Nf6 O-O O-O Nxe7+ Qxe7 b3 Be6 Bb2 Qc7 Nc2 Qb6 
                            Bc3 Bg4 Qd2 f3 Qe3 Qxe3 Nxe3 Nd4 Nxg4 Nxg4 
20   +0.14   00:03   9962K  Nd5 Nf6 O-O O-O Bd2 Nxd5 cxd5 Nd4 f3 b5 Be1 Bd7 Nc2 
                            Nxc2 Qxc2 Rc8 Qf2 a5 Qa7 Ra8 Qb7 Qc8 Qb6 b4 
21   +0.06   00:07  41385K  Nd5 Nf6 O-O O-O Nc2 Be6 Bd2 Nd7 b4 Bg5 Qh5 g6 Qf3 
                            Rc8 Rfc1 Nb6 b5 axb5 cxb5 Ne7 Nxb6 Qxb6 Bb4 Bh4 
22   +0.26   00:11  65239K  O-O Nf6 Nd5 O-O Bd2 Nxd5 cxd5 Nd4 f3 b5 Be1 Qb6 Bf2 
                            Bh4 Qd2 Bxf2+ Qxf2 Qa5 Nc2 Nxc2 Bxc2 Bb7 Bb3 Rac8 
                            Rac1 Rxc1 Rxc1 Rc8 Rxc8+ Bxc8 a3 Qc7 Qc2 Qxc2 Bxc2 
23   +0.26   00:12  69702K  O-O Nf6 Nd5 O-O Bd2 Nxd5 cxd5 Nd4 f3 b5 Be1 Qb6 Bf2 
                            Bh4 Qd2 Bxf2+ Qxf2 Qa5 Nc2 Nxc2 Bxc2 Bb7 Bb3 Rac8 
                            Rac1 Rxc1 Rxc1 Rc8 Rxc8+ Bxc8 a3 Qc7 Qc2 Qxc2 Bxc2 
24   +0.24   00:14  87341K  O-O Nf6 Nd5 O-O Bd2 Nxd5 cxd5 Nd4 f3 b5 Be1 Qb6 Bf2 
                            Bh4 Qd2 Bxf2+ Qxf2 Qa5 Nc2 Nxc2 Bxc2 Bb7 Bb3 Rac8 
                            Rac1 Qb4 Rfd1 a5 Qb6 Rxc1 Rxc1 Qd4+ Qxd4 exd4 
25   +0.26   00:18 109962K  O-O Nf6 Nd5 O-O Bd2 Nxd5 cxd5 Nd4 f3 b5 Be1 Qb6 Bf2 
                            Bh4 Qd2 Bxf2+ Qxf2 Qa5 Nc2 Nxc2 Bxc2 Bb7 Bb3 Rac8 
                            Rac1 Rxc1 Rxc1 Rc8 Rxc8+ Bxc8 a3 Qc7 Qc2 Qxc2 Bxc2 
26   +0.18   00:20 129216K  O-O Nf6 Nd5 O-O Bd2 Nxd5 cxd5 Nd4 f3 b5 Be1 Qb6 Kh1 
                            Bd7 Bf2 Qa5 Bxd4 exd4 Nc2 Bf6 a3 Rac8 Rc1 Qb6 Nb4 
                            Rxc1 Qxc1 Bg5 Kg1 Rc8 Qd2 
27   +0.24   00:33 224417K  O-O Nf6 Nd5 O-O Bd2 Nxd5 cxd5 Nd4 f3 b5 Be1 Qb6 Kh1 
                            Bd7 Bf2 Qa5 Nc2 Nxc2 Qxc2 Rfc8 Qb3 Be8 Rad1 Bd7 Be1 
                            Qc7 Bd2 Qc5 Rc1 Qd4 Bb4 Rxc1 Rxc1 a5 Bd2 b4 Rc7 
28   +0.28   01:21 570621K  O-O Nf6 Nd5 O-O Bd2 Be6 Nc2 Kh8 b4 Rc8 a4 Nd7 Bc3 
                            Bh4 a5 Ne7 Ra3 Nxd5 cxd5 Bf7 Ne1 Bg6 Nf3 Be7 h3 Nf6 
                            Qe2 Rc7 Rb1 Rc8 Rc1 
29   +0.26   01:47 760920K  O-O Nf6 Nd5 O-O Bd2 Be6 Nc2 Kh8 b4 Rc8 a4 Nd7 Be2 
                            Bh4 Bg4 Bxg4 Qxg4 Bf6 Rac1 Ne7 Na3 Nb6 a5 Qd7 Nxf6 
                            Rxf6 Qxd7 Nxd7 Rfd1 Rff8 Bc3 Nf6 
30   +0.24   02:51   1236M  O-O Nf6 Nd5 O-O Bd2 Be6 Nc2 Rc8 Bc3 Kh8 b3 f3 g3 Qe8 
                            Nxe7 Nxe7 Ne3 Qh5 h4 Nc6 Bc2 Bh3 Re1 Rcd8 Nf5 Bxf5 
                            exf5 Qg4 Rc1 Nd4 Bxd4 exd4 Re7 Rd7 Re6 Rdd8 Bd3 
Nodes: 1236465551
Nodes/second: 7190425
Best move: O-O
Ponder move: Nf6

