Hardware used in AlphaZero vs Stockfish match I understand that AlphaZero has to use a different kind of hardware than regular Stockfish. I would expect that the hardware has a large effect on engine strength. That's why I wonder whether there have been any attempts made to provide comparable hardware to both. Also what would "comparable" mean here?

Specifically I read that people complain about:

Stockfish being given only 1 GB of cache, and
the time limit of 1 min/move (How would this disadvantage Stockfish?)

That's why I wonder whether there have been any attempts made to
  provide comparable hardware to both.

This is Google you're talking about! So the answer is obviously "No".

From the original paper hardware used for initialising and training -

  Training proceeded for 700,000 steps (mini-batches of size 4,096)
  starting from randomly initialised parameters, using 5,000
  first-generation TPUs (15) to generate self-play games and 64
  second-generation TPUs to train the neural networks

and hardware used for the games -

  AlphaZero and the previous AlphaGo Zero used a single machine with 4
  TPUs Stockfish and Elmo played at their strongest skill level using 64
  threads and a hash size of 1GB.

So, AlphaZero used special hardware developed by Google. It used specialized Tensor Processor Units (TPUs) rather than general Central Processing Units (CPUs) as are available commercially.

This is how Wikipedia describes the second generation TPUs they used -

  The second generation TPU was announced in May 2017. Google stated the
  first generation TPU design was memory bandwidth limited, and using 16
  GB of High Bandwidth Memory in the second generation design increased
  bandwidth to 600 GB/s and performance to 45 TFLOPS. The TPUs are then
  arranged into 4-chip 180 TFLOPS modules

They used 4 TPUs for the games, so a processing power of 180 TFLOPS.
Note TFLOPS = 1000 billion floating point operations per second.

For comparison Intel's latest most powerful chip is the Core i9 Extreme Edition processor which clocks in at 1 TFLOP. A top of the line I7 that you would find in a gaming machine would typically be about 100 GFLOPs (i.e. one tenth of a TFLOP).

I think it's fair to say that AlphaZero was using an 800 pound gorilla of a hardware configuration compared to Stockfishes mouse.


Where can I download and how do I set up a 5-man tablebase in Arena GUI? So, I want to download a 5-man tablebase (I have no disk space for a 6-man one) and set it up so that it works with Stockfish in Arena GUI. Where can I download the tablebase, and how do I install it in Arena GUI?

http://www.cruxis.com/chess/manual/end_game_table_base_support.htm

This is from the developers of Houdini's site.


Extract anonymized games out of a pgn I'm a big fan of pgn-extract, but I am open to other linux-friendly tools. I have a big pgn file (over 5 million games) and a set of ECO codes. My goal is to fetch all the games matching those ECO codes, but with removing or fuzzying the players names and ratings, the year played, and the game result.
I then plan to open a random game with Scid and analyze it, since removing the players' data and game result will help me avoid any bias.
So far Im using pgn-extract like this:
pgn-extract -t filter_for_naked --noresults --notags --nocomments --noduplicates -bl20 --output naked.pgn my.pgn
But Scid is having problems opening the file. As expected each game is just the set of moves (no headers at all) and I suspect Scid requires at least some headers.
Any advise on how to use pgn-extract or Scid to achieve this?

Thanks for your compliment about pgn-extract (I am its author). You might be able to make the task a little easier by adding --linelength 1000 to the argument list in order to get each game on a single line, then use sed to add an unknown result to the end of the game and re-process the game with pgn-extract to add an empty 7-tag roster. Finally, use sed again to edit the White and Black tags.
The resulting command would look something like the following, although sed experts might be able to clean it up a bit:
pgn-extract -t filter_for_naked --noresults --notags --nocomments --noduplicates -bl20 --linelength 1000 my.pgn | sed -e 's/..*/& */' | pgn-extract -7 | sed -e 's/White "?"/White "AnonW"/;s/Black "?"/Black "AnonB"/' > naked.pgn

You will get some error reports for games that end in mate having inconsistent results but you can hide those in a logfile.


Giuoco Piano, Steinitz Variation [fen ""]

1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d4 exd4 6. cxd4 Bb4+ 7. Nc3 Nxe4 8. O-O Bxc3 9. bxc3 d5 10. Ba3

Steinitz Variation.

We play this in regular tournaments and it is very interesting. White gives the sacrifice of Bishop and also blocks Black's ...O-O. When we studied this line it contains lot of interesting variations. In modern times most players are not playing this variation, why?

This line looks unsound.

White's plan seems to be to threaten to win back the piece by 10...dxc4 11. Re1 (pinning the knight), teasing Black into weakening his king's position further by 11...f5 to defend e4, which then leads to a very complicated situation that White hopes to manage better.

However, Black is fine if he just lets go of the knight, since he's still a pawn up. Obviously, his kingside is very weak, but he can move out his queen with tempo (by attacking e4) and castle long.

11...Be6 12. Rxe4 Qd5 13. Re1/Re2/Qe2 etc. 0-0-0

The black king is safe and c4 is actually well protected. White doesn't have enough compensation left for that pawn.

To back this up, according to the Lichess online database, White has a win rate of 62% if Black plays 11...f5 (71 games), but only one of 27%/38% respectively if the answer is 11...Qd5 or 11...Be6 (11/8 games). 11...Bf5 also seems to work (35%, 20 games).

That's just not enough to make the variation appealing for grandmasters (who probably consider the refutation too obvious), and if none of them play a line it will hardly become very popular. It's a nice Blitz surprise weapon though, as you can see the majority of players from a database leaning towards fast games will choose 11...f5.


How to use crafty chess engine in the gui chess64.exe link provided Given below is the crafty chess engine of xboard or winboard version free version.

https://github.com/MichaelB7/Crafty/releases/download/25.2/Crafty-25.2-Win64.zip

Given below is the book

https://github.com/MichaelB7/Crafty/releases/download/25.2/Crafty_Chess_Informant.Opening_Books.zip

Given below is the GUI open version.

https://github.com/SigmaPT/asm.git

I could not able to use xboard or winboard protocol in the gui.

Please help me in fixing the issue. Please tell the command to be inserted in console window of the gui. Please note I request to put crafty chess engine ONLY in GUI and test.Other UCI chess engines are working GUI.

I played a quick game as White.

1.e4 Nc6 2.Ke2 d5 3.Ke3 dxe4

xboard
st 1
e2e4
e1e2
e2e3

Logs:

./crafty-25.3-gcc
unable to open book file [./book.bin].
book is disabled
unable to open book file [./books.bin].

Crafty v25.3

machine has 8 processors

White(1): st 1
search time set to 1.00.
White(1): e2e4
              time used:   4.80
        time surplus   0.00  time limit 1.00 (1.00)
        depth     time       score   variation (1)
         18->   1.00/1.00     0.33   1. ... Nc6 2. Nf3 e5 3. Bc4 Nf6 4. Nc3 Bc5
                                     5. O-O O-O 6. d3 Na5 7. Nxe5 Bd4 8. Nxf7
                                     Rxf7 9. Bxf7+ Kxf7 10. Bg5 d6
        time=1.00(100%)  nodes=5906541(5.9M)  fh1=92%  pred=0  nps=5.9M
        chk=40.8K  qchk=64.5K  fp=1.7M  mcp=1.4M  50move=1
        LMReductions:  1/236.3K  2/183.8K  3/125.8K  4/33.9K  5/1.3K
        null-move (R):  3/295.8K  4/20.0K  5/377
Black(1): Nc6
              time used:   1.00
White(2): Nf3 [pondering]
        time surplus  29.00  time limit 1.00 (1.00)
        depth     time       score   variation (17)
         19     1.15/1.00     0.22   2. (Nf3) e5 3. Bc4 Be7 4. Nc3 Nf6 5. O-O
                                     O-O 6. d3 d6 7. a3 a6 8. Be3 b5 9. Bd5 Bd7
                                     10. Qe2 Nxd5 11. Nxd5 Kh8
         19->   1.28/1.00     0.22   2. (Nf3) e5 3. Bc4 Be7 4. Nc3 Nf6 5. O-O
                                     O-O 6. d3 d6 7. a3 a6 8. Be3 b5 9. Bd5 Bd7
                                     10. Qe2 Nxd5 11. Nxd5 Kh8
         20     1.94/1.00     0.26   2. (Nf3) e5 3. Bc4 Be7 4. Nc3 Nf6 5. O-O
                                     O-O 6. d3 d6 7. a3 a6 8. h3 b5 9. Ba2 Be6
                                     10. Bxe6 fxe6 11. Be3 Qd7 12. Qe2
         20->   2.22/1.00     0.26   2. (Nf3) e5 3. Bc4 Be7 4. Nc3 Nf6 5. O-O
                                     O-O 6. d3 d6 7. a3 a6 8. h3 b5 9. Ba2 Be6
                                     10. Bxe6 fxe6 11. Be3 Qd7 12. Qe2
         21     4.24/1.00     0.24   2. (Nf3) e5 3. Bc4 Nf6 4. Nc3 Be7 5. O-O
                                     d6 6. d4 exd4 7. Nxd4 Nxd4 8. Qxd4 O-O
                                     9. Qd3 Be6 10. Bxe6 fxe6 11. Be3 Ng4
                                     12. f3 Nxe3 13. Qxe3
         21->   4.56/1.00     0.24   2. (Nf3) e5 3. Bc4 Nf6 4. Nc3 Be7 5. O-O
                                     d6 6. d4 exd4 7. Nxd4 Nxd4 8. Qxd4 O-O
                                     9. Qd3 Be6 10. Bxe6 fxe6 11. Be3 Ng4
                                     12. f3 Nxe3 13. Qxe3
         22    11.23/1.00     0.13   2. (Nf3) e5 3. Bc4 Bc5 4. O-O Nf6 5. d3 d6
                                     6. Nc3 O-O 7. Bg5 Be6 8. Bxe6 fxe6 9. Qd2
                                     Qe7 10. Kh1 Nd4 11. Nxd4 exd4 12. Bxf6
                                     Rxf6 13. Nb5
         22->  11.51/1.00     0.13   2. (Nf3) e5 3. Bc4 Bc5 4. O-O Nf6 5. d3 d6
                                     6. Nc3 O-O 7. Bg5 Be6 8. Bxe6 fxe6 9. Qd2
                                     Qe7 10. Kh1 Nd4 11. Nxd4 exd4 12. Bxf6
                                     Rxf6 13. Nb5
         23    15.56/1.00     0.18   2. (Nf3) e5 3. Bc4 Nf6 4. Ng5 d5 5. exd5
                                     Nxd5 6. O-O f6 7. Nf3 Bg4 8. Re1 Nd4 9. c3
                                     Nxf3+ 10. gxf3 Bh5 11. d4 Nb6 12. Be6 Bd6
                                     13. Nd2 Qe7 14. dxe5 Bxe5
         23->  16.08/1.00     0.18   2. (Nf3) e5 3. Bc4 Nf6 4. Ng5 d5 5. exd5
                                     Nxd5 6. O-O f6 7. Nf3 Bg4 8. Re1 Nd4 9. c3
                                     Nxf3+ 10. gxf3 Bh5 11. d4 Nb6 12. Be6 Bd6
                                     13. Nd2 Qe7 14. dxe5 Bxe5
         24    19.01/1.00     0.25   2. (Nf3) e5 3. Bc4 Nf6 4. Ng5 d5 5. exd5
                                     Nxd5 6. O-O f6 7. Nf3 Bg4 8. Re1 Nd4 9. c3
                                     Nxf3+ 10. gxf3 Bh5 11. d4 Nb6 12. Bb3 Be7
                                     13. Na3 Bxa3 14. bxa3 Qd6
         24->  20.78/1.00     0.25   2. (Nf3) e5 3. Bc4 Nf6 4. Ng5 d5 5. exd5
                                     Nxd5 6. O-O f6 7. Nf3 Bg4 8. Re1 Nd4 9. c3
                                     Nxf3+ 10. gxf3 Bh5 11. d4 Nb6 12. Bb3 Be7
                                     13. Na3 Bxa3 14. bxa3 Qd6
         25    30.02/1.00     1/22?  2. ... e5      (6.4Mnps)
ok.

