What is the best line of the Colle to play against KID set up by Black?

The English GM Simon Williams has just tweeted this -

  Just finished filming 'The Colle' a DVD for @ChessBase. I must say
  that the Colle with 1 d4 2 Nf3 3 e3 4 c3 5 Nd2 and 6 Bd3 is basically
  rubbish. But the 'Colle-Zukertort' with 4 b3 is another matter
  entirely... Learnt a lot filming this week.

That sounds reasonable to me. In other words you are wasting your time.

In general the answer to the question "Given that I always play opening X how should I use opening X to reply to opening Y by my opponent?" is nearly always something along the lines of - "You should not dogmatically play opening X in all circumstances. You should always play the position in front of you and try and find the best moves. If your opponent plays something against which your standard opening is rubbish then play something else."

Against the KID the Colle is a silly opening to play. The same could probably be said of the London. Classical lines involving putting your pawns on c4, d4 and e4 with a knight on c3 can't be bad but obviously there is a lot to learn.

If you want to frighten your opponent and take him out of his comfort zone then something like the Barry / 150 attack should do the job. That is where you play d4, Bf4, Nf3 following up with e4 if your opponent doesn't play d5 and then aiming for Qd2, 0-0-0 and an early h4.

I believe that along with the Colle DVD he has also been working on a DVD about the Torre attack. When these are released (probably take a couple of months for Chessbase to do their editing, tidying up and marketing) you might be interested.

Disclaimer: I have nothing to do with either Chessbase or Simon Williams although I have bought their DVDs in the past.


Is there any software or web service for club-level Elo ratings?

Even if it is not available, something like this is not too hard to implement yourself. Here is an example with extremely silly and simple rating system that is just meant to give you an idea. But I don't think that using actual Elo formula that much harder.

EDIT: I edit my implementation to use Elo formula (not including floors) given by the formula here

def get_exp_score_a(rating_a, rating_b):
    return 1.0 /(1 + 10**((rating_b - rating_a)/400.0))

def rating_adj(rating, exp_score, score, k=32):
    return rating + k * (score - exp_score)

class ChessPlayer(object):
    def __init__(self, name, rating):
        self.rating = rating
        self.name = name
    def match(self, other, result):

        exp_score_a = get_exp_score_a(self.rating, other.rating)

        if result == self.name:
            self.rating = rating_adj(self.rating, exp_score_a, 1)
            other.rating = rating_adj(other.rating, 1 - exp_score_a, 0)
        elif result == other.name:
            self.rating = rating_adj(self.rating, exp_score_a, 0)
            other.rating = rating_adj(other.rating, 1 - exp_score_a, 1)
        elif result == 'Draw':
            self.rating = rating_adj(self.rating, exp_score_a, 0.5)
            other.rating = rating_adj(other.rating, 1 - exp_score_a, 0.5)

This works as follows:

>>> bob = ChessPlayer('Bob', 1600)
>>> john = ChessPlayer('John', 1900)
>>> bob.rating
1600
>>> john.rating
1900
>>> bob.match(john, 'Bob')
>>> bob.rating
1627.1686541692377
>>> john.rating
1872.8313458307623
>>> mark = ChessPlayer('Mark', 2100)
>>> mark.match(bob, 'Draw')
>>> mark.rating
2085.974306956907
>>> bob.rating
1641.1943472123305

Here is my original python implementation:

class ChessPlayer(object):
    def __init__(self, name, rating):
        self.rating = rating
        self.name = name
    def match(self, other, result):
        if result == self.name:
            self.rating += 10
            other.rating -= 10
        elif result == other.name:
            self.rating += 10
            other.rating -= 10
        elif result == 'Draw':
            pass

This works as follows:

>>> bob = ChessPlayer('Bob', 1600)
>>> john = ChessPlayer('John', 1900)
>>> bob.match(john, 'Bob')
>>> bob.rating
1610
>>> john.rating
1890
>>> mark = ChessPlayer('Mark', 2100)
>>> mark.match(bob, 'Mark')
>>> mark.rating
2110
>>> bob.rating
1600
>>> mark.match(john, 'Draw')
>>> mark.rating
2110
>>> john.rating
1890


Should I recapture the queen with my king or knight in the Scotch Game?

As you say, each of the options 5. ... Nxd8 and 5. ... Kxd8 has its own drawbacks: the former drops a pawn and the latter gives up castling rights. In this situation Kelley is right that losing the pawn is significantly worse than giving up the right to castle.

In a typical middlegame that features a lot of firepower on board for both sides, a king stuck in the center of the board can be in a great deal of danger of facing a mating attack. But in this case, the king gets stuck in the center only after the queens come off the board, which means Black has much less to worry about in terms of facing an attack. This queenless middlegame is not so far removed from an endgame, in which centralization of the king is generally a plus rather than a minus. Now there are still a lot of pieces on the board, so it's not a walk in the park for the Black king; I'm just saying it's not as dire as things can be with the ladies still around.

This particular position still has certain problems for Black (which is one reason why 3. ... d6 isn't the best choice); for instance, the king having been pulled to d8 means that the f-pawn is undefended, so with something like 6. Bc4 White develops the bishop, and the Black either must waste a tempo moving the king back to defend the f-pawn, or play 6. ... Be6 to defend the pawn, allowing White the chance to give Black doubled, isolated pawns by 7. Bxe6 fxe6. That's not the end of the world, and in this kind of position those pawns do at least help control some central squares. The main point: Black will probably end up with some structural problems, or lag behind in development for a bit, but this is better than the alternative.

Losing a pawn isn't the end of the world either, it's true, but here it's much closer. After 5. ... Nxd8 6. Nxe5, White is a clear pawn up without any compensating factors in Black's favor; in fact White has a lead in development as well. This is something Black definitely shouldn't allow, especially since we really are getting toward the realm of the endgame, where having an extra pawn is of crucial importance. Going this route puts White in the enviable situation of "playing for two results," meaning that from here either a White win or a draw are nearly certain, with a loss for White being very unlikely (barring a big mistake later of course). That's one of the worst things Black can do to herself in the opening.


As a coach what is the process to create a repertoire for a child?

A repertoire is not built overnight, and for most players, having a deep theoretical knowledge is not required. They simply need to understand opening pawn structures.

That said, if this child is showing a great deal of aptitude, it may be worth adding this to your study regime earlier than I would normally recommend. I have seen two prodigies up close, and I will share what I have seen: I have known GM Josh Friedel since he was 6 or 7, and his first coach, who was the first player that I REALLY wanted to beat, has been a close friend for 40 years, so I know that he taught Josh openings even at a very young age.

My second encounter with a prodigy is the amazing 8-year-old Ryan Sun, who is now already rated above 2000 (and plays stronger than that). I faced him in my first game back after 16 years, and again, just this past weekend. I went 0-2, but in our game this weekend, it was especially clear that he was well-versed in the opening. So, for certain kids, who are gaining strength at an incredible pace, they do need a repertoire early since they will soon be facing players, who are booked up.

Unless you are an expert at opening play, you need to do one of two things at a certain point: Pass him off to a stronger coach. In Josh's case, he "graduated" from my friend to a GM coach, I think at around age 11. The other option is to buy repertoire books, that were written by grandmasters.

For kids, who calculate like little computers, you probably want books that focus on aggressive repertoires, typically 1.e4 as white, the Sicilian Defense as black versus 1.e4, and then a GM-suggested repertoire versus 1.d4. There are a lot of such repertoire books out there.

I hope this helps.

Below, the original poster asks about how to prepare to present the material, and how to prepare to present it, and I added a comment. I will that here too.

Usually, those books are pretty complete repertoires, and you need to go through a good portion of the book to make sure you cover everything. So, take each chapter, and they do not have to be in order (for example, if the first chapter is oddball sidelines, that is not the place to start), and read it yourself, and get a feel for the plans and ideas; and then start presenting them chapter by chapter until you are done with the book. He will not have to memorize everything, but this way, he will be exposed to all of it. Just keep building on that.


I do this often in blitz, although it is considered somewhat inappropriate in a tournament setting.

The quick way to castle with one hand is to make a motion where you "capture" the rook. In a typical capture, you pick up your piece and knock the opposing piece into your hand. You then take the piece off the board.

What I mean by "capturing" your rook is that you perform the same motion, but instead of using your palm to carry the piece off the board, you use it to guide the rook to its appropriate square. At the same time, your king is knocking the rook over to where it belongs.

It takes a bit of practice to knock the rook over, but when done properly you can castle in a fluid motion without having to make multiple motions with your hand.


Going to the dusty databanks in my skull, this indeed has been written about before. It appears in Journey Entry #153 of Tim Krabbe's Chess Diary. Since you define the ply count to the position before the selfmating move, the given examples are valid (although, Krabbe does not count the forcing move either, leading to counts of 5.0). This answers your second and third wonderings.
Here are the given games, which, unsurprisingly, all have Fool's Mate setups. All are 5.5 moves, the same as yours. I can offer no proof of optimality, however. I do think, though, that it seems unlikely that faster can be done.
[Title "Pim Blijlevens, Tim Krabbe's Website #153, 12/10/2001, PG in 6.0"]
[FEN ""]

1. f4 e5 2. g4 Ke7 3. Nc3 Kf6 4. Nf3 Kg6 5. Nd5 Nh6 6. Nh4+ Qxh4#

[Title "Pim Blijlevens, Tim Krabbe's Website #153, 12/10/2001, PG in 6.0"]
[FEN ""]

1. e4 f5 2. Ke2 g5 3. Kf3 Nc6 4. Kg3 Nf6 5. Nh3 Nd4 6. Qh5+ Nxh5#

[Title "Sasho Kalajdzievski, Tim Krabbe's Website #153, 12/11/2001, PG in 6.0"]
[FEN ""]

 1. e4 h5 2. f4 g5 3. Kf2 f5 4. Kg3 gxf4+ 5. Kh3 a6 6. Qxh5+ Rxh5#


Just tested it and it may have been fixed. It let me complete the mating move.

Just in case, the site is https://fritz.chessbase.com/


Longest chess game possible (maximum moves)

Some cleaning up is required, I think:

The number on the website you link to differs from the results published in     Bonsdorff et al., Schach und Zahl. Unterhaltsame Schachmathematik. pp. 11–13.
There they say that if the 50-move-rule is mandatory the longest possible game (i.e. where both players cooperate to achieve the weird goal of a game of maximal duration) lasts 5899 moves.
Possibly, the web site used a simpler upper estimate for the "gaps" between pawn moves and captures that cannot be achieved in all occasions.

However, the 50-move-rule (and also the position-repeated-three-times-rule) is not mandatory, i.e. whether or not a player demands remis by that rule is up to him! The players may decide to ignore the rule and play on, thus allowing for an eventually periodic sequence of moves, i.e. an infinite game.


Chess puzzles in newspapers and magazines which offer a prize

The only one I am aware of is chesspuzzles.com offering a prize drawing for:

Mate in 1 problem: Chess Rules for Students (RRP $4.50)
Mate in 2 problem: Checkmate! Ideas for Students (RRP $5.00)
Mate in 3 problem: Chess Tactics for Students (RRP $16.00, but on sales for $12.80 now)

All prizes written by John Bain. The latest prize drawing was week ending Saturday 16-December-2016, at the time of answering this post.


Can you estimate a player's Elo rating using tests?

Obviously the best test is playing in an actual competition, and most trainers will advise their players to play in as many as possible.

Other than that, there are books that try to do this. I don't know how accurate they can be, but it's likely that they need to be taken with a grain of salt: there is probably too much variance in the concentration level and time taken to solve the problems between different readers that they can't all get good answers. Also, chess skill isn't only related to skill in solving chess positions: confidence, controlling nerves, concentrating deeply for hours, judging when to play for a win and when to be content with a draw, most of those are competition skills that will only be reliably judged by actually playing in a competition.

