Testing Monte Carlo Tree Search
When Deep Mind unveiled their AlphaZero, it broke the chains of status quo irrevocably on a variety of fronts. On the one hand, there was their self-learning neural network, and on the other, there was their use of the MCTS search system, which is vastly different from the hitherto ubiquitous alpha-beta search system that ruled the day.
Because of how new it is, very little advanced development has been made to fine-tune it, and as a result, it still performs worse on a pure Elo level. However, Mark Lefler, the chief programmer of Komodo, has been working hard with nearly daily breakthroughs, and promises to release updates soon (“but [we] are waiting for the rather significant daily Elo gains to slow a bit.”), available for free to owners of Komodo 12.
That said, what is the value of this new MCTS system, and does it work even when not coupled to a neural network? The answer is a very vocal ‘yes’.
Have you ever watched a game of Magnus Carlsen, as he does his unique boa constrictor act on his opponents, and wondered how he seemed to be able to win these ‘drawn’ endgames? Perhaps you are watching with one of the top engines, and it invariably says the position is dead drawn until all of a sudden with the snap of a finger Magnus is winning. Is it Voodoo? Hypnotism? Or was the engine just wrong? It is actually none of these things.
What a player such as Carlsen does is to outplay his opponents, even though the evaluation by the engines is a big fat 0.00. How can he be outplaying them if the evaluation never changes? Behind the curtains of that game, he is slowly reducing the number of available moves to his opponent. At first, they might have three or four perfectly viable choices, all of which draw, but as the game proceeds, they now only have two or three viable choices, until before long they are walking a tightrope act with only one move to keep it together or lose.
For classic engines, as long as there is one single move that can save, they will declare it a draw. Objectively, they are not wrong, since that one saving move does save, and it is there, but that doesn’t begin to tell the story. MCTS search looks at the various options, some losing, some winning, and some drawn, and chooses the move that offers the best chances to win or save. Naturally, if there is only one right move, it must choose it, but if given a fork in the road, then much like Carlsen, it will choose the continuation that presents the most practical chances.
In order to illustrate this, GM Karsten Mueller has shared a few examples that show the difference, and value, of this sort of analysis:
Tricky to the end — Part 1
71.Rbf2?! 71.Kh1!? b4! 71...Qh6+? 72.Rh2 Qe3 73.Rhc2+ Kd1 74.Rf2 Qh6+ 75.Kg1 Kc1 76.Rbe2 Kd1 77.Ra2+- 71...Qe1+? 72.Kh2 b4 73.Ra2 Kb1 74.Rgb2+ Kc1 75.Ra1+ Kxb2 76.Rxe1 Kc3 77.Kg2 b3 78.Kf2 Kxd4 79.Ke2 Kc3 80.Rc1++- 71...Qxd4? 72.Rbf2 Qh8+ 73.Rh2 Qxh2+ 74.Kxh2 b4 75.Rf5 b3 76.Rxd5 b2 77.Rc5+ Kd2 78.Rb5 Kc1 79.Kg2+- 72.Rxb4 72.Rbf2 Qxf2 73.Rxf2 b3= 72...Qh6+ 72...Qe1+? 73.Rg1+- 73.Kg1 73.Rh2 Qe3= 73...Qe3+ 74.Kh2 Qh6+= 71...b4! 72.Kh1 Qh6+ 73.Rh2 Qxh2+ 74.Kxh2 b3 75.Kg2 b2 76.Rf1+ Kc2 77.Kf2 b1R 78.Rxb1 Kxb1 79.Ke3 Kc2 80.Kf4 80.Kf4 Kd3 81.Kxg4 Kxd4 82.Kf5 Ke3 83.g4 d4= ½–½ - Start an analysis engine:
- Try maximizing the board:
- Use the four cursor keys to replay the game. Make moves to analyse yourself.
- Press Ctrl-B to rotate the board.
- Drag the split bars between window panes.
- Download&Clip PGN/GIF/FEN/QR Codes. Share the game.
- Games viewed here will automatically be stored in your cloud clipboard (if you are logged in). Use the cloud clipboard also in ChessBase.
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Gaifullin,A | 2413 | Van Foreest,L | 2485 | ½–½ | 2017 | D35 | 27th EY BU16 2017 | 9.3 |
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In the next example, we see the MCTS search play like a grandmaster, not because of 'perfect' moves, but for making it as hard for the opponent as possible to keep control.
