jefk wrote: ↑Mon Jul 09, 2018 7:11 pm
also analyzed this gambit some time ago, with various engines (Gull sometimes gives intesting moves/lines)/ anyway i still believe in 5...c6! as strongest response..
So i wouldn't play it against a computer (if Stockfish with Black gives -0.6 for White in this position, you are already in trouble). Second probably 5...e6!, 5...g6 is an idea but drawish imho.
For me it looks currently like the opposite, after 5..g6 black (that means: stockfish) can claim an advantage, but after 5..c6 white gets away with at least some kind of compensation. I will post my personal notes here, clicked together on two afternoons. Feel free to point out doubts. These notes are not meant to be used for correspondence chess. I can confirm, that an analysis up to play 40 is often required but i don't have the cluster to do that on any position.

There is always the danger to run into some attack which is trivial for stockfish, but not so trivial for humans, e.g. the incorrect "Studier Attack" 6.Bc4 Bg7 7.0-0 0-0 8.Qe1
[pgn][Event "Blackmar-Diemer"]
[Site "?"]
[Date "2018.07.10"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
[EventDate "2018.07.10"]
1.d4 Nf6 2.f3
( 2.Nc3 d5 3.e4 Nxe4 4.Nxe4 dxe4 5.Bf4
( 5.Be3 e6
( 5...Bf5 6.g4 Bg6 7.Ne2
( 7.Ne2 )
( 7.c3 h5 8.g5 )
7...Nc6 8.c3 e6
( 8...Qd7 )
( 8...e5 9.h4 h5 10.Qa4
( 10.Qb3 Qd7 11.Qxb7 Rb8 12.Qa6 Rxb2 13.d5 Nb8 14.Qxa7
c6 15.Qxd7+ Kxd7 16.dxc6+ Kxc6 17.a4 hxg4 18.h5 Bh7
( 18...Rxh5 19.Rxh5 Bxh5 20.a5 )
19.h6 gxh6 20.a5 Na6 21.Ng3 Nc7 22.Bxh6 Bc5 23.Be3
Bxe3 24.fxe3 Nd5 25.a6 Nxe3 26.Rxh7 Rxh7 27.a7 Rh8 28.
a8=Q+ Rxa8 29.Rxa8 f5 30.Ra6+ Kd7 31.Be2 f4 32.Nxe4 g3
33.Nd2 e4 )
10...Qd7 )
9.h4 h6 10.Nf4 Bh7 11.Qb3 Qd7 12.Qxb7
( 12.O-O-O Na5 13.Qc2 O-O-O 14.b4 Nc6 15.Qa4 a6 16.Bxa6
Nxb4 17.Bb5 c6 18.Qa8+ Kc7 19.Qa5+ b6 20.Qa7+ Kc8 21.Qa8+
Kc7 )
12...Rb8 13.Qa6 e5
( 13...Rxb2 14.Bb5 )
14.Nh5 exd4 15.O-O-O d3 16.g5 Qd5 17.gxh6 )
6.Qd2 )
( 5.f3 e5 6.dxe5
( 6.Be3 exd4 7.Qxd4 Qxd4 8.Bxd4 Nc6 )
6...Qxd1+ 7.Kxd1 Bf5 )
( 5.Bc4 Nc6 6.Be3
( 6.d5 Na5 7.Qe2
( 7.Be2 e6 )
7...Nxc4 8.Qxc4 e6 )
( 6.c3 e5 7.Qb3 Qf6 8.Ne2 exd4 9.O-O Bd6 10.Ng3 Qe7 )
)
5...Bf5
( )
( 5...e6 6.Qd2 Bd6
( 6...Nd7 7.f3 )
7.O-O-O
( 7.f3 Bxf4 8.Qxf4 Qxd4 )
7...Nd7 8.f3 Nf6 9.Kb1 Bd7 10.Bg5 exf3 11.Nxf3 Ne4 12.Qe3 Nxg5 13.
Nxg5 Qf6 14.Ne4 Qf4 15.Nxd6+ Qxd6 16.Be2 O-O-O 17.Bf3 Kb8 )
6.g4
( 6.c3 Nd7 7.Qb3 e5 8.Bxe5 Nxe5 9.dxe5 e3 10.Nf3 exf2+ 11.Kxf2
Bc5+ 12.Kg3 Qe7 13.Rd1
( 13.Qxb7 O-O )
13...h5 14.h4 c6 )
( 6.Ne2 e6 )
6...Bg6 7.h4 h5 8.g5 e6 9.Bg2
( 9.Ne2 Bd6 10.Bg2 )
9...Bd6 10.Ne2 O-O 11.Qd2 Nc6 12.O-O-O Qd7
( 12...a5 13.a3
( 13.Ng3 Bxf4 14.Qxf4 Qd5 )
13...Ne7 14.Ng3 b5 15.Bxe4 Qd7
( 15...Bxe4 16.Nxe4 )
16.Bxa8 Rxa8 )
13.a3 Rad8 14.Kb1 Ne7 15.Bxd6 cxd6 16.Nf4 d5 17.f3 exf3 18.Bxf3 Rc8
19.Nxg6 fxg6 20.Be2 Rf2 21.Qe3 Rcf8 22.Rhe1 R8f4 23.Bd3 Nf5 24.Qxe6+
Qxe6 25.Rxe6 Rxh4 26.Re8+ Kh7 27.Ra8 Nxd4 28.Rxa7 Rg4 29.Rxb7 Rxg5 30.
