# Question
Title: Poison Qb2 and prerequisites for Vaganian
What does black achieve with 1.d4 c6?

Contributor mentions 1. d4 c6 2. Bf4 Qb6. Database shows few such openings, all responding 3.b3 with *white winning no matches*. Should white offer Qxb2 poison? Can white follow with Vaganian Gambit given Nb5 is no threat. Without Nb5, can white still trap the Q?

# Answer
> 2 votes
Computer variants (Lichess/Stockfish) are no answer ;-), but since it would get way too long for a comment...

1.d4 c6 (Playable, +0.3 vs e.g. +0.2 for d5, but very tame.) 2.Bf4 (Also uncommon, back to +0.1 vs. a normal developing move.) 2...Qb6 (Back to +0.3, again a normal move like Nf6 is preferrable) 3.Nf3 (+0.3, b3 is only +0.1) 3...Qxb2 (Asking for it, +0.9.) After the following, say, 4.Nbd2 d5 5.e4 White has a scary development advantage which, as the computer assessment shows, compensates for the pawn big time. On the other hand, White must play energically to justify it, since +0.9 also means Black is not immediately busted and might defend to "teeth's skin" and bring home the bacon resp. pawn in the endgame, as *my* typical games go...

---
Tags: caro-kann, 1.d4, london-system, poisoned-pawn
---


title: Erenburg vs Nakamura 2004

text:
# Question
Title: Erenburg vs Nakamura 2004
Did Erenburg operated a winning exchange sacrifice vs Nakamura in the Reykjavik 2004 game , Sicilian Najdorf opening ? Or could Nakamura have defended the position ?

I analyzed the following position with Houdini 6.02 but reached only depth = 34 after 40 minutes. The position is the following. White to move.

```
[FEN "2rq3r/1p3pk1/p1Pp2p1/P2Pp2n/1P4P1/5P2/6Pp/N1bRQB1K w - - 0 1"]
[White "Erenburg"]
[Black "Nakamura"]

```

Is this position a win for White or a draw?

# Answer
> 3 votes
# TL;DR

Stockfish 14+ NNUE (depth = 47, 4143k nodes/s) evaluates this position as **+1.1** due to 1. gxh5 and the follow-on perfect play (the 2nd best variation starting with 1. cxb7 evaluates at **-1.7**). See position on Lichess.

Engine evaluation suggests perfect play leads to a theoretical win for White (using 7 piece tablebases). There are multiple positions along the way where White has only 1 move to retain advantage where the 2nd best move loses (not draws).

# The Game

```
[Title "Erenburg - Nakamura, Reykjavik (2004)"]
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
[startply "54"]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. f3 e5
7. Nb3 Be6 8. Be3 Nbd7 9. Qd2 h5 10. a4 Be7 11. Be2 g6 12. a5
h4 13. O-O Kf8 14. Nd5 Bxd5 15. exd5 Rc8 16. c4 Kg7 17. Rac1
Nh5 18. Rfd1 Nf4 19. Bf1 Bg5 20. Na1 Nf6 21. b4 N6h5 22. c5
Ng3 23. c6 h3 24. hxg3 h2+ 25. Kh1 Nh5 26. Qe1 Bxe3 27. g4
Bxc1 28. gxh5 Bb2 29. Nb3 b5 30. Qd2 Bd4 31. Nxd4 exd4
32. hxg6 fxg6 33. Qxd4+ Kf7 34. Bd3 Re8 35. Be4 Qf6 36. Qb6
Rb8 37. Qa7+ Qe7 38. Qe3 Qf6 39. Rc1 Re7 40. Qh6 Qg7 41. Qh3
Rh8 42. Qg4 Qh6 43. Rc2 Qg7 44. Rc1 Qh6 45. Re1 g5 46. Rc1 Rc7
47. Bf5 Qh4 48. Bd7 Qxg4 49. Bxg4 Ke7 50. Re1+ Kd8 51. Re6 Rf7
52. Rxd6+ Kc7 53. Rg6 Rf4 54. Rg7+ Kd6 55. Rd7+ Ke5 56. c7 Rc4
57. Bh3 Rh6 58. Kxh2 g4 59. fxg4 Rd6 60. Rf7 Kxd5 61. g5 Rdc6
62. g6 1-0

```

# Analysis after 27...Bxc1

Using Stockfish's principal variation, after 8 moves Black controls the c-file while White's Bishop and Queen have open diagonals to the kingside. White has advanced the a-pawn to the 6th rank. Play proceeds with some exchanges and shuffling before heading to a QB+4 vs QB+2 ending with opposite colored Bishops and a dominant Black King.

However, perfect play seemingly results in a Q+2 vs Q+1 endgame where White is theoretically winning (using 7 piece tablebases).

```
[Title "Analysis - Position after 27...Bxc1"]
[FEN "2rq3r/1p3pk1/p1Pp2p1/P2Pp2n/1P4P1/5P2/6Pp/N1bRQB1K w Q - 0 1"]

1. gxh5 {Stockfish 14+ NNUE (depth = 47, 4143k nodes/s) evaluates this position as +1.1} Bf4 2. cxb7 Rb8 3. hxg6 Rxb7 4. Bxa6 Rc7 5. Bd3 Qc8 6. Nb3 fxg6 7. a6 Rf8 8. Ra1 Rh8 {Continuing (depth = 38, 4404k nodes/s)} 9. Rd1 Rf8 10. Na5 Rc3 11. Qe4 Qf5 12. Qe2 Qf7 13. Qe1 Ra3 14. Nc4 Rxa6 15. Nxe5 Bxe5 16. Bxa6 Ra8 {Continuing (depth = 43, 4506k nodes/s)} 17. Bd3 Qf4 18. b5 Ra3 19. b6 Rb3 20. Rb1 Rxb1 21. Bxb1 Qd4 22. b7 Bg3 23. Qe7+ Kh6 24. Qf8+ Kg5 {Continuing (depth = 64, 7058k nodes/s). From here, top two moves are 25. f4++ or 25. Qe7+, both with favorable evaluations at +2.3.} 25. f4+ Bxf4 26. Qe7+ Kh6 27. Qe1 Qb6 28. b8=Q Qxb8 29. Qe4 Kg7 30. Qxg6+ Kf8 31. Qf6+ Kg8 32. Qxf4 Qxb1+ (25. Qe7+ Kh6 26. Qf8+ Kg5 27. f4+ Bxf4 28. Qe7+ Kh6 29. Qe1 Qb6 30. b8=Q Qxb8 31. Qe4 Kg7 32. Qxg6+ Kf8 33. Qf6+ Kg8 34. Qxf4 Qxb1+ 35. Kxh2 {And White wins based on the 7 piece tablebases.}) 33. Kxh2 {And White wins based on the 7 piece tablebases.}

```

---
Tags: analysis, nakamura
---


title: Chessgames.com board theme and pieces

text:
# Question
Title: Chessgames.com board theme and pieces
What lichess and chess.com setups are the most similar to the board theme and pieces of chessgames.com? I love their setup and I'm feeling the most comfortable with it.

# Answer
For chess.com, I believe I have found the best setup.

Comparing it to chessgames.com, the piece design is exactly the same and the tan color is extremely close.

Lichess is a little trickier for the board color, although the pieces are to be found as well.

The piece type is the third option from the left in the top row.

As for the board type I chose, it is in the right column, six down from the top.
> 2 votes

---
Tags: online-chess, pieces, chessboards
---


# Question
Title: How does Anna Rudolf beat Hikaru Nakamura in this rook vs queen endgame fortress that came from a choker game (chess + poker)?
Position that follows is from Anna Rudolf's video 'Challenging Top Chess Grandmaster Hikaru Nakamura for a Choker Match!':

```
[FEN "8/5p2/8/2qkp3/4R1P1/5P2/3KP3/8 b - - 0 1"]

```

Also, here's a screenshot:

In the game, Anna was running low on time and forced a draw by repetition (there was no draw offer button at the time and maybe even now).

1. How does Anna beat Hikaru? I tried checking out lichess and it seems an idea is to trade rook and pawn for queen but even though it's 2 pawn vs 2 pawns, the pawn endgame is winning for black (Anna). Below is what I got from the 1st time I pressed spacebar until the pawn endgame. (At higher depth, I didn't get this again.)

---

```
[FEN "8/5p2/8/2qkp3/4R1P1/5P2/3KP3/8 b - - 0 1"]

1... Qa7 2. Ke1 Qg1+ 3. Kd2 Qb1 4. Ke3 Qc2 5. Kf2 Qxe4 6. fxe4+ Kxe4

```

---

2. Hikaru says something about 'zugzwang with Qd1'. What is Hikaru talking about? I know it's possibly related to fortresses (hence i tagged fortress) because in the video they were talking about 'I don't believe in fortresses' lol

# Answer
> 3 votes
Eric Half-An-Answer: He talks about a fortress, obviously :-) As far as one can talk generally, when trying to storm a fortress in a position with material Q/R plus pawns, the win method often is to use zugzwang to pass with the king through the blockade line built by the rook (here: at the moment the black king can't make it over the 4th) and then attack the pawn basis with the king from below.

BTW, another common strategy (but I bet it is not applicable here, since White is a pawn up) we just recently saw in a top game is the queen shielding the king with her own life (as taking her would create a passer), for example Kh2 Rh3 Pg2 - Ke4 Qd4 Pf4, where Qe3! wins fastest. Again the idea is attacking the base from below with the king.

This is only Eric Half-An-Answer as I am too weak a player to "see" the concrete zugzwang position with Qd1. I can make an educated guess: Assuming that the wR is fixed to e4 as Re3 allows the bK to near further, and R?4 runs into a fork (which I don't see yet), Kf2 vs Qd1 is already zugzwang: Ke3 Qe1 and the rook must move, Kg2 Qe1 ditto. Let Stockfish sort that out.

---
Tags: endgame, zugzwang, fortress, choker, queen-and-rook-endgame
---


# Question
Title: What is the need for repetition rules given the 50 & 75 move rules?
Given the existence of the (optional) 50-move rule and the (mandatory) 75-move rule, are the (optional) threefold-repetition rule and the (mandatory) fivefold-repetition strictly necessary? Do the repetition rules serve any purpose other than to (potentially) shorten the time to draw of a game that is futile for both sides?

# Answer
An important, but not the sole, reason for allowing draws in chess (outside of stalemate) is to prevent infinitely long games. Hence, when helpmate is unachievable for either side (a condition loosely termed "insufficient material"), a draw is immediately declared.

Now, n-fold repetition is introduced so that draws can be claimed in positions where neither player is willing to tolerate the risk involved in deviating. Hence even if helpmate is available (indeed, even if checkmate is achievable, but beyond the player's search horizon) mutual consensus may be that a draw is safe. Note that n-fold repetition is by itself **sufficient** to ensure no game is infinitely long, since if the number of moves reaches n multiplied by the total number of possible chess positions, it is guaranteed that at least one position has been repeated \>= n times. I know of no estimate to suggest how long this would take with, for example, random movers or in the worst case, but I imagine it would take astronomically many moves.

