Which line(s) pose Black problem(s) in the King's Indian defense on the highest level of competition? King's Indian defense is rarely seen in the highest level these days.
Queen's gambit declined took over for now.
I am trying to find out if there are any lines that put so much pressure on Black that top GMs decide not to play it.

GM Vassilios Kotronias has written a detailed series of books covering more or less every system that white can try against the KID. In the final volume of his series, he notes four systems as the most dangerous ones at white's disposal. These are:

Mar del Plata
Makogonov
Gligoric
Sämisch

As someone who has played the KID for most of my chess career so far, I can only say that Kotronias' assessment is more or less spot on (which shouldn't come as a surprise to anyone who has read his series on the KID). The main lines in these systems are truly nasty.
Edit: after rereading the question I wish to give a perspective on why top GMs refrain from using the KID. I don't believe the KID is an unsound opening, and from a theoretical perspective there is no specific line that causes black too much headache to deal with. The problem with the KID is that it carries serious risk for black, regardless of its theoretical status. Black will often need to "trust the engine" and enter dangerous and sharp lines in order not to fall into a horrible position (just look at what Grischuk had to do in the 2013 candidates tournament when he played the KID against Svidler - the line he played looks like the work of a mad man, but is in fact the only real way for black to maintain equality after 12.f4). While this risky play is fun, it is not always viable for a top GM. When you play the KID as black you cannot force a calm game, and for professionals who need reliable openings that they can play when they need at least a draw the risk that the KID carries is simply not acceptable.


With only the King left, how can you get a draw? Let's say I have only the King left.

I've read several rules and posts of people saying there is a limit to the number of moves your opponent has to check mate you in, but there are some inconsistencies:

I found the number of moves varying depending on where I found the info. It seems to be 50, but I am not 100% sure.
It seems there are some exceptions and cases where the count is reset, but the information seems quite spread all over.

I'd like to understand this rule in detail and know all the special cases if possible, as it seems way too fuzzy for me and the people I play with.

If a player has a theoretical win, that person has a move limit (50 moves) with "no fundamental alteration of the position." That means no captures of pawns or pieces, and no pawn moves. The count is reset if either of these things happens.

There used to be an  exception for positions like king, bishop, and knight vs. King (a checkmate). It was known to be winnable in a maximum of 34 moves. But players got twice this maximum, or 68 moves (Milton Hanauer, "Chess Made Simple"). Apparently, this, and other exceptions, were removed later, according to a comment below.


Endgame FEN generator is it possible to generate FEN strings for endgames based on specific criteria:  n-pieces, w/d/l, and side to move?

So say I wanted all FEN strings for King plus Rook vs King plus Pawn (KPKR) endgames, where it is white to move, and white draws with perfect play.

I know there would be an extremly large number of results, and the next step would be to then categorize those results further by other criteria, like say white king is in front of the pawn, or the black pawn has passed the 6th rank.

I assume an endgame tablebase (egtb) has this information stored in it already, but how to get this information out of them?  Or is there some other way of generating this?

Thanks!!

Firstly, FEN notation is used to describe a board state or permutation, not a family of board states or permutations.

What you are talking about, is a way to index board positions based on your criteria. i.e. Rook vs Knight end games or such

This can be done by most database software (Fritz, Chessbase). This is done by searching games in the database, and pulling them out based on the board positions.

For example, if I want to get a bunch of rook vs knight end games, I can search for all FEN strings that contain only K,k,p,P,r,R,n,N. Basically, positions that contain pawns, knights, rooks and kings.

As for egtb, the format are stored using bit bases and the positions are assigned to a unique index. I would assume this is how Chess Position Trainer stores its FEN strings in order to determine transpositions.


Looking for SmallChess source code? I'm currently looking for this chess engine: http://www.smallchess.com/ but the link to access it is dead.

Can anyone help ?

The source code for SmallChess is not available as it is closed source. The link for the source code is for SmallFish.

If you still want the source code you might have to wait, as neither does Google have that page cached nor does The Wayback Machine.


What website is this? Someone sent me a screenshot of a chess website with detailed analysis. What is this website? Where does it come from? It doesn't look like lichess to me, I have no idea.

The board here looks similar: http://analysis.sesse.net


Why does 4.dxc5 work well for white in the Advance variation of Caro-Kann? [FEN ""]
1.e4 c6 2.d4 d5 3.e5 c5 4. dxc5

I don't want to play 3...bf5 instead, but this 4.dxc5 line in the Advance Variation gives me so much trouble, whether they go with 5.Be3, 5.a3 or 5.Nf3.

What's a good way for black to deal with this 4.dxc5 line?

First, I would wonder why you do not want to play 3...Bf5 first? That is the most common move, and the most natural.

3...c5 almost forces you to gambit a pawn, and if you are not comfortable playing very tactical positions down a pawn, you will want to avoid the immediate c5 in the future (it is still the move you will want to play eventually to free your game, but you will want to prepare it so you are not just losing a pawn for play).

After 3...c5 4 dxc5, here is the main line. (There are a fair amount of written prose notes in the comments below, so make sure you read those too.)

 [FEN ""]

 1. e4 c6 2. d4 d5 3. e5 c5 4. dxc5 Nc6 5. Bb5 (5. Nf3 Bg4 6. c3 e6 (6... Bxf3 7. Qxf3 Nxe5 8. Bb5+ Nc6 9. O-O $16) (6... Nxe5 $4 7. Nxe5 $1 Bxd1 8. Bb5+ Qd7 9. Bxd7+ $18) 7. Be3 Nge7 8. Nbd2 Nf5 9. Bd4 $14 Nfxd4 $2 10. cxd4 Nxd4 $4 11. Qa4+ $18) 5...e6 6. Be3 Nge7 7. c3 Bd7 8. Bxc6 Nxc6 9. f4 {And there are several moves here, most requiring black to be a pawn down. In exchange for that, black has the bishop pair, the white king has been weakened with f4, and black is slightly ahead in development, so you have to play very actively.  Here, I would recommend either b6, or the main book move, g5. a5 is also possible trying to round up c5 at some point.} g5 (9... b6 10. cxb6 axb6 {And now, you also have an open rook file, and can aim for b5-b4 after getting the Bf8 out. you may also play the Bf8 to c5 with the idea that if white trades, you will have strong pressure for the pawn down the a-file and b-file...a bit like the Benko, but reversed.}) 10. fxg5 Nxe5 (10... h6 $5 {Has been played.}) 11. Nf3 {With a wild game with chances for both sides.}


A digital tree (with annotations) of all chess opening moves discovered by theoreticians I am looking for a tree of sorts, like the one of Chessmaster XI, but with deeper analysis, like why is this move good.
For example, e4 gets the center, with the idea of opening the bishop. e5 comss.with the same idea, and go as far as 30 moves in theoretical lines such as the Najdorf with ideas behind them.
So a compilation of opening theory in digital format, of everything, including new developements.
For MCO, I am looking for a digital software that can fully explore it, like a ChessBase Tree.

Did you ever find a tree like this?  I have a Chessmaster file that I have created that documents every move of every named opening line recognized by the program.  Yes, it took me ten years and spanned 4 computers and probably 5 versions of ChessMaster to complete...and yes, I do account for transitions...its very awkward to use sometimes when stepping through successive transistions because its sort of a manual process. Here are some screen shots...oh, and at the end of every opening line, I analyzed the final position, scored it, and walked the score back to the previous branch...I did this for every position where there are several candidate moves, all the way back to the starting position of the game...the first screenshot shows that result.  The second screen shot shows a position a few moves in (Note the references to possible transitions).  The third screen shot shows one of hundreds of thousand of ending positions I had chessmaster analyse

The .CMG file is 30 megabytes and I continue to expand it by adding in all the non-book moves I've encounted and explored as well...Sadly, I believe the file is actually reaching the limits set by the program and lately I've been losing work because the latest file I save frequently becomes corrupted and unusable (I back it up every few edits however, then back up the backup every few days).  But still there have been times where I have lost weeks of analysis and added chesslines.

Therefore, I'm looking for a new platform to migrate all this work to and to continue this project on a modern platform.  the .CMG format is probably 30+ years old now!  Definitely could be improved!


How to use opening books on mac/linux I would like to use opening books for my stockfish chess engine, but I'm not sure how to do this. As far as I understand stockfish doesn't support these, so I though I setup a system next to stockfish, which is used until it doesn't return any moves anymore.

These .bin files can be found anywhere, for example

http://rebel13.nl/download/books.html

or

https://github.com/joeyrobert/ceruleanjs_opening_books

Anyway, I downloaded a couple of .bin files, and thought to use it with polyglot-chess

var Polyglot = require('polyglot-chess');

var obj = new Polyglot();

var fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
console.log("Polyglot hash for fen " + fen + " is: " + obj.hash(fen));
console.log("Best move in the book is: " + obj.find(fen, "book.bin", true));
console.log("Random move in the book is: " + obj.find(fen, "book.bin", false));

Now when I try to run it

$> node index.js
internal/modules/cjs/loader.js:615
   throw err;
   ^

Error: Cannot find module '../build/Release/polyglot'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:613:15)
...

I checked the build folder from polyglot-chess, but there isn't a polyglot file at that location.

You can do this on your own in a customized fashion (i.e. you control when to run the engine or to use the book) with a bit of scripting in python, using the python-chess module and a polyglot opening book of your choice. In this example I'm using gm2001.bin, which you can get from here.

As dummy example I have chosen two positions:

fen = 'rnbqkb1r/ppp1pppp/5n2/3p4/3P4/5NP1/PPP1PP1P/RNBQKB1R b KQkq - 0 3' A basic Catalan position for which I know the book still has a move.
fen2 = 'rnbqkb1r/ppp1ppp1/5n2/3p3p/3P4/5NP1/PPP1PP1P/RNBQKB1R w KQkq - 0 4' A position for which there are no book moves left in the chosen opening book.