Bxg6+ Kxg6 31.Rxd4 Rg1+ 32.Ka2 )
2...d5
( 2...c5 3.d5 e6
( 3...d6 4.c4 e6
( 4...b5 5.cxb5 a6 6.e4 g6 7.Na3 $5 Bg7 8.Ne2 O-O 9.Nc3 $14 )
5.e4 exd5 6.cxd5 g6 $14 )
( 3...g6 4.Nh3 $5 )
4.e4
( 4.c4 b5 $1 )
4...exd5 5.exd5 d6 $13 )
3.e4 dxe4
( 3...c5 $5 4.e5 Ng8 5.f4 cxd4 )
( 3...e5 4.dxe5 Nxe4 5.fxe4 Qh4+ 6.Kd2 Qg5+ 7.Ke2 Qh5+ 8.Ke1 $10 )
4.Nc3 exf3
( 4...c6 5.Bc4
( 5.Nxe4 Nbd7 $1 $15 )
( 5.fxe4 e5 6.dxe5 Qxd1+ 7.Nxd1 Nxe4 $13 )
5...Bf5
( 5...exf3 6.Nxf3 Bf5 7.Nh4 Bg6 8.Nxg6 hxg6 $15 )
6.g4 Bg6 7.g5 Nd5 8.Nxe4
( 8.fxe4 Nxc3 9.bxc3 Bxe4 10.Nf3 Bd5 11.Bd3 g6 12.c4 Be6 13.Rb1
Qc8 14.O-O Bg7 15.Bf4 Nd7 $17 )
8...Nd7 9.Ne2 $15 )
5.Nxf3 g6 6.Be3
( 6.Bc4 Bg7 7.O-O
( 7.Ne5 O-O 8.O-O Nc6 $1 9.Nxc6 bxc6 $17 )
7...O-O 8.Qe1
( 8.Be3 Nc6
( 8...c6 9.Qe2 Bg4 10.h3 Bxf3 11.Qxf3 Nbd7 12.Rad1 $15 )
( 8...Bg4 $6 9.h3 Bxf3 10.Qxf3 c6 11.Rad1 Nbd7 $13 )
( 8...a6 9.Ne5
( 9.a4 )
9...Nc6
( 9...b5 $2 10.Qf3 Ra7 11.Bb3 $14 )
10.Nxc6 bxc6 11.h3 )
( 8...Bf5 9.h3 Nc6 )
9.h3
( 9.d5 $2 Ng4 $1 $17 )
9...a6 $5 10.a4
( 10.Qd2 b5 11.Bd3 Bb7 12.a4 Nb4 $1 13.axb5 Nxd3 14.Qxd3 axb5
15.Rxa8 Qxa8 16.Nxb5 Be4 17.Qe2 Nh5 18.Qf2 Qb7 19.c4 c6 20.Nc3
Bxf3 21.Qxf3 Qxb2 $17 )
( 10.a3 b5 11.Be2
( 11.Ba2 e6 12.Qd2 Bb7 13.Rae1 Ne7 $17 )
11...Bb7 12.Qe1 e6 13.Rd1 Ne7 14.Bg5 h6 15.Bf4 Ned5 $17 )
10...Qd6
( 10...b6 $6 11.Qe1 e6 12.Rd1 Qe7 $13
( 12...Ne7 13.Bg5 Nf5
( 13...Bb7 14.Ne5 Nfd5 15.Bxd5 exd5 16.Qh4 $18 )
( 13...h6 14.d5 $1 $14 )
14.d5 $13 )
)
( 10...Bf5 11.d5 )
11.Qd2 Bf5 12.Bb3
( 12.Qf2 Qb4 13.Bb3 Na5 14.d5
( 14.Qh4 Nxb3 15.cxb3 Qxb3 16.Rf2 h5 $1 $19 )
14...Nxb3 15.cxb3 Ne4 16.Nxe4 Qxe4 $17 )
( 12.Rad1 Qb4 13.b3 Rad8 $17 )
12...Na5 13.Ba2 c5 14.Rad1
( 14.Rae1 Rad8 15.d5
( 15.dxc5 Qxd2 16.Bxd2 Nc6 17.Bb3 h5 $17 )
15...Qb6 16.g4 Bc8 17.Ng5 Nc6 18.Nge4 Nxe4 19.Nxe4 Qxb2 20.c3
Qxd2 21.Bxd2 Ne5 $17 )
( 14.d5 $2 b5 $1 15.axb5 axb5 16.Nxb5 Qb6 17.c4
( 17.Nc3 Qxb2 $19 )
17...Ne4 $19 )
14...Rad8 15.Qf2 c4 16.d5 Qb4 17.Bb6 Rd6 18.Bd4 Qxb2 19.g4 Bc8 20.