ok.
e1e2
White(2): e1e2
              time used:  35.73
        time surplus  29.00  time limit 1.00 (1.00)
        depth     time       score   variation (1)
         17->   1.01/1.00    -0.94   2. ... d5 3. exd5 Qxd5 4. Ke1 Bf5 5. Nc3
                                     Qc5 6. Nge2 O-O-O 7. Ng3 Qe5+ 8. Be2 Be6
                                     9. d3 Nf6 10. Kf1 Nd4 11. Nge4
        time=1.01(100%)  nodes=6286981(6.3M)  fh1=87%  pred=0  nps=6.2M
        chk=177.9K  qchk=408.3K  fp=2.1M  mcp=805.1K  50move=3
        LMReductions:  1/119.7K  2/76.9K  3/51.9K  4/20.2K  5/1.8K  6/1
        null-move (R):  3/160.8K  4/10.7K  5/175
Black(2): d5
              time used:   1.01
White(3): exd5 [pondering]
        time surplus  57.99  time limit 1.00 (1.00)
        depth     time       score   variation (16)
         19     1.25/1.00    -0.83   3. (exd5) Qxd5 4. Ke1 Bf5 5. Nc3 Qc5
                                     6. Bb5 O-O-O 7. Bxc6 Qxc6 8. Nf3 Nf6 9. d3
                                     e6 10. Kf1 Bg4 11. Ne5 Qxc3 12. Nxg4 Qc4
         19->   1.80/1.00    -0.83   3. (exd5) Qxd5 4. Ke1 Bf5 5. Nc3 Qc5
                                     6. Bb5 O-O-O 7. Bxc6 Qxc6 8. Nf3 Nf6 9. d3
                                     e6 10. Kf1 Bg4 11. Ne5 Qxc3 12. Nxg4 Qc4
e2e         20     4.67/1.00    -0.71   3. (exd5) Qxd5 4. Ke1 Nf6 5. Nc3 Qc5 6. d3
                                     e5 7. Nf3 Bd6 8. Be2 O-O 9. Kf1 Re8
                                     10. Ng5 Nd4 11. Bh5 g6 12. Bf3 h6 13. Nge4
3        20     4.67/1.00     2/29?  3. ... Bg4+    (7.0Mnps)
White(3): e2e3
              time used:   4.93
        time surplus  57.99  time limit 1.00 (1.00)
        depth     time       score   variation (1)
         14->   1.01/1.00    -2.57   3. ... dxe4 4. Ke2 Bg4+ 5. f3 exf3+
                                     6. Nxf3 Qd6 7. Nc3 O-O-O 8. Ke1 Nf6 9. d3
                                     Nd4 10. Be2 Qb4 11. Kf1
        time=1.01(100%)  nodes=6260401(6.3M)  fh1=86%  pred=0  nps=6.2M
        chk=169.6K  qchk=373.8K  fp=2.4M  mcp=534.1K  50move=2
        LMReductions:  1/100.5K  2/56.5K  3/38.1K  4/16.5K  5/1.0K
        null-move (R):  3/134.8K  4/6.3K  5/23
Black(3): dxe4
              time used:   1.01
White(4): Ke2 [pondering]
        time surplus   1:26  time limit 1.00 (1.00)
        depth     time       score   variation (13)
         16     1.38/1.00    -2.33   4. (Ke2) Bg4+ 5. f3 exf3+ 6. Nxf3 Bxf3+
                                     7. gxf3 Qd6 8. Bh3 e6 9. Nc3 O-O-O 10. d3
                                     Nf6 11. Kf1 Nd4 12. Be3 Qb4 13. Bxd4 Rxd4
         16->   1.44/1.00    -2.33   4. (Ke2) Bg4+ 5. f3 exf3+ 6. Nxf3 Bxf3+
                                     7. gxf3 Qd6 8. Bh3 e6 9. Nc3 O-O-O 10. d3
                                     Nf6 11. Kf1 Nd4 12. Be3 Qb4 13. Bxd4 Rxd4
         17     5.31/1.00    -2.52   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. c3 e6 8. d4 Qh4 9. Be3 O-O-O 10. Qe1
                                     Bd3+ 11. Kd2 Qxe1+ 12. Kxe1 Bxf1 13. Kxf1
                                     Nf6 14. Ne2
         17->   5.34/1.00    -2.52   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. c3 e6 8. d4 Qh4 9. Be3 O-O-O 10. Qe1
                                     Bd3+ 11. Kd2 Qxe1+ 12. Kxe1 Bxf1 13. Kxf1
                                     Nf6 14. Ne2
         18     5.34/1.00     1/33?  4. ... Bg4+    (6.3Mnps)
ok.
         18     7.00/1.00    -2.62   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. d3 e6 8. Qe1 Qe7 9. Kd1 O-O-O 10. Nc3
                                     Nf6 11. Nge2 Ne5 12. Ng1 Nc4 13. b3 Nd6
                                     14. Be3
         18->   7.06/1.00    -2.62   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. d3 e6 8. Qe1 Qe7 9. Kd1 O-O-O 10. Nc3
                                     Nf6 11. Nge2 Ne5 12. Ng1 Nc4 13. b3 Nd6
                                     14. Be3
         19     8.82/1.00    -2.51   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. d3 Nf6 8. Nc3 Qd6 9. Ke1 O-O-O 10. Nge2
                                     Qb4 11. Bg2 Qh4+ 12. Kf1 e5 13. Be3 Bh3
                                     14. Qe1 Qh5 15. Rg1
         19->   8.98/1.00    -2.51   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. d3 Nf6 8. Nc3 Qd6 9. Ke1 O-O-O 10. Nge2
                                     Qb4 11. Bg2 Qh4+ 12. Kf1 e5 13. Be3 Bh3
                                     14. Qe1 Qh5 15. Rg1
         20    10.28/1.00    -2.56   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. d3 Nf6 8. Nc3 Qd6 9. Ke1 O-O-O 10. Bg2
                                     Qd4 11. Ne4 Qa4 12. Ne2 Nb4 13. b3 Qc6
                                     14. N4c3 Bg4 15. Rf1
         20->  10.42/1.00    -2.56   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. d3 Nf6 8. Nc3 Qd6 9. Ke1 O-O-O 10. Bg2
                                     Qd4 11. Ne4 Qa4 12. Ne2 Nb4 13. b3 Qc6
                                     14. N4c3 Bg4 15. Rf1
         21    15.82/1.00    -2.50   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. d3 Nf6 8. Nc3 Nd5 9. Ne4 e6 10. Bg2
                                     Nd4+ 11. Kf1 Bxe4 12. fxe4 Nb4 13. c3 Ndc2
                                     14. cxb4 Nxa1 15. a3 c5 16. Bf4
         21->  16.34/1.00    -2.50   4. (Ke2) Bg4+ 5. f3 exf3+ 6. gxf3 Bf5
                                     7. d3 Nf6 8. Nc3 Nd5 9. Ne4 e6 10. Bg2
                                     Nd4+ 11. Kf1 Bxe4 12. fxe4 Nb4 13. c3 Ndc2
                                     14. cxb4 Nxa1 15. a3 c5 16. Bf4
         22    23.04/1.00     1/33?  4. ... Bg4+    (6.5Mnps)Nc6


I'm looking for informations about calculating ELO (FIDE) rank I'm looking this informations for new app to calculating ELO (FIDE) rank after games (live tournament etc.). So you can predict your future rank before it is pbulished on FIDE site.

Here is a blog post about elo calculation.

You can find the rules for determining the correct K-factor on this site, which also contains an official Fide rating calculator to check your results against.

Here is the official description of the rating calculation (based on tables instead of formulas).


Move comparison in this opening In this opening, being White, I want to understand, for the next move, why is e4 not as strong a move as e3 or Nf3? I am a beginner.
[FEN ""]

1. c4 e5 2. Nc3 Nc6

With e2-e4, you create "holes" at d3 and d4 that can never again be attacked by pawns. Any enemy pieces that land on those holes have to be kicked out by your pieces, which is harder to do (because every piece runs away from a pawn job).
World champion Botvinnik used to set pawns on c4-d3-e4 which we call The Botvinnik Triangle. The world champion can live with those holes, but beginners have a tougher time.
Beginners shouldn't be playing 1. c4.  If you'd played 1. d4, we wouldn't be having this conversation.


How to master the openings? I am a beginner in chess. I am finding it difficult to learn the openings. There seems to be tons of opening games in chess. Is there a way to learn them easily? Is there any website that has a collection of all the openings in chess?

First you should make sure you master the fundamental concepts of opening play. Once you understand those concepts most openings can be universally understood just based on those concepts alone. It's unnecessary (and impractical) to try to classify every opening as having "x - y - z" specific ideas related to it, especially if you're a beginner.

But I believe it's a counterproductive approach to try to "learn openings". You're better off just learning Chess, and the openings will simply come naturally. Yes, there are repeating themes in certain openings, but if you want to truly master the openings those themes should always be readily explainable by general understanding.

Only then do you research the specific lines of an opening and commit them to memory. As for a roundup of all the available openings, you can always just look at Wikipedia. http://en.wikipedia.org/wiki/Chess_opening


Programming three-fold repetition for my chess engine I'm making a chess engine that has to implement a three-fold repetition as my AI vs AI engine repeats the same moves over and over again (Have a look at my post here - My chess AI makes the same repeated moves). I've read the rules of this scenario from the wiki and would like to implement it. I'm not sure if I have understood the rules thoroughly, so what I'm doing here is -

Checking if the present move made (from the movelog I have) has already occurred before.
If it did, check for one more occurrence (as we need three in total).
If the moves pattern for all the three re-occurred moves is same, return true.

Please have a look at my Java code and suggest me the corrections.

    boolean isThreeFoldRepetition() {
        List<Move> allMoves = Table.get().getMoveLog().getMoves();
        int currentMoveIndex = allMoves.size()-1;
        int secondFoldMoveIndex = currentMoveIndex - 4;
        int firstFoldMoveIndex = secondFoldMoveIndex - 4;
        int distance = currentMoveIndex - secondFoldMoveIndex - 1;

        while(firstFoldMoveIndex >= 0){
            Move thirdFoldMoveMade = allMoves.get(currentMoveIndex);
            Move secondFoldMoveMade = allMoves.get(secondFoldMoveIndex);
            Move firstFoldMoveMade = allMoves.get(firstFoldMoveIndex);

            if(thirdFoldMoveMade.equals(secondFoldMoveMade) &&
               secondFoldMoveMade.equals(firstFoldMoveMade) &&
               firstFoldMoveIndex - distance >= 0){
                int gap;
                for(gap = 1; gap <= distance; gap++){
                    thirdFoldMoveMade = allMoves.get(currentMoveIndex - gap);
                    secondFoldMoveMade = allMoves.get(secondFoldMoveIndex - gap);
                    firstFoldMoveMade = allMoves.get(firstFoldMoveIndex - gap);

                    if(!thirdFoldMoveMade.equals(secondFoldMoveMade) || !secondFoldMoveMade.equals(firstFoldMoveMade))
                        break;
                }
                if(gap == distance)
                    return true;
            }

            secondFoldMoveIndex -= 2;
            firstFoldMoveIndex = secondFoldMoveIndex - distance - 3;
        }
        return false;
    }

Threefold-repetition is about a position (not moves) occurring three times. Those positions do not have to be reached by the same moves.

