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Missed Blocking Tactic

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Lately, I’ve been playing blitz games against MadChess 3.3 (not yet released) to get a feel for how strongly it plays when weakened to my patzer Elo level. Sparring against MadChess helps me calibrate its limit-strength parameters and perhaps glean ideas for classifying more unreasonable inferior moves.

My most recent game begins 1.e4 c5 2.Nf3 d6 3.d4 Nf6 4.Nc3 Nc6 5.Bb5 a5 6.Be3 d5 7.e5 Ng4 8.Qd2 Nxe3 9.Qxe3 cxd4 10.Nxd4 Qd7 11.O-O f5 12.e6 Qd6 13.Nxf5 Qxe6 14.Qxe6 Bxe6 15.Nd4 Bd7 16.Rad1 g6 17.a4 Nb4 18.Rfe1 h5 19.Rd2 b6.

So far I’ve played well enough for a player of my strength in the limited time available in 3m+2s blitz. I’ve developed my pieces, protected my king, and weakened Black’s pawn structure near its king. Material is even. I’ve missed opportunities to advance or attack with my central pawns, but haven’t outright blundered. I spot Black’s weak c7 square and realize my knight on d4 can reach it via e6 because Black’s light squared bishop is pinned to its king by my bishop on b5 and cannot capture on e6. If I can get my knight to c7 it will fork Black’s king and rook on a8.

r3kb1r/3bp3/1p4p1/pB1p3p/Pn1N4/2N5/1PPR1PPP/4R1K1 w kq - 0 20

I play 20.Ne6 and MadChess replies 20…Bxb5. Black trading bishops improves my position as it enables me to place a knight on the b5 outpost, controlling Black territory without fear of harassment from any Black pawns. Black should have developed the dark squared bishop via 20…Bh6 to harass my rook on d2.

r3kb1r/4p3/1p2N1p1/pb1p3p/Pn6/2N5/1PPR1PPP/4R1K1 w kq - 0 21

I should have played 21.Nxb5 to capture Black’s light squared bishop and place a knight on an outpost. But I was fixated on the fork on c7. Play continues 21.Nc7+ Kf7 22.Nxa8 Bh6.

N6r/4pk2/1p4pb/pb1p3p/Pn6/2N5/1PPR1PPP/4R1K1 w - - 1 23

Damn. By moving its dark squared bishop to a square where it attacks my rook on d2, MadChess also reveals an attack on my adventurous knight on a8. Now I’m under double attack. What to do? I can’t capture either of Black’s attacking pieces, so I should retreat the more valuable of my attacked pieces.

23.Rde2?? Doubling rooks on the e file, but blundering. I move my rook out of the crosshairs of Black’s dark squared bishop but into the crosshairs of the light squared bishop. Doh! I need to improve my “whole board” vision. I was focused on the lower half and upper right portion of the board and failed to see a ranged attack originating from the upper left portion of the board.

N6r/4pk2/1p4pb/pb1p3p/Pn6/2N5/1PP1RPPP/4R1K1 b - - 2 23

While reviewing the game after its conclusion, but before peeking at any engine suggestions, I thought I should have simply retreated my threatened rook via 23.Rdd1 Nxc2 24.axb5 Nxe1 25.Nxb6, which creates a passed pawn for White. However, I have a defensive resource in this position. Can you find it?

I missed this blocking tactic, thinking it was nothing more than a delaying move that loses a pawn. However, we see (in the puzzle above and annotated game below) that Black cannot capture the pawn on f4.

My blunder cost me an exchange and a knight, a net loss of five pawns using traditional material values. I played on, as patzer chess players should, attempting to force MadChess to blunder a piece back to me.

23…Bxe2 24.Rxe2 Rxa8 25.f3 Kf8 26.h3 Bf4 27.Kf2 Ke8 28.g3 Bc1 29.b3 Rd8 30.Re6 Rc8 31.Ne2 Rxc2 32.Rxb6 g5 0-1

But I ran out of time. Overall, a competitive game where MadChess played convincingly like a 635 Elo blitz player. (I’m attempting to calibrate “the feel of” MadChess’ UCI_Elo parameter to chess.com’s blitz Elo ratings. Other chess sites may differ by 200 Elo points or so. See Chess.com Versus Lichess Ratings.) The world-class Komodo Dragon chess engine believes MadChess played slightly worse than I. But as Grandmaster Savielly Tartakower said many years ago, “The winner of the game is the player who makes the next-to-last mistake.”

“The winner of the game is the player who makes the next-to-last mistake.” -Savielly Tartakower

I capitalized on MadChess’ 11… f5?? blunder with the correct 12.e6! and held the advantage (unevenly due to numerous inaccuracies) until I overlooked my 23.f4! defensive resource and this “last mistake” proved decisive.

I have annotated the game with a few variations and comments, which you may review below. In addition, I gave Komodo Dragon, a world-class chess engine, one minute and 60 CPU threads (I have a powerful home PC) to analyze the game and insert its evaluations and suggested variations.

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MadChess 3.2.2 Released

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I have released version 3.2.2 of my chess engine.

This release fixes a bug that caused truncated principal variations when MultiPV > 1. Also, it improves the efficiency of MultiPV search, so it gets deeper faster.

This release does not add any features nor playing strength. Testers may substitute this version for version 3.2 without any need to restart or re-run tournaments.

You may download x64 and x86 versions of MadChess 3.2.2 from the Downloads page. Install the appropriate version for your computer’s CPU. The x64 binary is the strongest version of the engine.

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MadChess 3.2.1 Released

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I have released version 3.2.1 of my chess engine.