To come to your question: does the N-move rule (N moves without piece capture or pawn move) stand on its own as well? The answer is of course that it does. It also guarantees termination of a game much more quickly than the n-fold repetition rule does (estimates come in at 'just' 6000 moves for N=50 and 9000 moves for N=75).

So why does the n-fold repetition rule exist? Namely, as implied earlier, it serves a *distinctly* different purpose from the helpmate-impossible and N-move draw rules. In particular, the latter rules are implemented to prevent an infinite-length game when it is clear that either any termination is impossible (helpmate-impossible rule) or when play is seen not to head towards any termination besides a helpmate-impossible draw (N-move draw rule). The n-fold repetition draw rule exists primarily not because it provides the above theoretical bound on game length, but practically, because it allows players to limit their risk or cost in scenarios where neither find it worthwhile to deviate (whether it decreases the ground-truth positional evaluation to do so, or not).

Under such circumstances, if neither player feels sufficient incentive to play anything other than the repeated response, requiring 50 repetitions of the same moves seems like a waste. Better to call it a day early.
> 3 votes

# Answer
> are the (optional) threefold-repetition rule and the (mandatory) fivefold-repetition strictly necessary?

Yes, they are necessary. Something which players sometimes forget is that arbiters are people too. We have homes to go to with warm beds waiting. If both players refuse to agree a draw but also refuse to make an effort to win and start repeating the position then after the fifth repetition we can call an end to the game and go home.

You don't think there are woodpushers out there who would do this? Check out this question and answer regarding the 75 move rule.
> 6 votes

---
Tags: rules, threefold-repetition, 50-move-rule, 75-move-rule, fivefold-repetition
---


title: What is this tactic called?

text:
# Question
Title: What is this tactic called?
```
[FEN "6k1/rp3ppq/p2p4/1p1Pr1nQ/1P2P3/4R1N1/P1B2P2/4R1K1 b - - 0 1"]

1... Nh3+ 2. Qxh3 (2. Kh2 Rxh5) 2... Qxh3

```

Black to move.

After Nh3+ white can move the king or take with the queen. Either way black can win the queen.

How is this tactic called?

# Answer
It's a **discovered attack** with check (the rook attacking the queen is the discovered attack, the check is the discovering move). As the discovering move is also an attack, this gives rise to a **double attack**. The check must be answered, so the queen takes the knight even though it is protected. This could also be considered a **desperado** from White's point of view; the queen can't be saved, so White might as well take the knight.
> 22 votes

# Answer
It's not uncommon that a tactical sequence makes use of more than one general pattern.

Here, we have a **double attack** where one of these attacks is a **discovered** one (the rook on the queen) and the other is a **decoy** (the knight check lures the queen to a square where it will be undefended).
> 15 votes

# Answer
I think it is a discovered attack. Normally at a discovered attack, you do give a check to the king, eventually a double check. Here what is different is that you do a check to the king but you discover an attack on the queen, not also towards the king.
> 9 votes

# Answer
(I'm going to refer to chesstempo.)

I don't think there's just 1 tactic here. As other answers have pointed out, besides discovery (discoverer checks), there's also double attack or desperado. (i don't think it falls under chesstempo's desperado though. i think it's more of trapped piece than desperado, but I don't think it's even trapped piece.)

Something else I notice is x-ray: As for X-Ray Attack or X-Ray Defense, I believe this is X-Ray Attack
> 0 votes

---
Tags: tactics, attack, patterns
---


title: How to a add draw offer to a PGN

text:
# Question
Title: How to a add draw offer to a PGN
Does PGN have any annotations for draw offers? Just adding `=` after a move doesn't seem to work everywhere. Among the standard NAGs there is `$10` (a drawish or even position) which translates as `=`; or I can use a comment. But I am wondering whether there's a specific way of adding a draw offer.

# Answer
> 8 votes
There is no symbol for a draw offer. Just add a comment {draw offered}

# Answer
> 3 votes
I think the answer should be, that the format has to include the parentheses. So a draw offer in some PGN notation should look like:

```
1. e4 e5 (=)

```

So black is offering a draw after his first move.

See the example game at the end of section C that looks like:

> 1. e4 e5 2. Nf3 Nf6 3. d4 exd4 4. e5 Ne4 5. Qxd4 d5 6. exd6e.p. Nxd6 7. Bg5 Nc6 8. Qe3+3 Be7 9. Nbd2 0-0 10. 0-0-0 Re8 11. Kb1 (=)

PS: Shameless plug: I have just implemented that in my pgn-parser, see #57.

---
Tags: draw, pgn
---


# Question
Title: What does it mean for a country to be a FIDE "Affiliated Organization" instead of a FIDE Member?
According to the latest FIDE newsletter the Isle of Man has become a *FIDE affiliated organization*:

> The General Assembly approved the admission of the Isle of Man Chess Association as an affiliated organization. This is in recognition of the Isle’s continued contribution to chess, including what promises to be one of the world’s major chess events next year, the FIDE Chess.com Grand Swiss. The vote saw 107 votes in favor and just 4 against, with a further 4 abstentions.
>
> The status of “Affiliated Organization” is slightly below that of full “Member Organization”, which according to Article 9.4 of the FIDE Charter, would demand a territory to be recognized by the United Nations and the International Olympic Committee.

According to the FIDE directory of affiliated associations these are either continental or linguistic groups of countries like the Portuguese-Speaking Federations Association, the European Chess Union, the African Chess Federation, the Chess Association of Black Sea Countries, the Confederation for Chess for Americas, or related chess associations which have nothing to do with countries like the International Correspondence Chess Association, the International Computer Games Association, the International Physically Disabled Chess Association, the World Federation for Chess Composition.

Member federations are normally countries although many of them do not satisfy the criteria of being members of the IOC or United Nations. So, for instance the UK has a seat at the UN and is an IOC member but there is no single UK FIDE member. Instead there are separate England, Scotland and Wales members and there is even one member which crosses borders, the Ireland member which includes the country of Ireland AND Northern Ireland which is part of the UK.

The Isle of Man is a slightly strange country in that it is a Crown Protectorate like Jersey and Guernsey, both of which are FIDE members. It has its own parliament and government with tax raising powers but relies on the UK for defence.

It is also quite small with a population about 85,000. However even in Europe there are several FIDE member countries which are smaller - Andorra (72,000), Guernsey (65,000), Faroe Islands (50,000), Monaco (38,000), Liechtenstein (37,000), San Marino (33,000).

What does this change mean for Isle of Man chess players, who will continue to be England players as far as FIDE registration and representation is concerned?

# Answer
> 2 votes
It doesn't appear that this will have a large impact on the players themselves. The organization can organize events and gets nonvoting representation in FIDE.

According to the FIDE Charter:

> 14.1 The General Assembly, following an advisory opinion of the Council, can be admitted as Affiliated Organisations:
> a) organisations grouping Member Federations;
> b) associations or organisations which represent some regions or transnational territories;
> c) associations or other organisations representing people with a common ground or with same interests on some specific chess activities.
>
> 14.2 Affiliated Organisations have the right to take part in FIDE Congresses and in the General Assembly, without voting.
>
> 14.3 Affiliated Organisations can organise and participate in some specific FIDE competitions or events, according with FIDE rules and regulations.
>
> 14.4 Affiliated Organisations can be authorised to organise events under the auspices of FIDE.
>
> 14.5 Affiliated Organisations can be temporarily suspended or permanently expelled by the General Assembly, for just cause.

As for why the situation with other UK protectorates is what it is, I suspect that these rules have something to do with it (emphasis mine):

> 9.2 Only one Federation for each country can be affiliated to FIDE as a Member. **This rule shall not apply to Federations that were accepted as FIDE Members before the date of this Charter entering into force**.

> 9.4 **For new members**, the country of the federation must be a country recognised by the United Nations and the International Olympic Committee(IOC).

# Answer
> 0 votes
> What does this change mean for Isle of Man chess players, who will continue to be England players as far as FIDE registration and representation is concerned?

It seems that when an individual country, rather than a continental or linguistic group of countries, becomes an affiliated organization it is a stepping stone to becoming a fully fledged member federation. This has now happened for the Isle of Man and the Isle of Man players can now move their federation registrations from ENG to IOM.

Interestingly the Isle of Man now appears in both FIDE's list of Member Federations and Affiliated Organizations. Here is the Isle of Man's FIDE directory entry as a member federation.

Here is the list of the first players to be members of the Isle of Man federation.

---
Tags: fide
---


# Question
Title: Why doesn't Lichess' Stockfish suggest this bishop sacrifice?
I arrived at the following position in an online game after the opponent left a queen hanging.

```
[FEN "r1b2r2/pp1p1ppk/2n1p3/6B1/2P5/5N2/PQ3PPP/R4RK1 w - - 0 16"]

```

In the game, I played 16. Bf6 with the idea that in case he accepts the sacrifice, my queen can come to an exposed king with mating ideas and possibility of exchanging the rook for the knight and I should probably be able to arrive with the rooks by lifting them sooner than his minor pieces are able to help significantly. If the opponent refuses, my bishop is still up with a better aim and I have possibilities of blasting the kingside with a major advantage.

I looked at the game with lichess' Stockfish to check if this was a blunder and the main lines lichess' Stockfish suggests to me are 16. Be3, 16. Qc2+, 16. Nd2, 16. c5 and 16. Qa3, the first line having an evaluation of +12.8. Bf6 is not suggested, but it has an evaluation of +18.0 after it is played, so it left me wondering why it doesn't suggest Bf6 in the first place. My guess is that maybe Stockfish does not consider sacrificial moves without a forced advantage if the player has a large lead, which seems reasonable, but this is only a guess.

Running an analysis in chess.com with the Komodo engine suggests Bf6 as the best move, with +11.6 evaluation, so it left me even more curious as to why Stockfish doesn't even consider it.

# Answer
> 7 votes
To expand on what heuristic pruning means for an alpha-beta negamax search, which many chess programs use, typically the evaluation function has some kind of depth parameter and the alpha-beta window. What it does is to test each possible move one by one, calling itself on the resulting position with the depth parameter reduced and with the appropriate alpha-beta window passed in. eval(d,α,β) searches to depth d and returns the value of the current position truncated to the interval \[α,β\]. At the start we call eval(D,−∞,∞) where D is the maximum depth. Note that the alpha-beta window depends on the evaluation results for previously tried moves as follows.

We first set m := α before testing any move. When testing each subsequent move we would call t := −eval(d',−β,−m) and then set m := max(m,t). If m≥β then we can immediately return β. At the end we return m. The reason for calling "eval(d',−β,−m)" is that if the resulting position has true value u outside \[−β,−m\] then it would have equivalent effect on the true value v of the current position as the truncated value. (If u\<−β, then −eval(d',−β,−m) yields β so we return β, which is correct since v\>β. If u\>−m, then −eval(d',−β,−m) yields m so it does not affect m, which is correct since that move led to true value of −u\<m.) Here d' is set by a heuristic (e.g. quiescence search may set d' := d−1 for normal moves but d' := d−1/2 for check and d' := d for captures).