Also (as this also seems to be confused sometimes) it is completely irrelevant when this happens, e.g. you can have the same positions after moves 10, 42 and 63 and it would still be a draw.

You should check whether the position is repeated. So basically at every move you need to check whether the position occurred in the game before. By position I mean the same position of all pieces on the board and the same castling rights and the same player to move and the same enpassant rights. That is, basically you are checking whether the FEN are the same (except for halfmove clock and fullmove number).

Something like:

int positionCount=0;
while(iterate through game positions) {
    if ( positionToCheck.piecesPosition == iterationPosition.piecesPosition &&
         positionToCheck.castleRights == iterationPosition.castleRights &&
         positionToCheck.enPassantRights == iterationPosition.enPassantRights &&
         positionToCheck.playerToMove == iterationPosition.playerToMove ) {
      positionCount++;
    }
    if (positionCount==3) { return true; }
}
return false;

Of course you can simplify the above algorithm. E.g. you only need to iterate over position with the same player to move. Also you only need to iterate over positions back to the last pawn move, capture or castling move.


How do I not play too fast when playing the computer? When I'm playing against a computer, it moves virtually instantly. Automatically, I'm speeding up as if trying to match it. Obviously, I'm not a computer, so I make horrible blunders if I move so quickly. When playing OTB against a live player, I take considerably longer for my moves (I'm fine with playing a three hour game) and consequently I play a lot better OTB. By the way, I virtually always play without a clock.

Is this common? Are there any tips besides "just don't do this"?

This is a very bad habit you are getting in to. Of course it doesn't really matter if you lose to the computer in this situation but you will face something similar in OTB play with clocks.

If you have 10 minutes left to finish the game and your opponent has less than 2 minutes then this is a very big advantage for you. If you are not playing with increments then your opponent will have to start blitzing his moves out to try and avoid losing on time. He is much more likely to make a mistake. If you copy him and start blitzing too then your advantage disappears.

You should try and have a set routine which you go through regardless of the opponent's speed of move, some questions you automatically ask yourself. Why did my opponent play his last move? What is he threatening? How does it stop my plans? Does it give me some new possibilities?

If you consider these kind of questions it will slow down your play and help you to stop blitzing unnecessarily.


Flexibility over solidity? Defending against 1. e4 When defending against 1. e4, I'm a French Defense player. I enjoy the French Defense very much, and my win rate with it is fairly good. Lately, though, I've been wanting to explore new defenses, only to spice my game up (I'm getting bored of the typical positions that come out of the french, as wild as some of them may be).

I consider the french to be solid, yet not flexible. By this I mean that the usual French setups are hard to break and resilient, but offer little strategical freedom (this is, there are few logical strategical plans that actually fit the position). It is as if I'm playing all my games with the same two or three long-term plans, not because of lack of imagination, but because this are the plans that usually emerge as logical in the typical positions.

In opposition to this, I'm looking for a new defense that prioritizes flexibility above all, even if not as solid as the french.  An opening that offers a wide variety of strategical ideas and creative play. The Sicilian is a candidate, but there are too many variations to learn and I'm not interested on it at the moment. I'm considering also the Pirc Defense, which I believe to be also flexible enough.

Can anyone recommend a flexible defense against 1. e4? Comments on the mere ideas of flexibility/solidity in the defensive setup are welcome too, as of course these relates to the actual question.

It sounds like you are drawn to the pirc so try it out and see.  The pirc/modern is very flexible and if you play the king's indian that you can transpose into that if White plays c4 to make a universal system.

I like the fluidity of being able to see how my opponent sets up first and then respond.  I like the dynamic potential.  Rather than backward black's position feels like a "coiled spring" ready to lash out.  I haven't been blown off the board with e2-e4-e5 and h2-h4-h5 in a while so I think I am getting the hang of the direct assault lines.


Chess Tempo #97369 - Is the problem's solution wrong? Can black force a win (against perfect play) after the following moves?

[FEN "6k1/5p2/1Pp3pb/2q4p/1rNpPP2/3Q2PP/8/5RK1 b - - 0 1"]
[StartPly "3"]

1... Rxc4 2. b7 (1. {Chess Tempo #97369})

A quick summary of this position is:

Black is initially an entire bishop ahead.
White has a passed pawn that is dangerously close to promotion.
Black has connected passed pawns.

Background

I recently asked "Chess Tempo #97369 - Theoretical win or draw?" about Chess Tempo problem #97369 where I asked what the theoretical value of the position is. From my own analysis (please feel free to check it for errors) I believe that black was in a winning position on the previous move, and at least one way to have won was to play Qxc4.

The only move that is accepted as correct by the Chess Tempo site is Rxc4 because it has a very high evaluation according to the site's engine (Toga II). However I'm not even sure that this move works against perfect play by white. If it doesn't work I will request the site's owner to disable the problem.

What do you think? Can black force a win from the position the diagram results in? If so, how? If not, why not? Opinions are welcome but using an engine to check your analysis is also encouraged.

I believe black can do no better than a draw from the starting position. First I'll give my own reasoning for it (and everything I'll say I've checked with Houdini, to rule out silly oversights on my part). Further below, I will suggest what I think is a very plausible explanation for why Chess Tempo's engine might have gotten it wrong.

The first move

1... Rb4

is forced, as it is the only way to keep white's b-pawn from queening without losing the rook. In turn, white's reply

2. Rb1

is forced, because without the b-pawn white will certainly be losing. Now white is threatening 3. b8=Q, which would force black to give up the rook. Since 2... Rxb1+ 3. Qxb1 doesn't help, black is thus forced to play

2... Qb6

Again white cannot let the b-pawn fall for nothing, and so has no choice but to play the sequence

3. Rxb4 Qxb4 4. Qa6

to stop black's threat of ...Qxb7. Now it is black to move from the following position:

[FEN "6k1/5p2/1Pp3pb/2q4p/1rNpPP2/3Q2PP/8/5RK1 b - - 0 1"]
[StartPly "9"]

1... Rxc4 2. b7 {Last given ply, white threatens b8=Q+} 2... Rb4 {First original move, prevent pawn promotion without loosing rook} 3. Rb1 {preserve pawn to avoid loosing}
3... Qb6 (3... Rxb1+?? 4. Qxb1 {pawn is just about promoted}) 4. Rxb4 Qxb4 5. Qa6 {black must now give perpetual check to avoid loosing}

Black would love to consolidate the position by getting the bishop to a spot where it eyes the b8 square along with black's queen (say by ...Bf8 followed by ...Bd6); doing so would eliminate any danger of white's pawn promoting, and allow black to regroup and win easily with the extra bishop. Unfortunately, if black tries 4... Bf8, then 5. Qa8 threatens to promote and simultaneously pins the bishop, preventing 5... Bd6. In that case, black has no better option than to play 5... Qe1+ and put white into perpetual check, draw. So 4... Bf8 doesn't work, but any other direct try by black to impede the advance of the b-pawn will just be slower. The problem is that, from the diagram position (meaning my diagram), black's forces are just uncoordinated enough that he doesn't have enough time to prevent Qa8 and promotion of the b-pawn directly, and must instead go in for perpetual check.

From a broad conceptual point of view, black has only one other idea to try and play for a win if he can't stop the b-pawn: to run his own d-pawn to promotion. But it's easy to see that that plan is also too slow. If black tries 4... d3, then after the white response 5. Qa8+ Kh7(g7) 6. b8=Q, black's queen is en prise and white is now threatening to mate. So black would again be forced to bail out and go for a perpetual check with 6... Qe1+.

What I think went wrong here

From your initial diagram position, an engine could search to a pretty healthy depth and keep seeing positions in which black retains a sizable material advantage (a full extra bishop). The reason for this is that though black cannot "really" stop the b-pawn from queening, he can give checks to push that event into the future, further down the engine's search. Now, of course, once an engine sees repetitions of the position in its search, it will recognize the draw and no longer see any advantage from the extra material. But ... (and this next part is indeed speculation, but it is not without sense)

A potentially problematic feature of this particular position, though, is that black doesn't just have, say, two checking squares from which the queen can carry out the perpetual. Checks can happen on e1, d2, d1, c2, c1, b2, b1 and in the meantime the white king could have at least 10 squares it could travel on; not to mention, a checking sequence could also get interrupted by, say, the white queen blocking a check, followed by the black queen getting back behind the b-pawn, and then the white queen returning to a6.

The point being, there are very many possible paths here; it's all still just a perpetual check, but the great variety of options here could make it so that, at whatever search depth it's working at in the Chess Tempo evaluation process, the engine couldn't quite see a repetition yet, because it keeps seeing things like, e.g. "Oh, I don't have to repeat with ...Qe1+, I'll check from d1 this time instead," pushing the recognition of a perpetual check beyond its horizon.

Again, I'm speculating, but it's at least not a nonsensical possibility.


Castling in the French Defense? How do you decide which way to castle?

It seems castling kingside can be dangerous because of white's extra kingside space he often gets in the French Defense. Also most of my pieces are naturally on the queenside making it difficult if they're needed for defense on the kingside.  I'm curious about if castling queenside is good or not, since you use your pawns to expand on the queenside its feels like a lack of a pawn cover for your king?

Sometimes I end up not castling at all in the French because of this. I understand that the answer is rather situational but can someone explain the theory on this?

If you can block the pawn structure on the queenside then you can consider castling queenside, for example in this line

  [StartPly "12"]
  [White "White"]
  [Black "Black"]
  [FEN ""]

  1. e4 e6 2. d4 d5 3. e5 c5 4. c3 Nc6 5. Nf3 Qb6 6. a3 c4

Also in the Winawer poisoned pawn black often castles queenside in the middlegame because kingside castling is not possible and to bring the a8 rook into play eg.

  [StartPly "32"]
  [White "White"]
  [Black "Black"]
  [FEN ""]

  1. e4 e6 2. d4 d5 3. Nc3 Bb4 4. e5 c5 5. a3 Bxc3 6. bxc3 Ne7 7. Qg4        Qc7 8. Qxg7 Rg8 9. Qxh7 cxd4 10. Ne2 Nbc6 11. f4 Bd7 12. Qd3 dxc3 13. Nxc3 a6 14. Rb1 Na5 15. h4 Nf5 16. Rh3 O-O-O

Otherwise you generally castle kingside. Sometimes Kf8 is played to defend a pawn on g7 eg after Qg4 but that depends on the specifics.


Looking for an iPhone app for working out chess problems I'm looking for an iPhone app that will allow me to set up a chess problem and work out its solution.  I've seen apps that present me with a battery of chess problems but don't allow me to set up my own.  I've also seen apps that allow me to play chess starting from the opening position.  But I haven't seen one that will allow me to configure the board as I choose.  Admittedly I haven't tried every existing iPhone app but none of the ones I've looked at allow this.