Tricky to the end — Part 2
Replay and check the LiveBook here |
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50...Rxf3!? 50...Ra3?! 51.Rxa6 b3 52.Ra8 b2 53.Rb8 Rxa5 54.Rfb3= 51.gxf3+ Kd3 52.Rxa6? 52.Rb6! Kc4 52...Bxb6? 53.axb6 b3 54.b7 b2 55.b8Q+- 53.Rxa6 b3 54.Rc6+ Kb5 55.Rc1 Kxa5 56.Kg3 Be3 56...Kb4 57.Kg4 b2 58.Rb1 Kb3 59.Kf5 Kc2 60.Rxb2+ Bxb2 61.f4= 57.Rc3 Bf4+ 58.Kg4 Kb4 59.Rc8 b2 60.Rb8+ Kc3 61.Rc8+ Kd2 62.Rb8 Kc2 63.Rc8+ Kb1 64.Kf5= 52...b3 53.Ra8 53.Rb6 Bxb6 54.axb6 b2 55.b7 b1Q-+ 53...e4! 54.Kg2 54.fxe4 b2 55.Rb8 Be5+-+ 54.a6 b2 55.Rb8 Be5+-+ 54...e3 55.a6 55.Kf1 e2+ 56.Ke1 Bc3+-+ 55...e2 55...e2 56.Re8 b2 57.a7 Bxa7 58.Rd8+ Bd4-+ 0–1 - Start an analysis engine:
- Try maximizing the board:
- Use the four cursor keys to replay the game. Make moves to analyse yourself.
- Press Ctrl-B to rotate the board.
- Drag the split bars between window panes.
- Download&Clip PGN/GIF/FEN/QR Codes. Share the game.
- Games viewed here will automatically be stored in your cloud clipboard (if you are logged in). Use the cloud clipboard also in ChessBase.
- Create an account to access the games cloud.
Goh,W | 2446 | Bosiocic,M | 2616 | 0–1 | 2017 | B48 | Helsingor Xtracon op | 9 |
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In the following position, White exploits some tactics to give Black more trouble than he had imagined.
Unexpected troubles
Replay and check the LiveBook here |
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88.Rxg5!? 88.Bc4?! 88...Rd7? 88...Re3! 89.Kf6+ 89.Be4 hxg5= 89.Kf4+ Rxd3= 89...Rxd3 90.Rg7+ Kh8 91.Rg6 Kh7= 88...Rf7+? 89.Ke6+ Kh8 90.Kxf7 hxg5 91.Kg6+- 88...hxg5? 89.Kf6+ Kh6 90.Kxe7 Kg7+- 89.Be4! hxg5 89...Rf7+ 90.Ke6+ Kh8 91.Kxf7 hxg5 92.Kg6+- 90.Ke6+ Kh6 91.Kxd7 Kg7 92.Ke6 92.Ke6 Kh6 93.Kf5 Kg7 94.Kxg5+- 1–0 - Start an analysis engine:
- Try maximizing the board:
- Use the four cursor keys to replay the game. Make moves to analyse yourself.
- Press Ctrl-B to rotate the board.
- Drag the split bars between window panes.
- Download&Clip PGN/GIF/FEN/QR Codes. Share the game.
- Games viewed here will automatically be stored in your cloud clipboard (if you are logged in). Use the cloud clipboard also in ChessBase.
- Create an account to access the games cloud.
Blagojevic,D | 2495 | Sahin,O | 2226 | 1–0 | 2017 | E62 | 31st Belgrade Trophy | 2.4 |
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As the grandmaster explains, it is a mistake to just push one's pawns blindly forward in an endgame with passed pawn by both sides.
When the knight trumps the bishop
Replay and check the LiveBook here |
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78.Nf5!? 78.f5 78...Kd3? 78...Bd5+! 79.Kg3 79.Kh3?! Be6 80.Kh4 80.Kg4? Kd3-+ 80...Bxf5 81.Kg5= 79...Kd3 79...Be6 80.g7 Kd3 81.Nxe3 Kxe3 82.f5 Bg8 83.Kg4 Ke4 84.Kg5 Ke5 85.Kg6 Kd6 86.f6 Ke6= 80.Nxe3 Kxe3 81.f5 81.Kg4 Ke4 82.Kg5 Bc4 83.g7 83.f5 Ke5 84.f6 Ke6= 83...Bg8 84.f5 Ke5 85.f6 Ke6 86.Kg6 Bf7+!= 81...Be4! 82.Kg4 Kd4 83.Kg5 Ke5 84.f6 Ke6 85.f7 Ke7= 78...Be6? 79.Nd4+ 79.Ng3+ Kd3 80.Kf3 Kd4 81.f5 Bd5+ 82.Kf4 Bc4 83.f6+- 79...Kd3 80.Nxe6 e2 81.g7 e1Q 82.g8Q+- 78...Kd2? 79.Ng3 e2 80.Nxe2 Kxe2 81.f5 Bd5+ 82.Kg3 Be4 83.Kf4+- 79.Ng3 Bd5+ 79...e2 80.Kf2 Be6 80...Kd4 81.Kxe2 Kd5 82.Kf3 Ke6 83.f5+ Kf6 84.Kf4+- 81.Ke1! Bc4 82.f5 Kd4 83.f6+- 80.Kh3 e2 80...Kd4 81.Kg4+- 81.Nxe2 Kxe2 82.f5 Be4 83.Kg4 Ke3 84.Kg5 1–0 - Start an analysis engine:
- Try maximizing the board:
- Use the four cursor keys to replay the game. Make moves to analyse yourself.