[zullil]

Ran the search again. This time, within the depth 30 iteration, SF switched to Qh5, but returned to O-O by the end of the iteration. I had asked for a search only to depth 30. I'll search the position again, with no specified stopping depth.

I doubt this is a bug. Stockfish may simply have some deeper reason for forcing the pawn to g6, even at the cost of some time.

Code: Select all

info depth 29 seldepth 48 score cp 20 nodes 1229616426 nps 7288257 time 168712 multipv 1 pv e1g1 g8f6 a3c2 e8g8 d3e2 d8d7 d1d3 e7d8 b2b3 d8b6 c1a3 c6d4 c2d4 b6d4 a1c1 f8d8 c3d5 f6d5 c4d5 d7e8 d3f3 e8g6 g1h1 c8d7 c1c7 b7b5 f1c1 a8c8 a3b4 d4b6 c7c8 d8c8
info depth 30 currmove e1g1 currmovenumber 1
info depth 30 currmove c1e3 currmovenumber 6
info depth 30 currmove a3c2 currmovenumber 7
info depth 30 currmove h1g1 currmovenumber 8
info depth 30 currmove d1g4 currmovenumber 9
info depth 30 currmove d1b3 currmovenumber 10
info depth 30 currmove d1f3 currmovenumber 11
info depth 30 currmove d1d2 currmovenumber 12
info depth 30 currmove c4c5 currmovenumber 13
info depth 30 currmove h1f1 currmovenumber 14
info depth 30 currmove d1c2 currmovenumber 15
info depth 30 currmove d1e2 currmovenumber 16
info depth 30 currmove d3e2 currmovenumber 17
info depth 30 currmove d3c2 currmovenumber 18
info depth 30 currmove e1e2 currmovenumber 24
info depth 30 currmove h2h4 currmovenumber 25
info depth 30 currmove d3b1 currmovenumber 26
info depth 30 currmove c3b1 currmovenumber 29
info depth 30 currmove c3a4 currmovenumber 32
info depth 30 currmove b2b4 currmovenumber 33
info depth 30 currmove g2g4 currmovenumber 34
info depth 30 currmove c3e2 currmovenumber 35
info depth 30 currmove a3b5 currmovenumber 37
info depth 30 seldepth 48 score cp 28 lowerbound nodes 1784833412 nps 7314771 time 244004 multipv 1 pv d1h5 g7g6 h5d1 e7g5 e1g1 g8f6 a3c2 e8g8 d3e2 c8e6 b2b3 d8d7 c1a3 f8d8 d1d3 a8c8 c3d5
info depth 30 currmove d1h5 currmovenumber 1
info depth 30 currmove d3e2 currmovenumber 7
info depth 30 seldepth 53 score cp 20 nodes 3420698441 nps 7552361 time 452931 multipv 1 pv e1g1 g8f6 a3c2 e8g8 d3e2 d8d7 d1d3 e7d8 b2b3 d8b6 c1a3 c6d4 c2d4 b6d4 a1c1 f8d8 c3d5 f6d5 c4d5 d7e8 d3f3 e8g6 g1h1 c8d7 c1c7 b7b5 f1c1 a8c8 a3b4 d4b6 c7c8
info nodes 3420698473 time 452931
bestmove e1g1 ponder g8f6

[zullil]

[D]r1bqk1nr/1p2b1pp/p1np4/4p3/2P1Pp2/N1NB4/PP3PPP/R1BQK2R w KQkq - 0 10

In this position, Stockfish4 (and the latest updates), tends to play the baffling 10.Qh5+ [not every single time]
Regards,
CL

Asking Stockfish to analyze the position to depth 30 with MultiPV=5 was illuminating. The top five moves all returned a score of 26 centipawns in favor of White. So move selection here might appear rather "chaotic".