There are many many books of exercises, and some of those try to do Elo estimation based on how many of them you got correct.

Books that I think that do that (there must be more):

The classic "The Best Move", by Vlastimil Hort and Vlastimil Jansa was probably the first of this type.
Barden's "How Good is Your Chess"
Keene's "Discover Your Chess Strength"
Alburt's "Test & Improve Your Chess" (I think)
Bosch's "The Chess Combat Simulator"
King's "How Good Is Your Chess?" (yep, same title as Barden)
Evans' "How Good Is Your Chess?" (seriously, I'm finding these on Amazon and they have different covers)

There's also this site: The Automated Chess Rating Utility website

Sites like Chesstempo have only tactics puzzles, but they also ask users to enter their FIDE rating and use this to calculate a correlation between Chesstempo and FIDE ratings; inaccurate, but better than nothing.

But again: a rating is an estimate of how well you did in competitions. Estimating ratings some other way seems a bit besides the point -- why not just play in competitions?


How much should I rely on an external board or diagram when reading a chess book?

I can copy the diagram on a board or simply on my computer (and do not
move the pieces), but I wonder whether I should.

It is very much worth while setting up a board and following the game on the board. But you should go beyond just passively playing out the moves on the board. You should stop after each move and actively consider what you would play next for each side. That will benefit you much more.
There is also the aspect of involving more of your 5 senses as I say in this answer to a different question.


What did Bobby Fischer mean in this quote?

It means that even he, Bobby Fischer, was susceptible to overlooking his opponent's good replies.

From the book, "Counterplay: An Anthropologist at the Chessboard", here is a quote on page 74:

"So intense was Fischer's concentration, and so single-minded his intent, that he would sometimes become immersed in his own ideas at the board and forget certain possibilities available to his opponent. "Yet possessing a tremendous will to win," Elie Agur writes of Fischer, "he might have "forgotten' his opponent at times, carrying out his plans as though no obstacle could be put up to stop them." Or to quote the man himself: "My opponents make good moves too--Sometimes I don't take these things into consideration."

You are right that this is widely quoted, and attributed to him, but I would love to find where and when he said this exactly. I suspect it was in response to a game that he lost or drew. That I have been unable to find so far.


Starting positions in Chess960 where black is definitely worse

I asked myself the same question a year ago.

I found this interesting page: http://computerchess.org.uk/ccrl/404FRC/opening_report_by_white_score.html#table_start

With statistics for every 960 positions based on 144,300 games played by 123 engines.

Apparently the position that gives the biggest advantage to White is RKNQBBNR with a White score of 63.9%.

Note that on the previous page the standard position has a White score of 56.0%. I once read that the true White score in standard chess is 55.5% for GM games. Since these two numbers are pretty close it would seem that the statistics of the previous page are meaningful and pretty accurate.

Also, someone once told me that if we just inverted Knights and Rooks then White would have a big advantage: NRBQKBRN.
But the previous page actually says that White only scores 47.4% in that position, so maybe he was wrong.

Anyway, I seriously doubt there exists a position where White has an advantage of +0.50 or more. And every single one of the 960 positions are very probably just draws with best play.


How do I raise my tactic trainer rating to 2300?

As noted in the comments, 2300+ tactical ability is a ridiculous goal to aim for, if your current level is 1600-1700. This will only lead to disappointment on your part, as improving your tactical level to 2300+ will probably mean that you will have to raise your overall playing strength by maybe 300-400 rating points. This takes years to accomplish, unless you have lots of time, resources and talent, in which case it will probably still take at least a year.

A suitable primary goal is instead to raise your tactical level by roughly 100 points. Depending on your situation, this can be done in a few weeks. However, just doing tactics problems on problem sites will not accomplish this very efficiently. Exercises are good, but not doing anything else will not improve your play by much.

I suggest you read a good book about tactics if you haven't already. One that I enjoyed very much was "Understanding chess tactics" (I think later editions of the book is called "Chess tactics from scratch") by Martin Weteschnik, containing many good examples and clear explanations of themes. However, it's not the only good tactics book, and if you have a chess coach, that person may have some suggestions on what to read.

You'd probably also want to play against strong opponents (1800+ at your level), as they're very likely to be better than you tactically. This will be good for your overall play and toughness at the board, which goes hand in hand with tactical ability.


With black to move, he is not in check but he also has no legal moves. There is no square where his king can go without putting himself in check, and that would be an illegal move.

That situation is called stalemate (Wikipedia), and it is an immediate draw by the rules of the game. You've boxed him in too well.

As to why stalemate is a draw see Why is stalemate a draw? , and there are also a lot of further questions if you search the site for "stalemate".


Why does a knight combine better with the queen than a bishop does?

It is a fairly short and simple explanation:

They can combine to attack any square, not just squares on one color. As part of that they can also shift the attack better from one square to another.


You might find some luck looking to chess problem solvers. In chess compositions, a problem is 'cooked' if it has more than one solution (usually) or any solution that is unintended. If possible, problems are listed as C+ if they are proven by a computer to have only the intended solution(s). Obviously, these solvers do not throw away any moves to make such a proof.

Popeye Solver is one such solver. You can find more information about it on Wikipedia and the web.

You weren't very clear on what you were trying to accomplish though (this would have been important), so I'm not sure if it will work for you or not. Typically, with a program such as popeye it has a position, a stipulation, and a set of conditions. For example, a FEN position, "mate in 5", and "orthodox chess" (or perhaps varying rules).


Explanation of my game. Can someone explain the "why" to me?

This is a game between beginners. Nothing wrong with that, but there is not much point at this level giving a very deep explanation as to the "why". Both players should pay more attention to

not blunder pieces in one move
not miss mate in one move

Concretely:

From move 1 to move 4 a pawn was hanging on e5. White could/should have taken it earlier and black should not have allowed that (not move it there in the first place and later prevent it from being lost by either moving it away playing e4 or by capturing exd4.

...Nxe5 is a big mistake as it just drops a piece. Always check and double check if your pieces are attacked.

Qe4 just drops the queen. As above with every move you make, check whether your opponent can capture something (particularly if it is your strongest piece...)

Bc4 is another big mistake as it drops the bishop. Black should have responded with 20...Qxc4 winning a full piece for nothing.

22....d5 is a mistake because it drops a pawn.
24 Bd2 is a big mistake as it drops another piece. Admittedly this is a bit more tricky to see. Basically the bishop on d5 is protected only once by the knight on f4, because the pawn on e4 is pinned to the king, so you cannot recapture e4xd5. Black could have played 24...Bxd5 25 Nxd5 Qxd5 winning a piece.

Bf2 is a mistake because after 29...Qa1+ black will eventually win the pawn on b2 and the white king will be without protection in the middle of the board. For instance 29...Qa1+ 30. Kc2 Re2+ 31. Kd3 Qxb2 etc. A better move would have been 29. Rhe1 which prevents the black rook from entering with check via e2. Admittedly at your current level, this is not a big oversight unlike the other mistakes and I would not yet worry about it.

29....Re2 is a terrible mistake because it would lose to back-rank mate after Rd8+. Back rank mate is an extremely common tactics and you have to be aware of it at all times. You need to have the typical position (=three pawns in front of castled king and opponent queen or rook) ingrained subconsciously in your chess brain.

So in summary:

Pay more attention to hanging pieces (both yours and your opponent's and learn some basic tactics.


Are there starting positions in dobutsu shogi that are farther from a win/loss than the standard one?


I need help Identifying where exactly this set came from

Here's the same set on ebay. More pictures of yours would be helpful.

https://www.ebay.com/itm/Vtg-Ceramic-Duncan-Medieval-Style-32Pc-Chess-Set-Hand-Painted-Faces-Detailed-74/263416351119?hash=item3d54d6898f:g:GaoAAOSw4A5Y0WX2

Perhaps the seller can help you learn more.

If you Google for "ceramic duncan medieval chess", you'll get a lot of hits.


I think what you are experiencing is fairly common. I find that I have games that i feel like an absolute legend, able to come up with creative solutions and just not making any mistakes.... then there other games where i hang pieces , miscalculate large trades and just can't get things to click.
I think its partially due to fatigue though. If you are playing game after game after game, especially with blitz , theres little time to think and your brain starts to fatigue and you start making mistakes.
I think the best way to do deal with this just recognizing when you are starting to get fatigued and take a break. I find puzzles are really good for helping me with this. I usually do puzzles for half an hour, take my time try to calculate things out a little. then have a cup of tea, then good to go.


Engines are far better at spotting mistakes than at recognizing "brilliancies". You made a move that is much better than all the alternatives which isn't something obvious like a recapture or a fork in one move, so that's probably what the engine identified as "brilliant". Just don't pay too much attention to it and congratulations for this beautiful win!


Quintuple pawns / Interesting pawn structures

According to Tim Krabbé, Kovacs - Barth, Balatonbereny 1994 was the game with the longest living quadrupled pawns (23 moves). That would imply that he (an authority when it comes to chess records) doesn't know of any games with quintupled pawns.


Is it possible for stockfish to tell that mate is in X moves, when mate is in X + Y moves?

No, it isn't possible because, before Stockfish says it is Mate in 8, it views the position from the aspect of the losing side, i.e, the evaluation is the best that can be obtained by the losing side.

In other words, Mate in 8 is what happens if the losing side plays the possibly best defense. If the losing side plays sub-optimally, it could lose faster, but 8 moves is the longest possible postponement of Checkmate


You can't. That's how Stockfish internally works. You are going to need to check your previous line with the current line. If the current line has fewer moves, discard it.


Has a woman ever defeated a reigning undisputed World Chess Champion in classical chess?

Sorry, but the answer is "no".

I used ChessBase and the Mega 2020 database to search various combinations of players, focusing primarily on Women's World Champions, Judit Polgar, Hou Yifan, Vera Menchik from the 1920's and 1930's, Lyudmila Rudenko, Elisaveta Bykova, Olga Rubtsova, Nona Gaprindashvili, and Maia Chiburdanidze. I stopped after Maia Chiburdanidze with the exception of Polgar and Yifan since I would have remembered a victory by the more recent Women's World Champions starting with Xie Jun next. With the exception of Vera Menchik, who played Capablanca a number of games, none of the old Soviet women ever played any of the world champions.

Given that you were looking for a defeat of a sitting world champion in classical, no woman has ever done that yet.

The only ones to ever beat men, who already had been world champions, were Judit Polgar's victories over Karpov in classical at Hoogeveen in 2003, and Chorus in 2003, and the Champions League in 2007 (still the only victories by any woman in classical over even a former World Champion), and 8 wins in rapid, and a few blitz. Also, she beat Kasparov in rapid at the World Rapid Championship in 2002. She also had one rapid victory over Magnus Carlsen in 2012 in Mexico City, but that was a year before he won the title.

Hou Yifan had two wins over Kramnik at the Media Kings Rapid in 2016. She also has had some victories in blitz.

  After a bunch of back-and-forth comments below, I was asked to add my
  methodology to the answer, which I agreed to do. I do not claim my
  answer to be worthy of a scientific study and the scrutiny that would
  be associated with it. I was just trying to give a reasonably educated
  answer to the question. Whether I missed a rapid game against a former
  World Champion in my list, that is possible, but that was also just
  supplemental information I provided, and was not really part of the
  answer to the OP’s question since the question was officially only
  about classical chess. I would also take classical chess to mean
  over-the-board in a tournament since for it to mean anything, it had
  to be serious chess (this is not to be confused with relays of OTB
  tournaments, where the games are not really being played on the
  Internet).