To understand how heuristic pruning helps, one must first understand how alpha-beta helps. When the move-ordering is optimal (it always tests an optimal move first), then alpha-beta eliminates all the other moves at every alternate recursion level in most of the cases. To intuitively see why, consider the first move. To find an optimal first move X, we really have to check all possible first moves. But after we test an optimal one first, m would be set to that value, and we call eval(,−∞,−m) for every other tested first move X'. But since we first test an optimal opponent response Y to X', we will find that it results in a value at least −m (since X' is not better than X), and hence immediately return (discarding all other opponent responses because the first one already confirms that X' is not better than X). This happens throughout the search tree, and so the branching factor is more or less reduced to 1 at every alternate level in the search tree. This effectively doubles the search-depth possible with the same resources.

Mathematically, it is impossible to do better than alpha-beta search if we want to prove that a move is optimal. However, in many games such as chess we can perform better on average by using heuristic pruning. Instead of testing all the moves required by the alpha-beta search, we discard many of the moves! Heuristics inform this process. For example, if d\>4 then we could for each possible move X, perform X then set t\[X\] := −eval(4,−β,−α) then undo X. After that, t\[X\] represents a depth-4 evaluation of those moves truncated to \[α,β\]. We might then choose to discard any move X if t\[X\]+3≤m; Informally, if move X causes a depth-4 evaluation that is at least a 'bishop' worse than the current best, we assume that it is poor enough that ignoring it will not affect the evaluation result.

Heuristic pruning (beyond alpha-beta) can hence reduce the effective branching factor (not just at every alternate level). That is why it is used in many modern chess programs today. The example heuristic I gave above is just for illustrative purposes; actual chess programs use a whole variety of complex heuristics to prune (e.g. null-move heuristic), as well as heuristics to **not** prune (e.g. the killer/history heuristic).

Now looking at the situation you have here, it is easy for many heuristics to prune off the best move `Bf6` unless the depth-0 evaluation gives high enough weight to king danger, because `Bf6` drops the bishop for a pawn and it takes quite a lot of quiet moves to see any benefits besides increased Black king danger. I am not sure, but the best line appears to be:

```
[Title ""]
[FEN "r1b2r2/pp1p1ppk/2n1p3/6B1/2P5/5N2/PQ3PPP/R4RK1 w Q - 0 1"]

1. Bf6 gxf6 2. Qxf6 Rg8 3. Ng5+ Rxg5 4. Qxg5

```

This line takes 2 quiet moves, 1 check and 4 captures. However, a pruning heuristic will very likely prune based on the first few moves of the following line:

```
[Title ""]
[FEN "r1b2r2/pp1p1ppk/2n1p3/6B1/2P5/5N2/PQ3PPP/R4RK1 w Q - 0 1"]

1. Bf6 gxf6 2. Qxf6 Kg8 3. Ng5 Nd8 4. Rad1 e5

```

Since it cannot see that this line ends in checkmate, it may believe that the bishop has been lost for a pawn. If the evaluation function had counted the position after `3. Ng5` as high king danger, it would not have pruned the `Bf6` line away. As it is, it likely weighed the king danger against the bishop loss and thought it was worse than keeping the bishop. Furthermore, since there are many possible moves instead of `Bf6` that keep the bishop, they would likely have pushed the `Bf6` line far down in the move-ordering, hence it never got searched deep.

# Answer
> 26 votes
Good question. I let Stockfish 11 think on the position, and even by around depth 25-26 it didn't suggest Bf6. But like in your case, after making the move on the board, Stockfish suddenly realizes it is the best move. Although what's also odd is that after Bf6 gxf6 Qxf6, it takes Stockfish longer than at least depth 27 to realize it's a mate in 9 moves/18 ply (instead of some evaluation that's "only" over +20).

One possible explanation for all this is due to how engines prune. If an engine spends an equal amount of time examining every single move in its calculations, it will be very slow (there's an average of roughly 30 moves in a given position, so the complexity for searching everything is on the order of 30^depth). Therefore, they will spend more time thinking on moves that look more promising, and stop wasting as many resources on moves that look clearly worse.

In the position you posted, there are multiple moves that give at least a +12 evaluation. Meanwhile, Bf6 drops a bishop, and perhaps it is only multiple moves further that White's overwhelming compensation for it becomes apparent. There are already many +12 moves available from the starting position, so an engine could decide not to waste time going deep into the Bf6 branch, stopping at a point before it realizes how good it is.

But then when you actually play Bf6 on the board, there's nothing else for the engine to look at. It's "forced" to examine the Bf6 branch, and then it quickly realizes it's very good (although in Stockfish's case taking a while to realize it's a forced mate, likely due to this same pruning issue).

Note that all the above is just my own understanding of things, and there could be other factors at play. If I had to guess why Komodo suggested Bf6 to you but not Stockfish, it would be because Stockfish prunes more aggressively in order to be *extremely* fast in searching.

# Answer
> 8 votes
It's all a matter of pruning. If you're not familiar with this concept, it's a key part of how engines search so deeply from a position. They are based on heuristics, e.g. the engine will search moves that give away a queen for no material compensation less. This allows it to focus its attention on the main moves in the position and search those deeper.

Good pruning contributes a huge amount to engine strength, but it's possible that pruning also cuts off the best move if the compensation is too deep (more technical term here is "beyond the search horizon"). That's what you're seeing. The heuristics for this position tell Stockfish to focus on other moves.\*

In any case, if you let Stockfish analyze deeper, it'll spot that Bf6 is the best move. At depth 38, it's suggesting Bf6 (+37.0), Be3 (+14.5) and Rad1 (+14.3).

\*I'm not sure if Stockfish has "if everything wins, search X less" code. It's possible. After all, Stockfish patches are tested against previous versions of the same program, and if everything wins then a patch that moves Bf6 up the move ordering isn't really an improvement - they yield the same result.

# Answer
> 0 votes
it is Bf6 after you let it run higher depth

But good for you for being like wesley so in breaking stockfish

---
Tags: strategy, stockfish, sacrifice
---


# Question
Title: When should I care about an opponent's pin?
This has been a problem that has been vexing me for a while, and it manifested again in my most recent game in which I played Black:

```
[FEN ""]

1. d4 d5 2. c4 c6 3. Nc3 Nf6 4. Nf3 e6 5. Bg5 h6 6. Bh4 Be7 7. cxd5 cxd5 8. e3 Qb6 9. Qc2 O-O 10. Bd3 Nc6 11. O-O Bd7 12. a3 Na5 13. b4 Nc4 14. Bxc4 dxc4 15. Ne5 Rfd8 16. Rfc1 Rac8 17. f4 Kf8 18. f5 exf5 19. Nxd7+ Rxd7 20. Qxf5 a6 21. Bxf6 Bxf6 22. Qxd7 Qc6 23. Qxc8+ Qxc8 24. Nd5 Qe6 25. Nxf6 Qxe3+ 26. Kh1 gxf6 27. Rxc4 b5 28. Rc8+ Ke7 29. d5 Qd4 30. Re1+ Kd7 31. Rcc1 Qxd5 32. Red1 Qxd1+ 33. Rxd1+ Ke6 34. Rc1 Kd5 35. Rc5+ Kd6 36. g4 Kd7 1-0

```

On move 6 I was forced to choose between breaking the pin on my knight or weakening my kingside. I chose to ignore the pin, which then furnished my opponent's position with many tactical opportunities. So, are there any rules or principles regarding pins, such as you should always break a pin as long as you are not immediately losing material? In games like this, how do you make the right decision when the threat is not immediately tactical, but will manifest later? How do you measure breaking the pin against other possible goods like development, king safety, and positional advantages?

# Answer
> 2 votes
As Hauke Reddmann wrote in the comments, the answer is "it depends". It's not a problem until you need the pinned piece to move.

In this game, your knight wasn't pinned after 6...Be7, but you proceeded to "self pin" after 8...Qb6 and 9...O-O. Even this wasn't a problem because you didn't need the knight to move. It did mean you can't play ...Nxd5, but White wasn't threatening to take on d5, so the knight wasn't immediately necessary. It did briefly become necessary when you played 17...Kf8 (White didn't play 18. Bxf6 Bxf6 19. Qh7 which would've made your king very uncomfortable), and in fact never was a problem at all, until you missed the tactic that won the game on move 21.

Could you have broken the pin with ...g5? Yes, but it's risky because after Bg3 your opponent has obvious plans to attack on the kingside. f4 or h4 would come with extra threat, and you'd have to fend it off when most of your pieces (and the pawn structure) want to play on the queenside.

...g5 makes more sense when you want to play on the kingside. Here's an example sequence from Ivanchuk-Yusupov. It doesn't involve a pin, but it illustrates when the move is OK.

```
[FEN "r3rnk1/pp2qpbp/2pp1np1/5bN1/1PPP1P2/BQN1p1P1/P3P1BP/R2R2K1 b - - 2 15"]

```

In this position, Black is definitely going to mount a kingside attack while White plays on the queenside, and the way you do it is by pushing the h- and g-pawns. Hence Yusupov played 16...h6 followed by 17...g5. Note White cannot play on the kingside because they lack space on the wing. This is in contrast to your game, where White can move pieces to the kingside much easier.

---
Tags: positional-play, pins
---


# Question
Title: What previous results match/compare to Alireza Firouzja's 3000+ performance in the European Team Championships?
Firouzja has just scored 8/9 against opposition with an average rating of 2664 - 7 wins and 2 draws. According to the video clip in this tweet his performance rating was 3017. According to chess-results.com it was 3015. Either way a stunning performance.

Has anybody produced a similar level of chess in standard FIDE rated competitions, 3000+? If not which players have got closest?

# Answer
> 14 votes
An unofficial list of the highest Tournament Performance Ratings (TPRs) on record in standard FIDE classical tournaments since 1970 is here: https://deletionpedia.org/en/List\_of\_highest\_chess\_Tournament\_Performance\_Ratings

Because this list was last updated in May 2015, high TPRs after that would not be included. However, I'm tentatively doubtful there has been a 3000+ rated performance since 2015. Usually Carlsen's best performance is thought to be Pearl Spring, Nanjing 2009, which barely crossed 3000. That's included on this list.

Adding in Firouzja, there are only 3 performances at 3000+:

1. Fabiano Caruana - St Louis, 2014 - 3098
2. Alireza Firouzja - ETCC, 2021 - 3015
3. Magnus Carlsen - Nanjing, 2009 - 3002

Not accounting for inflation, it appears Firouzja may have already surpassed Carlsen's highest-ever TPR. As you say, incredible stuff.

You might also find Jeff Sonas' attempt to correct for inflation interesting. (He concludes Karpov at Linares 1994 is the greatest tournament performance ever.) It's quite possible, given this article was written in the wake of Nanjing 2009, that similar analyses will be shortly produced on Chessmetrics so we can compare Firouzja's achievement.

EDIT: note that 100% pointscore results are generally excluded from discussions of TPR because the estimation cannot follow normal elo methods and is done by a separate and little-validated heuristic.