Code: Select all

info depth 30 seldepth 51 score cp 26 nodes 6112517170 nps 7409830 time 824920 multipv 1 pv d1h5 g7g6 h5d1 g8f6 e1g1 c8g4 f2f3 g4e6 c3d5 g6g5 c1d2 g5g4 g1h1 e8g8 d2c3 a8c8 a3c2 g8h8 d3e2 g4f3 e2f3 b7b5 d5e7 d8e7 c4b5 a6b5 b2b3 f8d8 c2b4 e7b7 b4d5 e6d5 e4d5

info depth 30 seldepth 51 score cp 26 nodes 6112517170 nps 7409830 time 824920 multipv 2 pv a3c2 g8f6 e1g1 c8e6 c1d2 e8g8 c3d5 a8c8 b2b3 g8h8 f2f3 f6d7 d5e7 d8e7 c2b4 c6b4 d2b4 f8f6 d1e1 d7c5 a1d1 f6h6 e1f2 b7b6 d3c2 e6d7 d1d2 e7g5 f1d1

info depth 30 seldepth 51 score cp 26 nodes 6112517170 nps 7409830 time 824920 multipv 3 pv e1g1 g8f6 a3c2 c8e6 c1d2 e8g8 c3d5 a8c8 b2b3 g8h8 f2f3 f6d7 d5e7 d8e7 c2b4 c6b4 d2b4 f8f6 d1e1 d7c5 a1d1 f6h6 e1f2 b7b6 d3c2 e6d7 d1d2 e7g5 f1d1

info depth 30 seldepth 51 score cp 26 nodes 6112517170 nps 7409830 time 824920 multipv 4 pv c3d5 g8f6 e1g1 e8g8 c1d2 c8e6 a3c2 a8c8 b2b3 g8h8 f2f3 f6d7 d5e7 d8e7 c2b4 c6b4 d2b4 f8f6 d1e1 d7c5 a1d1 f6h6 e1f2 b7b6 d3c2 e6d7 d1d2 e7g5

info depth 30 seldepth 51 score cp 26 nodes 6112517170 nps 7409830 time 824920 multipv 5 pv c1d2 c8e6 a3c2 g8f6 e1g1 e8g8 c3d5 a8c8 b2b3 g8h8 f2f3 f6d7 d5e7 d8e7 c2b4 c6b4 d2b4 f8f6 d1e1 d7c5 a1d1 f6h6 e1f2 b7b6 d3c2 e6d7 d1d2 e7g5

info nodes 6112517170 time 824920
bestmove d1h5 ponder g7g6

Looks like the last four pv's lead to the same position; don't have time to check carefully.

[shrapnel]

Pawns do not go back

THIS is the correct reason !
A weakness is thus created in the Enemy position by the rapidly moving queen !
Loss in Tempo....hmmm...... I think its more than made up for by the creation of a permanent weakness in Black's position !

[zullil]

[D]r1bqk1nr/1p2b1pp/p1np4/4p3/2P1Pp2/N1NB4/PP3PPP/R1BQK2R w KQkq - 0 10

In this position, Stockfish4 (and the latest updates), tends to play the baffling 10.Qh5+ [not every single time]
Regards,
CL

A long search with the latest Stockfish shows that the engine prefers Qh5+:

Code: Select all

Searching: r1bqk1nr/1p2b1pp/p1np4/4p3/2P1Pp2/N1NB4/PP3PPP/R1BQK2R w KQkq - 0 10
infinite: 1 ponder: 0 time: 0 increment: 0 moves to go: 0
 1   +0.65   00:00     198  O-O Nf6 
 2   +0.97   00:00     560  O-O Nf6 Nd5 
 3   +0.46   00:00    1778  O-O Nf6 Nd5 O-O Bd2 
 4   +0.12   00:00    2628  O-O Nf6 Nd5 O-O Bd2 Bd7 
 5   +0.28   00:00    4296  Nd5 Nf6 Nxe7 Qxe7 O-O O-O Bd2 
 6   -0.04   00:00    8481  Nd5 Nf6 O-O O-O Bd2 Be6 Nxe7+ Qxe7 f3 
 7   +0.16   00:00   14260  Nd5 Nf6 O-O O-O Bd2 Be6 Nc2 Bf7 Nxe7+ Qxe7 Nb4 
 8   +0.30   00:00   31634  Nd5 Nf6 O-O O-O Bd2 Be6 Qb3 f3 Qxb7 Nxd5 cxd5 fxg2 
                            Kxg2 
 9   +0.08   00:00   74316  Nd5 Nf6 O-O O-O Bd2 Bd7 Nc2 Rc8 Rc1 Be6 f3 Kh8 Nxe7 
                            Qxe7 
10   +0.16   00:00   95500  Nd5 Nf6 O-O O-O Bd2 Bd7 Nc2 Rc8 Rc1 Be6 f3 Kh8 Nxe7 
                            Qxe7 Nb4 
11   +0.16   00:00  131935  Nd5 Nf6 O-O O-O Bd2 Bd7 Nc2 Rc8 Rc1 Be6 f3 Kh8 Nxe7 
                            Qxe7 Nb4 
12   +0.16   00:00  302012  Nd5 Nf6 O-O O-O Nc2 Be6 Bd2 Rc8 Bc3 Re8 f3 Bd7 Nxe7+ 
                            Rxe7 Be2 Be6 b3 Qb6+ Kh1 
13   +0.06   00:01  833676  Nd5 Nf6 O-O O-O Nc2 Be6 b3 Nd7 Nxe7+ Qxe7 f3 Nc5 Bb2 
                            Bd7 Be2 b6 Rb1 Rac8 
14   +0.12   00:01  965208  Nd5 Nf6 O-O O-O Nc2 Be6 b3 Nd7 Nxe7+ Qxe7 f3 Nc5 Bb2 
                            a5 Be2 b6 Rb1 Rac8 Re1 Bd7 Qd5+ Ne6 
15   +0.12   00:01   1279K  Nd5 Nf6 O-O O-O Nc2 Be6 b3 Nd7 Nxe7+ Qxe7 f3 Nc5 Bb2 
                            a5 Be2 b6 Rb1 Rac8 Re1 Bd7 Qd5+ Ne6 
16   +0.12   00:01   1570K  Nd5 Nf6 O-O O-O Nc2 Be6 b3 Nd7 Nxe7+ Qxe7 f3 Nc5 Bb2 
                            a5 Be2 b6 Rb1 Rac8 Re1 Bd7 Qd5+ Ne6 
17   +0.14   00:01   2394K  Nd5 Nf6 O-O O-O Nc2 Be6 b3 Nd7 Be2 Nc5 Nxe7+ Qxe7 f3 
                            Rac8 Bd2 b6 b4 Nd7 b5 axb5 cxb5 Na5 
18   +0.14   00:01   2619K  Nd5 Nf6 O-O O-O Nc2 Be6 b3 Nd7 Be2 Nc5 Nxe7+ Qxe7 f3 
                            Rac8 Bd2 b6 b4 Nd7 b5 axb5 cxb5 Na5 
19   +0.12   00:02   3689K  Nd5 Nf6 O-O O-O Nc2 Be6 b3 Nd7 Be2 Nc5 Nxe7+ Qxe7 f3 
                            Rfd8 Bd2 a5 Bc3 b6 Qe1 Qg5 Qd2 Rab8 Rfd1 Qh4 
20   +0.12   00:02   7861K  Nd5 Nf6 O-O O-O Nc2 Be6 b3 Nd7 Be2 Nc5 Nxe7+ Qxe7 f3 
                            Rfd8 Bd2 a5 Bc3 b6 Qe1 Qg5 Qd2 Rab8 Rfd1 Qh4 
21   +0.08   00:07  40015K  O-O Nf6 Nc2 O-O Bd2 Bg4 f3 Bh5 Nd5 Nxd5 cxd5 Nb8 Bc4 
                            Nd7 Nb4 Rc8 Rc1 Bf7 Kh1 Re8 Nd3 b5 Bb3 Rxc1 Qxc1 a5 