What the code does is very basic: if it finds an opening move, then it makes that move (if there are more opening branches, you need to figure out how you want to choose the line to play), otherwise, it calls Stockfish with 10 seconds of movetime and makes the top engine move.

import chess
import chess.uci
import chess.polyglot

fen = 'rnbqkb1r/ppp1pppp/5n2/3p4/3P4/5NP1/PPP1PP1P/RNBQKB1R b KQkq - 0 3'
fen2 = 'rnbqkb1r/ppp1ppp1/5n2/3p3p/3P4/5NP1/PPP1PP1P/RNBQKB1R w KQkq - 0 4'
board = chess.Board(fen)
print board

handler = chess.uci.InfoHandler()
engine = chess.uci.popen_engine('stockfish_8_x64') #Provide correct address to where your engine is stored
evaltime = 10000

reader = chess.polyglot.open_reader('gm2001.bin') #Provide correct address to where your bin file is stored
n = sum(1 for _ in reader.find_all(board))

if n==0:
    print 'empty, using SF top move with 10 sec movetime'
    engine.info_handlers.append(handler)
    if board.is_checkmate():
        print 'Game has ended: checkmate'
    else:
        engine.position(board)
        eval = engine.go(movetime=evaltime)
        nextmove = board.san(eval[0])
        if handler.info["score"][1].cp != None:
            print 'Top move: ', nextmove, ' Evaluation: ',round(handler.info["score"][1].cp/100.0,2)
        else:
            print nextmove
        print board.variation_san(handler.info["pv"][1])
        print 'nodes: ', handler.info["nodes"], ' depth: ', handler.info["depth"], ' time: ', handler.info["time"]
        board.push_san(nextmove)
        print '---- Updated position:'
        print board
else:
    for entry in reader.find_all(board):
        print 'Found book moves:'
        nextmove = board.san(entry.move())
        print str(nextmove)
        board.push_san(nextmove)
        print '---- Updated position:'
        print board
        break

Output for the first fen:

r n b q k b . r
p p p . p p p p
. . . . . n . .
. . . p . . . .
. . . P . . . .
. . . . . N P .
P P P . P P . P
R N B Q K B . R
Found book moves:
c6
---- Updated position:
r n b q k b . r
p p . . p p p p
. . p . . n . .
. . . p . . . .
. . . P . . . .
. . . . . N P .
P P P . P P . P
R N B Q K B . R

and output for the 2nd fen (fen2):

r n b q k b . r
p p p . p p p .
. . . . . n . .
. . . p . . . p
. . . P . . . .
. . . . . N P .
P P P . P P . P
R N B Q K B . R
empty, using SF top move with 10 sec movetime
Top move:  Bg2  Evaluation:  0.24
4. Bg2 c5 5. c4 cxd4 6. cxd5 Qxd5 7. Qxd4 Nc6 8. Qxd5 Nxd5 9. Bd2 Ndb4 10. Na3 Be6 11. Ng5 Bd5 12. Bxd5 Nxd5 13. e4 Ndb4 14. Nb5 Nd3+ 15. Ke2
nodes:  14946976  depth:  21  time:  10001
---- Updated position:
r n b q k b . r
p p p . p p p .
. . . . . n . .
. . . p . . . p
. . . P . . . .
. . . . . N P .
P P P . P P B P
R N B Q K . . R

You should be able to take it from here and extend the code however you want.


Is it possible to castle with checkmate? I am new to chess.  Please answer this for me:

  Is it possible to castle with checkmate?

I can think of two questions you might be meaning to ask, given the wording of your question. Maybe neither of these is what you're after, but just in case:

1. Is it possible to castle out of check or even checkmate? Here the answer is no. If your king is in check, then castling is not a legal move.

2. Is it possible to castle while checkmating your opponent? Here the answer is yes, it is possible, though it does not happen often. For instance, the game Ed.Lasker-Thomas (1912), with its famous queen sacrifice and king hunt, could have finished with a castling mate:

[fen ""]
1. d4 e6 2. Nf3 f5 3. Nc3 Nf6 4. Bg5 Be7 5. Bxf6 Bxf6 6. e4
fxe4 7. Nxe4 b6 8. Ne5 O-O 9. Bd3 Bb7 10. Qh5 Qe7 11. Qxh7+
Kxh7 12. Nxf6+ Kh6 13. Neg4+ Kg5 14. h4+ Kf4 15. g3+ Kf3
16. Be2+ Kg2 17. Rh2+ Kg1 18. Kd2# (18.O-O-O#)1-0


Giuoco Piano / Two Knights Defense / Fried Liver Attack [FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Nxd5 6. Nxf7 Kxf7 7. Qf3+ Ke6 8. Nc3 Ncb4

White can play 9. Qe4 (Old variation protecting c2 square from ... Nxc2+ forking King and Rook and also with attack of d4 etc.

White can also play 9. a3 allowing 9... Nxc2+ 10. Kd1 Nxa1 allowing Black to attack the Rook. Further White will play strong attacking moves like 11. Nxd5 etc. and continue the strong attack.

Is 5... Nxd5 correct or he should go to main line of Two Knights Defense with 5... Na5?
After 5... Nxd5, can White continue with 6. Nxf7 for strong attack?
After 7. Qf3+, can Black continue with 7... Ke6 challenging White in further game? Hence can we play 7... Ke6 in tournaments and continue our attack and study of opening variations?
Between 9. Qe4 and 9. a3, which variation is better for White?

Most people agree that the Fried Liver attack is better for white. So black's 5...Nxd5 is inferior to the less scary 5... Na5. Assuming that black goes in for the Fried liver though, white can play either 6. Nxf7 or 6. d4. Both lead to similar attacks.

In the Nxd5 Nxf7 line, however, black's moves are forced until move 8, where black has the choice to defend the pinned knight with Ne7 or Nb4. Any other moves just admit defeat and give back the piece to white for a completely misplaced king and underdeveloped position.

Most pros play 9. 0-0 or 9. a3. Interestingly, Qe4 is recommended by my engine... but the a3 lines are so good for white, that I don't really see any reason to deviate. Personally, I've only played a3 with good success.


How to calculate pinned chess moves I am writing a legal move generator, and the last piece of the puzzle is preventing pinned pieces from being moved such that the king will be in check.

I have read a lot of posts here and on stackoverflow and the only answers given seem to be vague references to stockfish's code which I can't seem to decipher or an incomplete explanation.

I am writing my generator in Python and would really appreciate a detailed explanation of an approach I can take.

Thanks.

There are two approaches:

1) For the piece in question you're considering to move, look at the vector going through it to the king. For example, if they king and the piece are separated horizontally/vertically, look at the line going through it to the king. Is there an enemy rook/queen on this line, such that your piece is currently between it and your king? Or, if the piece is on a diagonal from the king, see if there's an enemy bishop/queen on this diagonal. However, if your piece moves along this vector (and thus continues blocking your king), it's fine. For example, assume your king is on h8, your queen is on e5, and the opponent's bishop is on a1. There's an enemy piece on the a1-h8 vector (which your queen and king are on), so moving the queen off this vector/diagonal is illegal. But moving the queen along the vector (e.g., anywhere from b2 to g7) won't violate the pin.

2) The simpler approach is a general purpose illegal move checker. Make a list of all pseudo-legal moves, and then check each to see if it results in an illegal position where your king is en prise. This encompasses what you're trying to do with not moving a pinned piece out of the way, since it would result in an illegal position.


Caro-Kann advanced variation pawn sacrifice I used to play the Caro-Kann a lot as black. One line that I reached many times in advanced variation is:

   [FEN ""]
1. e4 c6 2. d4 d5 3. e5 Bf5 4. g4

In this position I saw one game where Anand played Bc8 and in my experience this line is very solid. The move Bg6 suffers some pressure from the pawn sacrifice e6, when the development of the bishop on f8 becomes difficult, and white easily controls e5. I saw one game Topalov vs Morozevich where Morozevich played Bg6, but then Topalov did not commit himself with e6.

My question is: should the pawn sacrifice e6 be feared?

The move 4. g4 is slightly dubious compared to the more solid option of 4. Nc3 (among Nc3), as it forces white to play 5. f3 if black opts for the mainline 4... Be4. Therefore I recommend this choice in general. It does, to an extent, weaken the idea of e6. However, 4... Bg6 is an option and a more common one at that.

The pawn sacrifice is actually quite common at the amateur level and can be an issue for the unprepared. Your most principled choice in your line is 5... fxe6 and it does work quite often well. After the mainline (if it can be so called) 6. Bd3, black should continue 6... Bxd3 7. Qxd3 Qd6 followed by the eventual fianchettoing of the bishop.

While this will not give you a simple win as black, it is clear that black's position is at least equal.


confused about a move played by a grandmaster In this site :

https://www.365chess.com/game.php?gid=2941895

I saw a game between two chess professional players :

Efimenko, Zahar (2566) vs. Kaliuzhny, Andrey (2213)

[fen ""]
1. e4 d6 2. d4 Nf6 3. Nc3 g6 4. Be3 Bg7 5. Nf3 c6 6. h3 O-O 7. Qd2 b5 8. Bd3 Nbd7 9. O-O e5 10. dxe5 Nxe5 11. Nxe5 dxe5 12. Bc5 Re8 13. a4 Nd7 14. Be3 b4 15. Ne2 a5 16. c3 Rb8 17. cxb4 Rxb4 18. Qc2 Nf8 19. Rfd1 Ne6 20. Qxc6 Bd7 21. Qc2 Qb8 22. Bc4 Rxb2 23. Qc3 Rc8 24. Rxd7 Rxe2 25. Rad1 Bf6 26. Qd3 Rb2 27. Rxf7 Rxc4 28. Rxf6 Qe8 1-0

In move 12 , efimenko which is white played  Bc5 which I could not understand :

So I have two questions

1) why he did not play 12 . Bh6 , instead of Bc5 , to get rid of the dark square bishop on Bg7

which protects the king ? and 2) what is the reason of playing Bc5 ?

I am really confused and I do not understand . Help

We can note a few things about the position before Bc5 was played on move 12. First of all, white's dark squared bishop is both his good bishop (due to the fixed pawn on e4) and an active contributor in the position (dissuading black from playing c5 and taking more space in the center/queenside). Moreover, black's dark squared bishop is his bad bishop and is currently blocked in by the pawn on e5. There is not any foreseeable attack on the black king because the knight and light squared bishop are hemmed in by the e4 pawn (and the c6 pawn), there are no open diagonals or files on the kingside, and black has more defenders around his king than white has attackers.

Therefore to answer your first question, Bh6 doesn't make sense in this position. Yes it weakens black's kingside dark squares, but white has no way to ever take advantage of that. You are also willingly trading a good and active bishop with a bad, blocked bishop.

As to why Bc5 was played... that one's a little bit harder. It's basically a high quality passing move assuming black plays perfectly. Bc5 forces Re8, a move that black does not want to play (moving a rook from a closed file to another closed file), so black will have to spend another move later if he wants to activate the rook. But on the other side, the bishop on c5 can be attacked by Nd7, which is arguably not a demotion of the knight. So the bishop will have to return to e3 eventually, effectively trading tempi with black. Maybe white figured that "forcing" black to play Nd7 wouldn't ultimately be useful for black.

Personally, I would be playing 12. a4 and just getting on with it, as I agree it's unclear what white truly gains from this maneuver (especially because we later see that Nf6-d7-f8-e6 is a useful maneuver for black to make).


Where do black's centre pawns and light square bishop belong in the symmetrical English? I played a rapid game last night and got this symmetrical English position as black:

[FEN ""]
[StartPly "116"]

1. c4 c5 2. Nf3 Nf6 3. Nc3 Nc6 4. g3 g6 5. Bg2 Bg7 6. d4 cxd4 7. Nxd4 O-O 8. Nxc6 bxc6

I found it hard to know where to put my d and e pawns, and how to develop my light square bishop. So, thematically where do black's central pawns and light square bishop develop to and why?

