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AlphaZero (Computer) vs Stockfish (Computer)
AlphaZero - Stockfish (2017), London ENG, Dec-04
Queen's Indian Defense: Fianchetto. Nimzowitsch Variation (E15)  ·  1-0

ANALYSIS [x]

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sac: 47.Rxc5 PGN: download | view | print Help: general | java-troubleshooting

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Kibitzer's Corner
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Dec-08-17
Premium Chessgames Member
  virginmind: At first I thought why not 50.Qg5 and after Rxg6 on the next move it's mate in two. Not quite, as after 50...Re6 51.Bxe6 dxe6 black is still 2 pawns up and white's attack is likely over.
Dec-08-17  talwnbe4: 22.. Nd5

45.. Qh8?? isn't a move Stockfish would play on a single core at 5 seconds a move. 45.. Qc7

22..Nd5!?

Dec-08-17  cata008: zugzwang masterpiece
Dec-08-17  jeffwadsworth: This is probably the best game IMO. Not just the sacrifices all over the board, but that ending squeeze.
Dec-08-17  Imran Iskandar: This is simply majestic chess.
Dec-08-17  WorstPlayerEver: Yeah, it's amazing. I tried to simulate the style of A0 for Black in this line. Whereupon Stockfish started to sac like crazy on f7 and d5. Black to move:


click for larger view

Stockfish thinks it equal. Truly weird.

Dec-08-17
Premium Chessgames Member
  varishnakov: <talwnbe4>

Yes, it's true that Stockfish on a single core at 5 seconds would not play 45...Qh8.

But Stockfish at 60 minutes (41 ply) would.
analysis of move 45...?

Dec-08-17  dehanne: Putting back the fish in Stockfish.
Dec-09-17  birimbombum: The disaster apparently happened on move ..43, when sf play Rf8 instead of Kf8. When analyzed with my own sf it happens that... I have random results. Strange, very very strange. Someone can explain this move? I can't.
Dec-09-17  birimbombum: Sorry. The move is ..49.
Dec-10-17  talwnbe4: Stockfish 8 x64
53/102 1:01:42 4,762,015k 1,286k -0.41 49..Kg8-f8 Qh4-f4 Qh8-g8 Qf4-c7 c5-c4 Qc7xc4 Re8-d8 Qc4-c7 Kf8-e8 Qc7xa7 Qg8-f8 Qa7-b6 Qf8xh6 Bb3xf7+ Re7xf7 Rf6xf7 Ke8xf7 Qb6xd8 Qh6-d2 Qd8-a8 Qd2-d4 a2-a4 Kf7-e6

Stockfish 8 x64

41/66 02:43 191,844k 1,175k +5.90 49..Rf8?? Qh4-f4 a7-a5 Bb3-d5 a5-a4 g3-g4 c5-c4 Bd5xc4 d7-d5 Bc4xd5 Re7-d7 Bd5-c6 Rd7-a7 g4-g5 Ra7-a5 Bc6-d7 Rf8-a8 Qf4-e3 Ra8-f8 Bd7-e6 Qh8xf6 g5xf6 Ra5-a8 Be6-c4 Ra8-c8

Dec-10-17  notyetagm: AlphaZero vs Stockfish, 2017

<Nerwal: <If 54...Rd4, then?>

<<The prettiest is 54... ♖d4 55. ♖xf7 ♖xf4 56. ♖g7+ double check and mate.>>>


click for larger view


click for larger view


click for larger view

Dec-12-17  dehanne: Stockfish was Fake Chess all along.
Dec-12-17  Grandma Sturleigh: No Alpha beater.
Dec-12-17  sudoplatov: What's the configuration of the computers? Does Stockfish have its opening tables and ending tables and transposition tables? Similarly for AlphaZero; are the implementations comparable?
Dec-13-17  s4life: I don't think the implementations are comparable, one is a self trained black box which is extremely hard to understand and interpret and the other one is a carefully crafted recipe with lots of thought and tuning invested into it... I guess you could say the machines truly won in this match
Dec-13-17  BenRedic: I do not understand why Stockfish played 49.. Rf8 here.

I have tried to reproduce this on my own computer. Google ran it on 64 threads, yielding like 70 million nps. On 6 cores I get around 8 million nps, so in 9 minutes Stockfish should come up with the same evaluation as it did in 1 minute for Google.

