Lc0 v0.18.0 has been released.


Can be downloaded here.



  • Ponder is ON
  • There is per move increment


TCEC Cup in the next days!






And here comes the dangerous part about Leela.


Lc0 v0.18.0-rc2 has been released.

Available to download here.

    Could produce incorrect search results.








Lc0 v0.18.0-rc1 has been released.

The release candidate of a new Leela version has been released:





Change highlights:

  • MultiPV support is added.


GUIDE: Setting up Leela on a Chess GUI.




Leela Chess Zero works with the help of 2 things:



Komodo even had 15 consecutive draws!



Standings so far:


CCCC Stage 2 has started and running.....



Top 2 will promote to the super final.



CCCC rounds 43,44 and 45. First stage is over!




TB Rescoring



  • The data from these games are sent to the server.



CCCC quiz. 12 impressive moves!


CCCC rounds 37 to 42. Leela promoted to 2nd stage!







Probability to promote:
Stockfish 100 %
Komodo    100 %
Houdini   100 %
Fire      100 %
Lc0       99.67 %
Shredder  90.33 %
Booot     81.67 %
Andscacs  77.67 %
Ethereal  44.67 %



A Standard Dataset



Introducing the CCRL Dataset



Baseline results


dataset: num_chunks: 2500000
train_ratio: 0.80
training: batch_size: 1024
num_batch_splits: 1
test_steps: 1000
train_avg_report_steps: 500
total_steps: 200000
checkpoint_steps: 10000
shuffle_size: 250000
lr_values: - 0.1
- 0.01
- 0.001
- 0.0001
lr_boundaries: - 80000
- 140000
- 180000
model: filters: 128
residual_blocks: 10


Potential ideas

  • Testing a multigpu training algorithm
  • Different neural network architectures
  • Different input encoding (e.g. removing history planes)
  • Different move encoding on the policy head
And much more...

Final notes















Top 3 continued with wins but Shredder drew.

265 Andscacs vs Arasan 1-0
266 Xiphos vs Booot 1/2-1/2
267 Crafty vs Wasp 1/2-1/2
268 Vajolet vs Ethereal 1/2-1/2
269 Fire vs Texel 1-0
270 Stockfish vs Fizbo 1-0
271 Fritz vs Shredder 1/2-1/2
272 Senpai vs Gull 0-1
273 Houdini vs Pedone 1-0
274 Nirvana vs Ivanhoe 1-0
275 Komodo vs Nemorino 1-0
276 Lco vs Laser 1-0


First half of the CCCC tournament has ended.
Top 8 engines promote to next round.










CCCC rounds 17, 18 and 19. Leela with 2 wins and 1 draw.

 CCCC continues with Houdini on the lead a full point ahead of the 2nd Stockfish. Houdini till now seems unstoppable and is killing every other engine except for the top ones. Leela is 5th for now even though she won 2 games and drew the other.

Houdini won against Fire in a nice game where after just a single mistake of Fire leaving its Rook in b2 Houdini took the chance and punished it winning the exchange of a Rook for a Knight and after some deep maneuvering it won a Pawn also and the game was essentially over.

CCCC standings, ratings and statistics after round 17.

Chess.com Computer World Championship continues with engines battling for the first 8 positions that would bring them to next stage.
Round 17 has been completed out of 46 that will be played.

Here are some statistics from the games so far:

The crosstable of the engines. Only the first 8 promote to the next round.


CCCC rounds 14,15 and 16. Leela draws against Crafty....

After another 3 rounds have completed and we reached round 16 of 46 that would be played, Houdini continues its comfortable lead being 1 full point ahead of the second. Leela had a nice win against Fritz but didn't manage to win against the weakest engine of the tournament Crafty!


The round of draws. Out of 12 games, the 10 were drawn and only 2 were decided.
Leela was one of them by winning against Fritz. A nice game where in late middlegame she outplayed Fritz creating a strong Kingside attack step by step, with Fritz making not optimal moves and losing tempos for Leela to obtain a Kingside attack.

Another clash of titans with Houdini-Komodo game where in a Ruy Lopez, after all Bishops were traded already in the opening, it got an interesting position with black to have a pressure with double Rooks on the Kingside but white was very solid and black couldn't make any progress so it ended quickly with a draw. Not that quickly over the board of course, since even though after move 68 it was a dead draw for these engines, they were forced to play till insufficient material till move 135.
Shredder while in first 6 games with white had 6 wins, it now dropped another half point with white by drawing with Booot.