  First, it is important to understand that if no woman has ever beaten
  a sitting World Champion in classical chess, it would be asking to
  prove a negative, so you can always some up with a “what if” situation
  that I did not search for. I had to draw the line somewhere, and I
  drew the line based on my searches of the best women players of their
  times (and all the world champions of their eras they may have faced),
  my fairly extensive knowledge of chess history, and 40 years of
  reading MANY sources on a once monthly (before the Internet, when all
  I was “Chess Life” and “New in Chess” magazine), and since the
  Internet, I read an average of three sites per day, every day
  (currently chessbase.com, chess.com, and chess24.com, and twic and
  chessninja in the past).

  It is also important to know, and this is where the history comes in,
  that the best women of the generations prior to the Polgar sisters,
  were MUCH weaker, often only in the 2300-2400 range, but it was also
  before the ELO system existed, so that is an estimate. I also know
  that back then, men simply did not play women virtually at all…Vera
  Menchik was the exception.

  All of the major advances in women’s chess strength to the Grandmaster
  level have come during my lifetime, when I was active playing, and
  actively reading the sources I referenced above, so I also ask for a
  little common sense: This would have been HUGE news, as was Polgar
  beat Kasparov in RAPID. I cannot find anything on Google about a woman
  beating a sitting World Champion in classical chess. I would not have
  missed it.

  Lastly, World Champions since Fischer have been 2700+, and there are
  only two women, who reasonably have had a shot at beating a World
  Champion in classical, and a lot of that is due to opportunity and
  invitations to elite events: Judit Polgar, and Hou Yifan, so you
  really do not have to look much further than their games, which limits
  the searching a lot.


The best move in this Crazyhouse position according to Stockfish

I can not exactly reproduce it on the lichess analysis board, but the move Nxc4 still seems to be among the top 3-4 moves with a similar evaluation as the top moves. The main idea in this position should be to undermine the dark squares f6, g7, h6 on the king side. Nxc4 aligns well with this idea, since it opens up the bishop's attack to h6 and gives an additional pawn in hand, so after a subsequent P@f6 white still has another pawn for the attack.
The Stockfish fork used on lichess is far above human level in crazyhouse, so usually its analysis should be quite reliable, although it of course also is not infallible and might miss moves/ideas or misevaluate resulting positions.


According to Hans Berliner, correspondence chess champion, Bg5 is the best.
From his book "The System. A World Champion's Approach to Chess" he stated, and Fischer agrees, that Bg5 maintain the most amount of pressure.  Nf3 is not as good, because you has three major plans in the QGD exchange variation and only one has the knight on f3.

My opinion is that Bf4 is stronger below master level.  I like the idea of Bxb8, not having the question put to the bishop on g5, and it reduces the possibility of Bd6.  There are disadvantages to putting the bishop of f4.

The answer depends upon what type of positions you like to play.  For positional games, the knight goes to f3, for center control and kingside attacks, the knight goes to g3 via e2.


Is there a reason AlphaZero hasn't been allowed to learn for longer?

Check out the AlphaZero paper, figure 1.

As you can see from the leftmost figure, you can let AlphaZero train, but that doesn't mean it'll improve. In fact, AlphaZero peaked at a level slightly above Stockfish 8 (in other words, it'll likely lose to Stockfish 10).

I'm no expert, but I understand Leela is competitive with Stockfish 10 not because she has trained for longer, but because she's doing certain things that AlphaZero didn't do (such as "squeeze excitation" as in the latest Test 40).


Are there statistics on the frequency of tactical motifs?

I'm going to suppose that compiling this sort of data would be nearly impossible because the question is, while it seems very specific, is actually far too broad. As a database developer I face these kinds of scenarios very often. One of my special favorites is just the idea of a date and time. It seems so simple but the second you start to really look at it you see it is in fact very deep and has many facets.

Let's start breaking this apart.
1. We assume you mean in Grand Master level games only.
2. Do you consider only tactical motifs that actually occur in the game or do you consider positions that are directly threatened? These positions would actually be highly important for study because even though they do not occur in the actual game, both players needed to consider them.
3. If you consider positions that do not actually occur over the board, how deep in the analysis do you go?
4. Do you consider tactical motifs that are standard operations like a simple pin or do you only consider tactical motifs used in a combination?
5. Do you consider tactical motifs that occur in any combination or only those that actually work?
6. If you only consider those in combinations that work, what do you mean by "work"?

You see where I am going with this. There are so many things that need to be considered before the data can actually be transformed into something informative that it becomes impractical. This should not really be surprising for a topic that chess players through the centuries have had a difficult time defining: what is a tactic? What is a combination? Is a combination just a set of forcing moves even if it leaves the position exactly equal? What if it leaves the player who initiated it weaker? It's like the US supreme court justice said. We might not be able to define it, but we "know it when we see it." But that sort of definition doesn't help us transform a mass of data into actual information.


Stalemate is defined as the player's whose turn it is to not be in check, & cannot make a legal move (black's only piece, the king, can only move to squares where it will be in check, which is illegal).

By playing Rb6 (or possibly Rxb6), your friend walked into that exact situation. Essentially, she blocked off all the squares the King could move to, which is stalemate (& the result is a draw). It might have been a mistake, or it could have been the best move given the situation.

Additional discussion beyond the original question

If there was a black queen on b6, your friend capturing (Rxb6) was the best move, because they would have to get out of check. They can capture with the queen, the rook, or the pawn, but all three lead to stalemate (a draw is all they can hope for here). If they try to move the king out of check, black takes their queen and has a tiny advantage going into the endgame.

Interestingly, if there was a black bishop on b6 threatening the king, the best move would be to move the king and give up the queen. A rook plus several pawns will eventually overpower a lone bishop in the endgame.

If your friend captured anything other than a queen or bishop on b6, that was a blunder that forced stalemate from a winning position.

If there was no black piece on b6, your friend also had the game basically won. They could have finished it with:

1.Rb8# (Rook moves to the dark square up and to the left of the Queen, and checkmate)

Another option:

1.Qb8# (Queen moves to the same square, and checkmate) among other moves.

The last two cases are perfect examples of how chess can punish or reward you in one move; you can be totally winning and then end up with what is essentially a tie because you messed up.


Online resource for estimating my elo rating using my games?

For example, if I can upload the recent 100 games that I played under
  some standard time control, will there be a way to estimate my elo
  based on how I play?

If, as part of that upload, you also supply the ratings of opponents in the same rating system (i.e. all FIDE or all lichess or all chess.com) for at least 5 of the games in which you score at least half a point, then yes. Of course the moves played would be irrelevant.

The point being that no rating system gives a measure of absolute playing strength. Every single rating system gives a measure of relative playing strength.


Why is 2...e6 the most common move after 1 d4 Nf6 2 c4, but not after 1 d4 Nf6 2 Nf3?

I believe the reason is that from a theoretical point of view it makes a lot of sense to go for the Queen's Gambit declined, only after white has played Nf3. The most aggressive tries for white in the QGD involve Nge2 and f3, aiming for e4, a plan that was introduced by Botvinnik and is still very dangerous. Obviously this isn't possible if white has already played Nf3.

Also if white goes for d4/c4/Nc3 it makes sense to go for the Nimzo-Indian because the Nimzo is theoretically in excellent shape. Whereas the Queen's Indian at least right now is apparently under some pressure.

I would further argue that the Queen's Indian or the Bogo-Indian aren't closer in terms of "set up" to the Nimzo then the QGD. There is actually a very trendy line right now, that can be reached from both the Nimzo and the QGD: The Ragozin variation.

So this isn't a case of Nimzo-setup against King's Indian-setup, it is just the case that the theoretically soundest repertoire for black against d4 is a combination of Nimzo and QGD. With that in mind the statistics make sense: Basically you go for the QGD whenever Nf3 happens, otherwise you keep the Nimzo option open.


Why is 5.c3 the most common move in the Ruy Lopez, Berlin defence, Beverwijk variation?

I'm not really familiar with this variation, but c3 is a typical move in the Ruy Lopez for a couple of reasons: one, which you already mentioned, is to support d4 (and in this variation, d4 has the added benefit of forcing the black bishop to retreat). The other is to open c2 as a retreat for the bishop, which has a tendency to get pushed back by pawns and then threatened with being traded for a knight. In the Ruy Lopez, the b1 knight is often developed via d2.


Searching for a position in the mega database 2020 with ChessBase 15

I am not sure what you are doing wrong. I get plenty of games that way. It is possible you did a previous search that still has some residual information in the "search mask" (this is what ChessBase traditionally called the search feature).

I will first show you how to do that and get results, and then I will show you one or two better ways. First, as you noted, it is important to make sure that the Mega 2020 database is the "reference database". I am going to include full instructions since you may not be the only person to read this.

To set Mega 2020 as the reference database, right-click on it, and open the properties. Click the the "Reference-DB" box", and click "OK"

Next, rather than set the position in the search mask, I suggest that you open a blank board and enter in your Najdorf position. 1.e4 c5 2.Nf3 d6 3.d4 cd 4.Nd4 Nf6 5.Nc3 a6.

Now, open the search mask, and click "Reset" first, and then "Copy Board". Then click "OK. This returns 200,471 games for me.

That said, I really only use this feature when I am looking for generic positions. For example, all positions with pawns on f2, g3, and h4, etc. If I am looking for all Naijdorfs, there are much better ways to get them.

First, you could use the opening keys, and drill down, and open the specific ECO keys that you are looking for.

Next, from any opening position, you can use the "Find Novelty" function. To use this feature, you right-click the board, and click "Find Novelty" or the shortcut is "Shift+F6" (the picture I added is in German as I took it from the help file...it is hard to get a screenshot because the menu closes). You can then sort by the "Notation" column. For many years, this was the best way, but they have since added a much better way if you are looking for a specific position. You mentioned that you do not want to do this, but I have no idea why that would be. I am still going to add this in for others, who may read this.

Enter the position, and simply click the "Reference" tab. You can then refine it by the next move, or just go down to the games at the bottom, and start clicking. It also gives you information about the scoring percentages, and notable players, who played it. For me, this has become the best way to search for specific positions.

I have also been using this method as I watch the "Method in Chess" videos on chess24.com. GM Dorfman mentions the names of the players when he starts, but often it is hard to know the name he said. So, I plug in the starting position, click "Reference", and if you go in far enough, it has limited the number of names enough that you can pick them out of a list even if you could not spell them, and enter them.


Puzzle training: rotating tactical themes or exhausting each one?

Whatever works best for you.

I guess for a beginner it does make sense to see / study different variations of the same theme first. If you feel that it is too easy studying one chapter at a time, i.e. if you can spot the solution within a few seconds, it would make sense to mix it up a bit. You can do this by randomly picking problems from your book or online at sites like chesstempo or lichess or many others that have chess puzzles and that automatically adapt to your strength.

Once you get to more advanced puzzles you will see that the solution usually consists of several motives, e.g. a "clearance" followed by a "fork". At that stage you will not run into the problem of being stuck with one motif.


What chess games have violated commonly accepted principles?

Here are some principles we teach beginners but grandmasters regularly break.

Don't bring your queen out too early.

This principle was successfully broken by Korchnoi in an important match.