This does not seem symmetrical to me.

After 8...dxc6 you could have reached a symmetrical and very drawish position.

Playing 8...bxc6 seems more ambitious. Seems like black will want to play d5 sooner or later to get rid of that backward pawn on d7 and to limit the white bishop on g2. Depending on what white does, this might require to play e6 and/or to put the bishop on b7 to support d5 or to a6 to ask white how he wants to defend the c4 pawn. I don't see how the c8 bishop could find any good square along the h3-c8 diagonal anytime soon.


Looking for a defense against 1.d4 I wanted to learn a good opening against 1.d4 that does not involve the second move being 1...d5. I personally don't like symmetric positions very much. To give you an idea of the type of openings I play right now, for white, I play Catalan and I play French against 1. e4. Anyone have any ideas for responses I should look into?

I suggest c5. As commented by @NoseKnowsAll it is called the Old Benoni Defense. If white is a pro they will probably have an edge because of their experience but generally, for your criteria (it is not symmetrical) it has the highest statistics for black winning in some of the databases such as https://www.365chess.com/opening.php?m=2&n=7&ms=d4&ns=7.
Note that it is moderately common (+16k games in the database cited above) which makes the statistics more meaningful than some uncommon moves like a5.


Is the English opening the most suitable for beginners? Here are my understandings of the English opening:

The English opening is as good as 1.d4.
Since it is less common than 1.e4 and 1.d4; it is more likely that an average amateur player is less familar with it and thus it is easier for white to play against an amateur player using the English opening.
There are less lines than say 1. e4. When white plays 1. e4, he needs to be familiar with 1. ... e5, the Sicilian Defense, the Scandinavian Defense, the Caro-Kann Defense, the French Defense etc. On the other hand, when white plays the English, he almost always knows where each piece goes to, regardless of how black replies (except for some rare and dubious lines, such as 1. ... d5). For example, after the 8th move, the following two formations for white are natural and common:

It is lessly that white will fall into a surprising trap.

Do these factors make the English opening ideal for beginners?

Do these factors make the English opening ideal for beginners?

No. As a beginner it is OK to study the English along with other openings but what you seem to be suggesting, that it be the only white opening a beginner learns, is very bad.

By definition a beginner doesn't know very much about chess and to progress needs to learn much. In openings the standard approach, therefore, is to learn the classics: Ruy Lopez, Italian, Kings Gambit, 4 Knights, Scotch, Sicilian, French, Caro Kann.

You notice these are all e4 openings and the list starts with the reply e5 by black before moving on to other replies. A beginner needs to start by learning about control of the centre in the most direct way. He needs to learn about the importance of development and then tactics.

Some chess teachers would start by teaching the Kings Gambit for this reason. Chess needs to be fun and tactics are fun and most games end because of some missed tactic by the opponent. If you only ever learn how to play calm positions then you will lose all your games where your opponent manages to make the game tactical.

You also seem to suggest a formulaic way of playing the opening. Play more or less the same moves in the English and you will end up in one of two tabiyas which you give. This is also very wrong. One of the key skills a beginner needs to develop is to always consider the ideas and aims of his opponent's moves. Just playing automatic moves will lead to many quick defeats.

There are many ways for black to respond and they give rise to different problems for white which can't be addressed by just playing more or less the same moves. The opening theorist IM John Watson actually wrote 4 separate books on the English because of this. He wrote one book each for black's responses: 1 ... e5, 1 ... c5, 1 ... Nf6 and a catch-all "other replies".

So, no, the English is close to being the least suitable opening for beginners. Better than the Grob, obviously, also better than Bird's, but a long way behind 1. d4 and even further behind 1. e4 openings.


Why not 5.Bd2 in the French Defense: Exchange Variation? After the initial moves of the French Defense: Exchange Variation, my opponent played 4.Bb4+. I followed with 5.Bd2, but after analyzing it, I saw that it is not in the master games opening on chess.com and 5.c3 and 5.Nc3 are considered better moves.
[fen ""]
1. e4 e6 2. Nf3 d5 3. exd5 exd5 4. d4 Bb4+ 5. Bd2

It looks like the most natural move to me, because:

It forces the bishop away or to take my bishop which I can recapture with my knight, therefore developing it if he decides to take
c3 looks like a less natural move because although it pushes back the bishop, it prevents my knight from developing on c3 in the future
Nc3 looks like a less natural move because it pins the knight to the king, and if he takes my knight, he gets my pawns double stacked on the c file, which I always have thought you should try to prevent

So, why the move is weaker?

It appears to be 4...Bb4+ that's the unusual move here. The chess.com database only shows one game with it, and that's the game that continued with 5.c3. When you have the position after Bb4+ on the board and it shows 5.Nc3 with a bunch of games, it's actually showing games that transposed into that position - the Nc3 was played earlier in the game.
Given that there's only one actual game in the database with Bb4+, there very well may be nothing wrong with Bd2. It hasn't been played simply because the position almost never came up.


Professional games that ended with mate What are some professional games where the losing side did not resign before receiving mate?

And how sure are people of the record? In old books they did not care much for complete historical accuracy, so a reference that makes the mate story believable would be better.

Most of the games that end in checkmate are where the weak side allows checkmate for whatever reason (he thinks it's a nice win / checkmate, to ruin the publishability of the game, etc), but the strongest example I can think of where a player allowed mate on the board accidentally is Deep Fritz vs Kramnik:
http://www.chessgames.com/perl/chessgame?gid=1440796


Chess960 tips and strategies I have recently stared to play chess variants, and I want become better at them. Are there any strategies for chess960 given that the piece placement is random each time?

Everything you have learned in classical chess but opening variations also applies in Chess960 : respective values of the pieces, king safety, development, center, activity, concrete calculations, open lines, pawn structure, endgame theory, initiative, etc.

All those concepts are essential to Chess960's strategy. This explains why the best Chess960 players are the best chess players: they don't need specific training or strategy to adapt to the game, as they would if they wanted to try bughouse or loser chess or 4-players chess.


Why almost nobody plays ...6...b5 in the Lipnitsky Najdorf? [FEN ""]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bc4

After 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bc4 everybody plays 6... e6 and then ...b5. Is 6...b5 right now a mistake? I don't see 7.Bxf7 as a threat. Is the move order just blindly following "theory" or else?

This is a good question, and I'd like to provide you an in-depth analysis but I don't have time right now, so here's a short answer, more to be added later:

Short answer: An immediate b5, before preparing it with e6, allows maneuvers such as Bd5 to be played, and you noticed correctly that here Bxf7+ is not really a threat.

Black should preferably avoid allowing Bd5, when his bishop's still on c8, for the sole reason that the consequent lines seem relatively (bit exaggerating here) forced for black, and the resulting positions are usually about equal but with white being up a few tempi. (and black very much delayed with his castling). I showcase one such line:

[FEN ""]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bc4 b5 7.Bd5 Ra7 8.Nc6 Nxc6 9.Bxc6+ Bd7 10.Qd4 Rc7 11.Bxd7+ Qxd7 12.a4 Rc4 13.Qd3

I'll try to compile more concrete variations on this, but it should give you an idea as to why one tends to avoid all such undesirable lines.

Moral: with e6 first, one avoids all possible shenanigans that can result from either Bxf7+ in some lines, or Bd5 type of forcing lines.

Addition after comments, in reply to why 7...Nxd5 is not really objectively playable for black:

user2569 has already given you the gist of it, so I'm not going to repeat the same ideas again. Instead I simply decided to play this line as black, vs Stockfish 6, and tryout few seemingly ok-looking variations against it in 5-minute games (so bear with me, these won't comprise the best of the best moves, but they are illustrative). In neither of the lines I could end up with anything close to playable... take the time to go through them yourself, specially since this line seems to be of importance to your repertoire, and make sure to train yourself similarly against the engine, in order to acquaint yourself with the underlying difficulties of black's position after 7...Nxd5.

[Title "8...g6"]
[fen "rnbqkb1r/4pppp/p2p4/1p1P4/3N4/2N5/PPP2PPP/R1BQK2R b KQkq - 0 8"]

8...g6 9.O-O Bg7 10.Bg5 O-O 11.Re1 Re8 12.a4 b4 13.Ne4 Bb7 14.c4 h6 15.Bf4 Nd7 16.Qd2 Kh7 17.Re3 Qb6 18.Nb3 Nf6 19.Nxf6+ Bxf6 20.Rf3 h5 21.Bg5 Kg7 22.Bxf6+ exf6 23.a5 Qc7

Another attempt, trying to make use of a quick b4 to gain some activity (instead of the slow g6 play):

[Title "8...Nd7"]
[fen "rnbqkb1r/4pppp/p2p4/1p1P4/3N4/2N5/PPP2PPP/R1BQK2R b KQkq - 0 8"]

8...Nd7 9.a4 b4 10.Nc6 Qc7 11.Nxb4 Qc4 12.Nc6 Ne5 13.Nxe5 dxe5 14.Qh5 Qc7 15.O-O g6 16.Qf3 Bb7 17.Ra3 Bg7 18.Rb3 Rb8 19.Be3 O-O 20.Rd1

A slight variation of the previous line (without Nd7):

[Title "8...b4"]
[fen "rnbqkb1r/4pppp/p2p4/1p1P4/3N4/2N5/PPP2PPP/R1BQK2R b KQkq - 0 8"]

8...b4 9.Ne4 Bb7 10.c4 bxc3 11.Nxc3 g6 12.O-O Bg7 13.Be3 Nd7 14.Rc1 O-O 15.Nc6 Qe8 16.Qb3 Bxc6 17.dxc6 Nc5 18.Qc4 Rc8 19.b4 Ne6 20.Nd5 Kh8 21.Rfd1

Another just for the sake of illustration, I tried a quick e6 out of plain ignorance:

[Title "8...e6"]
[fen "rnbqkb1r/4pppp/p2p4/1p1P4/3N4/2N5/PPP2PPP/R1BQK2R b KQkq - 0 8"]

8...e6 9.dxe6 Bxe6 10.O-O Be7 11.Nxe6 fxe6 12.Qg4 O-O 13.Qxe6+ Kh8 14.Nd5 Nc6 15.a4

No words are required for this last line...

I strongly encourage you to pick up these lines and train yourself in them, just like I victimized myself playing out these lines as black vs. Stockfish. Let me know if I can further assist you in your analysis.


Why is 5...Be7 played before ...b5 in the main line of the Closed Ruy Lopez? Here is what I've seen described as the main line of the Closed Ruy Lopez up to move 7:

[fen ""]

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6
5. O-O Be7 (5... b5 6. Bb3 Be7 7. Re1 d6) 6. Re1 b5 7. Bb3 d6

I'm interested in Black's fifth move in particular. The top three options, with number of games according to the lichess opening book, are

Be7 (43,520). Described in books as going to the Closed Ruy Lopez.
b5 (8,126). Described as going to the Arkhangelsk variation.
Nxe4 (4,844). Open Ruy Lopez.

