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MonteCarlo wrote: ↑Sat May 02, 2020 2:28 pm A few points on the original post:

1) Even if we were blindly trusting that SF's first choice at some arbitrary depth was "the truth", the evals for exd4 and Nbd7 are very close at most depths, certainly not different enough to think SF clearly prefers one over the other. Which it prefers could easily change at a future iteration.

2) Unassisted engine analysis from a position so early in the game is unlikely to distinguish all that well between similar options, i.e., we shouldn't blindly trust them.

3) exd4 Nxd4 transposes to the old main line of the Philidor, played thousands of times over the last ~180 years by humans. It's not some crazy engine line no human could manage to play.

4) Some rule of thumb articulated by a master of yore shouldn't be blindly trusted either.

Especially for human play, you're better off choosing between those moves based on which one leads to positions you enjoy playing the most, as you'll be more likely to put time into understanding the position.

For human play, you're much better off playing something you enjoy and will stick with long enough to understand well, even if all engines think it's 15 cp worse than some alternative, and even if it violates a rule of thumb articulated by some strong human player.

Cheers!

Henk wrote: ↑Sat May 02, 2020 2:26 pm It is different when pawn on c4 because you can't play Bc4. Stockfish suggests you have to play Be6 after Bc4 instead of Bg5.


[pgn]
[Event "Edited game"]
[Date "2020.05.02"]
[Round "-"]
[White "-"]
[Black "-"]
[Result "*"]

1. e4 d6 2. d4 e5 3. Nf3 Nf6 4. Nc3 Nc6 5. dxe5 dxe5 6. Qxd8+ Kxd8 7. Bc4
Be6 8. Bxe6 fxe6
*
[/pgn]

Henk wrote: ↑Sat May 02, 2020 2:26 pm But I don't like Be6 fe6. And you are stuck with an isolated double pawn.

MonteCarlo wrote: ↑Sat May 02, 2020 2:28 pm
For human play, you're much better off playing something you enjoy and will stick with long enough to understand well, even if all engines think it's 15 cp worse than some alternative, and even if it violates a rule of thumb articulated by some strong human player.

Karol Majewski wrote: ↑Sat May 02, 2020 2:14 pm I have a question to a similar position:

[d]r1bqkb1r/ppp2ppp/2np1n2/8/3NP3/2N5/PPP2PPP/R1BQKB1R w KQkq - 0 6

This can happen out of Philidor or Scotch, so that's very common position on an amateur level. So what's White's best way to continue? I guess many good moves here. Leela favours Bb5, while Stockfish switches between Bf4, Be2, Nxc6. Can someone with a strong CPU run Stockfish for a long time in this position?

BrendanJNorman wrote: ↑Sat May 02, 2020 3:03 pm

Henk wrote: ↑Sat May 02, 2020 2:26 pm It is different when pawn on c4 because you can't play Bc4. Stockfish suggests you have to play Be6 after Bc4 instead of Bg5.


[pgn]
[Event "Edited game"]
[Date "2020.05.02"]
[Round "-"]
[White "-"]
[Black "-"]
[Result "*"]

1. e4 d6 2. d4 e5 3. Nf3 Nf6 4. Nc3 Nc6 5. dxe5 dxe5 6. Qxd8+ Kxd8 7. Bc4
Be6 8. Bxe6 fxe6
*
[/pgn]

Why do you play 5...dxe5?! in your analysis? Play 5....Nxe5 first.

There is no danger for black at all in this line. and no reason to double/isolate your pawns either.

[pgn][Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
[PlyCount "18"]

1. e4 e5 2. Nf3 d6 3. d4 Nf6 4. Nc3 Nc6 5. dxe5 Nxe5 6. Nxe5 dxe5 7. Qxd8+ Kxd8
8. Bc4 Bb4 9. f3 Ke7 *[/pgn]

That being said, the doubled/isolated structure isn't as bad as club players tend to think.

You said:

Henk wrote: ↑Sat May 02, 2020 2:26 pm But I don't like Be6 fe6. And you are stuck with an isolated double pawn.

But remember, a weakness is only a weakness if it can be attacked.

Even Smyslov allowed such a concession once in the exact same structure.

[d]r1bq1rk1/2p1bppp/p1n2n2/1p2p3/4P3/1BP2N2/PP2QPPP/R1B1KN1R b KQ - 0 11

Here Smyslov played 11...Be6 which Fischer gave an ! in his famous memorable games book.



[pgn][Event "Havana"]
[Site "Havana CUB"]
[Date "1965.08.26"]
[Round "2"]
[White "Robert James Fischer"]
[Black "Vasily Smyslov"]
[Result "1-0"]
[ECO "C77"]
[SetUp "1"]
[FEN "r1bq1rk1/2p1bppp/p1n2n2/1p2p3/4P3/1BP2N2/PP2QPPP/R1B1KN1R b KQ - 0 11"]
[PlyCount "7"]
[EventDate "1965.08.25"]

11... Be6 12. Bxe6 fxe6 13. Ng3 Qd7 14. O-O Rad8 1-0[/pgn]

In the position after Rad8 white is only slightly better, and Fischer won mostly because he was simply the stronger player.

I'd suggest anybody to study the classic games of World Champions before analyzing move 5 of an opening with an elite engine, because, without such foundational knowledge, you'll have no idea what you're looking at.

Henk wrote: ↑Sat May 02, 2020 2:35 pm I know from experience that 4 ed: is difficult to play. If you make one more bad move in that position it is certainly lost.

zullil wrote: ↑Sat May 02, 2020 3:28 pm

Karol Majewski wrote: ↑Sat May 02, 2020 2:14 pm I have a question to a similar position:

[d]r1bqkb1r/ppp2ppp/2np1n2/8/3NP3/2N5/PPP2PPP/R1BQKB1R w KQkq - 0 6

This can happen out of Philidor or Scotch, so that's very common position on an amateur level. So what's White's best way to continue? I guess many good moves here. Leela favours Bb5, while Stockfish switches between Bf4, Be2, Nxc6. Can someone with a strong CPU run Stockfish for a long time in this position?

As you say, Stockfish's choices vary considerably from iteration to iteration. Here's what Stockfish-dev offers at depth 50:

info depth 50 seldepth 83 multipv 1 score cp 84 nodes 95191474646 nps 29182257 hashfull 1000 tbhits 0 time 3261964 pv d4c6 b7c6 f1d3 f8e7 e1g1 e8g8 f2f4 a7a5 h2h3 c8b7 c1d2 f6d7 d1f3 e7f6 a1d1 f6d4 d2e3 d4e3 f3e3 d7c5 d3c4 a5a4 f1e1 d8b8 e4e5 b7c8 e3d4 c8e6 b2b3 a4b3 a2b3 e6c4 d4c4 b8b6 g1h1 d6d5 c4d4 c5d7 d4d2 f8e8 h1h2 d7c5 f4f5 b6b4 d2e3 c5d7 e3g3 b4e7 f5f6 e7f8 d1d4 g7g6 d4a4 a8a4 c3a4 d5d4 c2c3

I'll let the search continue, and report again later.