22   +0.06   00:08  47778K  O-O Nf6 Nc2 O-O Bd2 Bg4 f3 Bh5 Nd5 Nxd5 cxd5 Nb8 Rc1 
                            Nd7 Be2 Qb6+ Kh1 Rac8 b3 Bh4 Bc4 Qd8 Nb4 Nb6 Be2 
                            Rxc1 Qxc1 a5 
23   +0.06   00:17 110162K  O-O Nf6 Nc2 O-O Bd2 Qe8 Nd5 Bd8 f3 Bd7 Rc1 Rc8 Kh1 
                            Be6 Bc3 Qg6 b4 Nd7 b5 Ne7 Ncb4 Nc5 Bc2 Qg5 Nxe7+ 
                            Bxe7 Nd5 
24   +0.12   00:19 127449K  O-O Nf6 Nc2 O-O Bd2 Qe8 Nd5 Bd8 Kh1 Qg6 f3 Be6 Be2 
                            Rc8 b3 Nd7 Be1 Kh8 Rb1 Ne7 Ncb4 Nc5 Nxe7 Bxe7 Nd5 
                            Bxd5 cxd5 
25   +0.10   00:22 148120K  O-O Nf6 Nc2 O-O Bd2 Qe8 Nd5 Bd8 Kh1 Qg6 f3 Be6 Be2 
                            Rc8 b3 Nd7 Be1 Kh8 Rb1 a5 a3 Qh6 b4 axb4 axb4 Ne7 
                            Bf2 Nxd5 cxd5 
26   +0.20   01:18 571800K  Qh5+ g6 Qd1 Nf6 O-O O-O Nc2 Qb6 Be2 Nd8 b3 Ne6 Ba3 
                            Kg7 Kh1 Bd7 Bb2 Rac8 f3 Nc5 Rb1 Kg8 Qd2 Rfd8 Rfd1 
                            Re8 Nd5 Nxd5 cxd5 Bb5 Bxb5 Qxb5 
27   +0.28   01:44 759648K  Qh5+ g6 Qd1 Nf6 O-O O-O Nc2 Qb6 Be2 Nd8 b3 Ne6 Ba3 
                            Kg7 Kh1 Bd7 Bb2 Rac8 f3 Nc5 Rb1 Kg8 Qd2 Ne6 Rbd1 Nc5 
                            Rc1 Rfd8 Rcd1 Re8 Rc1 Rf8 Ra1 Ne6 Rab1 Nc5 Rbc1 
28   +0.28   01:45 765233K  Qh5+ g6 Qd1 Nf6 O-O O-O Nc2 Qb6 Be2 Nd8 b3 Ne6 Ba3 
                            Kg7 Kh1 Bd7 Bb2 Rac8 f3 Nc5 Rb1 Kg8 Qd2 Ne6 Rbd1 Nc5 
                            Rc1 Rfd8 Rcd1 Re8 Rc1 Rf8 Ra1 Ne6 Rab1 Nc5 Rbc1 
29   +0.28   01:58 857929K  Qh5+ g6 Qd1 Nf6 O-O O-O Nc2 Qb6 Be2 Nd8 b3 Ne6 Ba3 
                            Kg7 Kh1 Bd7 Bb2 Rac8 f3 Nc5 Rb1 Kg8 Qd2 Ne6 Rbd1 Nc5 
                            Rc1 Rfd8 Rcd1 Re8 Rc1 Rf8 Ra1 Ne6 Rab1 Nc5 Rbc1 
30   +0.28   02:13 966932K  Qh5+ g6 Qd1 Nf6 O-O O-O Nc2 Qb6 Be2 Nd8 b3 Ne6 Ba3 
                            Kg7 Kh1 Bd7 Bb2 Rac8 f3 Nc5 Rb1 Kg8 Qd2 Ne6 Rbd1 Nc5 
                            Rc1 Rfd8 Ra1 Rf8 Rab1 
31   +0.24   10:23   4694M  Qh5+ g6 Qd1 Nf6 O-O Bg4 f3 Be6 Nd5 g5 Bd2 g4 Kh1 O-O 
                            Nc2 Kh8 Be2 gxf3 Bxf3 Rc8 Bc3 Nb8 Qe2 Nxd5 cxd5 Bd7 
                            Na3 Rg8 Rac1 b5 Nc2 Qb6 Qf2 Qxf2 
32   +0.28   20:09   9145M  Qh5+ g6 Qd1 Nf6 Nc2 O-O O-O Qd7 Nd5 Bd8 Bd2 Qg7 Rc1 
                            Be6 Qe2 Rc8 Rfd1 Nd7 b4 Nb6 Rb1 Qd7 Rdc1 Rf7 f3 Ne7 
                            b5 Na4 bxa6 bxa6 Ncb4 a5 Nxe7+ Qxe7 Nd5 Qa7+ Qf2 Nc5 
                            Be2 Rb7 