Now 5...Be7 is clearly the most popular choice, but after 5... b5 6. Bb3, Black could choose to transpose to the Closed Ruy Lopez with 6... Be7 (shown as a variant in the diagram above). Here are the frequencies after 6. Bb3:

Bb7 (3,452). Arkhangelsk variation.
Bc5 (2,827). Neo-Arkhangelsk variation.
Be7 (1,765). Transposing back to the Closed Ruy Lopez.

My question is why is 5...Be7 overwhelmingly more popular than 5...b5? Assuming Black wants to get into the Closed Ruy Lopez, what would they lose by playing 5...b5? An argument for the latter is that by playing 5...b5, Black doesn't need to worry about the Delayed Exchange variation.

Judging by the book, the transposition is doable and some people do play it, but they are a small minority (less than 5%).

After 5....b5 6.Bb3 Be7, white has the strong option to play 7.d4. Now, 7....exd4 is a mistake, as white obtains a big advantage after 8.e5 Ne4 9.Bd5, which was played in Grischuk-Nepomniachtchi (blitz). Instead, 7....d6 is more stubborn.

In contrast, after 5....Be7, 6.d4 is relatively harmless for black, for example 6....exd4 7.e5 Ne4 8.Re1 Nc5.

      [StartPly "9"]

      [FEN ""]
      1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O b5 (5...Be7 6.d4?! exd4 7.e5 Ne4 8.Re1 Nc5) 6.Bb3 Be7 7.d4! exd4? (7...d6) 8.e5 Ne4 9.Bd5


What are the characteristics of a good chess board? I just read the question: What are some good quality magnetic chess sets? and I was left with a few more general questions:

What is a comfortable board size for home vs travel?
What height of chess pieces are most common?
What type of wood indicates a quality board?
What board companies are most reputable?
Are magnetic boards good to have for home tables?
Any other important things to consider when purchasing a board?

home - 3.75" king on 2.25" squares. Travel - no opinion. But the USCF used to sell a chess board 'wallet' that would fold up (with the pieces) and go in your pocket. Perhaps they still do.
3.75" King for me. No more, no less.
Any hardwood.  I like maple and walnut.
House of Staunton, but you'll pay top dollar. While you are there, check out their Reykjavic II chess set.  Ah, the board and set combo (with a box!) is on sale. I prefer boxwood and ebony, but boxwood and ebonized boxwood works for me too.
It is unnecessary.
A vinyl board just rolls up - easy to store, easy to take to the club. Another option is to make your own. Here's one I made.  And here's another, with the steps I took.


Why does ChessMaster recommend 24. Rg3 in this position? I reached this position when playing against ChessMaster's cyber personality Laura. The engine recommends the line starting with 25. Rg3:

[FEN ""]
[White "Bad_Bishop"]
[Black "Laura"]
[StartPly "48"]

  1. d4             Nf6
  2. Nf3            c5
  3. d5             d6
  4. c4             Qa5+
  5. Bd2            Qa6
  6. Qc2            Bg4
  7. Nc3            Nbd7
  8. e4             Bxf3
  9. gxf3           h6
 10. h4             e6
 11. O-O-O          Ne5
 12. Be2            exd5
 13. exd5           Be7
 14. f4             Ned7
 15. Rhg1           Kf8
 16. Rg2            Ne8
 17. h5             Bf6
 18. b3             Qa3+
 19. Kb1            Bxc3
 20. Bxc3           Ndf6
 21. Rdg1           Rg8
 22. Bf3            Qa6
 23. Qe2            Qb6
 24. Re1            Qd8 25. Rg3 b5 26. cxb5 Nc7 27. Qd3 Rb8 28. Ba5 Qc8 29. a4 Qb7 *

To me 25. Rg3 is not intuitive and I did not consider it all in choosing a move. Granted, in the line that ChessMaster recommends, black throws away a pawn, but my question is, what is the purpose behind 25. Rg3 and why is it the best move?

All of White's other pieces are placed well except the Bishop on f3.  If Black moved the a8 rook back and forth then White would probably like to play Rg3, Bg2-h3, and maybe Rg3-e3.
Simply put Rg3 increases the scope of the rook and the bishop.


Does black really have a disadvantage? Most people say chess is a draw, and it is quite believable, white is but a tempo up, and skill plays a lot of part in the game. But even the most skillful agree that blunders are made, in some games more than other.

How have blunders affected black losses? Have games where black lost been only played best or second best moves?

How many games, out of the ones that white won, ended because of blunders, and could have been saved otherwise? Is there a statistic for this?

We have no way of knowing this, chess isn't remotely close to being solved. We only know that as opening theory digs deeper, it finds it harder and harder to find advantages for white, so the game is probably a draw. But that's no proof.

If the game is a draw, then any game that is won by either side must involve at least 1 wrong move. But we don't know which move was wrong. It is likely that most games involve quite a few bad moves. Mine do, anyway.

Using a computer doesn't help -- they're nowhere near strong enough. A match between the two strongest computers on really strong hardware gives many decisive results, so they're not playing perfectly, and they look much deeper than 10 ply. Their scores (+2, -2, etc) are merely estimates and not the final truth.

White does have a practical advantage, proven by the fact that white consistently scores a little bit better than black on all levels. Apparently, white gets positions that are easier to play right.


Has anyone had positive results using the Ruy Lopez Norwegian variation nightingale gambit? There is a variation of the Ruy lopez that I have recently played and made two sacrifices and ended up with a very good game, and I wanted to know if anyone else could or have tried it? Here is the move order:

[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 b5
5. Bb3 Na5 6. Bxf7+

Then the continuation that was played was

[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 b5
5. Bb3 Na5 6. Bxf7+ Kxf7 7. Nxe5+ Ke8 8. Qh5+ g6
9. Nxg6

and black resigned. This was all played with a 2+0 time control so I saw this nice little gambit.

7...Ke8?? is a blunder for black. Instead, 7...Ke7!? is a much better try with the idea of weathering the attack with moves like ...Nf6 ...d6 and ...Qe8 (not necessarily in that order). Hard to prove that white is winning.


Which approach is better to teach tactics? I have been teaching my wife tactics, we are doing the book by Fred Reinfeld "1001 Winning Chess Sacrifices and Combinations". We are still in the first chapter which discusses pins and  I can tell that she is improving rapidly because she is finding the pinned piece with less effort.

My problems with this book are:

You can tell a lot of the positions are composed.
There is no difficulty progression, simple and hard puzzles are mixed together.

On the other hand I came upon the book "Tactics Time" by Tim Brennan and Anthea Carson. This book has the advantage that all the puzzles come from games people have played on the internet so no composed ones and are much simpler for a beginner. The problem with this one is that there is no separation by motifs so she might not find the knight fork or the back rank weakness and there will not be constant repetition of a single motif to ensure she assimilates it.

So my question would be, which book approach do you think would be more beneficial for a beginner to follow and why?

Thank you

I would use the second approach, almost entirely just because the problems are much easier, but also because those sorts of simple two-move tactics are more likely to come up in games between beginners and just spotting them at all will give her a big advantage at that level.

I would actually suggest a few other sources of tactics which might be even better:

Chess Tactics for Students by John Bain has quite simple puzzles and is grouped by theme.
The Manual of Chess Combinations, vols. 1a and 1b, also starts with very simple puzzles and is grouped as well, although it's by goal (e.g., "win a rook"), not by theme (e.g., "fork").
The online site Chess Tempo will feed you tactical problems from real games that are matched to your ability, so there's no worry about getting a book that is too easy or too hard.


Can a set of moves be a transposition and a variation? I am confused about the differences between a transposition and variation.  I know that a transposition is when you start of with one opening and a set of moves after that leads to another opening and a variation is a deviation from the main line of an opening.  They seem really close to me, so can a set of moves be a transposition and a variation?  What/Who determines if a set of moves is a transposition or variation?

While I don't disagree with the spirit of Wes' answer, I want to answer your question in a somewhat stronger way, one that I think goes further toward relieving any possible confusion about this issue. Your question is:

  Can a set of moves be a transposition and a variation?

My answer would be that neither transpositions nor variations should be thought of as sets of moves, and that doing so in the first place is what creates confusion here.

While particular chess openings (e.g. the Sicilian Defense, the French Defense) are often thought of as consisting of a multitude of opening lines (sequences of moves), for the purpose of making the distinction that you're after it is most useful to think of an opening as a multitude of positions (which happen to be linked together by moves). If I show you the following diagram,

and ask you what opening we're in, you know that it's the Scotch Game, even though I only gave you the position and not the exact moves we used to get there. That's because the Scotch Game can be characterized by the positions that belong to it, whatever the move-orders involved might be.

Similarly, a variation can be seen as just a particular subset of positions from one opening, ones that we've decided to give their own special additional name. We recognize each of these positions,

as being part of the Sicilian Defense. Going into more detail, we say that the first one belongs to the Najdorf Variation, while the latter belongs to the Dragon Variation. Again, we didn't need to specify move-orders at all in order to make this classification, because a variation can be characterized by a set of positions rather than sequences of moves.

A nice thing about thinking of particular opening variations as sets of positions is that it is now clearer how transpositions differ from (and relate to) variations. A transposition is an event; namely, it is what happens when a move is made that takes us from a position that is labeled as being part of one opening/variation to a position that is labeled as being part of another. Simple as that. After the moves 1. e4 d5 we're in the earliest position that belongs to the Scandinavian Defense. If White continues 2. exd5 then we're in another position that still goes by that name. But if White plays 2. d4, a transposition has occurred, because this new position is part of the Blackmar-Diemer Gambit family instead of the Scandinavian family.

In sum, an opening/variation can be seen as a family of positions that are linked together by moves, and then a transposition is just when a move leads us out of one such family and into another.


What is this position called? I'm working on a problem for this cyber security camp, and we're doing a CTF right now. I have one problem left, and I'm almost certain in relates to chess, so I've come here for advice!

Having determined the name of the bank, the FBI’s last step is to find Hax0r’s personal account. Strangely, when confronted with this question during interrogation, Hax0r agreed to tell us - but only if we played him in a game of chess. The FBI agreed, but when we got to the position on the board as shown below, Hax0r exclaimed, “You got it!” Can you figure it out what Hax0r meant? What is Hax0r’s account name in the offshore bank?

The position doesn't make any sense.
But the pieces spell out several letters.
Clockwise from the top left: o,t,o,r
Maybe that's helpful?


Pawn promotion to queen of the other color A Black pawn reached the end of board and Black himself picked it up and placed a White queen on the board. He removed his hand from the piece.

I am not concerned with 'the spirit of the game' but want to know technically if this counts as any other break in concentration during a game, and thus a move played to Black's (extreme) disadvantage?

Promoting to a piece of the opposite color is an illegal move. Because of the touch move rule, Black must make a different legal move with that pawn, such as promoting to a Black queen. As a penalty for making an illegal move, two minutes are added to White's clock.