The only chess app on my iPhone is Stockfish, and it has a menu option Game -> Edit position where you can set up your own board. You'd also have to change the Level/Game mode to 'Two player'.

It's a free app.


Is it beneficial to play blindfolded chess? I've played only two blindfold games so far, but it was against someone who was maybe at a 1000 uscf rating strength, and hence was fairly easy to beat, and once against my friend, who's also rated about 1650, like myself. I also managed to beat him with a sneaky tactical shot, but it was a lot more challenging, as I found it hard to remember where certain pieces were. I've also read that while it benefits your board vision for tournament games, it puts too much strain on your mind to be beneficial overall. Is this true? Any other arguments for/against playing blindfold chess?

In my opinion

I cannot speak to the health benefits or drawbacks of playing blindfold chess (which I find to be, in my opinion, baseless).

What I can say is from experience. I have attempted playing blindfold chess when I was not a very strong player and found it challenging and not worthwhile. However, as my chess progressed I found playing blindfold to be a lot easier, and was even recently able to play a game to the 62nd move where I checkmated my friend. It took 90 minutes.

My main point is that that blindfold chess more than likely does not affect your chess ability. It is your chess ability that affects your blindfold chess.

Here is are some conclusions from an in depth study

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2972788/

In their review of the literature, Hearst and Knott document a number of notable conclusions that may surprise chess players and non-chess players alike:

The general memory of chess masters, including those able to play many blindfold games simultaneously, is no better than that of the average person.
Highly skilled players can form long-term memories of full-board chess positions within seconds of viewing them.
High level chess skill (not just blindfold chess) requires a recognition-action repertoire of some 50,000 to 100,000 features of chess positions and associated responses.
Some of the strongest masters find the actual sight of a chess position to be more distracting than helpful when thinking ahead during a game.
Practicing blindfold chess improves sighted chess skill.
Some of the strongest blindfold chess masters claim that the strength of their blindfold play is similar to that of their sighted play.

Bonus material

In case you really want to read up on the subject: http://www.wjh.harvard.edu/~cfc/Chabris1999d.pdf


Where can I find images for vector chess diagrams? Chess diagrams are simple, icon-based images and there's no reason they need to be raster images. I've seen many threads started on this topic throughout the web, always unanswered.

Someone has just posted a collection of tools for creating vector chess diagrams on reddit. You can find them here. If anyone knows of some more resources like this I'd love to hear about them.


Recent research, or analysis sites, about some chess variants? I would appreciate some links to recent (within the last 8 years) chess variant analyses and research. As to standard chess it seems like the source code for a lot of the computer chess programs usually contains a new tidbit gleaned from various pruning and optimization techniques. What's extremely difficult to find is new insight into games such as Glinskis Hexagonal Chess or Capablanca Chess or even Millenium 3d Chess.

[Cameron Browne has done a lot of work on connection games and of course there are the small short games of no chance in the "Games of No Chance" books containing various papers on games; but, I'm really looking for some heavy information w.r.t. the above 3 chess variants.]

I'm not sure if this is the sort of item you might be interested in, but Dave McCooey generated complete (pawnless) 4-man tablebases for hexagonal chess on the 91-"square" board, and has a full tabulation of the results; since there are no pawns involved, the analysis there is applicable both to Glinski's hexagonal chess that you mention, as well as McCooey's own version (which differs from Glinski's where pawn movement is concerned). McCooey went beyond providing tablebases for the usual chess pieces, and also included a great variety of fairy pieces, including the Chancellor and Archbishop (called there the Pegasus) of Capablanca chess.

Beyond the hexagonal chess board, he also created some 4-man and 5-man tablebases involving fairy pieces on the standard 8x8 chessboard. Those results involving only standard chess pieces along with Chancellors and Archbishops/Pegasi are somewhat relevant to endgames for Capablanca chess. Since Capablanca chess is played on a 10x8 board, the results aren't directly applicable to that game, but they are suggestive of how things would play out on the 10x8 board, and in any case they are directly applicable to Seirawan chess, which uses the same piece set as Capablanca chess -- with yet different names: Chancellor = Elephant, Archbishop = Hawk -- but is played on the standard board.


Can I play on Lichess with my own "client"? I love Lichess. It's web based client, but I want to use a program like Scid, scid vs Pc, or babaschess, or any of this clients programs used in FICS: see bottom links this page. Those programs offer possibilities Lichess doesn't such as annotate games move per move, choose engines to run in your own PC (to the contrary on the cloud like lichess, wich could be slower). Can you help me?

Lichess does not support the FICS-interface, therefore clients used for FICS do not support it. At the moment you can only play it via a web-client.

Maybe in the future the Lichess-API allows sending and receiving moves, etc. Apparently it is already possible as the API already allows it via HTTP, see Link.

EDIT:
As stated in this issue tracker thread pychess is interested in integrating Lichess support. An official desktop client will most likely not come in the near future as the web GUI is fantastic already and developers can use the time to further improve the current codebase.


How can I use Scid to figure how I should divide study time for each opening line? I have a database (Scid) that is mostly made up of games downloaded from TWIC. I know my rating (low 2000s).

As an example, I want to play the Classical Sicilian as black. It can be reached either as 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6, or with 2...Nc6 and 5...d6, my choice.

Of course, White has many other options as well, and I want to divide my time proportionally. If I reach the Classical 50% of the time (after 1.e4), I should devote 50% of my 1.e4 black training time to it. Maybe 20% of the time 3.Bb5 is played, et cetera.

What's the best way to figure out such percentages correctly?

I would recommend an iterative approach to study an opening system. Use it in a game, then analyze the opening with a large opening tree, book and engine. For example, you can use the Chessbase mobile app or the corresponding Chessbase Online site. You can record your conclusions in your own opening database file, e.g. using Scid.

By continuously using and improving an opening system, learning and winning will go hand in hand. By immediately analyzing the opening after every played game (online as well as over the board), you will improve your opening skills step by step.


Variant chess effect Variant chess is a relaxing break from standard chess. But in my chess club we are usually discouraged from playing such chess. I have  not seen any visible problem in my games. Can anyone tell me why variant chess is supposed to be bad for your game?

Well it's not necessarily bad for your game, but it can easily lead to confusion because the evaluation and the gameplay in general in chess variants are very different compared to standard chess. As a result, because you are in a completely different mindset, routinely playing these variants may make your understanding or judgement over standard chess games a bit rusty.

tldr: Obsessively playing a variant may make your standard chess feel a bit rusty, and also consume a lot of time that you would otherwise be spending to study standard chess (say endgames...), specially if you are a serious club player. On the flip-side, playing variants can potentially make for good training of your calculation skills and attacking techniques/instincts, to name a few. But all in all, a healthy dose of them can be a lot of fun in fact, specially among friends :)

To explain a tad on what I mean by different mindset or gameplay:

Let's take crazyhouse as our first variant of choice: In this variant, any piece you capture from your opponent goes to your pocket (and vice versa), which means that during your turns you can either make a normal move according to the rules of chess, or insert a piece into play from your pocket. First consequence is the fact that there will be no endgame emerging from this variant of chess, because the pieces keep getting reshuffled around and re-enter the game. On the other hand, any gambit opening becomes unplayable, becomes you'd be giving free pawns that your opponent can place now anywhere they need! Finally, how you assess a given position would have to take into account all the variations branching out from different piece insertions. So naturally, when returning to standard chess, you'll be left with a strange feeling at first, but I wouldn't necessarily argue that playing crazyhouse will have a negative effect on your play. Because if anything, it does teach in a very direct way how to exploit weaknesses by immediately setting an attack using your pocket pieces (for instance you'll get a lot of chances to practice different checkmating techniques such as the smothered-mate). Simple example below:

 [title "Checkmate in 2: white to play (pocket: 1 pawn, 1 queen)"]
 [fen "r1bk3r/ppppbppp/1p1N4/2n5/1pQ1N3/8/PPP2PPP/R1B1KB1R w KQ - 0 1"]

Solution:

   1.Q@e8+ Rxe8 2.Nxf7#

Three-check chess:

This is more of a extreme example where even though usual checkmating is still valid, the game becomes all about avoiding checks no matter what, because one can also win by giving 3 checks to the opponent king. So you will be exposing and sacrificing all sorts of good material just to prevent a check (and conversely to give checks) that in standard chess wouldn't be a problem to face. So again, you see the mindset with which you will play and assess positions will be widely different from standard chess (see example below). All to say that, hopping back and forth between variants and standard chess, will at first leave you with confusing feelings when returning to standard chess and your evaluation will become a bit shaky, but after some playing you will quickly re-adjust again and it all comes back again of course ;)

 [title "Three-check variant, typical mis-play example:"]
 [fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

 1.e4 e5 2.Nf3 Nc6 3.Bc4 h6 {`h6` would be a somewhat acceptable move to play had it been standard chess, to prevent Ng4, but in three-check it's a disaster of a move, because multiple forced wins in 6 moves follow for white from here! Try to find it one.}

Solution:

   One possible solution: 4.Bxf7+ Ke7 (4...Kxf7 loses in 2, with e.g., Nxe5+ and Qf3+ last 2 checks) 5.Nh4 Nb4 {black's only attempt to delay the incoming two last checks by forcing a check with Nxc2+} 6.Ng6+ Kd6 7.d4 Nxc2+ 8.Qxc2 c6 {doesn't matter which move, the last queen check is unavoidable} 9.Qxc6+ {game over by 3 checks.}


King's Indian Defense - When to play 6...c5 or 6...e5 I'm a casual player who enjoys playing the King's Indian Defense as Black, but I don't fully understand yet when it is better to play 6...e5 or 6...c5. These are my main doubts:

What are the aims and differences about playing one move instead of the other?
In which conditions (such as position of opponent's pieces) should I play 6...c5 instead of the more characteristic 6...e5?

I've looked at this very interesting question about the aims of playing 6...e5, but it does not mention anything about the difference between the two aforementioned moves.

Any extra insight or suggestion is of course more than welcome!

I'm not a KID expert, but Joe Gallagher GM is, so I'll quote him from "Starting out: The King's Indian":

  "If you are going to play the King's Indian with Black you may be a
  little confused as to whether you should aim for ... c7-c5 or ...
  e7-e5. I tend to adhere to the following rule:

  Play ... e7-e5 except when White develops his queen bishop early. Then
  it's time to start thinking (just thinking mind you) about ... c7-c5.
  The move ... c7-c5 is likely to prise open the long diagonal (after
  ... e7-e5 it usually becomes totally blocked) and the absence of the
  white bishop from the queenside means the dark squares there (such as
  b2) may become vulnerable to pressure from the g7 bishop"


Computer being right and human being wrong Of course, computers have changed the evaluation of more than one endgame position (BB vs N being the most known, I guess), which humans thought to be drawn.
Having read another question here, I'm more after a specific question. Usually, computers have [had?] big troubles to recognize a fortress as a draw, but can you offhand give an example where humans thought this is a fortress, but computer proved it isn't because all humans overlooked a tactical point? (Arguably already BB vs N, or Q vs BB[?] counts, but I'm more after the pawn chain salad type here.)

This has definitely happened in endgames, e.g.:

Queen and a minor piece versus two rooks: this is usually a draw for a knight and a win for a bishop, although the win takes up to eighty-five moves. The best method of defense is to double the rooks on the third rank with the opposing king on the other side and keep the king behind the rooks. This case with a bishop and queen versus rooks is unusual in that such a small material advantage forces a win. It was thought to be a draw by human analysis, but computer analysis revealed a long forced win (Müller & Lamprecht 2001:404), (Nunn 2002a:328–29,367,372).