# Answer
> 3 votes
In addition to the information in last reply, There are also Wesly So 3183 and Karen Grigoryan 3103. But the level of the tournaments are not as sophisticated as Caruana and Firouzja case.

---
Tags: history, performance
---


title: Two seriesmover stalemate constructions

text:
# Question
Title: Two seriesmover stalemate constructions
Easy one: Starting position, but Black never moves. White makes n moves (no checking!) until Black is stalemated. Minimize n. Hint: You don't need to capture all Black pieces, pawns can also be blocked.

A bit tougher (it's already a bit of a challenge to find a position): Same, but until *White* is stalemated.

EDIT: To beat: 51 (Michael Caillaud, selfstalemate), 19 (Arno Tüngler, stalemate)

# Answer
For reference, Hauke's edit refers to a new Matplus.net Forum thread. Here are diagrams for each game.

Challenge A: White Stalemates Black

```
[Title "Arno Tungler, Matplus.net Forum 11/22/2021, ser-=19"]
[FEN ""]

1. d4 null 2. d5 null 3. d6 null 4. dxc7 null 5. cxb8=R null 6. Rxc8 null 7. Rxa8 null 8. Rxa7 null 9. Rxb7 null  10. Rxd7 null 11. Bg5 null 12. Bxe7 null 13. Bxd8 null 14. Rxf7 null 15. Rxg7 null 16. Rxh7 null 17. Rxh8 null 18. Rxg8 null 19. Qd5=

```

Challenge B: White Stalemates Themselves

Original Source: https://www.france-echecs.com/article.php?art=20010824124929501

```
[Title "Michel Caillaud, France Echecs 4/5/2004, ser-=51"]
[FEN ""]

1.a4 null 2. a5 null 3. a6 null 4. Ra3 null 5. Rf3 null 6. Rxf7 null 7. Nc3 null 8. Nd5 null 9. Nxe7 null 10. Nxg8 null 11. b4 null 12. b5 null 13. b6 null 14. bxc7 null 15. cxb8=R null 16. Ba3 null 17. Bxf8 null 18. c4 null 19. c5 null 20. c6 null 21. cxb7 null 22. bxc8=N null 23. Nce7 null 24. Rb6 null 25. Re6 null 26. d4 null 27. d5 null 28. d6 null 29. Qd2 null 30. Qh6 null  31. e4 null 32. e5 null 33. h4 null 34. h5 null 35. Rh3 null 36. Rg3 null 37. Rgxg7 null 38. Kd2 null 39. Kd3 null 40. Ke4 null 41. Kf5 null 42. Kf6 null 43. Bd3 null 44. Bg6 null 45. f4 null 46. f5 null 47. Nh3 null 48. Ng5 null 49. Nxh7 null 50. g4 null 51. g5!=

```
> 1 votes

---
Tags: problems, records, stalemate
---


title: Ruy Lopez - why does Black not take e4?

text:
# Question
Title: Ruy Lopez - why does Black not take e4?
In the following Ruy Lopez opening;

```
[FEN ""]
1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O Be7 (5... Nxe4)

```

Now the question, instead of Be7 why does Black not play Nxe4 as e4 is not defended?

Thanks

# Answer
5...Nxe4 leads to the Open Spanish. It's a respectable opening with some very long lines, as is typical of the Ruy Lopez.

One thing it does not do though is win a pawn, because White can easily win it back after 6. Re1 (the main line is actually 6. d4 because Black cannot hold on to the pawn anyway). The knight is threatened and will eventually be forced to move, after which the e5-pawn falls.

Here's an illustration of what might happen if Black tries to hold on to the pawn:

```
[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Nxe4 6. d4 exd4 {Or the e5-pawn is lost.} 7. Re1 {Threatening the e4-knight. It is pinned to the king.} d5 {Or 7...f5, which is also met by 8. Nxd4 except this time it threatens Nxf5. 7...Qe7 would be even worse, since after 8. Nxd4 the knight is still pinned and White threatens to exploit it with 9. f3.} 8. Nxd4 {White threatens to take twice on c6 and also to exploit the pin with 9.f3. Black cannot keep the extra material.}

```
> 14 votes

# Answer
White does not lose a pawn here as e4 was indirectly defended via castling. For example, after ...Nxe4 6. Re1 Nf6 white can take the e5 pawn to restore material balance.
> 8 votes

# Answer
William: (1) Taking is the Open Spanish, which is perfectly playable for Black. (2) But, as others have noted, Black doesn't keep the pawn. (3) If Black tries to keep the pawn, he can get himself into trouble along the e-file. A relevant game to look at is Fischer-Trifunovic 1961. Another is Daskalov-Belchev 1975. Be sure to look at them with an engine, so as to spot the weak moves--especially in the latter game.

Edited to add: I have the game saved here: https://www.chess.com/a/kd2jsHzW1KMk . In case you cannot see it, here is the game score:

```
[Event ""]
[Site "Bulgaria"]
[Date "1975.??.??"]
[Round "?"]
[White "Daskalov Georgi (BUL)"]
[Black "Belchev B"]
[Result "1-0"]
[ECO "C80"]
[WhiteElo "2355"]
[BlackElo "0"]
[Annotator ""]
[Source ""]
[Remark ""]
[FEN ""]

 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O b5 6. Bb3 Nxe4 7. d4
    exd4 8. Re1 d5 9. Nc3 dxc3 10. Bxd5 Bb7 11. Bg5 f6 12. Rxe4+ Be7 13.
    Bxf6 gxf6 14. Ng5 fxg5
    15. Qh5+ Kd7 16. Qh3+ Ke8 17. Rd1 Qd6 18. Re6 Qf4 19. Qxc3 Rf8 20. Bxc6+ Bxc6
    21. Qxc6+ Kf7 22. Rxe7+ Kg8 23. f3 Rad8 24. Qe6+ Kh8 25. Rxd8 Rxd8 26. Qe5+ Qxe5
    27. Rxe5 h6 28. Rc5 Rd1+ 29. Kf2 Ra1 30. a3 Ra2 31. b3 Rxa3 32. Kg3 Ra1 33. Kg4 Rg1 34. g3 Rg2 35. h4 gxh4 36. Kxh4 a5 37. Rxc7 a4 38.
    bxa4 bxa4 39. c4 a3 40. Ra7 a2 41. f4 Rc2 42. Kh5 Rxc4 43. Kxh6 Rc6+
    44. Kg5 Rc2 45. f5 Kg8 46. Kg6 Kf8
    47. g4 Rf2 48. g5 Ke8 49. f6 {Game may have continued...} (49. f6 a1=Q 50. Rxa1 Kd7 51. f7 Ke6 52. Re1+ Kd5 {+M20}) 1-0

```

Alas, I am not sure where I first saw it--possibly in an article somewhere.
> 4 votes

---
Tags: opening, ruy-lopez
---


# Question
Title: Why don't engines show explicitly that a certain move takes to a threefold repetition (instead of just showing 0.00)?
I get that from the point of view of the engine there's no difference; equal is equal. But for a human analyzing with an engine, I find quite important to note that a move takes to a balanced position or to a threefold repetition (which finishes the game).

For example, say I'm analyzing a position from my favorite opening, and the engine says the best move is d4(+0.10), and the second one is h6(0.00). But it happens that h6 will be draw by repetition. Depending on my mood or my position on a tournament or whatever other factors, I could prefer one or another, and the fact that h6 just finishes the game is quite important in my opinion.

To me the main difference is that threefold repetition just immediately finishes the game in a draw, whilst a 0.00 position can just have any final result.

Of course you can check the line provided by the engine to realize that it takes to threefold repetition, but wouldn't be much useful to use some special character for it?

# Answer
It's easy enough to make the engine say it's 0.00 because of a 3-fold repetition. If you look at the relevant part of Stockfish's code, they are basically if statements that return a particular value if the condition is met. If you want to know if there's a 3-fold, you could add a `print "this is a 3-fold"` command and you'll have it. I'm hard-pressed to see why it matters, though. 0.00 is 0.00, regardless of whether it's insufficient material or fortress or 3-fold or whatever.

It sounds like you want to know if the position is a dead draw or if it's still complex enough that you might be able to outplay your opponent. *This* is much harder to put in machine-understandable form. How would you define these things? There are certainly positions where engines have no trouble finding the best moves (and therefore all games end 1/2-1/2) while human games show it is very unbalanced.

That said, there is some effort in the computer chess community to go beyond finding the simple "best move". This started with contempt for handcrafted engines, which uses the material remaining on the board as a proxy for how complex the position is. The idea is that if you set contempt high, then the engine will play inferior moves as long as it keeps more material on the board, which leaves more scope to outplay a weaker opponent. Conversely if you set negative contempt, then the engine will simplify the position and shoot for a draw. That might be what you're looking for.

Today's strongest engines are all neural-network based, for which contempt is more difficult to implement. Neural network eval return W/D/L, which is the probability of a win, draw, or loss from that position; there is no number for complexity (and probably cannot be since you'd need a very large training set with labelled "complexity" to get started). People are trying the so-called *draw score*, which turns draws from worth 0.5 points to, say, worth 0.4 points. This, it is hoped, makes the engine avoid draws - after all if one move leads to a three-fold while another leads to a 10% chance of win, 80% chance of draw, and 10% chance of loss then the second move has a higher expected score and becomes preferable. But even this does not work perfectly, since your engine might assess a position as drawn while the opponent sees a big advantage, see e.g. this game where Leela saw 99.3% chance of draw on move 158, and still lost the game eventually.

Ultimately you still need a way to measure if a position is "dead", and a good way to do that doesn't exist (see this question). If you have a smart idea to measure how "live" the position is, you can probably get it published in a journal.
> 8 votes

# Answer
There is in general no such thing as a simple "this leads to threefold repetition". There may have been millions of different positions considered, and of those, if you select at each branch at your move the highest evaluation for you, and vice versa at the opponent's branch, that leads to a 0.00 evaluation that happened to come from a threefold.

That doesn't mean that that threefold was *forced* in any way. Maybe there were a thousand different things you could have done instead but they were -0.1, or the opponent could have done but they were +0.1. And then were another thousand that *also* led to 0.00 but for different reasons: tablebase draw, stalemate...

So, I guess engines could change the way they work, so that evaluation is not a fixed number but there can be different ways of being 0.00 - 0.00 (threefold) would be the same *value* as 0.00 (stalemate), but the user could still be shown which it is.

But it'd always be quite random which of the many 0.00s in the entire tree you'd get to see.
> 4 votes

---
Tags: engines, analysis, threefold-repetition
---


# Question
Title: Which online chessboard orientation do professional players prefer?
Do professional online players always prefer to play on a chessboard oriented with the Black pieces on the top or with their own pieces on the bottom? Is there a consensus on this, and has there ever been a formal or informal poll?

# Answer
Since over the board chess is played with each player's pieces starting on the side closest to them, the natural board orientation is with your own pieces on the bottom. This is the default orientation when a game starts on all the major chess-playing sites and is how all the top players like Nakamura, Carlsen, etc. play when they stream on Twitch. It is not common to play in the other orientation unless it for a specific reason, like as a challenge.