[FEN ""]
[Event "Candidates Semifinal"]
[Site "Évian-les-Bains FRA"]
[Date "1977.07.16"]
[Round "6"]
[Result "0-1"]
[White "Lev Polugaevsky"]
[Black "Viktor Korchnoi"]
[StartPly "8"]

1. d4 e6 2. c4 b6 3. e4 Bb7 4. Qc2 Qh4 5. Nd2 Bb4 6. Bd3 f5
7. Nf3 Bxd2+ 8. Kf1 Qh5 9. Bxd2 Nf6 10. exf5 Bxf3 11. gxf3 Nc6
12. Bc3 O-O 13. Re1 Qh3+ 14. Ke2 Rae8 15. Kd1 e5 16. dxe5 Nxe5
17. Be2 Nxf3 18. Qd3 Rxe2 19. Rxe2 Qg2 20. Rhe1 Nxe1 21. Kxe1
Qxh2 22. Re7 Qg1+ 23. Ke2 Qg4+ 24. Ke1 h5 25. Qg3 Qxg3
26. fxg3 Rf7 27. Bxf6 gxf6 28. Re8+ Kg7 29. Kf2 Kh6 30. b4 Kg5
31. Ra8 Kxf5 32. Rxa7 d6 33. a4 Ke6 34. a5 bxa5 35. Rxa5 f5
36. c5 Rh7 37. cxd6 cxd6 38. b5 h4 39. gxh4 Rxh4 40. Ra8 Rb4
41. Rb8 Kd5 42. Kf3 Rb3+ 43. Kf4 Kc5 44. Rc8+ Kxb5 45. Kxf5
Re3 46. Kf4 Re1 47. Rd8 Kc5 48. Rc8+ Kd4 49. Kf3 d5 50. Kf2
Re5 51. Ra8 Kc3 52. Ra3+ Kb4 53. Ra1 d4 54. Rc1 d3 55. Rc8 d2
56. Rb8+ Kc3 57. Rc8+ Kd3 58. Rd8+ Kc2 59. Rc8+ Kd1 0-1

Develop your pieces!

Here we see Polugaevsky successfully play his own variation where he uses the queen to grab a pawn, and then start to think about developing the minor pieces around move 15.

[FEN ""]
[Event "USSR"]
[Site "USSR"]
[Date "1959.??.??"]
[EventDate "?"]
[Round "?"]
[Result "0-1"]
[White "Vladimir Zagorovsky"]
[Black "Lev Polugaevsky"]
[StartPly "22"]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Bg5 e6
7. f4 b5 8. e5 dxe5 9. fxe5 Qc7 10. exf6 Qe5+ 11. Be2 Qxg5
12. O-O Ra7 13. Qd3 Rd7 14. Ne4 Qe5 15. c3 Bb7 16. Bf3 Bxe4
17. Bxe4 Bd6 18. g3 gxf6 19. Kh1 Bc5 20. Rad1 Kf8 21. Rfe1 Qg5
22. a4 Kg7 23. axb5 Bxd4 24. cxd4 Qxb5 25. Qe3 Rhd8 26. d5 Nc6
27. Rf1 exd5 28. Bd3 Qxb2 29. Rf5 Qd4 30. Qc1 Ne5 31. Rh5 Nxd3
32. Qh6+ Kg8 33. Qxh7+ Kf8 34. Rxd3 Qe4+ 35. Kg1 Qxh7 36. Rxh7
a5 37. Rh4 d4 38. Kf2 f5 39. Ke2 Ke7 40. Kd2 Ke6 41. Ra3 Rd5
42. Kd3 Ke5 43. Ra2 Ra8 44. Rh6 Rb5 45. Re2+ Kd5 46. Rf2 Rb3+
47. Kc2 Rab8 48. Rd2 a4 49. Ra6 a3 50. Ra7 R8b7 51. Ra8 Rb2+
52. Kd3 R2b3+ 53. Ke2 Re3+ 54. Kd1 Rb1+ 55. Kc2 Rb2+ 56. Kd1
d3 57. Rd8+ Ke4 0-1

Don't move the same piece twice in the opening.

Although Kasparov didn't win this game, he should get an award for moving the same knight 5 times in the 9 first moves.

[FEN ""]
[Event "21st Linares"]
[Site "Linares ESP"]
[Date "2004.02.20"]
[Round "2"]
[Result "1/2-1/2"]
[White "Garry Kasparov"]
[Black "Teimour Radjabov"]

1. e4 c5 2. Nf3 Nc6 3. Nc3 e5 4. Bc4 Be7 5. d3 Nf6 6. Nd2 d6
7. Nf1 Nd7 8. Ne3 Nb6 9. Ned5 O-O 10. O-O Nxd5 11. Nxd5 Rb8
12. a4 Be6 13. f4 exf4 14. Bxf4 Bg5 15. b3 Bxd5 16. Bxg5 Qxg5
17. Bxd5 Nb4 18. Bc4 d5 19. exd5 Nxd5 20. Qf3 Qe3+ 21. Rf2
Qxf3 22. Rxf3 Nb6 23. Bb5 a6 24. a5 axb5 25. axb6 Rfc8 26. Ra5
c4 27. Rxb5 cxd3 28. c4 Rd8 29. Rd5 Rxd5 30. cxd5 Rd8 31. Rxd3
Rd6 32. Kf2 Kf8 33. Ke3 Rxb6 34. Kd4 Ke7 35. Kc5 Rh6 36. h3
Rg6 37. g4 Rg5 38. b4 h5 39. Rd4 hxg4 40. hxg4 f5 41. gxf5
Rxf5 42. b5 Rf6 1/2-1/2


Why does Stockfish recommend this bishop exchange early on?

I wouldn't say it was a "sacrifice", it was more like an exchange of bishops.
My lichess engine was actually giving me ...Bd6 as the first move.

I don't understand why it wants me to move my bishop to b4 in the first place

Me neither. I doubt anyone here will have an idea. Stockfish doesn't tell us why. If I have to make a guess, I would say the bishop is being blocked by the d4-e5 pawn chain, so it makes sense to exchange the bad bishop off.


Amount of search per decision: GMs versus AlphaZero and Stockfish

I assume you're wondering about the speed of calculating moves. I'm not sure how you would go about figuring out the max #moves a GM can calculate (I guess the experiment runs until they fall asleep?).

I'm an FM and I can calculate a couple of moves per second (1-3), assuming the calculation is trivial enough. For more complicated positions where I need to analyze in the middle of my calculations, the speed significantly slows down to how long I need to analyze. This depends entirely on the complexity of the position. GMs are probably slightly faster than me on average. I'm not sure where the "10 moves per decision" figure came from.

From what I understand of AlphaZero, it uses a very strong intuitive (generated from playing itself thousands of times) combined with Monte Carlo Tree Search. This search plays out random simulations of games, starting from where AlphaZero is calculating, and then the move that ends up scoring the highest is chosen.

Stockfish uses the typical minimax with alpha-beta search algorithm, combined with other algorithms which increase efficiency (esp. iterative deepening). It doesn't calculate to the end of the game in each branch, but instead goes up to a certain point and evaluates the resulting position based off its evaluation heuristics.

As for the speed of moves/second between AlphaZero and Stockfish, it comes down to how fast (on average) they can evaluate one position/node. The overall way they traverse the calculation tree is irrelevant when talking about raw calculation speed. Calculation speed comes down to two things:

The speed of the computer the Engine is running on.
The algorithm used to evaluate a position.

Assuming Stock and AlphaZero are given equal computers, then on average I would assume AlphaZero is faster (I don't have any official sources for this though). This is because it evaluates based off a very fined tuned intuition which it learned by playing itself over and over. Meanwhile, Stockfish uses evaluation heuristics thought up by humans. They're very good heuristics, but still only human made.

On ChessBase, Stockfish evaluates over 1 million nodes/positions per second. I don't know what AlphaZero's speed is, but when they eventually publish the engine you could check it out then.


Deciding on an n-variable for an Elo rating system

It appears to be basically historical. From Arpad Elo's The Rating of Chess Players, Past and Present:

The present range originally took 2000 as the upper level for the strong amateur or club player, and arranged the other categories above and below (1.26)
Category designations and proficiencies among federations have become generally more comparable with the adoption of the Elo system by FIDE and by many of its member federations, but the numbers assigned to any given level of chess proficiency remain entirely arbitrary. Both the class subdivision into 200 points and the choice of 2000 as the reference point were already steeped in tradition when this author arrived on the scene. [...] These features were retained for their general acceptance by the players. (1.27)

In particular, the Elo system was designed to produce ratings on approximately the same scale as the Harkness system, which had already been in use by the USCF since the 1950s. The ~200 points per class difference in the Harkness system falls out of the simple equations used to describe that system.


What sort of strategies unfold on this elongated board?

As soon as you change the chessboard in chess, you have to re-assess the relative value of the pieces, as a piece's value is directly affected by its mobility and scope. Note that this is already the case in game on the conventional 8-by-8 boards since how much activity our pieces can benefit from depends on how much space we control, which itself depends on the pawn structure, etc. So in any game, the relative values are changing constantly based on the configuration of the pieces. Thus, to answer your question about finding viable strategies, we first have to develop a good feel for how the values of our pieces are being affected when placing them on a longer board.

What we seem to have is an l-by-8 chessboard where l denotes the length of the elongated side (units being a square's side, or simply the count of squares). Since we've only scaled one dimension of the board, here the vertical one, then only pieces that move vertically (or generally laterally) can benefit from the scaling of the board, as they gain mobility (number of legal moves available to them) proportionally to l. The only pieces that satisfy this kind of movement are the queen and the rooks, so clearly:

Rooks and queens are the most important pieces here and have a higher relative value to the other pieces (for l>8) w.r.t the known relative values on a 8-by-8 chessboard.

So in short, the scope of our queens and rooks become greater on the longer board and whatever strategy we adopt, should emphasise the activity (and protection) of these pieces, specially early on if we are to achieve any small advantage.

Now let's see how much the other pieces are affected:

Bishops: since we don't scale the board in both dimensions (and thus not changing the long diagonals), bishops's scope remains roughly the same. For example, when centralised they will have at most 14 legal moves on an empty board, while they have 13 on the 8-by-8. Moreover, they will have to go through a long zigzag across the board until they see the opponent's pieces (so they cost many tempi). Most importantly, we no longer have long diagonals that span the board, i.e., bishop fiachetti are much less meaningful now since they cannot eye the opponent's kingside or queenside, let alone taking away squares from their camp. So bishops, despite being still fast pieces, seem to be less effective on a longer board.
Knights: Knights as always are rather very slow pieces, and here it's the same. So naturally, for their activation they will cost us even more tempi that the bishops. Moreover, their scope is not affected by the scaling of the board (it would if l<8). So everything being the same, just placed on a longer board, will render knights into even slower pieces, thus their relative value suffers as well w.r.t the 8-by-8 case. Lastly, knights are particularly good when they can be estalished centrally and on permanent outposts: i.e. a square that is well covered by our own pawns but impossible to attack by our opponent's respective pawns. However, since the longer board means the pawns take l times longer to advance to anywhere near our opponent's camp, we will not be able to create meaningful outposts for our knights anytime soon. So, early on specially, knights seem to be rather useless.
Pawns: as already hinted at in the previous point, pawns will be ever slower the longer the board is. This means for a good chunk of the early game, we cannot secure any valuable space with our pawns. More importantly, there are no pawn moves that take away squares (and thus options) from our opponent's camp at the beginning, which makes a strong case for the fact that on an l-by-8 board with l much larger than 8, white's extra tempo becomes negligible and the game is already equal from the get-go. For the contrasting case of 8-by-8 see e.g. the discussions here.
Kings: King safety becomes funny to judge now, on the one hand, one can argue the king is even safer on the l-by-8 since our opponent's pieces are so far away which makes it very difficult for any threats to be made, which gives us lots of tempi to re-arrange our pieces however we want. On the other hand, if we are to start a long journey with our pieces to eventually reach the opponent's side, our king might be left stranded far away from our coverage and thus rather exposed (e.g. as soon as bishops, rooks and queens can sneak through the structure to reach our king). And if all this means that we need to collectively move our pieces towards the enemy, so they can constantly eye one another, then our advancement speed is bottlenecked by that of the king's... What is roughly the same, is the fact that the board still has edges, so castling our king so it can be tucked away to a corner and only accessible from one side is still possible, but how much of protection that offers, is hard to judge.
Rooks and queens: We have already covered those in the starting discussions.