It also happens earlier during the middlegame, although this will depend on the time the human spends analyzing. It's a lot easier for the human to find the winning line if they know there's a way to "break the fortress".
Example (39 minutes in):
[FEN "1q4rr/5p2/kpb2b2/p1p1pP2/P1PpP1pN/1P1P2P1/4QBN1/1K4R1 w - - 0 1"]

(Black to play)
Black is up the exchange, but the position is completely locked. Black could sacrifice an exchange on h4, but White has the g4-pawn well-covered and trades will only help White draw, since Black's c6-bishop is never penetrating White's position and it'd be an OCB endgame as well. Draw?
In fairness to Nakamura, he didn't actually say it was a draw (he was playing against Komodo, after all), but you can see his reaction to Komodo's next move.


Understanding Carlsen's resignation in the rook and pawn endgame vs MVL Why did Carlsen resign in the position shown below? (blitz game played in the London Chess Classic GCT Finals)

Can't white help the pawn queen after Ke3 and Kd3 then Kd4? I must be missing something.

[Title "Magnus Carlsen-Maxime Vachier-Lagrave, London Chess Classic GCT Finals, London England 12/02/2019"]
[FEN ""]
[startply "108"]

1. d4 Nf6 2. Nf3 g6 3. Nbd2 d5 4. b3 Bg7 5. Bb2 a5 6. a4 O-O 7. e3 Bf5 8. Be2 Nc6 9. O-O Nb4 10. Ne1 Ne4 11. c3 Nxd2 12. Qxd2 Nc6 13. Nd3 e5 14. Nxe5 Nxe5 15. dxe5 Bxe5 16. Rfd1 Qd6 17. Ba3 c5 18. Qxd5 Qxd5 19. Rxd5 Bxc3 20. Rad1 Bb4 21. Bxb4 cxb4 22. Bc4 Be6 23. Rb5 Rfd8 24. Rd4 Rac8 25. Rxd8+ Rxd8 26. Kf1 Bxc4+ 27. bxc4 Rd2 28. Rxb7 Ra2 29. c5 Rxa4 30. Ke2 Ra3 31. c6 Rc3 32. c7 Kg7 33. Ra7 b3 34. Rxa5 Rxc7 35. Rb5 Rc2+ 36. Kf3 b2 37. Rb6 h5 38. h3 Kf8 39. g4 h4 40. g5 Ke7 41. e4 Kd7 42. Ke3 Kc7 43. Rb5 Kc6 44. Rb8 Kc5 45. f4 Kc4 46. f5 Kc3 47. Kf4 Rg2 48. fxg6 fxg6 49. e5 Re2 50. Rb6 Kc2 51. Rc6+ Kd1 52. Rd6+ Kc1 53. Rc6+ Rc2 54. Rb6 Rc4+

Intuitive plan

Notice that black's last check is pushing the white king one row away from their passed e-pawn. Once black promotes the b-pawn, white will have to give up the rook for it. After which white's king is simply not in position to cover the advance of the e-pawn and therefore additional tempi will have to be spent with king moves to try and reach the pawn, during which the rook can first simply capture white's h-pawn and only then sacrifice itself for the e-pawn. Then black's h-pawn promotes and wins trivially. Now let's see how all this pans out concretely (no matter how strong the intuition might be, in endgames one must always primarily rely on concrete calculations in order to realise whether our ideas or plans can actually be optimally implemented).

Annotated diagram

 [title "A simple continuation showcasing why white is lost here"]
 [fen "8/8/1R4p1/4P1P1/2r2K1p/7P/1p6/2k5 w - - 0 1"]

 1. Ke3 b1=Q 2. Rxb1+ Kxb1 3. Kd3 (3. e6 {blunders the e pawn away} Rc6 4. e7 Re6+) Ra4 4. Ke3 {again, the pawn advance would simply leave it hanging, so white has to make king moves while not allowing black to get behind the pawn} Ra3+ 5. Kd4 Rxh3 6. e6 Rh1 7. Kd5 h3 8. e7 Re1 9. Kd6 Rxe7 {though black doesn't even have to sacrifice the rook here, but it's simply a practical way of going about it, and in-line with our original plan} (9...h2 {much more accurate continuation as we can in fact keep our rook since white's tactically losing their queen immediately upon promotion, in fact you might find this line easier to calculate} 10. Kd7 h1=Q 11. e8=Q Qd5+ 12. Kc8 Rxe8+) 10. Kxe7 h2 {and it's easy to judge that black's winning here since the promoted queen is well in time to get to white's promotion square g8 and then simply bring the king over. I'll include this sequence} 11. Kf6 h1=Q 12. Kxg6 Qb7 {cutting off the king from accessing the 7th row} 13. Kf6 (13. Kh6 Qf7 14. g6 Qg8) Qh7 14. g6 Qg8 {and now black simply brings the king and wins the pawn}


Statistical Right Handedness Bias in Move Selection? It seems clear to me that there must be a statistical bias in the move selection of master level games in relation to the natural "hand" of the move, right or left.

Let me explain.  For the sake of argument let's select the population of  master level chess players who are right handed, and consider blitz games played by these players.  In each position, the vector of each legal move has a more-or-less clockwise or counterclockwise orientation with respect to the center of the board.  Yet for purely anatomical and biological reasons, clockwise moves may be easier to execute on the physical board as it is placed before the players.  Given a players hand literally hovering over a board searching for a move, there must be a bias in which more easily executed moves are preferred over less anatomically natural ones.

Is there any evidence of this sort of geometrical bias in move selection, beyond that expected from the actual theoretical value of the moves themselves?

There might be many statistical imbalances: towards advancing or retreating moves, towards kingside or queenside directed moves, and possibly towards clockwise or counter-clockwise flowing moves, as I mentioned above.

Edit: The key phrase here is 'actual theoretical value'.  I wish to compare human play against perfect play and suggest that the discrepancies which arise might indicate more than a deficit of mental chess ability but also because of the way the brain-body system and handedness might favor moves that are quicker to find with the hand.

I found no scientific literature on hand bias in Chess on Google Scholar.

From the comments there doesn't seem to be any database analysis supporting a theory of hand bias, e.g.

  Statistically, White is more likely to castle queenside than Black. Since 90-93% of people are right-handed, this is contrary to your theory.

Accredited to @Mike Jones.

Additionally, I haven't found any anecdotal evidence of hand biased in my own chess books. E.g. there is no mention of it in the 'Psychology' or 'Tournament Tactics' sections of The Wisest Things Ever Said About Chess.


How many materially equal positions are there? Reading about the Shannon number, I see that there are about 1043 positions in chess, but how many of them are even? That is, materially (as an approximation). A position with one king vs 8 pawns and a king is not really interesting.

What follows is basically a partial answer that is heavy on explanation, plus a pointer for using it to obtain a fuller answer if so desired.

Suppose we start with a blank 64-square chessboard and ask how many different positions we can make by placing down just 2 white knights. A quick answer is that it is 64*63 = 4032 positions, because we can place the first knight on any of 64 squares, and for each of those choices there are 63 remaining choices for the other knight. But this overcounts a bit. Specifically, that number double-counts every possibility, the reason being that our white knights are indistinguishable in terms of a chess position. What I mean is this: the counting scheme above treats (A) placing Knight1 at a1 and then Knight2 at a2, and (B) placing Knight1 at a2 and then Knight2 at a1, as two different chess positions. But they aren't: each has a white knight at a1 and at a2; they are the same chess position, as white knights don't come with individual labels. So the real answer should be (64*63)/2 = 2016 positions.

If we were instead placing 8 white pawns on an empty 64-square board, the number of possibilities is

(64*63*62*61*60*59*58*57) / 8! = 4,426,165,368

This is just like the previous example, where the numerator naively counts the ways to place the 8 pawns, and the 8! of the denominator accounts for the fact that our white pawns are indistinguishable from one another in a position (and there are 8! ways to order the 8 pawns). Note too that the numerator can be written more succinctly as 64! / 56!, so a snappier way to give the number is as

64! / (56! * 8!)

OK, so what about Shannon's paper itself? The estimate of the number of chess positions given there is that it is "of the general order of"

64! / (32! * (8!)^2 * (2!)^6) = 4.63E+42

From the examples above, we know what this is counting. The 64! / 32! naively counts the number of ways to drop 32 pieces onto the 64 squares of the chessboard. Then we divide by 8! twice to ignore the order of the white pawns and the black pawns. Finally, we divide by 2! = 2 a total of 6 times, to account for the white/black knights, bishops and rooks. So this 4.63E+42 is a rough estimate of the number of 32-piece positions, all of which have even material of course. (Note that we are totally ignoring legality, e.g. we can have pawns on the first rank, both kings in check, and so on; for an interesting thread on the proportion of positions that are actually legal, see this MathOverflow post. We are also ignoring promotions by saying that the original 32-piece set is all we get.)

A similar "Shannon estimate" for the number of 31-piece positions is given by

  1.40E+41 = 64! / (33! * (8!)^2 * (2^6))      remove white Q
  2.81E+41 = 64! / (33! * (8!)^2 * (2^5))      remove a white R
  2.81E+41 = 64! / (33! * (8!)^2 * (2^5))      remove a white B
  2.81E+41 = 64! / (33! * (8!)^2 * (2^5))      remove a white N
+ 1.12E+42 = 64! / (33! * 8! * 7! * (2^6))     remove a white P
----------
  2.11E+42
* 2           to count those positions removing a single black piece
----------
  4.21E+42

Note the huge drop in the number of positions: there are 4.21E+41 more 32-piece positions than there are 31-piece positions. The numbers will continue to drop dramatically, and in fact the proportion of 32-piece positions among all possible positions will be fairly sizable (hence so too will the number of even-material positions).

It wouldn't be too difficult for someone to write a program that produces these Shannon estimates for all numbers of pieces (one would just need to make sure to account for all combinations of a given number of pieces), and we could keep track of all those combinations that have equal material as we go. At the end we would have the Shannon estimate for all possible positions (though the 32-piece number already gives a rough sense of the total, as Shannon notes, because of the quick drop in positions as we drop pieces), as well as a count/proportion of how many of those (pseudo-legal) positions have equal material.


Help needed with a problem On an empty board, how can you place a White king, two White, rooks, and a Black king so that White can give mate in 4 ways from that position?

[FEN "8/8/8/8/8/8/2R5/k3K2R w K - 0 1"]

From this position, Kd2 Ke2 Kf2 and O-O deliver checkmate


What are the official rules if your opponent makes an illegal move? I heard that they lose some time or that they lose the game. I'm not sure what happens.

By the FIDE Laws of Chess, article 7.4:

7.4

a. If during a game it is found that an illegal move, including
failing to meet the requirements of the promotion of a pawn or
capturing the opponent’s king, has been completed, the position
immediately before the irregularity shall be reinstated. If the
position immediately before the irregularity cannot be determined the
game shall continue from the last identifiable position prior to the
irregularity. The clocks shall be adjusted according to Article 6.13.
The Articles 4.3 and 4.6 apply to the move replacing the illegal
move. The game shall then continue from this re-instated position.

b. After the action taken under Article 7.4.a, for the first two
illegal moves by a player the arbiter shall give two minutes extra
time to his opponent in each instance; for a third illegal move by
the same player, the arbiter shall declare the game lost by this
player. However, the game is drawn if the position is such that the
opponent cannot checkmate the player’s king by any possible series of
legal moves.