There are occasions where flipping the board can be helpful still, presumably even at the top level, such as when trying to remember opening theory that you play as one color but not the other. However, most grandmasters could visualize the flipped board in their head just as easily as flipping the orientation.

As a ~2000-rated player on Lichess, I occasionally find it helpful to analyze positions from the opponent's orientation before my move, especially when I'm making a choice between attacking moves. Having lost so many games when the opponent made a strong move into my position that I had not considered, I am usually better able to judge whether a move will be crushing or defendable from the defending orientation. However, this is also not so relevant for professionals since they are skilled at analyzing the board from any orientation. Part of the reason they are strong players is because their ability to see the best moves on the board is not directional.
> 8 votes

---
Tags: online-chess, chessboards, visualization
---


# Question
Title: Are there consumer-level game play analysis systems that overlay the analysis on the board real-time?
An example of what I mean would be Thinking Table, though the Thinking Table is not a consumer product:

> Thinking Table is a series of works that explore the invisible, elusive nature of thought. Play chess against a transparent intelligence, its evolving thought process visible on the board before you.

**CAPTION:** The above image is three images, from left to right, the images are of the opening, middle, and end of the same game. The lines shown on the board are the engine's "thoughts" for one move during the game.

> Each Thinking Machine is an artificial intelligence program – ready, willing and able to play chess with the viewer. If the viewer confronts the program, the computer’s thought process is sketched on screen as it plays. A map is created from the traces of literally thousands of possible futures as the program tries to decide its best move. Those traces become a key to the invisible lines of force in the game as well as a window into the spirit of a thinking machine. The pace of interaction is deliberative, unlike the rushed tempo of popular video games. Indeed the true subject of the piece is not games or chess, but contemplation and introspection.

# Answer
I'm pretty sure Fritz has something like this, not to the extent of going as deep as the images you provided, but any potential patterns that it likes are represented graphically, using coloured arrows and squares, while analysing.

---

**Example of Fritz visual output:**

**SOURCE:** Visualize search in Fritz 10 (21.05.2007)
> 6 votes

# Answer
Chess Tiger Pro (for iOS). Link to App Store
> 2 votes

# Answer
Thinking Machine 6 is an online JavaScript port of previous Thinking machines (I remember seeing Thinking Machine 4 over a decade ago and it dates back to 2004). The source code is publicly available by looking at the page's source js file.

Also, since Stockfish shows its top results while searching, it should be possible to build a UCI-compliant frontend to visualize all the currently searching top lines. Actually, Lichess's analysis board does show Stockfish's current best moves in real-time.
> 1 votes

---
Tags: analysis, software
---


# Question
Title: Why is it inappropriate to take a photo with the trophy according to Carlsen?
In the press conference (at about 44:20) of World Chess Championship, Maurice Ashley invites Nepo and Carlsen to take a photo with the trophy but Carlsen says that he finds it inappropriate. Why is that?

# Answer
> 8 votes
Taking a photograph with the trophy is like saying "I have won the trophy". Carlsen hasn't won the trophy (yet); it is possible Nepo wins the match as well in which case Nepo should be the one to take the photograph with the trophy.

# Answer
> 3 votes
He probably doesn't like that guy who told him to take photo which was pretty clear in the interview once in the past when Carlsen got angry on him for no apparent reason. Also Maurice works for chess.com that Carlsen apparently doesn't like too much neither. Maybe Carlsen doesn't like to be pushed around for someone to make a "cool" Instagram like photo. The most important reason though IMO would be that based on football (I don't know too much about other sports) they never make pictures in front of a trophy unless they're winners who already won it. Before the competition begins they either Photoshop the trophy somewhere in the promotional materials or like in the finals you can see players only walk next to the trophy before the match. Only the winner gets to be photographed posing with the trophy I believe at least in football that Carlsen is a fan of so he might think similar. He also is very experienced in many chess ceremonies so it might look the same in chess then.

---
Tags: world-championship, etiquette, carlsen
---


title: Was AlphaZero taught castling?

text:
# Question
Title: Was AlphaZero taught castling?
Since castling involves one player moving two pieces in one move, was AlphaZero just given this move, in the same way it was told that players take turns and a win is better than a loss? In other words, it didn't learn it on its own. (I guess it must have been; the range of possible two, three, four, or five piece moves, for all it knows, would just be too big to learn on its own.)

# Answer
Other answers are right in that AlphaZero was implicitly told that castling is a move that exists, I'll elaborate on how exactly that happens by explaining the inputs and outputs of the neural network.

# Input format

*Note: The exact details and screenshots are from my own implementation, which is broadly similar to AlphaZero. At the end of this answer I note the differences between this input format and the one the real AlphaZero uses.*

At the core of AlphaZero is a neural network, which gets as an input the current board state. This board state is encoded as a stack of images, from the point of view of the current player. For the starting position, this looks like this:

From left to right:

* 2 planes: Is it whites turn, is it blacks turn
* 4 planes: Castling rights for us left and right, castling rights for the opponent left and right
* 2 planes: Binary digits for the repetition counter
* 6 planes: The side to move's pieces
* 6 planes: The opponent pieces
* 1 plane: The en-passant square if any

In this context castling rights means whether the king or rooks have moved in the past, not whether castling is currently available as a move.

The network is never explicitly told that the 3rd to 6th planes have anything to do with castling or even moving the king, it has to figure that out itself during training.

# Output move format

The network has two outputs, the first is the estimated *value* of the position and the second is an estimation of how good each possible move is, called the *policy* head. This second output is again a stack of images, and looks like this:

In reality this is a stack of 72 images, I cut out a bunch of them in the center. The encoding here is that the square within the image is the square the move starts from, and the plane means what kind of move it is. For example, the first plane means "move one square forward", the second "move two squares forward", the 10th plane counting from the end means "do a knight move forward and left". As a full example, in this position the bottom left square in the first image means "move the rook on A1 to A2".

This encoding does not include which piece actually makes the move. Pushing the e pawn two squares looks the same as moving a hypothetical queen from e2 to e4.

The first row is the actual output of the network without any post processing. As you can see this output is full of nonsensical moves with starting squares on top of opponent pieces. To fix this only available moves are considered, the rest are set to zero and the output is re-normalized. The result is shown in the second row. As you can see in the starting position the network likes pushing the 4 center pawns two squares forward, and also moving the kingside knight to the center of the board.

**Importantly this step of ignoring of invalid moves and renormalizing is the only place where knowledge of chess moves is put into the AlphaZero training process! The valid moves are not actually given as a network input or anywhere else, they're only considered when computing the network output. The network is not discouraged from suggesting invalid moves, these suggestions are simply ignored.**

# Castling

Of course this question was actually about castling, so let's look at a position where the network wants to castle (and can). Like all other moves castling is encoded as moving from one square (e1) in certain way (two squares to the right for kingside castling).

Fen string:

`r1bqkb1r/1ppp1ppp/p1n2n2/4p3/B3P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 2 5`

The first row is the board input, the second row the policy before removing the invalid moves and the last row is the final policy output. The bright white pixel in the bottom center encodes "e1, two squares to the right" which means castle kingside. Other moves the network is considering are pushing more center pawns and moving the f3 knight again.

# Bonus

It's also possible to visualize the full network internals in this way, here are some examples:

I don't think much insight can be gained from this but it looks cool!

# Sources

Most of what is in this answer is also explained pretty well in the AlphaZero paper itself, specifically the "Representation" section.

The images were generated by my own work-in-progress implementation attempt, kZero. The network shown matches the actual AlphaZero network very closely, but was trained on the lichess database instead of by real selfplay.

# Differences with the real AlphaZero input format

* In the real AlphaZero, the position of the pieces is given for each of the 8 previous board states. Chess is not fully described by the current board state, see eg. the Fifty-move rule or Threefold repetition. Adding 8 steps of history helps, but it's still not really enough.
* AlphaZero doesn't need an en-passant plane since the network can just compare the previous two board states to see if en passant is possible.
* The are some slight differences around player colour and move counter planes, but these are not very significant.

All together this means AlphaZero had 8 * 14 + 7 = 119 planes, whereas I only talked about 21 for most of this answer.
> 53 votes

# Answer
> was AlphaZero just given this move

It was given this move in the same way that it was given all other moves. It started with complete knowledge of the rules of the game. In machine learning terms, castling would be part of its baseline knowledge of *state transitions*.
> 50 votes

# Answer
The AlphaZero paper "Mastering Chess and Shogi by Self-Play with a General Reinforcement Learning Algorithm" by David Silver et al. contains this explanation

> Knowledge of the rules is also used to encode the input planes (i.e. castling, repetition, no-progress) and output planes (how pieces move, promotions, and piece drops in shogi).

(An input and output plane are the terms of art for how the board and possible moves are represented to the AlphaZero model.)
> 12 votes

# Answer
> was AlphaZero just given this move, in the same way it was told that players take turns and a win is better than a loss?

Actually you've hit upon 3 very distinct ways that AlphaZero was programmed. Castling is a potential move that's built into the algorithm; AlphaZero doesn't need to learn how to do it, just when to do it. The authors list the all the knowledge encoded into the algorithm on page 12 of their paper:

> Domain Knowledge
>
> 1. The input features describing the position, and the output features describing the move, are structured as a set of planes; i.e. the neural network architecture is matched to the grid-structure of the board.
> 2. AlphaZero is provided with perfect knowledge of the game rules. These are used during MCTS, to simulate the positions resulting from a sequence of moves, to determine game termination, and to score any simulations that reach a terminal state.
> 3. Knowledge of the rules is also used to encode the input planes (i.e. castling, repetition, no-progress) and output planes (how pieces move, promotions, and piece drops in shogi).
> 4. The typical number of legal moves is used to scale the exploration noise (see below).
> 5. Chess and shogi games exceeding a maximum number of steps (determined by typical game length) were terminated and assigned a drawn outcome; Go games were terminated and scored with Tromp-Taylor rules, similarly to previous work (29).
>
> AlphaZero did not use any form of domain knowledge beyond the points listed above.

In short, at every turn the neural network at the core of AlphaZero receives information about every piece on the board and outputs a number for every possible move allowed in chess. On top of that neural network there is an algorithm that controls the gameplay, and that zeroes out all currently impossible moves (like the neural net wanting to move a queen despite having no queen) then it picks the valid move with the highest number outputted by the neural net (sort of, the actual move is probabilistic). In this sense it was pre-programmed how to castle, and in fact at the beginning of training it has an equal chance of castling as it does moving a pawn (assuming the board state at that turn allows castling). During training the neural net will learn when castling leads to winning the game.

The other answers already said as much, but I want to add to the other 2 things you mentioned. Taking turns is actually built into the algorithm that manages the game and it's such a central feature that the neural network was designed around it. It's actually quite hard to move away from turn based decision making when designing neural networks, and it's one of the features they address in their AlphaStar paper. AlphaStar plays Starcraft, a real time strategy based game where both players can make as many decisions as they want at any time. They actually don't really solve the continuous decision problem in AlphaStar, they just make the "turns" have a variable duration so the neural net can choose to make decisions every millisecond during intense battles or every 10 seconds if there's not much going on.