It does indeed consider Rf8 for a brief moment, but it switches to Kf8 after like 10 seconds, anticipating 50. Qf4. After 50 minutes and around 28 billion nodes, PV is 56/128 [+0.37] 49.... Kf8 50. Qf4 Qg8 51.Qc7 c4

Dec-13-17  WorstPlayerEver: <BenRedic>

You mean that the real Stockfish gives 49... Rf8 as the move which quickly loses (+6.5) and 49... Kf8= after a few secs.

?

Dec-15-17  jdoucette: 49...Rf8 is not chosen by my local Stockfish even given the same amount of processing time, yet it was played in the match...

This could be due to 1 GB of hash tables with 64 threads -- a bad idea, as each thread demolishes the hash table of the other threads, making the extra cores far less useful, and introducing far more chance of error:

Hash tables are how threads speak to each other, but too many using the same memory introduces errors -- a known but ignored (due to its slowdown) situation by chess engines since it is extremely unlikely to occur (and such errors normally have little impact).

This happened once before where Shredder doesn't finish the Bishop exchange: P Lafuente vs Shredder, 2005

Dec-15-17
Premium Chessgames Member
  AylerKupp: <<jdoucette> This could be due to 1 GB of hash tables with 64 threads -- a bad idea, as each thread demolishes the hash table of the other threads>

I don't know about you, but I found the reference to <threads> strange. To express the degree of parallelism available to a chess engine one typically (always?) refers to the number of <cores> available to the engine. References to 64 <threads> could mean many things, among them:

1. 64 threads executing in a system with 64 cores. The efficiency of the system then depends on whether the cores are tightly or loosely coupled.

2. 64 threads executing in an x86 system with 32 cores capable of hyperthreading with 2 threads executing in each of the 32 cores.

3. A multi-core system with << 64 cores. You could, in theory, run 64 threads in a single-core computer although there is no point in doing so since at any instant in time only one thread could be executing. And the chess engine will take longer to execute than when a single thread is specified since there will be a constant overhead when switching between the various threads.

Other configurations are possible. Without knowing the hardware configuration that Stockfish ran in this "exhibition", it's hard to reach any conclusions.

And remember that multi-core chess engines are notoriously non-deterministic. The same engine, running on the same computer, analyzing the same position, at the same search depth will come up with different move evaluations and possibly different move rankings in subsequent analyses. Not <may>, <will. Guaranteed. So it's not unreasonable that your local Stockfish came up with different suggested best moves than the Stockfish consideration used in the "exhibition".

But I don't understand your reference to one thread demolishing the hash table of the other threads. For best performance it's best that all threads share the same hash table since most of the hash table-related operations are read operations and do not affect the hash table. It's only when new elements are deleted from or added to the hash table that the hash table must be protected from inconsistent modifications and hash pointer disruptions.

In general, the larger the hash table the better, as long as it's small enough to prevent dish thrashing, since the number of deletions and updates will be reduced. I have no idea what the optimum hash table size would have been in a 64-thread Stockfish configuration since the amount of RAM in the system used for the "exhibition" was not specified.

Jan-17-18  talwnbe4: Incidentally Monte Carlo simulation is used to verify electronic circuit design and in IC verification, if any of you are interested in this. I took a crash course in this at an age when I was bit over the hill so I'm not an expert.
Jan-17-18
Premium Chessgames Member
  ChessHigherCat: < talwnbe4: Incidentally Monte Carlo simulation is used to verify electronic circuit design and in IC verification, if any of you are interested in this.>

Is that related to including "dummy circuits" in the IC so if they find the same dummy circuit in a Chinese chip, for example, the counterfeiters can't claim they just happened to light on the same idea?

Mar-17-18  RAlehin: Awesome play by Stockfish... until move 12 :-)
Jun-15-18  ThirdPawn: Stockfish 9 does not see 47.Rxc5 at 41 depth, but gives the best move for White as 47.a4 and also gives Black a near 2 point advantage. If Rook doesn't take the Black Knight, then there is threat from Black of Re5 along with Nxc3, while allowing the Black Queen to return to the game. Interesting sacrifice with no immediate win other than the intent of blocking the Black Queen from coming back into the game. That is certainly thinking like a human... in hindsight.
Jun-15-18  WorstPlayerEver: =0.00 (27 ply) 49... Kf8 50. Qf4 Qg8 51. Qc7 Qh8 52. Qf4 Qg8 53. Qc7 Qh8

=0.00 (48 ply) 49... Kf8 50. Qf4 Qg8 51. Bxf7 Rxf7 52. Qd6+ Re7 53. Qb8+ Re8 54. Qd6+

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