That is, on the two first illegal moves of your opponent, you gain time on your clock (two minutes, which likely does nothing), but on the third illegal move of your opponent, they lose the game (unless it was already impossible for them to lose it).


What is this opening trap I keep encountering in the Englund Gambit? [FEN ""]

1. d4 e5 { A40 Englund Gambit } 2. dxe5 Bc5 3. Nc3 b5 4. Nxb5 d6 5. exd6 Ne7 6. dxe7 Bxf2+ 7. Kxf2 Qxd1 8. Na3 Kxe7 9. Nf3 Qd6 10. Nb5 Qc6 11. a4 Qxc2 12. g3 Qc3 13. Nxc3 { Black resigns. } 1-0

I have suddenly encountered very similar opening lines several times in the past few days, where I play d4, my opponent plays the englund e5, I take the pawn, then take another pawn or piece with that pawn as they move their bishop out, then my opponent sacrifices their bishop to draw out my king and allow a queen queen capture.  Is their a name for this opening trap? Lichess doesn't recognize it.

This is just a series of bad moves by black.
The video linked to by koedem says it's a new "trap," and quite frankly, it requires white to resign after dropping the queen to qualify as a trap.  If white continues 8. Nxc7+, when the dust settles, white still has a slight advantage, having traded a queen for a rook, two pawns and a bishop.  (In this continuation, white will exchange the knight for a rook and lose the pawn on e7.)
If white plays 6. Nxc7+ and captures the knight before capturing the rook, white ends up winning a rook and two pawns outright, and remove's black's castling rights.  So black is taking the risk of a crushing loss in the hopes that white will blunder his way into equality instead.


How should black meet the Halloween Gambit? Although the Halloween Gambit is generally considered bad (and nearly losing for white), it is tricky to meet over the board, especially at the club level.

How should black play in order to refute white's gambit?

[White "Four Knights"]
[Black "Halloween Gambit"]
[FEN ""]

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Nxe5?! Nxe5 5. d4 Nc6 (5... Ng6)

After

[FEN ""]

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Nxe5?! Nxe5 5. d4 Nc6 6. d5

Instead of moving the c6 Knight, black should continue with Jan Pinski's 6...Bb4. Black will just give away the c6 knight and then black will take the e4 pawn with the f6 Knight.  White can't take the Knight because his own is pinned and if white moves their queen to d4, black can just move their queen to e7 to protect both the bishop and the knight.  A continuation might be something like this:

[FEN ""]

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Nxe5?! Nxe5 5. d4 Nc6 6. d5 Bb4 7. dxc6 Nxe4 8. Qd4 Qe7 9. Qxg7 Nxc3+ 10. Be3 Nd5+ 11. c3 Rf8

As you can see from above, if black plays accurately, there can be many discovered checks on white and if black wants, they can continue by taking the bishop on e3 eventually with another discovered check to follow or white will have to take the Knight, but either way, black will just take back with Qxe3+ and it is pretty much over for white.

Here is a professional game between Grigor Minchev and Aleksandr Pretov where black was unable to defend properly and was devastated.

  [FEN ""]
  1. e4 e5 2. Nf3 Nf6 3. Nc3 Nc6 4. Nxe5 Nxe5 5. d4 Nc6 6. d5
  Ne5 7. f4 Ng6 8. e5 Ng8 9. d6 cxd6 10. exd6 Qf6 11. Nb5 Rb8
  12. Be3 b6 13. Qe2 Kd8 14. O-O-O Qe6 15. f5 Qxf5 16. Qc4 Qe5
  17. Qc7+ Ke8 18. Bd4 Qf4+ 19. Kb1 Ra8 20. Re1+ Be7 21. g3 Qd2
  22. Bg2 Qxg2 23. dxe7 N8xe7 24. Nd6+ Kf8 25. Qd8# 1-0


Examples of recent early opening novelties at the top level The world elite usually practises extremely deep opening preparation based on established theory, with the first move that has never been played before often coming after the 20th turn.

What are some recent (last 20 years) examples of top-class players deviating from theory early (say, on the 8th move or before)?

Aronian vs Anand at Candidates 2014 (http://www.chessgames.com/perl/chessgame?gid=1751406) was out of theory after Black's 3rd move, but only because White played an extremely odd opening which will probably never be repeated at the top level.

Aronian vs Leko at Morelia-Linares 2008 (http://www.chessgames.com/perl/chessgame?gid=1486033) featured a strong novelty on White's 9th move.


Complete game Troitzky-Vogt? The Wikipedia on stalemate shows a position where Vogt became victim of a diabolic stalemate trap set by Troitzky.

[Title "Troitzky-Vogt"]
[FEN "2kr4/1ppb1pp1/1b4r1/pP2p3/P3P3/5qN1/2Q2P1P/2R1B1KR w - - 0 1"]

1. Rd1! Bh3? 2. Rxd8+ Kxd8 3. Qd1+ Qxd1 1/2-1/2

I would like to have the full game. Can anyone help?

Not to rain on your hopes - but the problem you're looking for at first appeared in:

  Troitzky, A. (1924), 500 Endspielstudien, Verlag Kagan, Berlin

Troitzky was an impeccable note-taker when it came to chess.  This book was End Game Studies and show endgame positions with only with a few endgame moves.  It didn't show complete games.

  Unfortunately all of his notes were destroyed in the siege of Leningrad, so there is likely no record of this complete game (not even in Russian sources). (He also died of starvation during the same siege)

Please don't shoot the messenger.


What are some advantages/disadvantages of accepting/declining gambits? Most of the time I see gambits are declined, but what are the advantages or disadvantages of accepting or declining gambits?  I know this depends on the type of gambit, but I am looking for a more general answer that might apply to all gambits.

Since you are after general considerations:

Accepting a gambit. The advantage here of course is that you are gaining a material advantage, which, if you can hold onto it, provides well for your long-term prospects in the game. But what makes something an established gambit, rather than a mistake or a blunder, is that the offer of material is supposed to be offset by some sort of positional compensation, e.g. a lead in development, as in, say, the Danish Gambit:

[FEN ""]
1.e4 e5 2.d4 exd4 3.c3 dxc3 4.Bc4 cxb2 5.Bxb2

Or better control of the center in, say, the Queen's Gambit:

[FEN ""]
1.d4 d5 2.c4 dxc4 3.e4

Or open lines for pieces (like those bishops surveying two nice, long diagonals in the Danish Gambit).

So the potential disadvantage of accepting a given gambit is that you may be left with positional problems by which your opponent can punish you, perhaps by winning back the sacrificed material and then some, or worse, mating your king directly. Whether the compensation for your opponent outweighs the extra material you'll be getting is something that has to be decided on a case-by-case basis.

Declining a gambit. Here the main advantage, in my opinion at least, is simply that you're not giving your opponent the kind of position that he or she wants. For example, the Smith-Morra Gambit in the Sicilian Defense is very rarely played at the highest levels of the chess world, because the consensus among strong players is that white just doesn't get enough dynamic positional compensation (development lead, initiative) for the extra central pawn that black gets. But at lower levels, it can be much more dangerous to defend for black. Thus, if you're one to prefer slightly quieter positions rather than potentially needing to sweat under pressure for a while, one possible reaction to the Smith-Morra is to decline it by pushing d3 instead of capturing white's c pawn:

[FEN ""]
1.e4 c5 2.d4 cxd4 3.c3 dxc3 (3... d3 4.Bxd3) 4.Nxc3

Now white is not going to get the sort of development that was envisioned (for instance, the white pawn that now remains on c3 takes away the square which was intended for the knight).

The main disadvantage of this approach is obvious: no free material. And one shouldn't be afraid of ghosts in chess. If material is offered, one should certainly be cautious, but if at the end of your thinking you believe it is worth any trade-offs, then you should take it. Sometimes you will be wrong and get punished for your greed, but mistakes can be made at any juncture in the game, so this isn't a problem particular to gambit play. And besides, some gambits cannot be reasonably refused, e.g. the Cochrane Gambit in the Petroff Defense:

[FEN ""]
1.e4 e5 2.Nf3 Nf6 3.Nxe5 d6 4.Nxf7

This is just like in many middlegames, where an attack will be launched with a sacrifice that cannot be refused, and one has no choice but to grab the material and hang on for dear life. So there is something to be said for not always declining aggressive gambits, because accepting can be good training for defending complicated positions, which aids one's overall development as a player.

In sum. As stated above, the decision as to whether the material offered in any given gambit is worth whatever positional trade-offs are involved is one that has to be made case-by-case. But hopefully I've given some useful general food for thought here.


How common/important is promotion to knight? Is a chess program without the ability to promote to knight unacceptably incomplete?

I have a chess program that implements most basic chess rules, such as en passant and castling. However, promotion automatically chooses a queen, as introducing a decision point there would complicate everything from the AI to the replay system to keybindings.

Is a chess program without promotion to knight just no good, or is the average chess player not likely to ever notice that it's missing? And if they do, would it be similar to "oh, no promotion to knight I guess" or more like "how in the world did someone think this was okay? I bet this wasn't even developed by a chess player!" (a safe bet)? I'm hoping that it's trivial enough to be overlooked, but if it really is important then I'll just have to figure it out.

Well I definitely wouldn't put it as unacceptably incomplete, after all it is a very rare event that you're forced to underpromote into a knight, unless you're fooling around.

That said, there are cases in real games, where you actually have to promote knights (again very rarely, but still every now and then you see one of those), because e.g. you have to promote with a check (otherwise you may get checkmated), so if in such scenarios it's only with knight that you can check, then you really need the knight-promotion option. A random example:

[Title "1.e8=N+ Forced knight promotion"]
[StartFlipped "0"]
[fen "3K4/4P3/2qk4/8/8/8/8/8 w - - 0 1"]

1. e8=N+ (1.e8=Q Qc7#)

Here's another one: (match between Tomic vs. Winzbeck)

[Title "Forced N or B promotion else stalemate"]
[StartFlipped "0"]
[fen "3rb2k/2P4p/6pP/p2B1pP1/Pp2pP2/1P2K3/8/8 w - - 0 1"]

1. cxd8=N (1. cxd8=B) (1. cxd8=Q)

On the other hand, it may also happen that if you promote into anything else than knight, you stalemate the position, so again knight-promotion needed. You'll find tons of examples from this chess SE post and links therein.

Whereas if you take online blitz games as example, then most often (for time controls < 5 mins at least) players set their automatic promotion to queen so that in case they're in time trouble and have to promote, they can premove it.

All in all, I would say that you should try to implement it for completeness, and if it turns out difficult for you, then don't worry too much about it, no big deal.

I actually do recall a very fun game between Hikaru Nakamura and Boris Savchenko in the previous world blitz championship, where Nakamura had to underpromote into knight with check in order to avoid a mate in 1, here's the clip, it's only 2 minutes, watch it from the start, but if you just want to see the promotion moment, here it is.