33   +0.24   23:07  10469M  Qh5+ g6 Qd1 Nf6 Nc2 Qd7 O-O O-O Nd5 Bd8 Kh1 Qg7 Bd2 
                            Be6 Bc3 Rc8 Ncb4 Nxb4 Bxb4 Qd7 f3 Nxd5 cxd5 Bf7 Bc3 
                            Bb6 Qb3 Bc5 Rfd1 Rfe8 Bb4 Be3 Qa3 Red8 Ba5 b6 Bc3 a5 
                            Qb3 
34   +0.24   25:04  11346M  Qh5+ g6 Qd1 Nf6 Nc2 Qd7 O-O O-O Nd5 Bd8 Kh1 Qg7 Bd2 
                            Be6 Bc3 Rc8 Ncb4 Nxb4 Bxb4 Qd7 f3 Nxd5 cxd5 Bf7 Bc3 
                            Bb6 Qb3 Bc5 Rfd1 Rfe8 Bb4 Be3 Qa3 Red8 Ba5 b6 Bc3 a5 
                            Qb3 
35   +0.24   26:04  11791M  Qh5+ g6 Qd1 Nf6 Nc2 Qd7 O-O O-O Nd5 Bd8 Kh1 Qg7 Bd2 
                            Be6 Bc3 Rc8 Ncb4 Nxb4 Bxb4 Qd7 f3 Nxd5 cxd5 Bf7 Bc3 
                            Bb6 Qb3 Bc5 Rfd1 Rfe8 Bb4 Be3 Qa3 Red8 Ba5 b6 Bc3 a5 
                            Qb3 
36   +0.34   53:08  23971M  Qh5+ g6 Qd1 Nf6 Nc2 O-O O-O Bg4 f3 Be6 b3 Qd7 Nd5 
                            Bd8 Kh1 Rc8 Ba3 Ne7 Nxf6+ Rxf6 Be2 Bc7 Qd2 Rd8 Rad1 
                            Rf7 Nb4 Bb6 Nd5 Bd4 Qe1 Rdf8 Rxd4 exd4 Qb4 Nc6 Qxd6 
                            Qxd6 Bxd6 Rd8 
37   +0.30 1:06:03  29954M  Qh5+ g6 Qd1 Nf6 Nc2 O-O O-O Bg4 f3 Be6 b3 Qd7 Nd5 
                            Bd8 Kh1 g5 Be2 Rc8 Ba3 Bxd5 cxd5 Ne7 Bb4 g4 Rc1 gxf3 
                            Bxf3 Bb6 Na3 Rxc1 Qxc1 Be3 Qe1 b5 Nc2 Bb6 Qh4 Ng6 
                            Qg5 a5 
38   +0.32 1:15:37  34298M  Qh5+ g6 Qd1 Nf6 Nc2 O-O O-O Bg4 f3 Be6 b3 Qd7 Nd5 
                            Bd8 Kh1 Ba5 Bd2 Bxd2 Qxd2 Qf7 Rac1 Kg7 Qf2 g5 Be2 
                            Rab8 Rcd1 Rfd8 Rd2 Bxd5 cxd5 Ne7 Nb4 Ng6 Rc2 Rbc8 
                            Rcc1 g4 Qb6 Qe7 Nd3 Rg8 a3 
39   +0.32 1:30:47  40848M  Qh5+ g6 Qd1 Nf6 Nc2 O-O O-O Bg4 f3 Be6 b3 Qd7 Nd5 
                            Bd8 Kh1 Ba5 Bd2 Bxd2 Qxd2 Qf7 Rac1 Kg7 Qf2 g5 Be2 
                            Rab8 Rcd1 Rfd8 Rd2 Bxd5 cxd5 Ne7 Nb4 Ng6 Rc2 Rbc8 
                            Rcc1 g4 Qb6 Qe7 Nd3 Rg8 a3 
40   +0.28 3:38:46  98102M  Qh5+ g6 Qd1 Nf6 Nc2 O-O O-O Be6 Nd5 Rf7 Bd2 Bf8 Rc1 
                            f3 g3 Rb8 Bg5 Bg7 Qd2 Qd7 Rfd1 Ng4 Bf1 h6 Be3 Nxe3 
                            Qxe3 Nd4 Nxd4 exd4 Qd3 Bh3 b3 Re8 Re1 Bg4 Rcd1 Be5 
                            a3 Bg7 Nf4 g5 
Nodes: 99374676573
Nodes/second: 7476160
Best move: Qh5+
Ponder move: g6

[carldaman]

Thanks for confirming my findings, Louis. In many of my runs, actually Qh5+ edges out the other (better) choices by a small eval margin. I'll post more on this later.