157 Ivanhoe vs Andscacs  1/2-1/2
158 Houdini vs Komodo 1/2-1/2
159 Laser vs Gull 1/2-1/2
160 Fritz vs Lco 0-1
161 Nemorino vs Fizbo 1/2-1/2
162 Fire vs Nirvana 1-0
163 Pedone vs Ethereal 1/2-1/2
164 Crafty vs Senpai 1/2-1/2
165 Shredder vs Booot 1/2-1/2
166 Arasan vs Stockfish 1/2-1/2
167 Texel vs Xiphos 1/2-1/2
168 Wasp vs Vajolet 1/2-1/2

Analysis of the Leela-Fritz very nice game:


Time management

As many of you have noticed, Leela's thinking time allocation seems suboptimal for during the CCCC games. It almost doesn't spend any time in the opening, and spends a lot in the endgame.

It's not completely clear whether time management is really as bad as it looks though. In this post I'll explain the time allocation algorithm, its parameters and explain effects that we see.

There are 7 parameters which affect time allocation:

  • --time-curve-peak
  • --time-curve-left
  • --time-curve-right
  • --slowmover
  • --move-overhead
  • --futile-search-aversion
  • --ponder
I agree that 7 parameters is too much, but there are attempts to add some more!

CCCC rounds 11, 12 and 13. Leela 3 draws against top opponents.

 This round saw Leela drawing rather not that comfortably a strong engine and currently in the top 8 engines(the top 8 of 24 engines are promoted to next round) Andscacs. In a strange game in semi-Slav, Meran variation, Leela playing black actually lost the Queenside and was strong in the center opposite of what one actually expects in this opening. By move 30 position for white seemed very good with total dominance on the Queenside and a Pawn of black ready to fall. Yet Leela defended very well and gave the exchange sacrifice giving her Rook for a Knight and because of the exposed white King managed to make a difficult draw.

 Shredder continued its superb performance by having another win with black. While Stockfish managed to get a miraculous save against Fritz, in a game with opposite color Bishops that looked very drawish, it played excellently and finally managed to win. It was the first loss of Fritz that till now had 2 wins and 8 draws!
Ethereal continues to underperform by not managing to win against the weaker Wasp engine.

121 Andscacs vs Lco 1/2-1/2
122 Laser vs Nemorino 1-0
123 Nirvana vs Komodo 0-1
124 Ivanhoe vs Pedone  1/2-1/2
125 Senpai vs Houdini 0-1
126 Gull vs Shredder 0-1
127 Stockfish vs Fritz 1-0
128 Fizbo vs Texel 1/2-1/2
129 Vajolet vs Fire 1/2-1/2
130 Ethereal vs Wasp 1/2-1/2
131 Xiphos vs Crafty 1-0
132 Booot vs Arasan 1/2-1/2


CCCC statistics.

Some statistics about Chess.com Computer Chess Championship till now.

                                  Game length                  Frequency      
                                 1-0   =-=    0-1            1-0      =-=     0-1 
 All games                 78     94     76         33.8%   46.2%   19.8%



Shortest wins (White)

  1:  1-0(35) Pedone 1.8 3090 - Crafty 25.2 3283
  2:  1-0(42) Lc0 17.11089 3300 - Nirvana 2.4 3090
  3:  1-0(51) Ethereal 10.88 3283 - Crafty 25.2 3099
  4:  1-0(53) Shredder 13 3287 - Nemorino 5.00 3287
  5:  1-0(53) Xiphos 0.3.17 3179 - Nirvana 2.4 3099

   Shortest wins (Black)
  1:  0-1(38) Nirvana 2.4 3186 - Booot 6.3.1 3013
  2:  0-1(40) Laser 1.6 3226 - Komodo 2118.00 3226
  3:  0-1(50) Nemorino 5.00 3099 - Fire 7.1 3259
  4:  0-1(61) Vajolet 2.6 3101 - Lc0 17.11089 3226
  5:  0-1(65) Senpai 2.0 3112 - Stockfish 220818 3144

CCCC rounds 9 and 10. Leela with the Knight underpromotion win!