Two questions about Wesley So vs Varuzhan Akobian (2016) Here is a link to the game itself.
[FEN ""]
[White "Wesley So"]
[Black "Varuzhan Akobian"]

1. e4 e6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Nd7 5. Nf3 Ngf6 6. Nxf6+ Nxf6 7. c3 c5 8. Be3 cxd4 9. Bxd4 Be7 10. Bd3 O-O 11. Qc2 h6 12. O-O-O Qa5 13. Kb1 Rd8 14. Ne5 Bd7 15. Qe2 Bc6 16. Rhe1 Bd5 17. c4 Bxg2 18. Bc3 Qb6 19. Rg1 Bc6 20. Nxf7 Kxf7 21. Rxg7+ Kxg7 22. Qxe6 Qxf2 23. Qxe7+ Kg8 24. Bh7+

I'm a chess newbie and was looking at this game and quite amazed by the White knight's attack. I have two questions.
First what point did Akobian go wrong? I really didn't see the attack coming. Only at 20. Nxf7 did I realize that the White knight must have some sort of plan and it was probably calculated way ahead. I assumed it was only on the next move that Akobian was also able to calculate ahead and see no chance of winning.  But at what point was the game not saveable, at what point did Akobian make a big mistake? I have a very limited chess program, but it never gives the White knight a big advantage for any of the moves until then so I can't figure it out.
Secondly, did the White knight make a mistake at the end? My computer gives 24. Bxf6 as the better move, forcing a checkmate in just a few moves. Meanwhile, the line played by the White knight is not forcing, at least not immediately.

But at what point was game not saveable, at what point did Akobian
  make a (big) mistake?

Qxf2 is a big mistake as after that it is forced mate in 7 moves. If So had played 24. Bxf6 there is no defense against all the mate threads and all black can do is prolong his suffering by throwing in some pieces.

[FEN ""]
[Event "US Chess Championships"]
[White "Wesley So (2773)"]
[Black "Varuzhan Akobian (2615)"]
[StartPly "46"]
[Result "1-0"]
[PlyCount "47"]
[ECO "C10"]
[Opening "French Defense: Rubinstein Variation, Kasparov Attack"]

1. e4 e6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Nd7 5. Nf3 Ngf6 6. Nxf6+ Nxf6 7. c3      c5 8. Be3 cxd4 9. Bxd4 Be7 10. Bd3 O-O 11. Qc2 h6 12. O-O-O Qa5 13. Kb1 Rd8 14. Ne5 Bd7 15. Qe2 Bc6 16. Rhe1 Bd5 17. c4 Bxg2 18. Bc3 Qb6 19. Rg1 Bc6 20. Nxf7 Kxf7 21. Rxg7+ Kxg7 22. Qxe6 Qxf2?? 23. Qxe7+ Kg8 24. Bh7+!? (24. Bxf6 Qxf6 25. Qxf6 Bg2 26. Rg1 Rxd3 27. Rxg2+ Rg3 28. Rxg3+ Kh7 29. Qg7#)

However So did not play 24. Bxf6 but went for Bh7+ instead which is of course also winning. Most likely he saw that after Bh7+ lots of material would  come off the board in a forced line and he would end up in an easily won endgame with queen plus 4 pawns vs. bishop plus 3 pawns
(no counterplay for black and no fortress either).

While mating quickly is more desirable for the beauty of chess, from a practical standpoint, going for a forced line which is easy to calculate and obviously won makes a lot of sense. 24. Bxf6 of course looks very good even without calculating concrete lines, but has more potential for error. Furthermore if So had played 24. Bxf6, he would have needed a bit more time for calculating consequences of that move and also Akobian might have fought on for a move or two. So in the end the second best move (Bh7+) might even have ended the game quicker, because it was obvious that white will win.

Back to Qxf2...

That's a curious choice as it leaves the bishop on e7 hanging and after that also the knight on f6 is hanging. I have no idea what Akobian was thinking here (probably desperation or time trouble?). He must (or should) have checked at least all the options of protecting the bishop on e7, like Qc5, Qc7, Re8 and Rd7. Both, Qc5 and Qc7 lose and it is easy to calculate this on the board. 22 .. Re8 seems to hold according to the computer. Black is still under a very dangerous looking attack and will have to find the correct moves to secure equality in the moves to come. 22 .. Rd7 will lose, but not as fast as 22 .. Qc5/c7. From a GM I would have expected to play one of Re8 or Rd7 at least.

Did Akobian go wrong before Qxf2?

Computers give more or less equality (small advantage for white) before that move, but from a human perspective I find 17 .. Bxg2 a strange choice as it opens the g file for white's rook. This will always be dangerous even if there is no immediate tactics.

Also I am not sure whether transferring the bishop from c8 to d5 via d7 and c6 was such a good idea. Wasted lots of tempi just to force white to play c4. Probably a better plan for black here was to go for a minority attack on the queen side with b5, b4...


Is there a term for when each player captures a sequence of pieces without recaptures? There is a situation that arises occasionally, where each player goes on a rampage through the other player's pieces (often using a queen), never stopping to recapture or defend. It usually ends when either there is no more material to safely capture, or with check.
Is there a term for this kind of war on two fronts?

If each of the marauding pieces is itself en prise
during most or all of the sequence, it can be called a desperado;
see for example the Bogolyubov-Schmid game cited in Wikipedia's article on
"Desperado (chess)":
https://en.wikipedia.org/wiki/Desperado_(chess)#Bogolyubov_versus_Schmid


Where to play with friend online with no need to register? Is there some site where you can play with your friend with no need to either of players having account there? Just searching for way how to make online training sessions with various people, everybody having different favorite chess sites.

Lichess is great for that.

When you click the 'play with a friend' button, it allows you to create a custom game to invite someone with a link, the amazing thing is that if the game is unrated, you can invite anonymous players, and it works even if you are not logged in at all, thus you can do anon vs anon games.

I have some online friends that are very timid, and don't want anyone knowing who they are online in any manner, they love lichess because of this possibility of playing completely anonymous.


Looking for way to “punish” the d5 push after 1. d4 Nf6 All is said in the title. I find the move 2. d5 after 1. d4 Nf6 pretty annoying even if it's probably not a great move. What are suitable moves to "punish”

  Blockquote

this opening play? I will add that I am more of a Benoni/Benko player.

If you're a Benoni player, there's nothing wrong with 2... c5, which will get you in familiar territory (3. dxc6 e.p. is harmless and not something White wants to play - exchanging a center pawn for a flank pawn).

While it's not a great move, Black isn't immediately better, just about equal. So it's dangerous to try to 'punish' this move, especially if White has probably more experience with this line than you (and less with the main Benoni/Benko lines).


What are the possible terms for interference in the bishop endgame? In various positions in elementary bishop endgames, the stronger side tries to prevent the sacrifice of the bishop for the last remaining pawn by interposing the diagonal with the bishop. For example, second position in this Centurini article. What are the possible terms for this idea? Besides 'interference', can it be called a 'bridge', by analogy with rook endgames?

Dvoretsky in Endgame Manual just calls this technique interferring.

Building a bridge in RPvR endgames is slightly different as it is about sheltering your king from checks from the enemy rook, not about preventing the rook from sacrificing itself for the last remaining pawn.


Confusion about the tie-break in the Grenke Chess Classics 2015 I am confused about the result of the Grenke Chess Classics 2015.

At the one hand, Magnus Carlsen won 3 games and Arkadij Naiditsch only 2, so due to
 the tiebreaker-rule, Carlsen should have won the tournament.

But then I noticed that 5 tie break games were added.

What is true and who won the tournament ?

Carlsen won the tie-break (and the tournament).

Quite dramatically, after trading wins in the rapid and draws in the blitz games, with a win in the armageddon game.

The tie-break rules were only used to sort out the places apart from the first place.

http://www.grenkechessclassic.de/en/grenke-chess-classic-2015/rules-regulations

http://en.chessbase.com/post/grenke-final-carlsen-wins-in-armageddon


What is the highest number of pieces from one side that can be involved in a checkmate? What is the highest number of pieces from one side that can be involved in a checkmate? "Involved in a checkmate" is defined below.
A non-king piece is involved in a checkmate 'if removing it from the checkmate position would change the position to one which is either not checkmate or is illegal'.  The king is involved in a checkmate if it is the only piece of the checkmating side that attacks one of the other king's escape squares.

Here is a solution with all 16 white pieces, all mandatory for checkmate, without promoted units and without needing to protect the white king from checks. If you remove any white piece but the king, the position is still legal but not a checkmate anymore. Moving the wK to a random square (say, h1) would also destroy the mate.

QNr1R1b1/P1BpnP2/3P4/qP4Pr/Rn2kP2/1N4PB/2P2K2/8 w - - 0 1

Last move is Nc6-b8# or d5-d6#.


Top players strongly in favor of 1.e4 Which are some top players known to be strongly in favor of 1.e4 in the opening?

In this respect I find interesting a comment by Fischer on Alekhine:
"there is nothing light or breezy in his style". As Fischer clearly belongs to the 1.e4 group, do you think this "light and breezy" feel is in some way attached to this move, or is it an entirely subjective opinion that cannot be taken too seriously?

Another notable top player was Karpov in the 70s and first half of the 80s. But after Kasparov successfully employed the Sicilian against him and took the world championship title, Karpov switched to 1.d4 mainly.

Kasparov also tended to favour 1.e4, although as he matured as a world champion he played other opening moves too (as any top player should).

Nowadays I can't think of many players who favour 1.e4 predominantly. One exception I can think of though is Maxime Vachier-Lagrave. He is known for being a strong proponent of 1.e4 as White and the Najdorf Sicilian as Black. In general though, most modern top players play 1.e4 and 1.d4 (as well as other moves) since it broadens their repertoire. If you always play 1.e4 then people can prepare to surprise you (and it's harder for you to surprise them).


Recommend chess software for windows 8.1 I've been running an old version Chessmaster: Grandmaster edition on my windows 8.1 laptop when I found a bug (Chessmaster recommended an illegal move), and I thought it was time to change my software.

I'm rated around 2000 elo and would like a program that has tutorials (tactics exercises, annotated games, endgame courses etc.)

Any recommendations?

PS. I've checked that my Chessmaster program has all the latest updates from Ubisoft.

Lucas is a good software but in my opinion I would say that Chessmaster is better than Lucas. Well you can try Lucas and see...


What is the Bongcloud opening? I have heard the Bongcloud opening mentioned on chess.com, but I have never heard of that. Is this a real opening, and if so, what is it?

The Bong-Cloud opening is a joke opening that is meant to give your opponent a chance, and also it is meant to show contempt for your opponent. You play it because you think you are much stronger than they are. It is, obviously, not a good opening.
GM Hikaru Nakamura is one of the jokesters, who plays this from time to time. There are multiple YouTube videos showing him playing this. Here is one.
P.S. Another chess.com joke you might hear is a reference to the the "Botez Gambit". It is a joke about WFM Alexandra Botez, who drops her queen a lot.
 [FEN ""]

 1. e4 e5 2. Ke2? {The Bong-Cloud!}


Why doesn't SimpleEval's eval change in multiples of 1? SimpleEval is Stockfish with simple eval - it only counts the material in the position and ignores all other evaluation factors like king safety or mobility. It is currently playing at TCEC.
If SimpleEval only counts material, how is it possible that it occasionally shows fractional eval? As I understand chess engines, they search the game tree and return the eval function on the final position of the search tree. Since SimpleEval only counts material, its eval ought to change in steps of 1. Yet on move 42 of this game, it shows an eval of -4.25. There's no material combination that could possibly yield that eval. What's going on?