Rb1 Qa3 21.Bxc4
( 21.Ra1 Bxg4 $19 )
21...Rd7 22.Bb3 $17 )
8...Nc6 9.Qh4 Bg4 10.Ne2
( 10.Ng5 Qxd4+ 11.Kh1 Qxc4 12.Rxf6 h6 13.Rf4 hxg5 14.Rxc4 gxh4 15.
Rxg4 Rad8 $19 )
( 10.Be3 e6
( 10...Na5 11.Bd3 c5 12.dxc5 $13 )
11.Bg5 $2 Bxf3 12.Rxf3 Qxd4+ 13.Qxd4 Nxd4 14.Rxf6 h6 15.Bh4 g5 16.
Rf2 gxh4 $19 )
( 10.Kh1 Bxf3 11.Rxf3 Qxd4 12.Rf4 Qb6 $19 )
10...Na5
( 10...e6 $6 11.Bg5 $14 )
11.Bd3 c5 12.Bh6 c4
( 12...Rc8 $5 13.c4 cxd4 14.Ng5 Bxe2 15.Bxe2
( 15.Bxg7 Kxg7 16.Rxf6 Bxd3 $1 $19 )
15...d3 16.Bxg7 Kxg7 17.Rxf6 dxe2 18.Rxf7+ Rxf7 19.Ne6+ Kg8 20.
Nxd8 Rxd8 $19 21.Qg4 Rd2 22.Re1 Nc6 23.h4 Nd4 24.h5 Kf8 $19 )
( 12...Bxh6 13.Qxh6 Bxf3 14.Rxf3 c4 15.Bf5 Kh8 16.Bh3 $17 )
13.Bxg7
( 13.Ng5 cxd3 14.Bxg7 Kxg7 15.Rxf6 h5 16.Rxf7+ Rxf7 17.Nxf7 Kxf7
18.Qf2+ Kg7 19.cxd3 Bxe2 )
13...Kxg7 14.Be4 Qb6 $17 )
( 6.Bg5 Bg7 7.Qd2
( 7.Bc4 O-O 8.Qe2 Nc6 $1
( 8...a6 9.O-O-O b5 10.Bb3 Nc6 11.Rhe1 Na5 12.Qxe7 Bb7 $15 )
9.O-O-O Bg4 10.Kb1 Bxf3 11.Qxf3 Nxd4 12.Qxb7 Qd6 13.Qa6 Qxa6 14.
Bxa6 Ne6 15.Bxf6 exf6 16.Nd5 Rab8 $17 )
7...O-O 8.O-O-O c6
( 8...c5 )
)
6...Bg7 7.Qd2 O-O 8.O-O-O c6 $5
( 8...Nc6 9.d5 Nb4 $5 10.a3 a5 11.Bc4
( 11.axb4 axb4 12.Nb1 Ra2 $13 )
11...Bf5 12.axb4 axb4 13.Nb1 Qd6 14.Bf4 Qc5 15.Qd4 Qa5 16.Be5 Bh6+ 17.
Bf4 Bg7 $10 )
9.Kb1
( 9.Bh6 Bg4 10.Be2 Nbd7 11.Bxg7 Kxg7 12.h3 Bxf3 13.Bxf3 Qa5 14.Kb1 e5
$1 15.d5 Nb6 $1
( 15...cxd5 16.Bxd5 Rad8 17.Qe2 Nb6 18.Bb3 $15 )
16.dxc6 bxc6 17.g4
( 17.Rhe1 Nc4 18.Qd3 Qb4 19.b3 Rab8 20.Be2 Nb6 21.g4 Nfd5 22.Nxd5
cxd5 $19 )
17...Nfd5
( 17...Nc4 $2 18.Qd3 Qb4 19.b3 Rab8 20.g5 Nd7 )
18.Bxd5 Rad8 19.Qe2 Nxd5 20.Qxe5+ f6 21.Qg3 Nxc3+ 22.Qxc3 Qxc3 23.bxc3
Rxd1+ 24.Rxd1 f5 $19 )
( 9.Ne5 Be6 10.Bh6 Nbd7 $17 )
( 9.Be2 Bf5
( 9...Bg4 10.h3 Bxf3 11.Bxf3 Nbd7 12.Kb1 $15 )
( 9...b5 10.Ne5 Nfd7 $5 11.Ng4 $15 )
10.Bh6 Nbd7 11.h3 Qa5 12.g4 Be6 13.Bxg7 Kxg7 $17 )
9...Bg4
( 9...b5 $5 )
( 9...Bf5 10.h3 b5 )
( 9...Be6 10.Ng5 Bd5 11.Bd3 Nbd7 $15 )
10.Be2 Nbd7 11.h3 Be6
( 11...Bxf3 12.Bxf3 Nb6
( 12...Qa5 $6 13.g4 $13 )
13.Qe2 e6 14.h4 h6 $15 )
12.Ng5 Bd5 13.Nxd5 cxd5 $17 *
[/pgn]