Why are opening books so popular? As title above, why are opening books so popular? I am sure that most players know that middlegame and endgame books are ultimately much more important for improving one's chess strength. That is not to say that openings are not important, but it seems to me that a good 80% or so of chess literature are opening / repertoire books, and that means that these are the most bought ones.

I think there are number of reasons why these are so popular:

It is easy to start learning openings. You can read about ideas and memorize some lines. It is not so easy to learn middle game or end game in similar fashion.
A lot of players want to get an edge from the start- hence the focus on openings.
People enjoy reading them
They are easier to write than good middle game books (as indicated by different chess authors)

It is questionable if middlegame or endgame books are more important. There is an argument to be made that you need something other than books to learn good middlegame / endgame skills. Openings on the other hand can be easily learned from books.


Please analyze my game Here is a recent game I played and I know it is bad, but wanted some input on ways to improve.

[FEN ""]
1.e4 e5 2.f4 Nc6 3.Nf3 d6 4.d4 Bg4 5.h3 Bxf3 6.Qxf3 Nf6 7.Bc4 Qd7 8.f5 Nxd4 9.Qd3 b5 10.Bb3 h5 11.c4 Rb8 12.Nc3 b4 13.Nb5 Rb7 14.a4 g6 15.O-O Bh6 16.Qd1 gxf5 17.Rxf5 Nxf5 18.exf5 a6 19.Bxh6 Rxh6 20.Qc1 axb5 21.Qxh6 Qxf5 22.Qh8+ Ke7 23.c5 dxc5

I resigned, but I find it difficult to see where the worst moves were.

Before I answer I'm sorry if my english is bad. This game opening using King's Gambit declined (C30). I make the assumption that you are aggressive player who like open game than close game based on your opening and moves. In my opinion the several your mistakes and blunders is:

5.h3; the best move is 5.d5. Why d5? Because you can push your opponent knight and you winning the center position. If your opponent play 5...Nd4, you can counter with 6. Be3 Nxf3+ 7.gxf3 exf4 8.Bxf4 Bd7 9.Nc3.... You absolutely win the center and have a pole position to develop your pawns and pieces
7.Bc4; Black move in 6...Nf6 is mistake, 6...Nd4 is better than 6...Nf6 because he can push your Queen. But you counter with Bc4, the move that you should take is 7.Bb5 because you can freeze your opponent knight. If your opponent moves is 7...exd4, you can counter with 8.0-0 and makes your opponent pawn hanging in the center
8.f5, Black move in 7.Qd7 is bad, but your counter move 8.f5 is bad too, you can counter with 8.d5. You will lost your pawn in the center if you take the other move than 8.d5
11.c4, In my opinion, black move in 10...h5 is not good. I don't know what his plans but he should take 10...c5 to backup the knight in d4 and can push your Queen and Bishop. Your move should 11.0-0 make your King safer than before. But Black made a mistakw again with 11...Rb8. He should take your pawn in c4 and next move maybe 12.Qxc4 d5 13.exd5. He make your f5 pawn hanging.
13.Nb5. It makes your bishop in b3 taken by Black knight
14.a4. Maybe it's your biggest mistake in this game. Your opponent 13...Rb7 is bad move. You can obtain his knight in d4 with your knight and next move is 14...exd4 15.Qxd4. You got his pawn in center!!!!
15.0-0. Black second biggest mistake is 14...g6??? He can focus in his right side(A-D) and push your pawn. The best Black move is 14...Nxb3. Your counter is  very bad. You should still take the 15.Nxd4 move.
16.Qd1. And this is your biggest mistake too. You are lead the game if you take 16.Nxd4 move. 3 move and maybe you still don't realize this is your greatest move so far in this game
17.Rxf5. Another biggest mistake too. 4 move and still don't realize.
20.Qc1. 20.Qf3 is better
22.Qh8+. 22.Rf1 is better
23.c5. 23.cxb5 is better

This is my analyze. I'm sorry if I made a mistake too in this analyze


Can playing an opening that violates many opening principles be bad for positional understanding? As the title says, and I have a concrete example in mind, g5 attack against the Italian:
[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. d3 h6
5. O-O d6 6. c3 g5

Which can go like this:
[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. d3 h6
5. O-O d6 6. c3 g5 7. Re1 g4 8. Nfd2 h5
9. Nf1 h4

It is a really interesting opening and probably results in some beautiful attacks; however, it violates so many opening principles:

Black does not develop pieces
Black does not get their King to safety
Black makes a lot pawn moves in the opening

The reason we learn about opening principles is that they work in most situations, could playing this opening mess with a players judgement in an unknown position? Would the answer differ depending on a player's level?

Generally speaking, violating positional elements, at any time, is bad for positional understanding.  When you win a lot of games with bad positional play, this provides positive reinforcement for playing badly.
This opening, often called the Black Bear of the Philidor, isn't really breaking the opening principles.  Black has gained space on the kingside, has equal control of the center, is just as developed as white (especially considering that there's no good places to put the bishops), and the king is safe as long as the center remains mostly closed.
Great players know when to break the rules.  https://www.chessgames.com/perl/chessgame?gid=1282302


How to make Lichess local analysis utilize more cpu and memory? I get around x12 faster evaluation when I run Stockfish myself, so I checked my utilization when running local analysis (Chromium and Firefox) and saw that it just utilizes one thread and few megabytes of memory.

So I am looking for a solution to make it fully utilize my hardware. Any ideas?

EDIT:

TL;DR Issue was user-agent specific, doesn't work on Chromium/Ubuntu.

The menu for the analysis board has sliders for CPUs and memory (see screenshot below). Have you tried adjusting those? Maybe whether they actually work or not depends on which browser you are using. If they don't, I think this question would be best suited for the Lichess feedback forum, since it might be a bug.


How to store moves for a magic bitboard system? I am currently trying to implement magic bitboards into my chess engine. Let's just talk about rooks here. Given a square, what I can currently do is:
-Calculate the sliding moves on an empty board.

Generate all blocker boards.
Calculate the corresponding mve board.

What I am having trouble with is the using of this information. I have downloaded an array of length 64, populated by "magic numbers" for the rook squares. Can I use this? I can generate a index from this information, but it doesn't correspond to the correct move board. Any ideas? I am happy to share more information and code upon a request.

It sounds like you have all the tools to do the job, you just need to put it all together.  And yes, you can use the magic numbers you found.
When your engine initializes (or any time before you begin the search, really) you'll need to pre-compute the move board for every possible permutation of blockers you might encounter during the search.
Initialization
for each square...
  ROOK_MASKS[square] = //rook attacks on an empty board

  int bits = bitCount(ROOK_MASKS[square]);
  ROOK_SHIFTS[square] = 64 - bits;

  int permutations = 1 << bits
  for each permutation (p)...
    int index = (ROOK_MAGICs[square] * ROOK_MASKS[square]) >>> ROOK_SHIFTS[square];
    long blockers = //the pth permutation of ROOK_MASKS[square]
    ROOK_ATTACKS[square][index] = //rook attacks with blockers

Then when it comes time to generate moves you need to perform a similar operation using the pieces actually on the board
Move Generation
  long blockers = ROOK_MASKS[square] & //all the pieces on the board
  int index = (ROOK_MAGICS[square] * blockers) >>> ROOK_SHIFTS[square];
  return ROOK_ATTACKS[square][index];


Creative chess puzzles! What are some of the creative chess problems that can never be solved by computers? Question changed to Creative chess puzzles!

What are some of the creative chess problems that computers can never solve? I'm attaching two examples below so that you can get an idea. My students seem to love these puzzles. I'm researching and learning about it now. Thank you in advance.

Example 2,
EDIT
Thanks @ETD for pointing out that it's possible to create programs to solve, at least by brute force solutions to any chess problems. What I mean though is normal chess computers.
EDIT 2: I realize that the question is a bit vague. What I really like to know is creative puzzles, which if given to a beginner player should not be solvable by putting it on his computer and running an analysis.

Here is a fun puzzle:

Construct a legal chess game where

white starts with 1. a3,
white delivers checkmate on move 5, and
the last move is made with the rook that started on a1.

   Hint: Black takes the pawn on a3.


What is the name of this Sicilian Variation? What is the name of this variation:

[FEN ""]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bg5 Nbd7

It's an old main line of Sicilian Najdorf, and according to Wikipedia, it's the De Verbeterde List, or Improved Strategem, due to recent efforts by Dutch players to revive it.


Which of these two endgame books? I am a beginner (approximately 1400) seeking to improve my endgame technique. Which one of these books would you recommend as suitable for my strength and why?

100 Endgames you must know by Jesus de la Villa
Silman's Complete Endgame Course: From Beginner to Master by Jeremy Silman

I have to say that in general I don't like Silman's writing style and methods at all (i.e. Reassess your chess), but then again, this is endgames - and hence a different topic.

Since you are a 1400, Silman's book is the way to go. His book will give you the solid endgame foundation that you need. Only once you read his book up to "Endgames for Class A" should you get the other book.


Are there awards or titles for writing chess engines? I recently found out that, in addition to the well-known titles for chess players, there are titles available for chess composers.
Is there such a thing as an award or title issued to those who have written especially good AI chess engines? I did some artificial intelligence scripting at university, and it occurred to me that I might be able to try out some of that neural net stuff to train up a chess engine that, while not quite reaching the level of world grandmaster, might win some local competitions or gain me some recognition on the regional coding circuit. Does such a thing exist?
I know that this is probably a pretty niche area, but if there are titles available for composers, it stands to reason that there might be some kind of recognition out there for those who have written some especially clever scripts (e.g. more than brute force "search the entire game space ten moves out" techniques that pretty much any programmer can write if they have enough time on their hands).

No, there are not. Engine chess does not have a governing body to award titles. There usually are not any prizes aside from bragging rights, either.


World championship games where underpromotion was necessary I have been frequenting tactics puzzles and a few books over the past year. I come across these underpromotion puzzles frequently, however, I never find them in real games. Has there ever been a world championship game where an underpromotion was necessary? And if not, what was the highest level game that involved an underpromotion?


How does one find the tactic here? 1rr3k1/p3p1b1/b2p2pB/q2P1p2/4P3/1PNn1PK1/P1RQN1PP/7R b - - 0 23

In the above position (reached after 1. Bxh6?) Stockfish points out that Black has a winning move, going from 0.00 to -2.25.

However, I cannot find the tactic. Here are some details I have pointed out.

Checks: Black can check with Be5+ or f4+.

Captures: Black can capture the knight on c3 if a defender is removed: There are three attackers and three defenders on the square. The Black knight on d3 is protected by the bishop and is not hanging, so it cannot be captured. White can capture the g7 bishop, an attacker of c3, on the next move.

Threats: White cannot take the pawn with the knight after 1... f4+ because that removes a defender of c3. White cannot take with the king either because that interferes with the queen's defense of h6, and thus Bxh6 is possible (skewer). The intermezzo 2. Nxf4 does not work because of 2... Bxc3, attacking the queen.