I took a peek at the code given in a comment. It seems to have a small semi-random factor added to the evaluation, probably so it can more easily just pick a move from all the ties that are going to come up. However, the size of the score difference appears to be greater than what could be explained by just this. Also, at move 65 it evaluates the position as -M3 but there is clearly not a mate in 3 from that position.
The false mate clearly shows that there is a bug somewhere.


What are the main ideas for White in the Queen's Gambit Accepted, 3.e4 variation? What are the main ideas for White after 1. d4 d5 2. c4 dxc4 3. e4?

[FEN ""]
[StartPly "5"]

1. d4 d5 2. c4 dxc4 3. e4

Black has 4 main tries and one dubious line. White's plans vary based on the tabiya. The positions below are the lines given in Starting Out: Queen's Gambit Accepted by Reatsky and Chetverik:

3...e5

[FEN ""]
[StartPly "5"]

  1. d4 d5 2. c4 dxc4 3. e4 e5 {Best and thematic. A strong central counterattack that made the 3. e4 QGA unpopular in the '80s.} 4. Nf3 {White defends the pawn and prepares to castle kingside.}

Now Black has 2 choices: 4...Bb4+ and 4...exd4.

4...Bb4+

[FEN ""]
[StartPly "7"]

  1. d4 d5 2. c4 dxc4 3. e4 e5 4. Nf3 Bb4+ {Black develops with tempo and blocks a defender of the d4 pawn.} 5. Bd2 Bxd2+ {Black is happy to trade, seeing as he is up material and has slightly less space when the c4 pawn falls.} 6. Nbxd2 {6. Qxd2 exd4 7. Qxd4 Nf6 8. Qxd8+ Kxd8 actually sucks the venom out of white's attack, as the queens are gone and the trades benefit black, whose king is open and has less space.} exd4 7. Bxc4 Nc6 8. O-O Qf6 {Black aims to play ...Nge7 and ...O-O.} 9. e5 {The queen has developed early and can be attacked, gaining space. The pawn cannot be taken due to tactics on the open e-file.} Qg6 10. Re1 Nge7 11. Nb3 {Thematically regaining the pawn.} O-O 12. Nfxd4 {The material is now even with quite even development and safe kings. But why was it the f3 knight that recaptured? Well: 1) 12...Na5, pestering the bishop, is prevented, and 2) The queen can develop to the kingside, e.g. Qf3 easily.}

4...exd4

[FEN ""]
[StartPly "7"]

  1. d4 d5 2. c4 dxc4 3. e4 e5 4. Nf3 exd4 {Black invites white to play 5. Qxd4? Qxd4 6. Nxd4 Bc5 which equalises. Similarly, 5. Nxd4? c5 6. Nf3 Qxd1+ is also good for black.} 5. Bxc4 {White should definitely develop the bishop to regain a pawn and take control of a key diagonal.} Nc6 6. O-O Be6 {Defending the diagonal leading to the weak f7 square, this almost forces a trade of a well developed piece.} 7. Bxe6 {7. Bb5 is playable. See Kaspaprov-Anand, Linares 1999} fxe6 8. Qb3 Qd7 {Why not 8...Qc8? Well this is too passive and can be punished by 9. Ng5!} 9. Qxb7 Rb8 10. Qa6 Nf6 11. Nbd2 Bd6 {The bishop develops to a flexible square that discourages e5.} 12. Qd3 O-O 13. a3 {Preventing any annoying ...Nb4 or ...Bb4 manoeuvres.} Ng4 {Black seeks to place a knight on e5, a well placed steed.} 14. b3 Nce5 15. Nxe5 Nxe5 16. Qxd4 Ng4 17. e5 Nxe5 18. Bb2 Rb5 19. Qe4 Nd3 20. Bd4 Rf4 21. Qa8+ Rf8 {With a likely draw by threefold repition.}

3...c5

[FEN ""]
[StartPly "5"]

1. d4 d5 2. c4 dxc4 3. e4 c5 4. d5 Nf6 5. Nc3 b5 {Principle: attacked in the centre, counter on the wing} 6. Bf4 {The Bishop thematically comes to f4 as in some variations the bishop takes on b8, often in conjunction with a rook on b1.} Ba6 {Black has to develop rapidly, as the game is somewhat open and Black is being squeezed in the centre.} 7. e5 b4 8. exf6 bxc3 9. bxc3 gxf6 10. Bxc4 {This initiates a combination that simplifies into an endgame where white plays against the pawn weaknesses on c5 and the kingside.} Bxc4 11. Qa4+ Nd7 12. Qxc4 Nb6 13. Qb5+ Qd7 14. Qxd7+ Kxd7

3...Nc6

[FEN ""]
[StartPly "5"]

1. d4 d5 2. c4 dxc4 3. e4 Nc6 4. Nf3 Bg4 5. d5 Ne5 6. Bf4 Ng6 {6...Nxf3 7. gxf3 Bd7 is not so strong for Black, as White now has a semi-open g-file to work with, and the White king is reasonably safe in the centre.} 7. Be3 e5 8. Bxc4 Nf6 9. Nc3 a6 {Black threatens to remove the defender of the e4 pawn with 10...b5 11. Be2 b4 12. Ng1 Nxe4} 10. Be2 {White would like to offer to trade the bad light square bishop with Nd2, when Black should preserve their light square bishop with ...Bd7} Bd6

3...Nf6

[FEN ""]
[StartPly "5"]

1. d4 d5 2. c4 dxc4 3. e4 Nf6 4. e5 {White gains a bit of space in this line but not much else.} Nd5 5. Bxc4 Nb6 6. Bb3 Nc6 7. Be3 {7. Nge2 is also playable, but 7. Nf3?! walks into the pin 7...Bg4, which is uncomfortable, seeing as Black doesn't mind trading his bad bishop if the question is put to it.} Bf5 8. Nc3 e6 9. Nge2 Be7 10. O-O O-O

3...b5?!

[FEN ""]
[StartPly "5"]

1. d4 d5 2. c4 dxc4 3. e4 b5 4. a4 {White challenges the base of the pawn chain.} c6 {Black reinforces the base...} 5. b3 {...so white attacks the head of the chain instead!} e5 {Thematic and best. Over and over we will see ...e5 as been a crucial move in the 3. e4 QGA variations.} 6. axb5 cxb5 7. bxc4 Bb4+ {Black is desperate to gain counterplay (and material!) seeing as white's central pawns are so menacing.} 8. Bd2 {Forced. Blocking with Nd2 enters into an uncomfortable pin, and Ke2 loses castling rights and blocks up the kingside.} Qxd4 9. Bxb4 Qxa1 10. Nf3 {Despite white being down in material, White has: 1) More space, 2) Better development, 3) A vulnerable enemy king, queen and rooks to go after.}


How to solve proof games? The following question deserves to be asked!
"I see a lot of proof game problems, where I am given a diagram and have to find the unique way to reach that position in the specified number of moves. They look fun, but difficult. Can I have some tips or strategy for solving them, please?"

Although solving proofgames is not that difficult, the large number of moves involved may seem impressive at first. Let me share you a few tips by showing how I solve a proofgame.
[Title "Étienne Dupuis, Problemesis 2001, PG in 13.5"]
[FEN "rn2k1nr/ppp3pp/4p3/8/4q3/1N1bb2P/PPPP1P1P/RNBQKB1R w KQq - 0 1"]

In this diagram, it is not obvious at first sight how white has spent 14 moves, as we count 3 for the Nb3, and 1 for Ph3. For black, we count a minimum of 2 moves for the queen, 2 for each bishop, and one for Pe6, for a total of 7 moves.
We need to find a hint, and here the hint is given by the white pawn h3. It must have captured a black piece, but which one? Since black is only missing pawns in the diagram and that no black pawn can reach h3, we must deduce that black has made a promotion.
Let us then enumerate various possibilities:

Black promoted a pawn on e1, and the promoted piece was captured on h3. This requires seven extra moves by black, yielding a total of 14 moves, one too many, hence impossible.
White pawn h3 captured a black piece and black promoted a pawn on e1 or g1 to replace this captured piece. This is the correct solution. No other promotion squares are possible since black can only capture one white piece.

Which black piece is an impostor?

The rooks and knights are too far away; it would take too many moves to reach h3 and bring back the promoted piece.
The dark square bishop cannot be captured on light colored square h3.
The light square bishop could, but cannot be promoted on dark squares e1 or g1.
The queen is the only candidate. It requires two moves to bring the queen to h3, and six moves to promote pawn d7 or f7 to a queen on e1 and bring it to e4.

At this stage, we have accounted for all thirteen black moves. We are not exactly sure if the queen played Qd8-h4-h3 or Qd8-d7-h3 or even Qd8-d3-h3 but we'll figure it out later.  We also do not know which black pawn promoted, but we know the one of the two did not move at all and was captured at home.
Turning to white's side, we must find moves to

Capture the d7 or f7 pawn.
Get the king out of the way for the black promotion to occur.

Getting the king out of the way not as easy as it looks like. Keeping in mind that black will promote a queen on e1, and then play Qe1-e4, the king must step at least two squares away and he cannot come back through e2. Hence he must come back from f1, indicating the Bf1 must also move out of the way. This requires at least 6 moves and the king would go at least to g1 or g2.
Who captured the black pawn?

The white pawn e2 can capture the d7 pawn, and then black would have played Qd8xPd7 before Qd7-h3 to get rid of the white pawn. This requires four white moves. However, it's not possible, as the f7 pawn would have no one to capture to reach e1.
A white knight can capture both. It would require two extra moves for Nb3 to capture on d7 and four extra moves to capture on f7.
White bishop and queen cannot capture as it would give check and black has no moves to spare.
White rook h1 could but would required eight moves. Impossible.

The missing black pawn was thus captured by the white knight.
It is now time to take out a chessboard and move the pieces along to try finding a solution keeping in minds all the deductions we have made.
Try moves, in any order. You will quickly stumble on an additional difficulty. To bring back the white king, we must shield the check from the Bd3. This bishop must be present on that square before black plays Qe1-e4, as the bishop played Bc8-f5-d3.
Who shields?

This shielding could be performed by the white bishop, in which case we need at least one extra move, if the bishop plays Bf1-a6-e2-f1 for example. But wait, Bd3 is in the way again. Hence if it's the bishop, it's from the other side and we need two extra moves.
Shielding could be performed by the white queen, also two extra moves.
Shielding can also be provided by the Nd3 for free, assuming it played Ng1-e2-d4-b3. However, this looks impossible, as who would capture the black pawn on d7 or f7?

With this additional observation, we get to eight moves for moving the white king out of the way (four for the king, two to move the Bf1 somewhere, and two for shielding on e2, by the queen or the bishop). This implies that the missing black pawn was captured by the white knight and that white Pe2 has not moved at all!
If it has not moved, white started by playing with the knight and black has no choice but to wait for the Pd7 to be captured; he cannot push Pe6 before playing Bc8-f5.
The solution is quickly found to be:
[Title "Étienne Dupuis, Problemesis 2001, PG in 13.5"]
[FEN ""]

1. Nf3 f5 2. Ne5 f4 3. Nxd7 f3 4. Nc5 Qd7 5. Nb3 Qh3 6. gxh3 Bf5 7. Bg2 Bd3 8. Kf1 fxe2+ 9. Kg1 e1=Q 10. Bf1 Qe4 11. Be2 e6 12. Kf1 Bc5 13. Ke1 Be3 14. Bf1

The reasoning made to find the solution gives us also a high confidence that the solution is unique, it cannot be something else.
Hopefully this extensive explanation will help you enjoy solving proof games!