Finally the win/loss thing is programmed into the optimizer side of AlphaZero's algorithm. The neural network at the core of AlphaZero is a mathematical function with lots of parameters, the value of the parameters determine what moves it thinks it's best. In essence you want to keep the parameters when it wins and you want to change parameters when it loses; but the exact way they make those changes is explained in the paper and it's quite ingenious. In any case it's actually quite easy to change the desired outcome (compared to the difficulty of moving away from turn based games). The authors desire the neural net to win at chess for obvious reasons, but they could very easily encode the desire to maximize pawn promotions, as an example.
> 2 votes

# Answer
I do not understand your point. It may be that you don't understand how engines work. AlphaZero is nothing special to be honest. Let me explain.

Engines do three things while searching for a move.

1. Find out the possible moves.
2. Trim out searching for moves which seem useless(in AlphaZero's case, it also trims out any invalid moves)
3. Evaluate the position.

(The neural network can actually evaluate any position but invalid moves are ignored and it figures out that those moves are not worth searching; so the neural network is never explicitly told that some moves are invalid and it has to figure it out itself but the engine itself is informed; this doesn't actually change anything because eventually illegal moves are trimmed out, just at a later stage)

The first two things that AlphaZero does is the same as any other engine. Castling, is a possible move, so the way that it is generated is the same as any other non neural network engine.

The thing is that when evaluating a position, other engines used to use a fixed tuned set of values. They would calculate king safety, space, mobility, etc using hardcoded values which were generated by years of tuning values. AlphaZero, on the other hand, uses neural networks for evaluating positions. It's all the difference. AlphaZero is no alien.
> 1 votes

---
Tags: castling, alphazero
---


# Question
Title: A deceptively simple eight piece endgame
I am in the dark about the following endgame, with white to move. May someone with FinalGen (or a powerful engine) give me a response? Is it a White win or a draw?

```
[FEN "8/1k6/5R2/P7/1KP4p/5P2/8/5r2 w - - 0 1"]

```

# Answer
Stockfish 14+ NNUE evaluates this position as +0.5 (depth = 62, 22036k nodes/s).

The principal variation (see below) leads to a **theoretical draw** according to the 7-piece tablebases.

```
[FEN "8/1k6/5R2/P7/1KP4p/5P2/8/5r2 w - - 0 1"]

1. Rf7+ Ka6 2. Rh7 Rxf3 {Theoretical Draw according to the 7-piece tablebases} (2. Rf6+ Kb7 3. f4 h3 4. Rb6+ Kc7 5. Rh6 Rxf4 {Theoretical Draw according to the 7-piece tablebases})

```

Other lines suggested:
From Justin Stafford's comment: 1. Rb6+ Ka7 2. Rh6 Rxf3 3. Rxh4 (**theoretical draw**)
From David's answer: 1. Rh6 Rxf3 (**theoretical draw**)
> 2 votes

# Answer
No need for engine analysis, that's a win for White since that parciular a+c pawn endgame is won. White can simply trade the other two pawns with Rh6
> -4 votes

---
Tags: analysis, endgame, rook-endgame
---


# Question
Title: Could you recommend me game collection books of attacking players?
I have found a lack of aggression in my style and I want to study aggressive players' games to develop my style. Please recommend books that fulfill this purpose. I am an advanced player.

# Answer
Players to look for (short list, makes a good place to start):

* Mikhail Tal (you can try looking up, say, 'attack like tal' on youtube. eg , )
* Alex Shirov
* Rashid Nezhmetdinov
* Leonid Stein

(Interesting edit, considering it's just video links and the OP specifically requested books, and the links are not even about the named book, which was already mentioned later in this answer.)

Books:

* Rocking The Ramparts - Larry Christiansen
* Storming The Barricades - Larry Christiansen
* The Modern Chess Sacrifice - Leonid Shamkovich
* Attack With Mikhail Tal - Damsky
* Attacking Manual (2 vols) - Jacob Aagaard

From the more recent pile:

* Sacrifice and The Initiative in Chess - Ivan Sokolov

And if more distant historical players are more your thing, look for:

* Alexander Alekhine
* Harry Nelson Pillsbury
* Rudolf Spielmann
* Frank Marshall
> 2 votes

# Answer
I am probably too weak to give advices (I am somewhere between 1700-1800 on chess.com), but since I am on a similar road maybe those books will help:

* *Attacking Chess: Aggressive Strategies and Inside Moves - Josh Waitzkin* \- I have read this book entirely. Actually it does not teach you a method, but various cases. It is a fun text to read, and it shows you about the mood and attitude you have to have. The examples are instructve but you have to take your time to absorb them
* *A Guide to Attacking Chess - Garry Lane* \- This teaches you elements and can constitute a method to attack. It is really instructive and a really good book
* *Looking for Trouble - Dan Heisman* \- This is not about attacking, but more about spotting mistakes. However this is important, since when you have advantage you have to push and when you are on defense you have to solidify. But any mistake can change that, and when a mistake is not spotted than everything changes.
* *How to Reasses Your Chess - Jeremy Silman* \- This is not a book about attack. It is about imbalances. But you can attack successfully if you have a reason (weaknesses, space, speed, etc). Otherwise attacking blindly is like trying to destroy a fortress by hitting your head into walls. No chance. Any alternative book about positional elements gives you reasons for attacks.
* (Addition edited in by H.R.) A classic is *Art of Attack in Chess - Vladimir Vukovic*, with special view on attacking the king (uncastled, castled with no weaknesses, castled with weaknesses, with pawns, with officers...).
> 6 votes

---
Tags: theory, books, recommendations
---


title: Why this exchange

text:
# Question
Title: Why this exchange
I’m reading a book saying that now black Knight at b4 is under attack so need move away.

However Stockfish app suggests take the white c3 Knight first using f6 Bishop , then black will Rcxc3 take the Bishop, the white can Nc6 move Knight away.

So, is there some reason to do this Bishop-Knight exchange before Nc6? Or I’m not using Stockfish properly?

# Answer
> 6 votes
The knight is going to have an amazing square on d5 so it's a great idea to trade it before that can happen. Probably an oversight by the author (specially if the book was written before the computer era). Black's position is lost either way so probably not much attention was given to this spot.

---
Tags: analysis
---


# Question
Title: Chess Engine: Generate a Bitboard of Pinned Pieces
I'm currently working on a chess engine and have a pseudo-legal move generator working. I'm looking for a way to efficiently generate a bitboard of pinned pieces, so I could skip them when generating legal moves. How would one go about doing this, given 12 bitboards for each piece, and a bitboard called UNSAFE with all the squares the opponent is threatening?

# Answer
This task is nontrivial and cannot be obtained easily or setwise from the available bitboards.

The following solution is an example for how such a task might be done for a generic slider - only obvious substitutions are necessary to convert this code to be usable for bishops, rooks and queens.

First, identify the set of possible pinn**ing** pieces by calculating sliding attacks *from the king square*, using the opposite side as the set of occupied squares.

```
BitBoard bb_pinners = slider_moves(king_square, bb_other_side) & bb_other_side;

```

All bitboard engines should have some function similar to `bishop_moves` or `rook_moves`, which uses magic bitboards, PEXT or Koch-Stone to generate sliding moves from a square, given a bitboard of occupied squares as blockers to the slider.

To determine the set of pinned pieces from the set of pinners, it is necessary to iterate through the set of possible pinners (this is why pinned pieces cannot be calculated setwise).

For each pinner, we consider the set of bits between the pinner square and the king square (using the utility function `between`), determine if there is only one bit set, and if so, add that bit to the set of pinned pieces.

```
BitBoard bb_pinned = 0;
while(bb_pinners) {
    Square sq = pop_bit(bb_pinners);
    BitBoard bb_possible_pinned = between(sq, king_square) & bb_own_side;
    if(only_one_bit(bb_possible_pinned)) {
        bb_pinned |= bb_possible_pinned;
    }
}

```

Here, `pop_bit` finds the index of and removes the least significant bit of bb\_pinners.

Stockfish implements a similar strategy in `slider_blockers` to determine possibly pinned pieces.

It is also worth mentioning that even with a set of these blockers, this does not mean that they may be excluded from legal move generation because if the pinned piece is a slider itself of the correct type, it may still have legal moves despite being pinned, under the above algorithm's definition.
> 6 votes

# Answer
Pinned pieces only exist when attackers are sliding pieces (bishop, rook, queen). Also pinned pieces can move along the attack ray to the king, you cannot exclude them from legal moves directly. For example, the rook can move d4 and d6 in the board image below and the pawn can do enpassant in the 2nd example. You can check all 8 directions N, W, E, S, NW, NE, SW, SE to get all pinned pieces.

A piece is pinned if it suits the rules below.

* It is a friend piece
* It is the closest piece to the friend king placed on the path from king to the end of the board on specific direction (NORTH, SOUTH-EAST etc.)
* The second closest piece after the friend is the enemy and can attack along the direction to the king. Rook and queen for the N-S-W-E. Bishop and queen for NW-NE-SW-SE.
* `UnpinnedMoves` = `Pseudolegalmoves(pinned_piece)` & `PathFromKingToTheEnemy`

For example I have shared my code to find the pinned piece on the NORTH. A8 is LSB and H1 is MSB in my bitboard. You can change `BitScanReverse()` into `BitScanForward()` according to your bitboard design and direction that is checking for pinned piece. (for south it must be `BitScanForward()` in my code)

```
public static ulong Pinned_NORTH(ulong king_loc, ulong friendPieces, ulong allPieces, ulong rookEnemies, ulong queenEnemies)
{
    //Gets all vertical sliding enemies
    ulong straightSlidingEnemies = rookEnemies | queenEnemies;

    //if no rook or queen enemies exist, there is no pinned piece
    if(straightSlidingEnemies == 0)
       return 0;

    //get all squares on the North side of the king
    ulong northSquares= CrossLookup.NORTH[king_loc];

    //get intersected pieces at the north side of the king, rook and queen in the example
    ulong intersectedPieces = northSquares& allPieces;

    //get closest piece to the king in intersectedPieces, rook in the example
    ulong closestPiece = intersectedPieces.BitScanReverse();

    //check if the closest piece is our friend
    ulong friend = closestPiece & friendPieces;

    //if it is ENEMY, there cannot be a pinned piece in the NORTH
    if (friend == 0)
        return 0;

    //Get second closest piece and check if it is an enemy that is a rook or a queen who can attack from the NORTH
    ulong slidingEnemy = (intersectedPieces & ~closestPiece ).BitScanReverse() & straightSlidingEnemies ;

    //if it is NOT A SLIDING ENEMY, there cannot be a pinned piece in the NORTH
    if (slidingEnemy == 0)
        return 0;

    //Otherwise closest piece is a pinned piece and can only move along the ray from king to the enemy
    return friend;
}

```
> 2 votes

---
Tags: engines, programming, pins, bitboard
---


# Question
Title: What will happen if all games are draws for a World Chess Championship?
What will happen if all the games in the World Chess Championship are draws? Who will be considered the world champion?