It was the round of draws, with only 4 games to be decided and 8 draws. All top 6 engines drew their games.
Ethereal had a pleasant game as it crashed the aging Crafty while Shredder couldn't take anything out of the opening it had and Laser had no problems so game ended a draw.
A clash of titans happened in this round between Stockfish and Komodo, in a game where Stockfish created a very good attacking position though a little closed and Komodo deployed a very good defense. Stockfish tried for the breakthrough but Komodo defended excellently and the game ended in a draw.
 Leela played against Senpai with black and while it managed to create a complicated game with attacking prospects against Senpai's King, never really managed to go beyond that due to some inaccuracies by playing many moves with her King and delaying the attack. Yet after some shuffling she had a chance to try to push for the win with 59...Kf8! but Leela missed it and played 59...Rc1? that is a drawish.

97 Andscacs vs Nirvana 1-0
98 Nemorino vs Pedone  1/2-1/2
99 Senpai vs Lco  1/2-1/2
100 Laser vs Shredder 1/2-1/2
101 Stockfish vs Komodo 1/2-1/2
102 Ivanhoe vs Texel 1/2-1/2
103 Vajolet vs Houdini 1/2-1/2
104 Gull vs Wasp 1-0
105 Xiphos vs Fritz 1/2-1/2
106 Fizbo vs Arasan 0-1
107 Booot vs Fire  1/2-1/2
108 Ethereal vs Crafty 1-0


CCCC rounds 6,7 and 8....

The Chess.com computer Chess championship continued with most top engines winning their games so little things changed in the top positions.
Leela had a good performance winning 2 games and drawing the 3rd against the mighty Stockfish! It was a boring draw though, with no big fights whatsoever.


 Leela played a very good game against Xiphos that till now has a good performance. On a semi-slav a normally complicated position arose and when black castled long Leela showed it understands the position very well. After some piece trade Leela immediately started to play on the queenside to expose black's position. It's incredible that she has shown big positive evaluations from the very early showing that she knew this is winning. And white was winning because after destroying black's queenside, black had some bad isolated Pawn islands and white a super strong play in Kingside where he could march his Pawns if heavy pieces are traded.

Ethereal on the other side managed with black to have an easy draw, with another French in this tournament, against the co-leader Houdini, while Shredder continued its excellent tournament winning against the strong Andscacs on another French obtaining a strong kingside attack.

The results:
61 Shredder vs Andscacs 1-0
62 Senpai vs Stockfish 0-1
63 Texel vs Pedone 1/2-1/2
64 Nirvana vs Vajolet 0-1
65 Wasp vs Nemorino 1/2-1/2
66 Lco vs Xiphos 1-0
67 Arasan vs Laser  1/2-1/2
68 Komodo vs Booot 1-0
69 Crafty vs Ivanhoe  1/2-1/2
70 Houdini vs Ethereal 1/2-1/2
71 Fire vs Gull 1-0
72 Fritz vs Fizbo 1/2-1/2

Leela Chess Zero - difficult positions. The new world of NN engines!

 Traditional Chess engines with classic Alpha-Beta search, sometimes have huge problems with some positions that require deep planning and understanding of the position. This is because they try to search all possible moves in a position and then their replies and then all the replies of the replies, etc. They discard most moves of course with clever algorithms that prune almost all moves but a few that they focus on. With a cost of course to discard a move, not good looking at first sight, but that after many moves ahead it proves to be a very good one. Traditional engines also have a handcrafted evaluation function. That means in order to judge a position they have to rely on human rules for it, e.g bonus for Rook on open file, bonus if a Pawn is on 6th rank etc, etc.

 Neural net engines with latest advances Deepmind brought with deep learning techniques used to train convolutional neutral networks, like Leela, on the other hand use a much more powerful evaluation function. One that acquired Chess knowledge about every single aspect of Chess by playing against itself millions of games. No need to manually put hundreds instructions like "if it's a closed position then Knight value increases and Rook's decreases" etc. You let them play against itself and they create by themselves millions of such "rules". Leela also uses a MCTS(Monte Carlo Tree Search) type of search that is completely different than traditional AlphaBeta search.

So it's no wonder that Leela plays very frequently now, moves that other top engines like Stockfish, Komodo, Houdini etc, can't find.
In some cases like these that would be shown here, it even plays moves that not a single one traditional engine can find, or that they need very long searching to do!
Of course that doesn't mean Leela finds most deep testpositions because this is not true. Leela is still not that good anyway in testpositions that require tactics. But when long strategical thinking is required without so much immediate tactics, then Leela usually shines!