So in a nutshell, our reassessment of the pieces is:

Rooks and queens are made even stronger relative to the other pieces.
Knights and pawns are made weaker since their mobility is not affected and they have only become slower (since it takes longer for them to cross the board and reach the opponent's side).
Bishops are neither here nor there: their scope is roughly the same (e.g. in terms of legal moves) but they are still quite fast pieces, and with a few zigzags they can cross the board and create threats or coordinate eventually with our heavy pieces. So they remain strong, but less than their worth on an 8-by-8 board since there are no long diagonals spanning the board. But clearly among minor pieces, they are definitely much stronger than knights on the elongated board.

Two basic strategies to consider:

Now that we have a better idea for how the relative value of our pieces is being affected by elongating the board, we have a better chance of finding good strategies. The obvious things that come to mind:

Use your early tempi to quickly activate your queen and rooks in order to already pose threats to your opponent, e.g. by being the first in having an active rook, you will be the first to slow down the advance of your opponent's pawns, and that ought to be your first easy way of gaining a small plus.
Once your heavy pieces activated, I see two separate options: (1) creating a small squad and moving that towards the opponent's side or (2) moving collectively all of our pieces across the board, which is safer since our king is less likely to become stranded compared to (1).

Let's delve bit deeper into each:

In (1): say your two bishops, the two rooks and the queen, that's a 5 piece squad that can coordinate an attack against your opponent rather quickly, either to win material, or to try and bait tension on one side, and sneak through on the other side with a heavy piece. Infiltrating behind your opponent's pieces and winning potentially lots of material, this is more the middle game since we're assuming our opponent's pieces are somewhat close to the center of the board. Admittedly, this strategy resembles more what typically occurs in the strategy game Stratego, where pieces have well-defined ranks which acts as their strength (a lower rank cannot capture a higher one etc), and thus, one typical strategy is to infiltrate our opponent's camp with a small squad of high ranked pieces and mop up their pieces (assuming we know where the bombs are...).
In (2): ultimately, once the gap in space between our pieces and our opponent's have become smaller, the gameplay will approach that of the conventional chess on an 8-by-8 board, and thus we can adopt our usual mindset and conventional strategies become viable again, which means we'll have a more normal game than in (1).


To illustrate what was discussed in the comments above...

If we can exclude computer bugs, or other problems (there were no other pieces on g1, or f1 were there?), the situation you describe is only possible if:

the last black move was a promotion of a pawn to a queen on e1 (this pawn could have come from e2 or by capture from f2), and...
a black rook or queen was positioned on h2, g2 or f2

One example of such situation:

[FEN "2k5/8/8/8/8/8/3Kp1r1/7R b - - 0 1"]

1... e1=Q+

The technical term for this situation is Double Check and the only response to a double check is a king move as capturing one piece would still leave your king exposed to a check from the other piece.

For the example above, the only legal moves are 2. Kd3 or Kxe1. If the black queen on e1 was protected by another piece (e.g. by a black bishop from g3), the only legal move for white would be 2. Kd3.


Assessment of O'Kelly Sicilian side line

Black's move 5...e5 seems questionable to me. The move 6. Nf5!? is a little unusual but definitely playable. The only well-known player ever to have tried it was Jacek Bednarski, who used to obtain a draw in one of his games in the Polish national championship back in the 1960s. Bednarski is best known for losing game #55 in Bobby Fischer's "My 60 Memorable Games."

The move is a good line in a club setting because it is provocative and will take your opponent out of the book. It has good surprise value, and the resulting positions are not standard patterns which a player will be familar with, therefore, White will definitely have the edge in preparation.

In my opinion, Black is better off playing in a non-committal fashion with 6...Nf6 and aiming for g6 later.

After:

[FEN ""]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 a6 5. Nc3 e5 6. Nf5 Bxf5 7. exf5 Nf6 8.Bg5 Be7 9. Bxf6 Bxf6 10. Qd5 Qd7 11. g4

White has a small but definite advantage.


Best Continuation for this Counter to Queen's Gambit Accepted

At that point Black is simply equal and there is nothing you can do to change it ( you would do better to play e4 instead e3 but ...e5 still solves all of Black's problems ). If you wish to play e4 instead of e3 then you need the book Lars Schandorff-Playing the Queen's Gambit ( 2012!) and be sure to get the  second edition ( first was in 2009 ). He covers this line quite well.

Your best bet is to try and steer the game into main lines with isolated queen pawn. There you will find subtle move orders that may offer you a small advantage. I can not remember the details, so I can not show you the lines, but the position you aim for is something like this :

[Title "Typical position for QGA"]
[StartFlipped "0"]
[fen "r1bq1rk1/pp2bppp/2n1pn2/8/2BP4/2N2N2/PP2QPPP/R1BR2K1 b - - 0 1"]

You will need good coverage of this opening as theory changes rapidly. I can recommend the following books:

To learn how to play with the isolated queen's pawn you can get Andrew Soltis-Pawn Structure Chess ( 1995 ) ( perhaps my answer to this question can help you too; if you need further help feel free to ask by leaving a comment ) and for Queen's Gambit accepted I will recommend the one written by Semkov & Sakaev or J.Rizzitano-How to beat d4. You can also get Starting out-Queen's Gambit Accepted ( 2006 ) if you need to grasp the basics.

SUMMARY:

Play Bxc4, then Nf3 and try to get into favorable line of the QGA. If you fail to do so, do not panic! You are both fine, better player wins here! Learn how to play these positions and you will have equal chances to win the game.

Good luck and best regards!


What is the highest number of forced checkmates in a legal position?

The answer to this has already been given as an answer in a related question. That answer was 55.

[Title "Ludwig Zagler, Feenschach 1972"]
[FEN "1rB1Q1Q1/1PRQ3Q/2b2k2/2pQ1N1Q/4KRPp/5N2/1R6/B3nn1b w - - 0 1"]

The position is taken from Tim Krabbe's website. According to Krabbe:

  There are 12 mates by Rb2; 1 by g5; 1 by Qd5; 7 by d7; 7 by Qe8, 7 by
  Qg8; 6 by Qh5; 6 by Qh7; and 8 by Nf5, for a total of 55.

The record with both sides to move is 39 according to this Matplus.net thread.

[Title "Ludwig Zagler, Fairy Chess 6/1974"]
[FEN "6B1/2p2R1B/2P1k1NR/2P1q1PP/1pp1Q1p1/brn1K1p1/1b1r2P1/n1b5 w - - 0 1"]


No, absolutely not. You are putting your king in check first from the Qd5.

If you think about this way: Who could take the other king first since that really is what checkmate is? In this case, Kxg2 Qxg2 captured the white king first, and only after would Bxg8 take the black king...White lost the king first.

Your thought also does not hold up to logic: White makes an illegal move, so black cannot?


Why is White's accuracy 99.7% instead of 100.0%?

Probably, as you pointed out, Bb5 instead of Bc4.
The Ruy Lopez is considered very very marginally better/more critical than the Italian by humans, so it'd make sense that the engine used here'd agree.
Certainly, however, the Italian is fine, and the difference is very marginal.


Understanding Carlsen's resignation in the rook and pawn endgame vs MVL

Intuitive plan

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

Annotated diagram

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

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


This is a tough question and depends a lot on where the f8 Bishop is going (b4, c5, e7, or even g7), as well as where is the Knight g1 is going (e2 or f3).

In the position of the diagram the most common move among top players is 4...Bc5. Then after 5.e3 with the idea to place the Knight g1 in e2 and to control the square d5 with the Bishop in g2, Black can still react by temporarily sacrificing a pawn with 5...d5 6.cxd5 Nb4 and a wild game. If Black prefers a more positional battle with 4...Bc5 5.e3 a6, then White prefers to expand on the queen-side: 6.Cge2 a6 7.0-0 0-0 8.a3 Ba7 9.b4 with a very flexible play.

Check this nice game between Nakamura and Grandelius at Gibraltar in 2015 (even if the move order is more subtle)


How should one decide which rook to put on a central file?

Essentially, you should ask yourself a broader question: where should both of my rooks go in this position? There might be another (half-)open file which can be used by the other rook. If there's only one open file and little chance of another one opening or a pawn needing extra protection, it might not even matter which rook you use, since it's rather likely for the rooks to be doubled up on the same file anyway.

[FEN "r4rk1/ppp2ppp/3p4/8/8/3P4/PPP2PPP/R4RK1 w - - 0 1"]

In a position like this (ignoring the position of other pieces) it's more common to move Rfe1, since the chance that one of the a, b and c pawns needs extra protection combined is greater than the chance that f2 becomes weak. Indeed, that's the nearest rook, as you already mentioned.


The Lucena is one of the most important endgame positions to know, and the nickname for it helps a bunch when trying to figure it out over the board. Remember this phrase - "Building a Bridge."

The idea is to get your rook to the fourth rank. Although the move looks rather odd, the idea is simple. Once you bring your king out, he needs to be protected. Your king can advance all the way to the fifth rank, and after the check the rook can block and your pawn can queen. Allow me to use your example to demonstrate the Lucena:

[fen "1K1k4/1P6/8/8/8/8/r7/2R5 w - - 4 1"]

1. Rd1+ Ke7 2. Rd4! Rb2 3. Kc7 (3. Ra4 Kd7 4. Ka7 Kc7 5. b8=Q+ Rxb8 6. Rc4+ {works as well, as referenced by @dfan in the comments}) Rc2+ 4. Kb6 Rb2+ 5. Kc6 Rc2+ (5... Rb1 6. Rd5! Rc1+ 7. Rc5 Rb1 8. Rb5) 6. Kb5! Rb2+ 7. Rb4

And the pawn queens easily. The very first check is important because it forces the opposing king an extra file away from the queening square. As you can see, in the final position the black king is one tempo too slow to stop the pawn from reaching the eighth rank.


To play a position, an engine is usually given a search depth. Arena always does this. Probably in your case the search depth was set to a limited number of nodes. You can check this by keying in CTRL+L. The adjust level box pops in. There, you can see how the depth was specified, whether a time limit, a nodes limit, a search depth limit or an infinite depth.


Playing Kg2 in this position would "put your king in check" in that the black king is attacking that square already. So, no, that would be an illegal move.
The fastest way to checkmate in this position would be Qd4 (forcing the black king to move to h2) followed by Qh4#.


As stated in my comment, I don't think this is a puzzle because there is no clear decisive tactical sequences.

A good move would be 13...Qe7, putting pressure on the e4 pawn and prepare for ...Bxc3. If White did nothing, Black could then continue with ...Be5 and ...Qf6. Note that it's unlikely a bishop pair can be retained in this position, as White can start the exchange by 14.Nd5 Bxd5.


Is learning the English Opening helpful for learning the Sicilian Defence? How about vice versa?

I'd say learning the Sicilian is great for playing the English. Ideas from the Closed Sicilian, King's Indian attack and many others appear all the time in the English with reversed colors.

However, I don't think it works the other way around, as the main lines in the Sicilian come form the opened variation, where the extra tempo is often critical and therefore the ideas played change way too much.