Please only provide hints and not the actual winning move. What are the tactics (such as deflection, coercion, attraction, etc.) that Black should look for?

I see you looking at "forcing" moves such as checks and captures.  This is probably a good place to start.  One of the best features about "forcing" moves (especially checks) is that the opponent is limited in their possible responses. Both checks you have available, for example, allow only six possible responses; that's way easier to calculate than the 36 or so moves he'd otherwise have.  A capture allows for more possible responses than a check, but most of them are obviously bad if they don't regain the material, so that also limits the required calculations.

So, for each candidate move, go through each of their responses, one by one, and see if you have a good reply to it.  You've started this with a couple of moves; finish it for those moves, and if they don't appear to be correct, move on to the other forcing moves.  If you still cannot find it, look for other candidate moves (such as ones that create threats.)

(I'm not going to provide an actual hint because I see someone else already did, and you probably don't want two.)


Von Popiel - Marco, Monte Carlo 1902, how to win as black? In the game: Von Popiel - Marco, Monte Carlo 1902:
why would Black win with Bg1?

Ultimate Blunder

Puzzle

The white player is about to lose the Queen. Does that alone immediately constitute as a loss in that level of Chess play?

The white player is about to lose the Queen. Does that alone immediately constitute as a loss in that level of Chess play?

Well, no. The problem with White position is that he lacks any real counterplay. He has weaknesses he can not defend in the long run, especially pawn at a2, and his piece coordination is not good enough to defend against the might of the queen.

Below illustrative lines prove that:

[Title "Von Popiel - Marco, Monte Carlo 1902"]
[StartFlipped "0"]
[fen "7k/1b1r2p1/p6p/1p2qN2/3bP3/3Q4/P5PP/1B1R3K b - - 0 1"]

1...Bg1 2.Kxg1 Rxd3 3.Bxd3 (3.Rxd3 Bxe4 4.Re3 Qa1 5.Re1 (5.Rxe4 Qxb1+ 6.Kf2 (6.Re1?? Qxe1#) 6...Qxe4-+) 5...Bxf5! 6.Re8+ Kh7-+) 3...Bxe4 4.Bxe4 (4.Re1?? Qc5+ 5.Ne3 (5.Re3 Bxf5!-+) 5...Bxd3-+) 4...Qxe4 5.Ng3 Qc2 6.Rd8+ Kh7 7.h3 (7.a3 Qc5+ 8.Kh1 Qc1+) 7...Qxa2-+

Black will simply take the a2 pawn and win by marching his extra 2 queenside pawns, and there is nothing White can do to stop it. Meanwhile, Queen easily defends any mating attack Rook + Knight conjure up by simply going to the a1-h8 diagonal with the move like ...Qb2 or ...Qc3...


(4 Queens + 3 Pawns) vs (Entire Standard Army) My club has recently been playing the variant Etchessera.  For those unfamiliar, this variant allows you to build an army consisting of a King and up to 39 points worth of pieces according to the following system:

Pawn - 1pt
Knight - 3pt
Bishop - 3pt
Rook   - 5pt
Queen  - 9pt

While I realize that the relative point values are often listed differently, and can change based upon what other pieces remain, we were wondering if there should be a clear winner between the standard chess army and one consisting of 4 queens and 3 pawns.

Through our own games, the match-up appears to still be about equal provided the classic army plays defensive openings and forces a few trades.  However, my club is a very small sample size and I was looking to see if this has ever been explored elsewhere.

A clarifying comment says "Pawns can be placed in any of the first 3 rows.
Any other piece must be placed in the back row. White moves first unless
black used less points to construct their army."  So the position I gave
earlier doesn't work, but since Black is allowed to move first with fewer than
39 points there's still a forced win:

[FEN "1b1qkqq1/8/8/8/8/8/PPPPPPPP/RNBQKBNR b - - 0 0"]

1. Qxf2+ Kxf2
2. Qh4+ g3
3. Qgxg3+ hxg3
4. Qxg3#


Are mind games effective? If you want a quick match and need a way to put off your opponent early on, what sort of tactics can i use to mess with their head? I am specifically interested in the opening and middlegame, however answers regarding the endgame would also be appreciated.

I'm thinking about tactics such as alternating extreme attack and defense; making confusing moves to put off your opponent; playing with them and forcing them to move pieces to areas they do not want them in; disrupting their pawn chains and other defenses to make for an easier middlegame; piling up attackers on one square in particular, when in fact you are indirectly preparing for a strong attack on the opposite side (or even simply retreating and creating a stronghold around your king). I am also interested in direct body language such as making eye contact; showing a lack of emotion; and trying not to look like you are thinking hard, either to make the opponent think you are likely to make mistakes or to trick them into thinking you are completely confident with your position.

Answers may include:

Addressing the strengths/weaknesses of a tactic, and how to perform it.
Specific examples of any of these tactics in GM games
Reviews on the use of such tactics and whether they are likely to work
General rules of thumb in how to force moves or disrupt defenses
Any tournament rules regarding mind tricks outside the game (either across the table or between games)
Suggesting tactics not mentioned in the question above and giving reasons and uses

Nigel Davies has a Fritz trainer DVD "chess for scoundrels" which works on this topic exactly. He shows some games and tells some anecdotes about how you can use mind games, to support your game (and he says that at GM level this is completely normal).

Examples by Davies: there was a Geller-Fisher game where Geller went for a drawing line with white, and offered a draw at move 7. Fisher laughed at his face (which is not so ethical imho) and then win in ~70 moves in a dead draw endgame, because Geller blundered.
Bronstein in a draw or little worse position saw a trap, but was fairly sure his opponent would see it, he offered draw, suspecting his opponent will not take it (and it was fine for him), and went for the trap. His opponent declined, was searching for a win, and didn't notice the trap.
I highly recomend buying the DVD, it's an amazing source in this topic.

People who were/are very good at this are for example Lasker, Tal, Fisher, Karpov, Kramnik. For examples read about the WC games Fisher vs Spassky, and Karpov vs Korchnoi with all the off board activities.

There was also a Benko book on psychology, but I didn't read it.


Is it inadvisable to analyze or play long chess games on a smartphone? I play a lot of online chess, but I am a federated player whose objective is to play well over-the-board games with 3D pieces.

During my hourly tactics exercises I turn on the computer and do it in the big screen because my results are better than on the smartphone.

For timed games I also play with the PC, as I am quicker with the mouse than with the finger.

But I also play correspondence daily; I use to have 20 games in progress.

I am getting used to analyze and make the moves on my smartphone, when I am not at home, or when I feel too much lazy to turn on the computer.

I know the best is to analyze on a physical chess board, which I sometimes do on correspondence when the position is interesting.

But my question is if I should be less lazy and turn on the computer when analyzing deeply with the analysis board.

I know, in deep, this is a neurology question, but at neurosciences SE they would say it is a question for a chess teacher or highly rated player as there are not specific neurology studies on it.

Just asking, as a 7 years old student could ask: "Teacher, should I always play on the PC or I can use my smartphone playing on the free net?"

Advisable to use smartphone?  Not really. Okay occasionally if you must look at a position.

As you noted a PC is more helpful to seeing the board and planning your moves.

I have found no difference between using PC screen adjusted to my preferences and using a real chessboard with physical items on it.
For me the difference between chess sets and boards is more than the difference between my preferred set and board and the PC screen with my choice of size and font.

Note that moving the men on your phone or pc will negate any OTB experience for a tournament that you would get by analyzing without moving them to improve your analysis vision for 'real' chess in an OTB tournament.


Is Fritz 15 a better chess software than Deep Fritz 14? I can only afford one. Would Fritz 15 be better to get than Deep Fritz 14?

I would like to use Fritz to study opening theory.

While I'm not sure what exactly Fritz 15 will offer (because it hasn't been released), but it's almost certain that there will be a "deep" version. Look at this ChessBase online search, so it's pretty safe to assume there will be Deep Fritz 15. My suggestion: wait for the upcoming version.

However, I don't think Deep Fritz 15 will offer you anything that Deep Fritz 14 doesn't. If we're talking about the user-interface experience, there shouldn't be much because ChessBase always ship an almost-identical software every year.

The most obvious change is the engine, unfortunately, this is not very interesting because Fritz is quite far behind Stockfish and Komodo. If you're looking for the strongest possible engine to study opening theory, you might as well download Stockfish and use it with any compatible client. It's free and plays better chess than Fritz.

You'll need to decide what exactly you want: an easy but expensive bundle from ChessBase or the strongest free chess engine.

EDIT (after product release)

It's nice ChessBase finally drops the "deep" term and it makes perfect sense, who is still using 32 bits in 2015? There is no Deep Fritz 15, just Fritz 15.


How not to use a chess engine? How not to use a chess engine? What are the bad practices when using a chess engine, and the good ones? How trustworthy are their suggestions and evaluations?

What's the purpose of this question & answer?

I see a lot of misuse of engines in this community. I see topics where people do opening "analysis" by copy pasting engine outputs. Even worse, I saw opening "analysis" by copy pasting in first move!

Lots of beginner in this community believe that engines give best possible move in every position, because they beat human players.

I tried to explain why this is wrong under several topics shortly, but I see short explanations are not enough, people don't want to believe some stranger saying that using the engine in such ways is wrong without explaining with every detail. So I, as a computer science student and hobby player(used to play OTB but quit it) wrote this very long, tiring answer, in hope of changing wrong beliefs.

Notes: This is a very long answer. I have probably a lot of grammar mistake and typo. Also it may be possible to explain these in a more fluent or in a shorter way. So, if you think you can improve this answer, please suggest edits, I would highly appreciate it.

How does an engine work? What are these numbers in analysis window?

Engines evaluate all positions using different metrics(which is very closely related to engines playing strength)

For example: Engines has predefined values for materials, like 1 points for a pawn, and 3 points for a bishop etc.

But that's not all of course, they use more advanced metrics too. For example: A passed pawn 0.2 points, bishop pair 0.1 points etc.

So, it evaluates all positions like this, and inserts into a tree(if you want to learn about tree's more, please take a look at this paper).

But, as the memory is not infinite, if computer runs out of memory, engine stops right? So engine has to use memory carefully. How? It deletes some nodes (positions) from tree which are not promising (has bad (it may not be easy to decide which is bad) evaluation score).

Longest possible path in the tree is the depth of the analysis. As every node represents a position, depth of 2 equals 1 move.

What are the strengths and weaknesses of engines comparing to humans?

Engines are absolutely better at tactics comparing to humans. Because tactics are

convertible to concrete (material, including checkmate) advantages in short-term (generally in less than 10 moves)
computers have overwhelmingly more memory comparing to humans (Can any chess player memorize and evaluate 10^3 different continuations in any position in 1 minute? No. But computers today can do it for more than 10^12)
computers don't make calculation mistakes(practically), but humans do.