Test position 1.

White to play.

White has created a nice concentration of its pieces in the Kingside but has many problems to solve, especially with Bxa3 pending that will destroy white's position. Defensive resources of black are big and King's position seems very solid. The c2 Knight is very annoying too for white. Most traditional engines give here black slightly better or even a lot better or even winning!
And want to play moves like Rh6, Bf2, Nd2. Moves that lead nowhere for white and probably are losing.

 But if you let Leela analyze the position(since Leela Chess Zero is just the project name, by saying LCZero, we're referring to the body of her the Lc0 binary that takes the neural net and provides the search, plus the brain of her, and that is the nets/weights, and here i tried about 9 nets and all find the same move) you will see her after only something less than 1 second of thought proposing Qf6+ sacrificing the Queen with a big plus score for white!!
And not only this but she is finding the correct continuation of Ng5 later on that white has to play!  h5 Bxh5 that she is playing are the correct move for black also(the toughest defense) and the best reply by white.


CCCC rounds 3, 4 and 5. Leela with a beautiful win!

CCCC rounds 3 and 4 and 5 were finished. Houdini is on the lead with 5.0/5 while Leela is doing well with 4.0/5.

In round 3 Leela with black against Fizbo, reached a material imbalanced position but with her King exposed she couldn't avoid a perpetual check with a draw.
 One of Leela's weak spots is that she is too weak in recognizing perpetual checks that lead to draw, but in this game this wasn't an issue since it didn't cost her anything because the position was draw anyway.
Xiphos with white also drew Stockfish.

The game of Leela against Fizbo:
[Event "CCCC 1: Rapid Rumble (15|5) Stage 1"] [Site "Chess.com"] [Date "2018.09.01"] [Round "?"] [White "Fizbo 1.9"] [Black "Lc0 17.11089"] [Result "1/2-1/2"] [ECO "B50"] [WhiteElo "3259"] [BlackElo "3226"] [PlyCount "83"] [EventDate "2018.??.??"] [EventType "rapid"] 1. e4 c5 2. Nf3 d6 3. c3 Nf6 4. Be2 g6 5. O-O Bg7 6. Bb5+ Nc6 7. d4 O-O 8. d5 a6 9. Bd3 Na5 10. Bg5 h6 11. Bh4 b5 12. Nbd2 e6 13. b4 Nb7 14. a4 bxa4 15. Rxa4 cxb4 16. cxb4 exd5 17. exd5 a5 18. Ne4 g5 19. Nexg5 hxg5 20. Bxg5 Bd7 21. b5 Nc5 22. Rf4 Nxd3 23. Qxd3 a4 24. Nd4 a3 25. Bxf6 Bxf6 26. Nc6 Bxc6 27. Rg4+ Bg7 28. Qd4 f6 29. Rxg7+ {Leela is very frequently missing these draws from perpetual checks. Here though, she probably didn't lose any half point because of that, since the position was relatively drawish anyway.} Kxg7 30. Qg4+ Kh6 31. Qf4+ Kh7 32. Qf5+ Kh6 33. Qf4+ Kg6 34. Qg4+ Kf7 35. Qh5+ Kg7 36. Qg4+ Kh8 37. Qh5+ Kg8 38. Qg6+ Kh8 39. Qh6+ Kg8 40. Qg6+ Kh8 41. Qh6+ Kg8 42. Qg6+ 1/2-1/2

In round 4 Leela had a good moment in this tournament as she outplayed Ethereal in a French game providing a very nice win. Some of its moves were very spectacular attacking Chess of deep positional understanding.
Shredder had its first non win result also and Houdini again won with white against Gull so it had 4 points out of 4 games.


CCCC rounds 1, 2 and 3.....

CCCC continues running and we are on round 3 currently. The level of play is very high as it was expected and interesting games and positions arise.
Shredder is on the lead now with 3 points out of 3 games but other engines can reach that too(Komodo, Houdini).

First 2 rounds, were not without many adventures for Leela since in the first round it was winning with black against Ivanhoe, but for some reason game crashed. It was not because of any engine's fault. Leela was clearly winning and Stockfish with 7-man tablebases show a win for black so this is a won position. Of course nothing says Leela would actually win the game.