FIDE norm chance expectation calculation question

Given the new requirements, I tried to do a calculation. I couldn't find one on the internet suitable for this task, but this one suggests that for one game between a 2150 and a 2450 player, the following probabilities hold (from the standpoint of the weaker player):

win   4.5%
loss 75.1%
draw 20.4%

To get a score of 4.5 or more, which is needed to score a TPR of at least 2450, the following results work:

5 or more wins              (0.0023%)
4 wins, and 1 or more draws (0.0434%)
3 wins, and 3 or more draws (0.0842%)
2 wins, and 5 or more draws (0.0490%)
1 win,  and 7 or more draws (0.0045%)
            9 draws         (0.0001%)
-------------------------------------
                             0.1835%

(you need some combinatorics to get the percentages)

So he will succeed once every 545 tournaments, on average.

It will depend on the strength of the opposition. To take two extremes: if your opponents all have a rating of 1000, you'll always win but never be able to get a TPR of 2450 (9/9 gives a TPR of +700). Conversely, if you're playing nine Stockfishes/Houdinis, rated 3300, you'll score 0/9 but that would give you a TPR of 2600. So the probability you're looking for can be 0%, 100% and everything in between.


If 1. e4 c6 is considered as a sound defense for black, why is 1. c3 so rare?

"Reversed" Openings in general

A black defense and its white mirror counterpart will often play out quite differently (compare the rather sharp Sicilian Defense and the rather quiet English Opening).

The right to move matters, in both ways. By moving, you give away information to your opponent - the set of variations you can choose from shrinks with every opening move. Early moves are usually played to either proactively increase your control over the board or reactively counter your opponent's moves (the best moves do both). This second category of moves only make sense as answer to one of the first category: If your opponent doesn't play a move that you have to react to, you'd want to play a move to advance your own plan rather than a "counter" to a plan your opponent has not committed to yet. Commitment is an important factor here. If you parry right before knowing which side your opponent will commit to, they can now simply swing left and catch you off-balance. Even if they cannot immediately strike that way, you will still have wasted time you could have used for more useful moves. The further in advance your opponent knows what setup you are heading for, the easier it is for them to screw your plan.

Most openings are a series of moves reacting to each other. Simply playing a "reversed" opening won't lead to the same result because the dynamics can be totally different depending on who strikes first.

Caro-Kann vs. 1.c3

The Caro-Kann defense strategically centers around the d5 square. Playing 1...c6 merely is a means to the end of playing 2...d5 next turn and being able to take back on d5 with a pawn if White plays exd5. Playing 1...d5 right away is certainly possible (leading to the Scandinavian Defense), but then Black concedes that he has to take back on d5 with a piece, when he will obtain a half open d- instead of c-file (generally speaking, a half-open c-file and two center pawns are more desirable than a half-open d-file and only one center pawn). Of course, White can refuse to take on d5, but that's the idea.

Now, let's have a look at the same idea, but from the white side. Sure, White can play 1.c3 to prepare 2.d4. But since Black obviously did not have time to play ...e5 yet, this is simply not necessary and White can play 1.d4 right away! Now Black won't even be able to play ...e5 with ease (the best moves: activity as well as prevention). Isn't preventing the black pawn from entering e5 not much better than preparing to attack it with 1.c3 after the fact? And remember, Black did not commit to this pawn move yet anyways and may answer 1.c3 with a completely different move, leaving White look rather silly for preparing against something that may never happen.

On the other hand, if Black does not play ...e5, White doesn't actually have to defend d4 by playing c3 ... and the c-pawn is free to be moved to c4, from where it attacks d5. If it now gets traded for Black's d-pawn, we may actually arrive at a similar situation as in the Caro-Kann exchange variation: White has pawns on both central files and a half-open c-file.

To no surprise (and in contrast to 1.c3), 1. d4 2. c4 is one of the most popular ways to open the game as White of all time. So why not go for a Queen's Gambit if you like the Caro-Kann?


1.e4 Nf6 2.e5 Nd5 3.c4 Nb6 4.c5 Nd5 is known as the Chase Variation and is playable, though not considered to be particularly great for White.

At the highest levels, the most popular variation for White is the Modern Variation, 1.e4 Nf6 2.e5 Nd5 3.d4 d6 4.Nf3. However, Black is left with a lot of freedom about how to continue, so White needs to be ready to handle a lot of continuations.

At club level the most common continuation seems to be the Exchange Variation, 1.e4 Nf6 2.e5 Nd5 3.d4 d6 4.c4 Nb6 5.exd6 (note that moves 3 and 4 are often reversed). Play proceeds differently depending on how Black recaptures the pawn.

The most aggressive (and most principled) choice for White is the Four Pawns Attack, 1.e4 Nf6 2.e5 Nd5 3.d4 d6 4.c4 Nb6 5.f4. White stakes out a ton of space but has to prove that he hasn't become overextended. Play often becomes very tactical.


Why should black not capture the knight here?

What comes to my mind (maybe someone can check with a computer):

After 10.Nxd5 ed 11.Bxd5 the rook is attacked and you have the motif of playing Bxf7+. The bishop cannot be taken because the king has to keep defending the queen. So after 11…Rb8 12.Bxf7 Ke7 you already have three pawns for the piece, i.e. material is equal and the black king has lost the right to castle and will come under attack. Possibly giving the exchange with 11…Be6 is better, but even then the intermediate check 12.Bb5 looks very nasty (After Bd7 there is always Re1+ as well and the maybe Bg5 ...).


What are the names of the seconds for Anand vs Gelfand WCC 2012?

Anand's seconds are:

Peter Heine Nielsen
Rustam Kasimdzhanov
Surya Shekhar Ganguly
Radosław Wojtaszek

Gelfand's seconds are:

Alexander Huzman
Michael Roiz
Evgeny Tomashevsky
Pavel Eljanov
Maxim Rodshtein
Levon Aronian (to a lesser extent)

Gelfand discussed his preparation and seconds in a post-match interview with chessvibes.com.


Check out en passant... a very common rule to overlook.


What are some activities besides chess which help improve chess play?

There's probably no better way to improve chess than to study chess.  I did seem to make an improvement by getting obsessed with Shogi, however.  But this is a close relative of chess.

Actually, I would recommend a more physical hobby (rugby, rodeo clown, being a double-naught spy) to give yourself a break from the game.  If you don't get burned out, you'll probably enjoy the game more and improve naturally.


Training to avoid elementary mistakes long into tournament games?

Fatigue leads to errors of judgment. Fatigue in long games manifests as 'seeing things that aren't there' and 'not seeing things that are there." As stated before, current health status, conditions of the room, even how much sleep was gotten the night before, are factors. Actually, errors in judgment is an integral part of the game, or as one grandmaster said, "whomever makes the last mistake loses."


How does an engine choose between two moves of equal evalulation?

The answer is simple for traditional engines like Stockfish and the like: if multiple moves have the same evaluation, they pick whichever move was searched first.

All strong alpha-beta engines employ move-ordering heuristics which guess the moves that are likely to be strongest in a position, before actually searching those moves. This is advantageous because the best case for alpha-beta search (especially for PVS) occurs when the strongest move is searched first, allowing beta cutoffs to occur as soon as possible and also avoiding repeated searches.

So when two moves are found to have the same evaluation, the tie is broken by move ordering heuristics.

Evaluation granularity also plays a role. Stockfish evaluates positions to the nearest 1/256th of a pawn, but only reports evaluations in 1/100th of a pawn, so there could be internal differentiation which is not visible to a user. MCTS engines like Lc0 make decisions based on the number of nodes searched in the subtrees of each move. This information wouldn't make sense to report as centipawns, so a conversion function is used. If many nodes have been searched, multiple moves may map to the same centipawn evaluation even if they can be differentiated internally.


Is the Ulvestad variation playable for black?

First, I think this is an excellent question for this forum, so thanks for posting it. I'm going to use a mix of computer analysis with stockfish and crafty, and the chesstempo game database to respond.

Your main question: Is Ulvestad playable for black? I think is a definite yes. There are many options unexplored still, but I think even in your specific game black can at least draw with 20. ... f5 to counter 20. Bd3, and it's not a picnic for white, either--they have to play fairly precisely to keep it even. I'll get back to this at the end.

To avoid making this overly long (I can tell it's going to be long!), I'll just point out some of the unexplored options you don't cover in the question. For example, move 8 isn't set in stone with 8. cxd4, there are also:

8. Ne4
8. Nxf7
8. h4

But we'll continue down your line with 8. cxd4 Qxg5 9. Bxb5+ Kd8, after which the options for white look like:

10. O-O Rb8 11. Bc6 exd4 12. d3 Qf5 13. Re1 Nf6 14. Nd2 Qxd3 ... (+0.80 D25 - stockfish)
10. Qf3 exd4 11. Bc6 Nb4 12. Bxa8 Nc2+ 13. Kd1 Bg4 14. Kxc2 Qc5+ ... (+0.56 D25 - stockfish)

After 8. cxd4 Qxg5 9. Bxb5+ Kd8 10. O-O there are another few potential options:

10. ... exd4 11. Bc6 Rb8 12. d3 Qf5 13. Re1 Nf6 14. Nd2 Qxd3 15. Nb3 Qxd1 ...(+0.60 D29 - stockfish)
10. ... Rb8 11. Bc6 exd4 12. d3 Qf5 13. Re1 Nf6 14. Nd2 Qxd3 15. Nb3 Qxd1 ...(+0.60 D29 - stockfish) (transposes to above)
10. ... Bb7 11. Qf3 exd4 12. d3 Qe5 13. Nd2 Bd6 14. g3 a6 15. Ba4 Qf6 ... (+0.72 D29 - stockfish)
10. ... Qg6 11. dxe5 Rb8 12. Nc3 Nf4 13. Qf3 Bb7 14. Qg3 Nxg2 15. d4 Nh4 ...(+.80 D29 - stockfish)
10. ... Bg4 11. Qb3 Nf4 12. dxe5 Bd7 13. Qg3 Qxg3 14. fxg3 Ng6 15. Nc3 Bc5+ ...(+.84 D29 - stockfish)

Again, we'll go with your line, 8. cxd4 Qxg5 9. Bxb5+ Kd8 10. O-O Bb7 11. Qf3, to which there are a few ideas possibly worth looking deeper at:

11. ... Rb8 12. dxe5 Ne3 13. Qh3 Qxg2+ 14. Qxg2 Nxg2 15. d4 Be7 16. Be2 Nh4 (+0.72 D26 - stockfish)
11. ... exd4 12. Re1 Be7 13. d3 Qf6 14. Nd2 Rb8 15. Bc4 Nb6 16. Qxf6 Bxf6 (+0.76 D26 - stockfish)
11. ... Qf4 12. Qxf4 exf4 13. Nc3 Nb4 14. Rb1 Bd6 15. d3 Nc2 16. d5 Nd4 (+1.01 D26 - stockfish)

Again we'll go with your line, 8. cxd4 Qxg5 9. Bxb5+ Kd8 10. O-O Bb7 11. Qf3 Rb8 12. dxe5 Ne3 13. Qh3 Qxg2 14. Qxg2 Nxg2 15. d4, and again black has several responses to explore:

15. ... Be7 16. f4 Nh4 17. Nc3 Nf3+ 18. Kf2 Nxd4 19. Rd1 c5 20. Be3 Bf3 (+0.84 D26 - stockfish)
15. ... f6 16. Be2 Nh4 17. f4 Bb4 18. Nd2 Nf5 19. Nc4 Ke8 20. Rd1 fxe5 (+0.92 D26 - stockfish)
15. ... Nh4 16. Bg5+ Be7 17. Bxh4 Bxh4 18. Nc3 Bf3 19. Rab1 Rb6 20. Bd3 Kc8 (+1.01 D25 - stockfish)
15. ... Kc8 16. f4 Nh4 17. Kf2 c5 18. Be3 Bg2 19. Nc3 Bxf1 20. Rxf1 cxd4 (+1.05 D25 - stockfish)

We're almost to the line you left us, but you can see you probably had several other possibilities. We'll continue with the line: 8. cxd4 Qxg5 9. Bxb5+ Kd8 10. O-O Bb7 11. Qf3 Rb8 12. dxe5 Ne3 13. Qh3 Qxg2 14. Qxg2 Nxg2 15. d4 Nh5 16. Bg5+ Be7 17. Bxh4 Bxh4 18. Nc3 Bf3 19. b3 Rb6 20. Bd3, which presents us with an interesting position.