- Press Ctrl-B to rotate the board.
- Drag the split bars between window panes.
- Download&Clip PGN/GIF/FEN/QR Codes. Share the game.
- Games viewed here will automatically be stored in your cloud clipboard (if you are logged in). Use the cloud clipboard also in ChessBase.
- Create an account to access the games cloud.
Zhao,Y | 2401 | Huang,R | 2156 | 1–0 | 2017 | D30 | CHN Team Men 2017 | 9.3 |
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Chess Endgames 14 - The golden guidelines of endgame play

Rules of thumb are the key to everything when you are having to set the correct course in a complex endgame. In this final DVD of his series on the endgame, our endgame specialist introduces you to the most important of these rules of thumb.
In the next and final example, the grandmaster cannot help himself as his teaching instincts take over and he serves up a highly illustrative example of Rauser's Drawing zone. Most readers will be familiar with the concept of the h-pawn and the wrong bishop to ensure a win, but there are exceptions, as below:

As GM Mueller explains: "Black wins, if he can force White's king to leave the zone illustrated by the green squares, permanently."
Almost counterintuitively, White played 98.Kb4?? and lost. See the game to know how and why.
The exception confirms the rule
Replay and check the LiveBook here |
Please, wait...
62.Ke2!? 62.b5?! 62.Kg1!? 62...Kf5? 62...Kd5 63.Kf3 Kc4+ 64.Kxg3 Kxb4 65.Kf4 Kxa5 66.Ke3 Kb4 67.Kd2 Kb3 68.Kc1 Ka2-+ 63.d7 Bxd7 64.Kf3 Ke5 65.Kxg3 Kd4 66.Kf2 Kd3 67.Ke1 Kc2 68.Ke2 Bc6 69.Ke1 Bb5 70.Kf2 Kd2 71.Kf3 Bc6+ 72.Kf2 Bb5 73.Kf3 Ba4 74.Kf2 Kc3 75.Ke3 Kxb4 76.Kd2 Kb3 77.Kd3 Bb5+ 78.Kd2 Kb2 79.Kd1 Bc6 80.Kd2 Be4 81.Kd1 Bd5 82.Kd2 Bf3 83.Ke3 Bg2 84.Kd2 Kb1 85.Kd1 Bc6 86.Kd2 Ba4 87.Kc3 Kc1 88.Kb4 Bc6 89.Ka3 Kb1 90.Kb3 Bd5+ 91.Ka3 Ka1 92.Ka4 Ka2 93.Kb4 Kb2 94.Ka4 Bc6+ 95.Kb4 Bb5 96.c6 Bxc6 97.Kc4 Bb5+ 98.Kb4? 98.Kd4 Kb3 99.Ke3 Kc3 100.Kf2 Kb4 100...Bd3 101.Ke3 Bg6 102.Ke2!= 101.Ke3 Kxa5 102.Kd2 Kb4 103.Kc2 Ka3 104.Kb1= 98...Be2 99.Ka4 Bd1+ 100.Kb4 Bb3 101.Kc5 Kc3 102.Kb6 Bc4 103.Kc5 Bf1 104.Kd5 Bg2+? 104...Bd3! 105.Ke5 Kb4 106.Kd4 Bh7 107.Ke3 Kxa5 108.Kd2 Kb4 109.Kc1 Kc3-+ 105.Kc5? 105.Ke5! Kc4 106.Kf4 Kb4 107.Ke3 Kxa5 108.Kd2 Kb4 109.Kc2 Ka3 110.Kb1= 105...Bb7 106.Kb6 Kb4 0–1 - Start an analysis engine:
- Try maximizing the board:
- Use the four cursor keys to replay the game. Make moves to analyse yourself.
- Press Ctrl-B to rotate the board.
- Drag the split bars between window panes.
- Download&Clip PGN/GIF/FEN/QR Codes. Share the game.
- Games viewed here will automatically be stored in your cloud clipboard (if you are logged in). Use the cloud clipboard also in ChessBase.
- Create an account to access the games cloud.
Chibnall,A | 1906 | Gonzalez Gonzalez,A | 2192 | 0–1 | 2018 | B28 | Gibraltar Masters 2018 | 4.114 |
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As you can see, the MCTS search has valuable insights to offer by its very own nature. Hopefully it will also help you make the most of your resources.
Correction June 19th: GM Dr Karsten Müller agrees that the definition as originally given above for "Rauser's drawing zone" was not correct, and it has been amended.

Komodo 12
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