# Answer
> 34 votes
From the Wikipedia page of WCC 2021:

> The match consists of 14 games, and a score of 7½ wins the world championship. If the score is equal after 14 games, tie-break games with faster time controls will be played:
>
> * 4 rapid games with 25 minutes each + 10 seconds increment starting from move 1. If a player scores 2½ points or more, \[they win\] the championship.
> * If the score is equal after the rapid portion, up to 5 mini-matches of 2 blitz games will be played. Time control is 5 minutes + 3 seconds increment. If any player wins one of these mini-matches, the tie-break ends and \[they win\] the championship.
> * If all 5 blitz mini-matches are drawn, 1 sudden death (Armageddon) game will be played, where black has draw odds and 4 minutes, and white has 5 minutes. Players receive 2 seconds increment starting move 61.

Meaning, if they draw the Armageddon match, it is counted as a win for black.

See also: Regulations for the FIDE World Championship Match 2021 (section 4.3.2)

---
Tags: draw, world-championship
---


# Question
Title: Did any other language than English ever use Descriptive notation? Which languages have always used Algebraic?
Descriptive notation seems to be limited to certain languages like English, and I found a Wikipedia article that mentions Spanish and French.

I have never seen a Russian book that uses Descriptive, and in fact, I can go back to the 1800's in Russian books, and they all use Algebraic.

In particular, I would like to see a list of languages that used Descriptive before finally adopting Algebraic, but I would also be interested in a list that have always used Algebraic.

# Answer
Stamma invented algebraic notation, and it was used sporadically by other writers (e.g. Allgaier) alongside several other systems. Algebraic notation really took off with the German Handbuch, first published in 1843, which was the MCO of its day and hugely influential. Algebraic has been standard in German language chess literature ever since.

There wasn't much Russian language chess literature until the 20th century, even Jaenisch actually wrote in French. I'm not sure if there was ever such a thing as Russian descriptive notation, all the 20th century Russian books adopted algebraic notation.

Spanish, Catalan and to a lesser extent French used a different form of descriptive notation. In Spanish descriptive, the move 1.c4 would be written as 1.P4AD (4th rank is given before "AD", Alfil de Dama, or Queen's Bishop).
> 3 votes

# Answer
Originally there was ONLY descriptive and it was used in ALMOST ALL languages, if not actually in ALL of them.

Each language used the letter from their words for the pieces to use to describe moves.

EG Spanish would say AxT for Bishop takes Rook French and other languages used their words to identify the letter for the pieces.

I never saw Russian magazines using algebraic before it became the standard but they may have been part of the movement to transition away from descriptive. Can't speak to Russian books as I never had any of those. And I am positive that if you go back far enough that descriptive was the only method used.

And I never saw algebraic used anywhere until long after the 50s. Not sure when it became popular but it did take a while to displace descriptive and really needed FIDE to make it happen.

Michael West noted elsewhere a German book for Carlsbad 1923 and said he had no problem playing through the games.
> 1 votes

---
Tags: history, books, notation
---


# Question
Title: What is the difference between a waiting move and zugzwang?
I can't see the difference between a waiting move and zugzwang.

# Answer
Zugzwang is when one side would like to "pass" but cannot. With a waiting move, you essentially do "pass". A waiting move *could* lead to zugzwang if one side has the ability to play them and the other does not, but this is by no means necessary.

An opponent might have their own waiting moves (in which case the game could be drawn by repetition unless one side decides to do something meaningful) or they might have a different evaluation of the position and decide to simply proceed with their plan.

For example, one side might play a waiting move to see which side the opponent castles on, but the opponent may well think that the benefits of castling right then outweigh the drawbacks of giving the first player that information.
> 15 votes

# Answer
A waiting move is a move to wait and see what your opponent will do.

If you are in zugzwang then all moves worsen your position.
> 8 votes

# Answer
The former is a *move* which passes the initiative on to the opponent.

The latter is a *position* where that initiative is a burden, and all moves are detrimental to the player with the move.
> 3 votes

---
Tags: terminology, zugzwang
---


title: Online blindfold chess

text:
# Question
Title: Online blindfold chess
Does anyone know a site where I can type the moves with keyboard, hide the board and only see the score sheet?

I want to play blindfolded. I used to play a lot but I want to play online.

# Answer
In addition to Brian's answer about chess24.com.

You can play blindfold chess too at chess.com

Here are the instructions how to activate blindfold on chess.com:

* `Tools`
* `Options`
* `Designs`
* `Board Colors`
* Select `BlindAll` from the drop down menu for pieces
* Then `apply`.

More info can be found here
> 4 votes

# Answer
In addition to the other answers, lichess allows you to do this.

Select the menu (three stacked lines to the right of your profile name), select Preferences, select Game Display, and at the bottom turn on Blindfold Chess.
> 7 votes

# Answer
Try https://www.tryit.in/blindchess. It's a very simple interface where you can play against an engine at different difficulty level by just keying in the moves in algebraic notation and see the board as and when you want. Full disclosure: I am the tool developer! :)
> 5 votes

# Answer
Chess24.com allows you to play blindfold in a different way by just hiding the pieces.

When you want to move you drag an invisible piece in the normal way. When your opponent moves you see a line on the board connecting the starting and ending squares of the move.
> 4 votes

# Answer
This is a bit late but in case you are still looking, we've been working on our blindfold chess website for the past few months and just released our beta. The main game is exactly what you describe: you can play by entering PGN moves while viewing the score sheet. The board is hidden and you can choose after how many moves you will be able to view the board.

We're building the entire website to help with blindfold chess. We have mini games to help learn PGN, a memory trainer, a tactics trainer that forces you to think of all the moves (you and your opponent's) in your head, and the main game, which is just classical chess.

Let us know if you have any feedback! Hope this helps you :)
> 3 votes

---
Tags: online-chess, blindfold-chess
---


title: Books on old tournaments

text:
# Question
Title: Books on old tournaments
I'm interested in books covering the major chess tournaments between 1880 and 1930, roughly speaking. I would prefer the official tournament books, like this one, but translated in English. Can I buy them online? Are they available for free somewhere?

**Update**: Some tournaments I'm particularly interested in:

Tournaments:

* Nuremberg 1896
* Vienna 1898
* Ostend 1905
* Ostend 1906
* Ostend 1907 (including the Master tournament, not only the Champion tournament)
* Barmen 1905
* Paris 1900
* Cambridge Springs 1904
* St. Petersburg 1909
* Carlsbad 1911
* Moscow 1925

Matches:

* Lasker-Steinitz 1894
* Tarrasch-Chigorin 1893
* Lasker-Schlechter 1910
* Lasker-Tarrasch 1908

# Answer
> 6 votes
**St-Petersburg 1914**

Dr. Siegbert Tarrasch wrote the book of the famous tournament St Petersburg 1914: it has been translated to American English by Dr. Robert Maxham, as *International Chess Tournament*, Caissa Editions, Yorklyn, DE, 1993

You may find it for a reasonnable price \- but not there.

Great discovery: the first translation from 1915 can be read online!

**Hastings 1895**

It is a great surprise to me that the Tournament book of the first Hastings tournament (won by Pillsbury in 1895), written by the players and compiled by Horace F. Cheshire, is available online.

**Vienna 1882**

One of the greatest tournaments of the 19th century, and of chess history, whose tournament book can be downloaded in pdf here \- or read online if you create a free account (they say - I haven't tried).

A reedition can also be purchased for a very affordable price.

**There will me be much more**

Many second-rank masters (Vidmar, Bernstein...) made some money from writing official tournaments books that were eagerly looked for by other players as the main source of information on the evolution of the game (no database, no internet).

---
Tags: history, tournament, books, famous-events
---


# Question
Title: Wrong inaugural move in game 2 of Carlsen - Nepomniachtchi
In the game 2 of the current World Championship Series, the FIDE president Arkady Dvorkovich made the inaugural move, which differed from what Carlsen wanted the move to be. How does this exactly work, are there any rulings on this? Is it just a "ceremonial move" which is then expected to be reverted/corrected by Carlsen and if so, why does Carlsen not let him know his actual first move for him to make the proper move? From the pictures I saw, Nepomniachtchi already started thinking once he saw 1.e4, which was not the actual opening, so I don't know if this opens up for silly, minor mind games and at the same time takes the symbolic power of the move away, since it has to be corrected anyway.

# Answer
> How does this exactly work, are there any rulings on this?

This is not a part of normal chess. I played white in a league game last night for my club and there was no famous person to make the first move in front of the cameras. This is something special for high level competitions. So, the obvious first place to look is in the special regulations FIDE publishes for these events.

For this world championship match the FIDE document is the "Regulations for the FIDE World Championship Match 2021".

This document covers many aspects of the match ranging from how sponsors can bid for the right to host the match through to remuneration for the arbiters, the appeals committee, the FIDE press officer, etc. There is one section covering the regulation of the match itself - **4. World Championship Match Regulations**.

Although there are subsections in this section covering photography, TV, broadcasting and commentary, there is nothing about a celebrity making the first move.

If we look for help in the \[FIDE Laws of Chess\] we find at the very beginning that:

> **Article 1: The nature and objectives of the game of chess**
>
> 1.1 The game of chess is played between two opponents who move their pieces on a square board called a ‘chessboard’.
>
> 1.2 ***The player with the light-coloured pieces (White) makes the first move***, then the players move alternately, with the player with the dark-coloured pieces (Black) making the next move.

So, it becomes clear. The game doesn't begin until the first player, the player of the white pieces, makes the first move. Anybody else moving one of the pieces is not part of the game. Indeed, it seems to be part of the advertising and promotion of the event made to look like it is part of the game.

Looking further we see that if this ceremonial "first move" could be considered "advice" then the white player should be penalised.

> 11.3.1 During play the players are forbidden to use any notes, sources of information or advice, or analyse any game on another chessboard.

Arguably the white player taking back the ceremonial first move and making their own could be see as the more correct play.
> 13 votes

# Answer
This is purely ceremonial. Some famous person is invited to make the first move, and they usually do it without consulting the player. Why doesn't the player tell the famous person what move to make? I can only speculate, but my guess would be that it removes agency - the famous person can no longer pretend they're making a decision. It's also a small indication what opening move people like to see (although most of these ceremonial first moves are 1. d4 and 1. e4).

Sometimes you also get funny things like this:

> President Gorbachev arrived at 4 p.m. and they were ready to start. Anatoly \[Karpov\] had white in the first game. Therefore, President Gorbachev would make the first move for Anatoly. As he arrived at the board, he told the audience that this is a wonderful match between two great champions. “I am going to cause some difficulties for the older player”, he said, then proceeded to play 1.g4 without asking Anatoly. Both Anatoly and Susan \[Polgar\] looked up at President Gorbachev in shock. Anatoly thought that the President was joking as Anatoly mentioned that he would like to make another first move. But the President was firm in saying there is no take back in chess. Then the players started their first game.

(For context 1. g4 is one of the worst possible first moves for White)

Needless to say, this won't happen in serious games.
> 16 votes

---
Tags: fide, world-championship
---


# Question
Title: Bronstein timing in DGT clocks and the related PGN
I have noticed a gap in the PGN spec and the Laws of Chess in section 6.2.2

> The time saved by a player during one period is added to his time available for the next period, except in the ‘time delay’ mode. In the time delay mode both players receive an allotted "main thinking time". ...