It looks like my f5 idea was pretty good, as it seems to be a solid draw for black if both sides play perfectly (as far as I can tell). Interestingly enough, computers don't tend to see f5 until they get 30 deep or so. The goal being to get the h8 rook involved ASAP. If white slips up, they can be in for some pain.

There are two reasonable responses to 20. ... f5:

21. Ne2 Rg6+ 22. Ng3 Rf8 23. Rae1 (+0.32 D28 - stockfish)
21. Bxf5 Rc6 22. Nd1 Rf8 23. Ne3 Bg5 24. Bg4 Rg6 25. Bxf3 Bxe3+ 26. Kh1 Bxd4 (+0.00 D28 - stockfish)

The rest look like probable bad news:

21. e6 Rxe6 22. Bxf5 Rc6 23. Rac1 Rf8 24. Bd3 Bg5 25. Rc2 Rf4 (-0.92 D28 - stockfish)
21. exf6 gxf6 22. Bc4 f5 23. Rfe1 Rg6+ 24. Kf1 Rg2 25. Re3 Rxf2+ (-1.53 D28 - stockfish)
21. Rfe1 Rg6+ 22. Kf1 Rg2 23. Re3 Rxf2+ 24. Kg1 f4 25. Rxf3 Rxf3 (-2.14 D28 - stockfish)
21. Rfd1 Rg6+ 22. Kf1 Rg2 23. Rd2 Rxh2 24. Ke1 Bg5 25. Rdd1 c6 (-2.70 D28 - stockfish)

I let stockfish think about this position for several hours, and when it gets to about 30-31 deep, the score for both of the best moves dwindles to 0.00 or 0.08 (which indicates a likely draw). I played out several scenarios which involved different colored bishops and rooks that had easily defended pawns, but that couldn't obviously make progress. Or Rook+Knight vs Rook+Bishop. There were a few times that black had a bishop traded for a couple of pawns, but couldn't do anything with it. Never got to a 6 piece EGTB position--always too many pawns leftover. If someone can find a win for white with 20. ... f5, I'd like to see it!

Update 6-20-2012

21. Bxf5 seems to be a bad choice after 21. ... Rc6 22. Rfc1 Rf8.

I haven't looked at other moves other than 22. Rfc1 deeply yet (such as 22. Rac1 and 22. Nd1), but white doesn't have many good options at 23. 23. Bxh7 looks like it has potential, but after 23. ... g6 the bishop becomes hard to use. 23. Bd3 is in second place so far, 23. Bd4 is in third, and 23. Bb1 is in fourth, but they all score negative with 30 depth.

21. Ne2 looks like it offers white a few chances for draw by repetition several moves in. This line, for example (I need to check some of the others for black to see if there's something better than 21. ... Rg6+, but that seems unlikely): 21. ... Rg6+ 22. Ng3 Rg5 23. Rac1 f4 24. Rc3 Rf8 25. Rfc1 c6 26. Bb5 fxg3 27. hxg3 Bxg3 28. fxg3 Rxg3+ 29. Kh2 Rg2+ 30. Kh3 Rg6 31.Bxc6 Rh6+ 32.Kg3 Rg6+ 33.Kh3 ends with a pretty straightforward draw by repetition drawish looking position:

Another update: 21. Ne2 Rg6+ 22. Ng3 f4 23. Rfc1 Rg5 24. Rc3 Bb7 looks promising for black.

Update: Here is some analysis, if anyone is interested: http://mongochess.skeweredrook.com/ulvestad-variation


Is pawns supporting pawns a good opening strategy?

Using pawns to support pawns is a common practice.  However, it seems you're taking it too far; in the beginning of the game you probably want to focus on controlling the center and getting some pieces into the game.

Moving pawns without reason can cause holes and reduce at least one bishop to uselessness.  It can make your king hard to defend.

Play through some master games and see how they do it; they don't move a lot of pawns.


It means both.  The 'center' is most common defined as d4, d5, e4, and e5.  (The squares immediately around these are also sometimes included.)  Pieces in the center have greater mobility and flexibility than those on the edges.  The knight in the corner versus a knight in the center is the classic example.  A bishop in the center may attack b8 and h8.  The same bishop on g2 is still powerful, but can't immediately control the opponent's king-side.

Putting pawns in the center cramps the opponent and removes his options.  If you control the center squares, you can begin thinking about working pieces into strong-points on the opponent's side of the board.  Pawns on the the 5th rank can protect pieces on the 6th.  These pieces are seriously in the opponent's business.

EDIT

It's hard to keep the queen or a rook in the center (during the middle game) since the opponent's minor pieces will probably be able to drive them away. Also, controlling the center doesn't mean your just plop your pieces and pawns in the center, but that you can keep them there.  Finally, controlling the center is only a means to an end.  Once your pieces are qualitatively better than your opponent's, you must strive for the win.


Why is this the solution to this puzzle?

There is a lot more to this, and this is really not a great tactics problem as much as it is a continuing the attack problem. The difference is that with a tactic problem, you can see the result all the way to the end. Other positions, you have just a feel for it, and you know that you are probably winning, but you have to play what you can calculate, you get there, and then you calculate more of the attack. Often, you do this while calculating places you could take a forced draw if it is not working out.

A great example of that is the game Dubov-Svane (here with copyrighted annotations), which I will give below. It was one of the best games of the year.

The move Qc7 is an example of why I am not a fan of online puzzles that have been computer checked, but no strong player has evaluated. After Rf6, if you do not take, you simply lose, and thus, Qc7 is not even an option to consider. The only lines that are important are the ones that include gf, but more importantly, the ones that include Bxe5, which comes closer to defending for a human than any other move.

 [FEN "2r3k1/5pp1/1q1bpn1p/pB1pN3/P2P4/5R2/1P3PPP/3Q2K1 w - - 0 1"]

 1. Rxf6 Bxe5 {This may be the most testing try in practice.} (1... gxf6 2. Qg4+ Kh7 (2... Kh8 3. Nxf7+ Kh7 4. g3 {The threat is Qe6.} Bb8 5. Qh4 Kg7 6. Qxh6+ Kxf7 7. Qh7+ Kf8 8. Qh8+ Kf7 9. Qxc8 $18) (2... Kf8 $2 3. Nd7+ Ke7 4. Nxb6 Rc1+ 5. Bf1 $18 {This is obviously important to see.}) 3. Bd3+ f5 4. Bxf5+ exf5 5. Qxf5+ Kh8 6. Qf6+ Kh7 7. Qxf7+ Kh8 8. Ng6#) 2. dxe5 gxf6 3. exf6 Kf8 (3... Kh8 4. Qd2 Kh7 5. Bd3+ Kg8 6. Qxh6 $18) (3... Kh7 4. Qd3+ Kh8 5. Qd2 Kh7 6. Bd3+ Kg8 7. Qxh6 $18) 4. Qd2 Rc6 5. Qxh6+ Ke8 6. g3 d4 {It is clear that that is heading to a queend ending, so maybe d4 would give some counter-chances under slightly more favorable circumstances.} 7. Qh7 d3 8. Qg8+ Kd7 9. Qxf7+ Kc8 10. Qg8+ Kb7 (10... Kc7 11. Qg7+ Kb8 (11... Kd6 12. Qe7+ Ke5 13. Bxc6 Qxc6 14. f7 d2 15. Qg5+ Ke4 16. Qe3+ Kd5 17. Qxd2+ $18) 12. Bxc6 Qxc6 13. f7 $18) 11. Bxc6+ Qxc6 12. Qh7+ Kb6 13. Qxd3 {There are other lines in here, but this line represents a moves that try to fight back until it is finally over totally.}

Here is that fantastic attack my Danil Dubov, which illustrates my point. Dubov most likely did not see everything from move 22 through to move 39, but rather, he saw chunks at a time, and there were probably places he could have bailed out with a draw. This type of attack, while containing tactics, is not one big tactic. I would describe the problem above in the same way, assuming that black played the best practical defense with 1...Bxe5 trying to keep equal material while trading off the key Ne5 attacker.

 [Event "EU-chT 22nd"]
 [Site "Batumi"]
 [Date "2019.10.31"]
 [Round "7.4"]
 [White "Dubov, Daniil"]
 [Black "Svane, Rasmus"]
 [Result "1-0"]
 [ECO "D37"]
 [WhiteElo "2699"]
 [BlackElo "2592"]
 [PlyCount "77"]
 [EventDate "2019.10.24"]
 [EventType "team-swiss"]
 [EventRounds "9"]
 [EventCountry "GEO"]
 [WhiteTeam "Russia"]
 [BlackTeam "Germany"]
 [WhiteTeamCountry "RUS"]
 [BlackTeamCountry "GER"]
 [FEN ""]

 1. c4 e6 2. Nc3 d5 3. d4 Nf6 4. Nf3 Be7 5. Bf4 O-O 6. e3 b6 7. Qc2 Ba6 8. O-O-O dxc4 9. Ng5 Nc6 10. a3 g6 11. h4 Bd6 12. g3 Qe7 13. h5 e5 14. hxg6 hxg6 15. Bg2 exf4 16. Bxc6 fxg3 17. Kb1 Rad8 18. f4 Bc8 19. Rde1 Kg7 20. Nd5 Nxd5 21. Rh7+ Kg8 22. Rxf7 Rxf7 23. Qxg6+ Kf8 24. Qh6+ Rg7 25. Bxd5 Ke8 26. Qh5+ Kd7 27. Qh3+ Ke8 28. Qh5+ Kd7 29. Be6+ Kc6 30. Qf3+ Kb5 31. Bxc4+ Ka5 32. Qd5+ Bc5 33. b4+ Ka4 34. Qg2 Bxb4 35. Qc6+ Kxa3 36. Bb3 Bd7 37. Qc1+ Kxb3 38. Qc2+ Ka3 39. Qa2# 1-0

P.S. The only "logic" to it is that someone, who was not that strong fed it to a computer, and posted only the computer's best moves, but not the ones that would challenge a human the most.


Online tools for scheduling teams round-robin events

What you are really looking for is a pairing program which will perform team round-robin pairing, allow you to enter results and display the results online.

There are two obvious candidates, one expensive and deluxe, and one cheap (free on Linux) which requires a bit more work on your part.

The expensive option is Swiss Manager. This does everything you could want and more but it costs 150 euros for the full version and 75 euros for the light version (limit 60 players / 11 rounds). This includes a website (chess-results.com) where your tournaments can be viewed.

The cheap / free option is Vega. It is free on Linux. On Windows and MacOS it is free for up to 30 players (individual tournament) and 8 teams (team tournament). I paid 50 euros for the full Windows version a few years ago.

Something which is new, which I see for the first time (new since the end of 2019), is that now it also has its own website like Swiss Manager. This is https://www.vegaresult.com/vr/. If you have up to 8 teams or you would run it on Linux then this looks like a very good free solution. Previous versions would generate the HTML for you to copy and paste into your own website. This could still be very useful for more tech-orientated clubs / administrators.


How can I send a UCI command to a chess engine in Python?