Humans are absolutely better at strategy and positional evaluations. Because:

after all, engines are using metrics to evaluate which are absolutely open to question, for example there is no correct metric for bishop pair, or pawn.
a master chess player is far more better when assessing metrics(machines are stupid)
humans are overwhelmingly stronger at pruning, our search tree is far more smaller(we can eliminate a lot of unnecessary positions, computers fall short in this)

Let me demonstrate these in this position, which a 1200 Elo player can assess a draw(rightfully) in 3 seconds.

 [Title "Komodo-9.3 depth=48, -17.61"]
 [FEN "rr2k3/6b1/8/p1p1p1p1/PpPpPpPp/1P1P1P1P/8/4K3 b - - 0 1"]

Engine says it's -17.61, after seeing 24 moves ahead. Why? Is it that stupid? Can't it understand black can't progress?

Yes! It is that stupid! And you are the one who needs to understand it's draw, not the engine, it's a tool for you!

-17.61 is result of the evaluation metrics. Is the evaluation wrong then? No, evaluation is correct, if you interpret it correctly. The engine sums up metrics, which results -17.61, because black has a lot of material advantage. Interesting thing is that much material advantage isn't enough in this position and that's the part you should assist the engine with your intelligence.

Evaluation scores are not position assessments!!!

There are only two things can be considered as an assessment in an engine's output:

Mate in x
Draw by 0.00

Other than these two all evaluation score outputs are opinion-based. Like in the position above -17 evaluation can be assessed as a draw, it's very unlikely but possible.

So, engines are really far from perfect, that's why we have tablebases. Tablebases are sources of the absolute truth of a given position. A tablebase gives an output which tells the position is either mate (in x moves) or draw. State of the art tablebases has covered all positions having at most seven pieces.

How to interpret evaluation scores?

As I mentioned earlier, engines do their best to use limited memory and computational power. Because these are limited, engines tell users that how deep they went.

Imagine that you are a commander (engine) of an army, and you are in an open terrain. Your army has 10k soldiers. You have 10km (depth of search) line of sight, and you see enemy forces 9km ahead, you guess (evaluate) their count as roughly 100 soldiers, and you decide to attack. You and your army starts to run towards enemy. But after getting 3kms closer to enemy forces (gaining 3km more line of sight), you suddenly see 100k more enemy, and you suddenly decide that this battle is lost.

This was an analogy of horizon effect problem. There are times, in which the key move happens out of the horizon of the engine, and engine evaluates the position falsely. This problem happens lot more in endgame, because in endgame, comparing to middlegame and opening, positions evolve slowly, more moves needed to get same amount of progress. Remember the long manoeuvres of endgames. That's why engines are using tablebases (precalculated, sure as death assessments of positions which have less than 8 piece on board), to fight with horizon effect.

Let's return to position above and clarify why we can so easily assess it as draw, but computer don't give 0.00?

Engine has calculated 24 moves deep, nice. But we are calculating all possible continuations, until the end! We are not faster than computers, but we are quicker than them. Because we understand, after checking several moves, all continuations are trivial, and prune them all. We only calculate few positions, and assess it as draw. But engine calculates tons of, because its not clever enough to understand its trivial to calculate all these positions.

Now, how not to use chess engines?

As an endgame god, like it knows it all
As an opening god, like it knows it all
As a strategy god, like it knows it all
As a tactical god, like it knows it all(it generally knows it all, but there are exceptions, because of the horizon effect)

But to use as:

A foolproof mate searcher
The best tactician in the world
A questionable advisor in strategical/positional evaluations

Don't forget that analysis and match are different tasks. Humans can't beat engines on matches doesn't mean it's the same in analysis. Actually these are very distinct tasks, because analysis aims to find the best move with infinite resources, but match aims to win with finite resources, and for winning, it's enough to play better than opponent. All competitive engines are tuned for matches, to get highest possible success in engine tournaments.

Read also

A nice article about chess engines, relevant to this topic.
A very instructive article about interpreting engine evaluations.
A related topic: Why do chess engines sometimes miss good moves (or take forever to spot)?
Another related topic: Computer evaluations: How trustworthy are they?

Examples of Engine Fails, for Unsatisfied Readers

More examples of positions, which state-of-the-art engines can't find the correct move, which was found by human-beings

[Event "Linares "]
[White "Topalov, Veselin"]
[Black "Shirov, Alexei"]
[FEN "8/8/4kpp1/3p1b2/p6P/2B5/6P1/6K1 b - - 0 47"]

1...Bh3!!-+ {Shirov played this} ( 1...a3? {Komodo-9.3 with 50 ply, 5GB Hashtable, evaluates -2.58} )

Analysis of Shirov's game


Need to say check if we are giving I want to give check to black and is it necessary to say check to other player?

No, it's not necessary. If the opponent doesn't notice it, it's their fault. Reasoning behind this is (probably) what happens if your opponent is not at the board when you make the move? You don't have to sit and wait for them (and stay away from the toilet...) just in order to inform them that you have just checked the king - which is something that any player should notice themselves anyway.

If the opponent doesn't notice and makes a move that doesn't prevent the check, there are procedures to correct this (and you should generally involve the arbiter in these).


What's the difference between movetime and the Slow Mover option? When I tell the engine to find the best move with

go movetime 1 depth 1

I expect it allows itself to take up to about 1 ms to make it's move. But what's the difference between that and the Slow Mover option:

option name Slow Mover type spin default 84 min 10 max 1000

Looking at this post from 2008 it seems like perhaps Slow Mover was implemented before the movetime option?

When you pass movetime to an engine via UCI, you're telling it to override any time management algorithms it might have, and to instead spend exactly x milliseconds analysing the position.

When playing games, the UCI movetime parameter typically isn't specified. Instead, the engine is told how much time each player has left on their clock (and the increment, if any). This allows the engine to decide how much time to use with its own time management.

The Slow Mover option is used to tell the engine how you would like it to manage time. It only means something in a game situation (i.e. when movetime isn't specified). Higher values will tell the engine, broadly, to use "more time", but it does not control the exact amount of time that is used.


C45g, where to find this ECO code? I have a text file with 10K+ ECO opening codes from the Scid source distribution, for example:

C45g Scotch: Steinitz, Berger Variation
C45q Scotch: 4.Nxd4 Bc5 5.Nb3 Bb6 6.a4 a6 7.Nc3 Qf6

I know C45 is the code for Scotch Game, but I'm not sure C45g and C45q are valid.

Q: Are C45g and C45q valid? Should I just rename them to C45? If they're valid, where should I look up for more information?

These codes are the extended ECO codes by SCID, and have no meaning outside it.

When classifying the games you can enable or disable the extended ECO codes to force SCID to use the standard ones, if you prefer so.

There's a short explanation of the reason for the extended ECO codes here: https://sourceforge.net/p/scid/wiki/TheECObrowser/


Why is 1. d4 Nf6 2. c4 e6 3. Bg5 almost never played? Why is

[fen ""]

1. d4 Nf6 2. c4 e6 3. Bg5

almost never played? Isn't it a logical opening move? OK, it goes against the rule of "Knights before Bishops in the Opening", but is a general rule enough for this move to be virtually never played at top level?

After 1.d4 Nf6 2.c4 e6 3.Bg5, the position resembles the Tromposvky Attack (1.d4 Nf6 2.Bg5), where white often gives up the bishop pair in exchange for a lead in development and the center. For example, one main line goes 2....e6 3.e4 h6 4.Bxf6 Qxf6.

However, in the position after 1.d4 Nf6 2.c4 e6 3.Bg5, the move c4 doesn't fit well in this plan. Moreover, it weakens the dark squares, helping black's plans with c5 or Bb4+.

      [StartPly "2"]

      [FEN ""]
      1.d4 Nf6 2.c4 (2.Bg5 e6 3.e4 h6 4.Bxf6 Qxf6) e6 3.Bg5 h6


Openings that keep the king in the center on purpose? Discounting cheap tricks to mate in only a few moves. Are there any serious openings that keep the king in the center with no intention of castling?

There are many respectable opening lines where the king stays in the center. A popular opening at the highest level is the Berlin Defense:

[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. O-O Nxe4 5. d4 Nd6 6. Bxc6 dxc6 7. dxe5 Nf5 8. Qxd8+ Kxd8


Strategic and tactical ideas for White in this KIA game What are the good strategic and tactical plans for White in this position?

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
1. e4 e6 2. d3 d5 3. Nd2 c5 4. g3 Nc6 5. Bg2 Nf6 6. Ngf3 Be7 7. O-O O-O 8. Re1 Qc7 9. e5 Nd7 10. Qe2 f5 11. exf6 Nxf6

I wonder what should I do with the Black's c, d, and e pawns. How to prevent them from pushing forward and after preventing them from pushing forward, what should be the next plan for White?

I had studied the KIA for a time in the early'90's, although with mixed results, so I don't claim to be an expert on the subject.  In this position 12.c3 would constrain the Black "d" pawn, but I think I would initially play 12.Bh3 to restrain the more important "e" pawn, which is currently backward on the open file.  Then if 12..., e5; 13.Bxc8 & 14.Nxe5 would win it. Or if Black decided to reinforce it by 12..., Nd8, then 13.Ne5 could occupy the hole and then support this N with subsequent 14. Ndf3 and 15.Bf4 moves.  And since the purpose of the KIA is a kingside attack, you would probably subsequently want to mobilize your kingside pawns once you had this center control.  I hope these suggestions are of some value.


Is certain opening determine relative pieces value as I know that certain opening will leads to certain positions, but I do not know if certain opening will determine relative value of chess pieces. Are there some sources to explained it??

as example :
if I choose Ruy Lopez, my knights will more worth than my bishops, and etc.

To some extent, yes. General rule: if certain opening/variant of opening will leads to open position, then bishops will be worth more than knights - and usually opposite in closed games.


Understanding magic bitboard I have read a lot of stuff about magic bitboard but some stuff is not clear. A lot of authors say to create the move masks for the piece avoiding the border positions. So, for a bishop at D3 the move mask would be this:

00000000
00000000
00000010
01000100
00101000
00000000
00101000
00000000

instead of this

00000000
00000001
00000010
01000100
00101000
00000000
00101000
01000100

They say this is good for convenience. I don't see how, but anyway, lets bear with this idea.

The problem is that, if we will avoid the border are, how will the move map for a hook at A1 be? All zeros? The hook at A1 will be like this:

10000000
10000000
10000000
10000000
10000000
10000000
10000000
11111111

but if we cannot have the numbers at the border it will be all zeros.

Is there another reason for that "avoid the border" rule? Is that OK if I forget that rule and make it to the border?

It's not about avoiding the border. It's about avoiding the last bit of the ray.

Given this:

10000000
10000000
10000000
10000000
10000000
10000000
10000000
01111111

(Note that A1 should be zero as the rook is unimportant)

You will note that along the first rank, if there is no piece on G1, then a rook can attack H1, regardless of what is on that square. This also applies along the A-file, where if there is no piece on A7, then A8 can always be attacked.