The delay mode is not mentioned in the PGN spec, so my question here is how to notate it in PGN tags then.

A game with TimeControl set to increment looks like:

```
[TimeControl "4500+30"]
1. e4 e5

```

This is a game started with 90 minutes for each player, and an increment of 30 seconds per move (used in our chess leagues in Germany a lot).

How do you record a variant when Bronstein timing (named "time delay" in the Laws of Chess) is used?

# Answer
> 3 votes
First, one thing to clear up, according to the Wikipedia article on Time control, Bronstein Delay is not exactly "time delay" from the Laws of Chess. With "time delay", the player's clock does not start ticking down until after a period of thinking time has elapsed. In Bronstein time, the clock ticks down immediately, so you can lose on time (as far as I'm aware), but time is added back to your clock after your move as in incremental timing except that you won't get more time added than you spent thinking (so if you thought for 7 seconds in a game with 15 second increments, you will only get 7 seconds added back to the clock, but if you thought for 30 seconds, you will get 15 seconds added back). The net effect is equivalent to the simple delay, but I believe Bronstein allows you to lose on time in situations where a simple delay would not. *Actually, upon further reading, the difference between Bronstein and simple delay is purely in how the clock presents the total remaining time as the delay is added at the beginning of the game on turn one, so a loss in time would occur after the same total thinking time for both time controls.*

---

Regardless, that isn't quite what your question is about. So let's move to the PGN specification. As best as I can tell, the PGN specification does not provide any standard way for notating a delay or a Bronstein increment. Of particular note is this answer to a similar question from about 7 years ago.

> The only suggestion is the standard one regarding these questions about PGN which is to put the information in a comment field. The standard is old and no longer maintained as far as I know.

I would agree. The TimeControl tag is optional, so you could omit it altogether in favor of an explanatory comment, or you could add a value that seems reasonable and then a comment to explain.

```
[TimeControl "?"] ; Bronstein, 30 min, 15 sec delay
[TimeControl "1800+15"] ; Bronstein
[TimeControl "1800"] ; 15 second time delay

```

Regardless, if you import this sort of notation into any parsing software, it would likely not show you any of your comments around the TimeControl tag, so depending on what you want to do with the PGN file, it may be irrelevant.

---
Tags: pgn, time-control
---


# Question
Title: What is the TimeControl format for FIDE tournament?
The TimeControl formats I've found on the web split the TimeControl in time periods separated by a special character, for instance:

G/90 (one period with 90min to end the game)

G/90+30 (one period with 90min to end the game and 30sec of increment)

40/90, SD/30+30 (two periods, 90min to play 40 moves followed by 30 min to end the game with 30sec of increment)

Now, in the last example the increment is related to the second period (the sudden death).

According to http://www.fide.com/fide/handbook.html?id=39&view=category for all major FIDE events the TimeControl is 90 minutes for the first 40 moves followed by 30 minutes for the rest of the game with an addition of 30 seconds per move starting from move one. Here the increment starts from move 1.

How can I describe that in a formal notation? Is 40/90+30, SD/30+30 the correct way?

PGN standard has a different approach (the separator character is ":" and the increment is allowed only in the sudden death period, which is simply expressed in seconds):

40/5400:1800+30

but it seems the increment is not allowed for the first period (in case of a multi-period time conrol).

How can I express the FIDE TimeControl in the PGN tag as well? I tryed to download PGN games of FIDE events but I couldn't find any of them with TimeControl tag.

# Answer
> but it seems the increment is not allowed for the first period

As far as I can see from the standard it is allowed in the first period only if there is only one period. Specifically it is allowed only in the last period.

> •The fifth TimeControl field kind is used for an "incremental" control period. It should only be used for the last descriptor in a TimeControl tag value and is usually the only descriptor in the value. The format consists of two positive integers separated by a plus sign ("+") character. The first integer gives the minimum number of seconds allocated for the period and the second integer gives the number of extra seconds added after each move is made. So, an incremental time control of 90 minutes plus one extra minute per move would be given by "4500+60" in the TimeControl tag value

The only suggestion is the standard one regarding these questions about PGN which is to put the information in a comment field. The standard is old and no longer maintained as far as I know.
> 3 votes

# Answer
From what I have found out from studying the PGN Specification, I think that the PGN spec allows to have the following:

* `40/5400+30:1800+30`
    + Start with 90 minutes
    + for the first 40 moves,
    + add then another 30 minutes for the rest of the game.
    + In both periods, use 30 seconds increment.

So it would be possible to have different increments (for whatever reason) in your tournament.

I have downloaded the DGT clock manuals (2010 and 3000), here are some quotes from it:

> 2010: Bonus. In Bonus settings players receive an additional amount of time for each move (typically 2-3 seconds bonus time per move in blitz, 10 seconds bonus time in rapid, and 30 seconds in classical chess). The bonus time is added before each move from the start of the game. Playing with bonus time per move is also called playing with increments or playing with Fischer Bonus after the 11 th World Chess Champion Bobby Fischer who championed the system. Playing with increments has become the standard in chess. Options 10-14 have a Bonus setting in the last period only (and Time settings in preceding periods). Options 15-21 have Bonus settings in all periods. Note that according to FIDE rules the clock can no longer be operated in Bonus settings when one of the players runs out of time in the last period. The clock then freezes and a blinking flag will be shown.

> 3000: Fischer Bonus This method was named after chess world champion Bobby Fischer: “Fischer Bonus” called FISCH in this manual. In this method a certain amount of time is added after each move. If players use less time per move than the set bonus time, then the time on the clock will be higher after the player has finished the move than at the start of the move. ...

> Period transitions with different bonus or delay times
> The DGT 3000 makes it possible to program subsequent periods with different bonus or delay times.

My conclusion from that is, that it should be possible to have different (or no) increment in different periods, and the only way to specify that is to have the increment in all periods repeated.
> 3 votes

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Tags: fide, pgn, time-control
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# Question
Title: Is there any website where I can play simultaneous chess against many opponents?
This is purely for my fun (and also practice!), but is there any place online where I can play simultaneous chess against many opponents?

This would be against human players, of course, not against computers.

# Answer
> 7 votes
You could do that on FICS, here's how:

```
Simuls

  "Simuls" = simultaneous chess matches; playing more than one opponent at a
time.  It is possible to play more than one opponent simultaneously on the
chess server.  Below are sections for Starting a Simul and for Joining a
Simul.

  Users using an interface that only supports a single board (that is if
two games are being observed a move from the second game will cause the
position of the first game to disappear  (such as Winboard and Xboard)) should
issue "iset singleboard 1" before starting a simul.  This will ensure that
when simul participants move, only the board the simul holder is at will
update.

STARTING A SIMUL

  In order to play more than one chess match simultaneously you need to do the
following:

1. Start the simul with the "simstart" command.  Announce your simul
   conditions on shout and cshout enough to get the word out, but not so much
   as to annoy users.

2. Other users must then challenge you with "simmatch".

3. Accept or reject the challenges as they come in.  The first game will be
   colored as is if was an ordinary match.  The next game will be the
   opposite color, the next the opposite to that and so on.

4. When you are satisfied that you have started the number of games that you
   can handle, turn off your open flag with "set open 0".  You can see your
   games with "simgames".

5. You can then start making moves on the board.  The "simnext" command moves
   you to the next board; "simprev" moves you to the previous board.  You
   will focus on one game at a time, going in a particular order.  If you
   wish to skip to a board of particular interest "goboard <player>" or
   "goboard <game number>" will take you to that board.

6. If you are bothered by how long a player is taking to make the next move,
   or they are being disruptive you can abort that game with "simabort".  You
   can also force an adjournment with "simadjourn".  Only games adjourned
   during the simul can be resumed.  After the simul any outstanding simul
   games may be resumed as normal matches.  Should there be a need to
   terminate the simul "simallabort" and "simalladjourn" will abort or adjourn
   all games respectively.  Both commands will also terminate the simul.

7. When you are finished type "simend".  This will return you to normal
   playing mode and inform you of your statistics for the simul.

Various commands you can use while running a simul include:  goboard,
simabort, simadjourn, simallabort, simalladjourn, simnext, simprev and simend.

JOINING A SIMUL

  In order to play against a user who is open for playing simultaneous
matches, here is what you do:

1. Using the "simmatch" command, challenge the person you will be playing.

2. You will be informed when the simul player is coming to your board.  You
   should be prepared to move either before or shortly after that player
   arrives at your board.  If you do not move within a reasonable time
   period, your game could be aborted.

3. It is impolite to offer a draw unless that player is at your board.  It
   could very easily confuse the simul player if offers come in from
   different users at once.

OBSERVING A SIMUL

  You can observe all games in a simul once they have started by typing
"simobserve simul_player".  All of the simul_player's simul games will be
added to your observation list.  As the simul_player moves from board to
board, so will you.  When the last game has ended, you will see the final
results from the simul games.  You can also use the "follow" command for this
purpose.  Using the "observe" command, however, is not reliable for this
purpose.

```

Reference.

I don't know if it affects your rating, never tried it. Be careful what you wish for :)

There's also RedHotPawn, it says that it offers that, maybe a member can verify that, I signed up there a year ago never used that site. But it's the second most popular online chess website after Chess.com I believe.

PlayChess server offers that as well but it's not free, but it's well known server, best of the best.

On Chess.com, you could play live chess and duplicate tabs, and you'll end up playing more than games at once, not the same window though.

There's also gameknot.com, I have never heard of it, but they claim it is possible to play such games on their site.

# Answer
> 11 votes
lichess is a good place for simuls: https://lichess.org/simul

# Answer
> 4 votes
As of 29 April 2020, Chess.com supports playing online simuls (simultaneous exhibitions) against human opponents.

To enable, users must select the setting "Play Multiple Games at a Time" at chess.com/settings/live.

Enabling the "Auto Switch Game" setting, "Chess.com will automatically take the simulgiver to the game in which they have the least time remaining as soon as they make a move."\[1\]

A player can manually shuffle between their ongoing simul games using the specially designed interface.

References:
\[1\] Chess.com article: How To Play Simuls On Chess.com
\[2\] Tutorial Video: How To Play Simuls On Chess.com
\[3\] Chess.com article More on Simuls On Chess.com

# Answer
> 2 votes
Chess.com allows nearly unlimited simultaneous chess games at the correspondence speed of 1-14 days per move. I believe they allow you to play live timed games against multiple opponents, but that is in a paid tier of membership that I don't subscribe to.

# Answer
> 1 votes
If nothing else, you can register several accounts, and open several games in different windows. I don't know whether that will set off flags, though, and it would be less convenient than something specifically set up for simuls.

# Answer
> 0 votes
another way to do it in lichess besides https://lichess.org/simul

you can issue challenges to several players by challenging them directly in their profiles (which you would open up in several tabs) and then you can play them all at once.

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Tags: online-chess, simultaneous
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