First, engine.options["NeverClearHash"] is wrong on two counts.
It is engine.option, not engine.options and that command queries the value rather than sets it.

To set the value you have to do something like:

engine.configure({"NeverClearHash": 1})
or perhaps:
engine.configure({"NeverClearHash": true})

Good programmers are never too proud to read the manual. I wholeheartedly recommend it.


Is it possible to manually alter initial values in a chess engine?

Yes. You can download the source code for Stockfish here. Once you have done that you need to work out where the evaluation functions are and change them according to your requirements. Then recompile and run.


Under the requirement of treating the attacked queen as if subject to check, 31 plies is possible. Additionally, there is not a White ply to spare here!
[FEN ""]
[startply "31"]

1. c4 d5 2. Qa4+ Nc6 3. d4 Bh3 4. g4 Rb8 5. Na3 b5 6. Nxb5 a6 7. Qxa6 Nxd4 8. Nxd4 f5 9. Nxf5 Nh6 10. Nxh6 dxc4 11. Be3 c3 12. f4 Qd7 13. Nxh3 Qd8 14. Nf2 Qd5 15. Rd1


What are the fastest vertical checkmates for both castlings?

Mate in 6.0 for kingside.

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 "]
1. e4 e6 2. Bc4 Bd6 3. Ke2 Qg5 4. Kf3 Nh6 5. Bxe6 fxe6 6. Qe2 O-O#

And 5.5 for queenside, even faster.

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 "]
1. d4 Nc6 2. Nc3 Nxd4 3. Qxd4 e5 4. Qc4 Ke7 5. Bg5+ Kd6 6. O-O-O#

This should be fastest.


Creating opportunities for tactics other than by enemy mistakes

Theoretically if both sides play perfectly the game should be drawn.  Someone has to make a mistake for the other side to win.  According to that logic, material-winning tactics would not be possible without an error, an unlikely scenario I know.  Or to invert that, if such tactics were possible, by definition a mistake must have occurred.  If you are gaining space, protecting everything and looking for imbalances that you can exploit, I'm not sure there's much else you can do, particularly against someone else who is doing the same.


What are the best opening moves and plan for a "pawn plus 2 moves" handicap game?

I do feel that in case of this 'game format' the best is probably playing 1.e4, d4 as first two moves. This way white open both diagonals for bishops and form a formidable stronghold in the center (yet unanswered threats due to the fact that you can make a move only later with black). White can 'pack a punch' much faster in this case, also they will need to play either d3 or d4 later to develop the other bishop. So, why wait!?

If you consider 2 ... e6 (after: 1. e4 ... 2. d4  e6)

Then if 3. Qh5+ g6 4. Qe5 Nf6 5. Nc3 (if 5. Bg5?! then 5. ... Be7 or Bg7 with complications where black may regain initiative due to weak white queen and a quick possibility to use file 'f' in potential counter-attack)  leads to complications where two extra tempos for white can be a really good handicap, however white's queen is a bit exposed and can become a positional weakness.

Other than that you got what you got - one pawn down and two tempos behind! Well, try to:

counter center offensive first by blocking white's pawns advances
protect the king by castling
use file 'f' to counterattack (if you give away f-pawn of course)


What can you deduce from my performance in different types of chess tactics?

Chess tactics frame different positions which we sometimes come across the Board . It may be Double attack , fork , Pin and many others . Just solving the Chess tactics lone is never the measurement because when you solve a tactic you know already that there is a sacrificial or a combinational move which will make you win or help to solve the tactic . In real games sometimes you even get an easy position but you fail to find the best move OTB .

Solving tactics just make you at ease that you are doing something and practicing Chess but it is never the complete homework to make the best judgement .

A different way to find the performance measurement is that how good you are making a calculation or even finding your own weaknesses in specific patterns . like for an example you have a habit of leaving your piece hanging in your own games . So you must solve tactics relating to Hanging pieces which will help to improve your weak point . They say in whichever tactic you find it difficult to solve you have a weakness in that area .


Experience of big difference between Elo and national rating?

As you suspect this can easily happen, if only very few tournaments are Elo rated, and the players are still developing in strength. The problem is often exacerbated by the lower k-factor in Elo, which means that Elo changes more slowly.

Despite not really being an up and coming player anymore, my Elo is still catching up to where it should be according to my national rating and, alas, I expect that to continue for quite some time.


Why did GM Godena resign in this position?

Transmissions can be inaccurate in real-time. I once saw 1.e4 a6 in a Follow Chess game, but it was actually 1. e4 c5.

In the real game, GM Godena lost on time.


Who is/was the lowest ranked World Chess Champion?

To answer my own question, numbers shown in bold below are the FIDE ranking of the player at the time they were crowned World Champion. Before 1964 there was no ranking system as far as I know. Ranking taken from FIDE rankings site and this chess USA education webpage.

Undisputed world champions 1886–1993
?? Wilhelm Steinitz (1886–1894)
?? Emanuel Lasker   (1894–1921)
?? José Raúl Capablanca (1921–1927)
?? Alexander Alekhine   (1927–1935, 1937–1946)
?? Max Euwe         (1935–1937)
?? Mikhail Botvinnik    (1948–1957, 1958–1960, 1961–1963)
?? Vasily Smyslov   (1957–1958)
?? Mikhail Tal      (1960–1961)
01 Tigran Petrosian (1963–1969) (first unofficial rankings list 1964)
02 Boris Spassky    (1969–1972)
01 Bobby Fischer    (1972–1975)
02 Anatoly Karpov   (1975–1985)
02 Garry Kasparov   (1985–1993)

Classical (PCA/Braingames) world champions 1993–2006
01 Garry Kasparov   (1993–2000)
03 Vladimir Kramnik     (2000–2006)

FIDE world champions 1993–2006
02 Anatoly Karpov   (1993–1999)
44 Alexander Khalifman  (1999–2000)
02 Viswanathan Anand    (2000–2002)
07 Ruslan Ponomariov    (2002–2004)
54 Rustam Kasimdzhanov  (2004–2005)
03 Veselin Topalov  (2005–2006)

Undisputed world champions 2006–present
09 Vladimir Kramnik     (2006–2007)
01 Viswanathan Anand    (2007–present)

Next undisputed world champion ?
04 Viswanathan Anand
20 Boris Gelfand

And as I write this Anand has won game 8.

Also, an interesting quote from Alexander Khalifman responding to his very low ranking at the time of his crowning FIDE world champion in 1999:

  "Rating systems work perfectly for players who play only in round robin closed events. I think most of them are overrated. Organizers invite the same people over and over because they have the same rating and their rating stays high."

Of course he would say that but perhaps some truth there.


Level the field when letting computers play against each other

You absolutely should, which is why the two most important computer chess tournaments (CCC and TCEC) both make all competitors play on the "same" hardware. "Same" in inverted commas because the recent advent of neural-network engines like AlphaZero, which run best on GPUs, meant that it's no longer fair to play on exactly the same hardware for everyone.

You can see the result of not using equal hardware from the 2019 WCCC results, which Komodo won. Komodo is almost a hundred elo behind Stockfish when run on equal hardware (and Stockfish doesn't play in the WCCC, because it's not a commercial engine and doesn't have full-time staff to attend the event).

The situation right now is traditional engines run on the same CPUs, NN engines run on the same GPUs, and whenever traditional engines play against NN engines, they run on consensus fair hardware. "Fair" here is a very controversial word, because there are several different measures of what is fair that I'm glossing over. Suffice to say unless you are a hardware expert yourself, I'd just trust the admins of CCC and TCEC to use something that's fair.

Edit: to illustrate the impact of hardware, here's the list of hardware the competitors played at in the 2019 WCCC. Note Jonny ran on 1200 (!) cores, and it just barely edged out Ginkgo, which was running on 1/20 of the cores. In TCEC Season 14, the two engines played with the same hardware in Division 1, and Ginkgo comfortably finished ahead of Jonny in spite of multiple crashes (which happen because Ginkgo doesn't run well at 43 cores; they result in auto-losses).

You can also see that these games were played is Division 1, not even Division Premier. Many of the strongest engines in the world simply don't participate in WCCC. I don't know the exact reasons why, but I'm confident hardware is a major issue for participants. In turn, this lack of participation is partly why the community don't take the WCCC very seriously.


What ELO is it good to learn and play the Kings Indian Defense OTB?

Elo points don't matter. Just play what opening you feel comfortable with most. If you play it well intuitively, then go ahead.


How is this retrograde analysis position legal?

White has made 6 captures. Clearly the h-pawn made at least 2, and the g-pawn 1. Meanwhile, the b-pawn made at least 1 (a7/c7), and the a-pawn at least 2 (to the b-file, then to either a7/c7). So White's c-d-e-f pawns made no captures, and thus Black's central pawn fence must have at some point had holes to allow them through. This requires 4 pawn captures, which is all that White has lost (knights and bishops).

Here is a stupid method.

[fen ""]
1. h4 Nh6 2. e4 f6 3. e5 Kf7 4. e6+ Kg6 5. f4 Ng4 6. f5+ Kh5 7. Nf3 a6
8. Ne5 fxe5 9. f6 Ra7 10. f7 Ra8 11. d4 Ra7 12. Bg5 Ra8 13. Bf6 exf6
14. Na3 Bb4+ 15. Ke2 Bd2 16. f8=R Bg5 17. hxg5+ Nh2 18. e7 Kh4 19. e8=R Ra7
20. Re6 Ra8 21. Rb6 Ra7 22. Rb3 Ra8 23. Re8 Ra7 24. Re6 Ra8 25. Reb6 Ra7
26. R6b4 Ra8 27. d5+ Kh5 28. g6 Rf8 29. Rg1 Rf7 30. gxf7 Ng4 31. f8=R Nh6
32. Re8 Nf7 33. g4+ Kh4 34. g5+ Kh5 35. Re6 Nc6 36. g6 Nb8 37. gxf7 Nc6
38. f8=R Nb8 39. Rc6 Ra7 40. Rcc3 Ra8 41. Re8 Ra7 42. Re6 Ra8 43. Rec6 Ra7
44. R6c4 Ra8 45. Rcg4 Ra7 46. R4g2 Ra8 47. Rbg4 Ra7 48. R4g3 Ra8 49. d6 c6
50. Nc4 Ra7 51. Ne3 Ra8 52. Nd5 cxd5 53. Rcf3 Kh6 54. c4 Ra7 55. c5 Ra8
56. c6 Ra7 57. c7 Ra8 58. Kf2 Ra7 59. Bb5 Ra8 60. Bc6 dxc6 61. Qe2 Bf5
62. c8=R Qe7 63. d7 Bd3 64. d8=R Bb5 65. a4 Ra7 66. axb5 Nd7 67. b6 Nc5
68. bxa7 Ne6 69. Rbe3 Nc7 70. b4 Qf7 71. a8=R Qg6 72. b5 Qg5 73. b6 Kg6
74. bxc7 Kf7 75. Ra7 Qf5 76. Rgc1 Qe6 77. Ke1 Qe7 78. Rd6 Qe6 79. Rcd8 Qe7
80. R8d7 Kf8 81. c8=R+ Qe8 82. Rcc7 Qf7 83. Re6 Qe7 84. Kd2 Qd6 85. Ree7
Qc5 86. Rf7+ Ke8 87. Rec3 Qb5 88. Qc4 Qb6 89. Qc5 Qb5 90. Qd6 Qb6 91. Kc2
Qc5 92. Kb2 Qc4 93. Rca3 Qc5 94. R3a2 Qb6+ 95. Rb3 Qb4 96. Rgc3 Qb5 97. Rc5
Qb6 98. Rb4 Qb5 99. Rgc2 Qxb4#