Because of this, we mask out the last bit of the ray, as we do not need to know what's at the end of the ray, producing this mask:

00000000
10000000
10000000
10000000
10000000
10000000
10000000
01111110

This produces a significant table reduction, as you need only 12 bits of occupancy to index the table, not 14.


Why is Na5 not played in this line of the French Defense, Advance Variation? I find Na5 a good resource for black in this line of the french, profiting from the fact that white's b-pawn is binned to the bishop. As far as I can understand this position with my limited chess, I find it a strong move, winning space on queenside with the plan of trying Bd7-Rc8-Nc4 on c-file.

[FEN "r1b1kbnr/pp3ppp/1qn1p3/2ppP3/3P4/2P2N2/PP3PPP/RNBQKB1R w KQkq - 3 6"]

6. a3 Nh6 7. b4 cxd4 8. cxd4 Nf5
9. Bb2 Na5

However, I don't find this move at the database of chesstempo I use to use for my correspondence games.

Stockfish neither considers it. It even don't play 10....Nbd2 (it plays Nc3) to defend on c4 (which I would expect), and doesn't wonder at all about Nc4 (it simply trades his bishop for the knight; apparently it should result an advantage on the center).

What's my misunderstanding here?

The Nbd2 --> Nc4 plan to protect the bishop doesn't work because c4 is attacked by black's pawn. Stockfish takes a more direct route to kick the pin:

[fen "r1b1kb1r/pp3ppp/1q2p3/n2pPn2/1P1P4/P4N2/1B3PPP/RN1QKB1R w KQkq - 0 1"]

1. Nc3 {White can kick the pin in a moment.} (1. Nbd2 {This move also poorly develops the knight - and as you can see, c4 is covered anyway.}) 1...Bd7 2. Na4

And the pin is already gone. Na5 didn't really do anything in the first place. It was interesting while it lasted, but that wasn't long. It wasn't exactly a bad move, even (lichess would call it an "inaccuracy," I'd wager); however, there are better ideas here, such as the simple developing move Bd7.


Touching an opponent's piece with one of your pieces If I touch one of my opponent's pieces with one of my pieces, but do not touch it with my fingers, do I then have to take it?
This question was raised in a junior school when one player touched his opponent's piece deliberately with one of his pieces and was about to take it, but decided against before touching it with his fingers. A dispute arose and as the tutor I was asked whether the piece was deemed to have been touched. Not a bad question from 10 year olds, and I was unable to give a definitive answer. I said I would find out and hence my plea for help. I face them again on Friday and still feel on shaky ground. Help appreciated.

According to the FIDE Laws of Chess, this all depends on whether it was intentional or not (of course, here I'm assuming you play under a Federation that follows the FIDE rules, or very similar ones). Article 4: The act of moving the pieces stands as follows (article 4.2 is the adjusting rule):

  4.3
  Except as provided in Article 4.2, if the player having the move deliberately touches on the chessboard:

  a.
  one or more of his own pieces, he must move the first piece touched which can be moved

  b.
  one or more of his opponent’s pieces, he must capture the first piece touched which can be captured

  c.
  one piece of each colour, he must capture the opponent’s piece with his piece or, if this is illegal, move or capture the first piece touched which can be moved or captured. If it is unclear, whether the player’s own piece or his opponent’s was touched first, the player’s own piece shall be considered to have been touched before his opponent’s.

If the move is not intentional (you drop your piece over an opponent's), then you don't have to take it. If it is intentional, it is certainly true that it is not specified if touching is with the fingers or the pieces, but as many players use both, I would say that both apply as touching.


Can you take back a draw offer? Is it possible to take back the draw offer if the opponent was not immediately replying to it?

No. Rule 9.1.2.1 of the FIDE rules says it all:

  9.1.2.1 A player wishing to offer a draw shall do so after having made a move on the chessboard and before pressing his clock. An offer
  at any other time during play is still valid but Article 11.5 must be
  considered. No conditions can be attached to the offer. In both cases
  the offer cannot be withdrawn and remains valid until the opponent
  accepts it, rejects it orally, rejects it by touching a piece with the
  intention of moving or capturing it, or the game is concluded in some
  other way.

(rule 11.5 is about not distracting the opponent during his move)

It's expected that the opponent takes his time to think about the offer, just as he probably spends time on thinking about his next move. He isn't required to actually refuse the offer, just making a move is quite normal too (once he touches a piece to move the offer is over, see above).


What is wrong with taking the e4 pawn in the Najdorf Sicilian after 6.Bc4? [FEN ""]
[StartPly "18"]
[Title "What is wrong with taking the pawn here?"]

1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bc4 e6 7.Bb3 b5 8.O-O b4 9.Na4 Nxe4

I have known this position for 25 years, having played it in blitz from both sides. I have looked into some books but the answers are too shallow. Looks to me like a gaping hole in opening theory. Is there an authoritative resource dealing with this line?

This is not a gaping hole in opening theory. Looking through my reference database, White has an excellent score after 10.Re1.
Black needs to reply with 10...d5 not to be clearly worse, because of the weakness on e6(White can just crash through if Black is careless). After this there aren't many games, but White's score after 11.c4 is 73.3% in 15 games. The computer evaluates the position as approximately +0.20 for White, which indicates that White has full compensation for the pawn.

This isn't hard to imagine. White has a development lead, has a weakness on e6 to work on, open lines for bishops and rooks etc. It is essentially a very sound gambit. The only reason why the computer gives White just +0.20 eval is because computers do not tend to make mistakes that humans make. They can handle scary looking positions in another way than humans can, and they don't make tactical errors. If you look through the games played after 11.c4, you will notice that virtually every black player has played a game-losing move at move 13 in this line (after 11... bxc3 12.Nxc3, Nxc3 13.bxc3, Be7?? and now White obtains a winning advantage after 14.Nf5!).

This means that the position is too expensive for Black to enter just for a pawn. It's totally not worth the risk, in my opinion.


Solvable studies that computers fail to crack Are there chess studies that require an outside of the box thinking that goes beyond the concrete calculation capabilities of today's engines (e.g. Stockfish)?

I have sometimes seen certain endgames that are known to be fortresses (drawn) but since the engine have depth limitations they cannot see all the way through and keep assessing them as winning for one side (for example giving +2 evaluation). But are there examples, to which we know the forced solution (checkmating line), but still the engines fail to solve?

Here is an outrageous mate in 57 puzzle which none of the top 3 engines are able to solve:

[fen "8/6pp/5p2/k7/3p4/1Q2p3/3prpp1/3Kbqrb w - - 0 1"]

1.Qc4 Kb6 2.Qd5 h6 3.Qc4 Ka5 4.Qb3 h5 5.Qc4 Kb6 6.Qd5 h4 7.Qc4 Ka5 8.Qb3 h3
9.Qc4 Kb6 10.Qd5 h2 11.Qc4 Ka5 12.Qb3 g6 13.Qc4 Kb6 14.Qd5 g5 15.Qc4 Ka5
16.Qb3 f5 17.Qc4 Kb6 18.Qb4+ Kc6 19.Qa5 f4 20.Qe5 g4 21.Qf5 Kd6 22.Qb5 f3
23.Qf5 Kc6 24.Qg5 Kd6 25.Qb5 d3 26.Qf5 Kc6 27.Qa5 Kd6 28.Qb5 Kc7 29.Qa6 Kb8
30.Qb6+ Ka8 31.Qc7 g3 32.Qc8+ Ka7 33.Qc6 Kb8 34.Qa6 Kc7 35.Qb5 Kc8 36.Qb6 Kd7
37.Qc5 Kd8 38.Qc6 Ke7 39.Qd5 Ke8 40.Qd6 Kf7 41.Qe5 Kf8 42.Qe6 Kg7 43.Qf5 Kh8
44.Qg5 Kh7 45.Qe5 Kg8 46.Qf6 Kh7 47.Qf8 Kg6 48.Qe7 Kh6 49.Qf7 Kg5 50.Qe6 Kh5
51.Qe8+ Kg4 52.Qf8 Kg5 53.Qf7 Kg4 54.Qf6 Kh5 55.Qg7 Kh4 56.Qg6 Kh3 57.Qh5#

Aside from the fact that the mating line is an absolute unit, an important reason why engines are unable to solve this is due to a technique called "Null move pruning".

Null move pruning assumes that playing no move is always worse than playing a move, which allows chess engines to search deeper by using this assumption to prune moves which are probably bad. However, because of this assumption, null move pruning is tactically vulnerable in zugzwang positions.

In the above position, black is pretty much perpetually in zugzwang, so null move pruning prevents most programs from being able to see how black's king is forced around the board. As a result, Houdini, Stockfish and Komodo all report draws.


Lecture/Book on AlphaGo/AlphaZero I am very interested in how AlphaGo resp. AlphaZero works. It seems to me, the related Google Papers are very dense and not easy to read.

Is there any textbook or lecture that explains on a technical level how it all works? I.e. starting with neural networks/deep learning, Monte Carlo Tree Search until reaching at AlphaGo/AlphaZero?

I have a master in computer science, but I never worked with artificial intelligence/machine learning.

Right now it looks to me that all the related information are scattered around, and I don't have time to listen to (online) lectures about machine learning that contain maybe only 10% on what is relevant to understand AlphaGo...

Can someone point me in the right direction?

EDIT

@unutbu's link in the comment is a good introductory read.

Solid understanding for AlphaZero most likely require a quantitative degree (PhD?). Are you asking for a crash course in AlphaZero?

Please note unless you invest significant amount of your time, nothing I say will work. There is no book that can possibly cover everything. You will need to work very hard.

Let's give a try. Crash course for AlphaZero.

1. Basic understanding in machine learning

Countless number of books. But if you don't have time, I'd recommend Professor Andrew Ng's machine learning courses on Coursera.

Your keywords: training sets, test sets, stochastic gradient descent, learning rate, GPU, cost function, cross entropy.

2. Deep neutral networks

You need to understand about neural networks. I'd recommend Professor Ian Goodfellow's deep learning book if you're serious. If you don't have time, please  again follow Professor Andrew Ng 's online course on Coursera. You don't have to go though all chapters (but you should!).

YouTube has many quick introduction to neural networks, try them.

Your keywords: neuron, layers, weights, bias, mini-batch, activation.

3. Monte Carlo Tree Search

You should understand what Monte Carlo is. Books about Monte Carlo is everywhere on Amazon. Read the wikipedia about MCTS if you don't have time.

Your keywords: sampling, expansion, simulation, rollouts, backpropagation.

3. Reinforcement learning

https://www.quora.com/What-is-the-REINFORCE-algorithm
http://www.scholarpedia.org/article/Policy_gradient_methods

Your keywords: policy gradient, gradient descent, learning rate

5. Chess board representation

The paper itself is simplest. The model encodes the board state (e.g. pieces) as a series of one-hot encoding binary values.

6. MCTS vs alpha-beta