This release fixes a bug that caused MadChess to report illegal principal variations. That is, PVs that contain illegal moves. To be clear, the bug never caused MadChess 3.2 to crash. Merely to report fantasy lines.

I didn’t notice the issue back in January because of my desire to transition from programming chess to playing chess- which involves fighting the urge to tinker with one more engine issue. I did wonder why MadChess occasionally reported truncated PVs in the CuteChess GUI. One factor contributing to my (chosen) ignorance is the CuteChess GUI (which I use to run tournaments so I can watch games in progress) silently truncates PVs that contain illegal moves. Whereas the CuteChess CLI (which I don’t use because I cannot watch games in progress) displays a warning. Despite my instinct that a bug infested the PV code, I decided not to go down that rabbit hole until this weekend.

This release does not add any features nor playing strength. Testers may substitute this version for version 3.2 without any need to restart or re-run tournaments.

Thanks to Steve who commented on the MadChess 3.2 Released post that CuteChess CLI complains of illegal PVs.

You may download x64 and x86 versions of MadChess 3.2.1 from the Downloads page. Install the appropriate version for your computer’s CPU. The x64 binary is the strongest version of the engine.

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MadChess 3.2 Released

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I have released version 3.2 of my chess engine.

The main feature in this release is a sophisticated limit-strength mode, including adjustments to chess knowledge, search speed, chance of erring or blundering, and severity of blunders. MadChess, in limit-strength mode, excludes moves it considers unreasonable (dumb moves even a chess novice wouldn’t play). I have extensively documented the settings and technical implementation of MadChess’ limit-strength mode in The MadChess UCI_LimitStrength Algorithm. I also provide a Limit-Strength FAQ.

MadChess 3.2 is slightly stronger than the prior release. I estimate it has gained 60 rating points, climbing to roughly 2770 Elo at bullet chess.

This likely is the last release of MadChess- at least for a long while. I plan to focus more on playing chess instead of coding chess. And I plan to move on to other (non-chess) programming projects. You may follow along on my general programming blog, ErikTheCoder. Nothing new there yet. But I intend to resume blogging there soon. I’ll keep blogging here also, focused as I said on playing the game, not coding it.

You may download x64 and x86 versions of MadChess 3.2 from the Downloads page. Install the appropriate version for your computer’s CPU. The x64 binary is the strongest version of the engine.

Enjoy!

Follow the discussion of MadChess 3.2 in the TalkChess forum.

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Never Resign!!

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The Moral Lesson

I love this video. We’ve all been there, so we can relate. We’ve all screwed up. You don’t have to play chess or even understand the rules of the game to know exactly how Alexandra Botez feels.

Chess is a very difficult, humbling game. But that’s the point. If we only attempted to do what was easy, we never would grow and mature as chess players, as human beings.

I love the raw energy of this video: Alexandra Botez’s obvious frustration. Her cathartic scream…

Fuck!!

How she wards off tilt and steels her nerves. Her determination to play on and make her opponent prove they can win. Her war cry of…

Never resign!!

… when she regains the initiative. The anxiety-inducing ticking of the clock in a one minute bullet game with no increment. (I don’t know how people can play 1 minute bullet. I have enough difficulty managing my time in 3 + 2 blitz .) Her ultimate triumph with only 0.4 seconds left on her clock.

Plus the backing music sounds like an outtake from Metallica’s Death Magnetic album.

The Game

The game begins 1.Nf3 f5 2.d3 Nf6 3.g3 e6 4.Bg2 Be7 5.O-O O-O 6.Nbd2 d6 7.c3 e5 8.e4 fxe4 9.Nxe4 Nxe4 10.dxe4 Qe8 11.Be3 Qh5 12.Qd2 Bh3 13.Ne1 Nd7 14.Bxh3 Qxh3 15.Ng2 Nf6 16.f3 a5 17.Bg5 Rae8 18.Bxf6 Rxf6 19.Qe3 Rh6 20.Kf2 b6 21.Rh1 d5 22.exd5 and arrives at this first critical position.

The game continues 22…Bc5 23.Rae1 Bxe3+ 24.Rxe3 Rf6 25.c4 Qf5 26.Rhe1 Qc2+ 27.R1e2 Qxc4 28.Rd2 Rd8 29.Rxe5 Rfd6 30.Ne3 Qc5 31.Ke2 h6 32.Rc2 Qd4 33.Re4 Qf6 34.Rd2 c6 35.Rf4 Qg6 36.Rg4 Qe8 37.Kf2 cxd5 38.Nf5 R6d7 39.Nxh6+ Kh7 40.Nf5 d4 41.Rh4+ Kg8 42.Rg4 d3 43.Re4 Qf7 44.Rg4 Kh7 45.Nh4 g6 46.Ng2 Kg7 47.Nf4 Qf6 and arrives at a second critical position.

Alexandra Botez captures her opponent’s queen to even the score- actually she’s up one pawn. Capitalizes when her opponent hangs a rook. Then wins two pawns, promotes a pawn to a queen, drives her opponent’s king to a corner, and maneuvers her rook and queen to deliver mate on the back rank a split-second before her time runs out. Amazing!

I gave my chess engine, MadChess (rated 2700 Elo = super Grandmaster), one minute to analyze the game. I also gave one minute to a world-class engine, Komodo Dragon (rated 3500 Elo = much stronger than the best human player). It seems appropriate to give the computers the same amount of time the human players had for the game. You can play through the game below, review suggested improvements by MadChess and Komodo Dragon, and read a few comments and explanations I added.

If you’ve never played chess online, and this video piques your curiosity about what you’re missing, consider signing up at chess.com. Don’t worry, you can play slower-paced games (or games with no clock) than what you see in the video above. You’ll be matched with players of a similar strength as you.