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Alexander Moiseenko vs Artur Yusupov
European Rapid Championship (2010) (rapid), Warsaw POL, rd 13, Dec-19
Queen's Gambit Declined: Miles Variation (D53)  ·  0-1

ANALYSIS [x]

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Kibitzer's Corner
< Earlier Kibitzing  · PAGE 2 OF 2 ·  Later Kibitzing>
Mar-06-19
Premium Chessgames Member
  al wazir: <Penguincw: Wow, this feels like the easiest puzzle of the week, and it's (checks calendar) Wednesday.> Right.

The ratings attached to the puzzles are a relic of the previous administration. They no longer have any relation to actual difficulty. I think we can disregard them.

Mar-06-19
Premium Chessgames Member
  drollere: i went with 24. .. Be3, which gives white a useless move or two before the forced mate.
Mar-06-19
Premium Chessgames Member
  drollere: <I think we can disregard them.>

most of us do already, or always have.

Mar-06-19
Premium Chessgames Member
  HeMateMe: Does 24...B-e3 also win? Awkward, but it seems to force mate.
Mar-06-19  saturn2: <drollere> I looked at this too.

24...Be3 25. Rxc8+ Kg7 26. h3 Bxf2+ 27. Kh2 Qxf1 now there is the threat Bg3+ folliwed by Qxg2

Mar-06-19  saturn2: Todays solution is a back rank mate the way Fisher has teached.
Mar-06-19  erixn: On 24..Be3 25.Rxc8+ Kg7 it seems to me White may try 26.Nd2!?, when 26...Rxd2 allows 27.Rg8+ Kxg8 28.Qa8+ Kg7 29.fxe3! when Pg2 is protected or (27.Rg8+) Kh6 30.Qxf7 protecting Pf2. And similarly if QxN. - I don't see any immediate mates, although Black's attack may still be dangerous.
Mar-06-19
Premium Chessgames Member
  malt: 24...Q:f2+ 25.R:f2 Rb1+ 26.Ne1
(26.Rf1 Be3+ )
26...R:e1+ 27.Rf1 Be3+ 28.Kh1 R:h1#
Mar-06-19  AlicesKnight: Found ...Qxf2+ followed by ....Rb1+ and the intrusion of the Black KB is decisive. Looks like Black saw it at least from move 21 and white saw nothing coming.
Mar-06-19  lost in space: Easy for a Wednesday
Mar-06-19  Sally Simpson: ***

Good Trap/Pitfall/Combo from a Rapid Game.

It should have been set from here. (Black to play)


click for larger view

This is where we know for certain Black saw the idea (and White obviously did not).

***

Mar-06-19  Yorkshire Fog: <HeMateMe: Does 24...Be3 also win?>

After 24...Be3 25.Rxc8+ Kg7 White can distract the bishop with 26.Rcc1 Bxc1 27.d5 Rxa2 28.Qe7 Ra1 29.Qf6+ and get a draw by perpetual check after 29...Kg8 30.Qd8+.

The alternatives at this point 29...Kh6 30.Qh8 and 29...Kf8 30.Qh8+ are both losing for Black.

Mar-06-19  eyalbd: After ♕xa7 and ♖xc7 :
Never go hunting remote pawns when your enemy controls your second rank.
Mar-06-19
Premium Chessgames Member
  HeMateMe: Was this game in Lev Albert's <300 Positions >?
Mar-06-19  ChatGrognon: Tactical combination to know: )
Mar-06-19
Premium Chessgames Member
  PawnSac: < Sally Simpson:
This is where we know for certain Black saw the idea (and White obviously did not). >

I suspect black saw the idea on move 22, but you're right that the puzzle set at 22. ..? would have been more interesting/challenging.

White blundered with < 23.Qxa7? >. After 23.Rc6 black has only a slight plus. Interestingly enough, after Qxa7 Stockfish 10 immediately and only displayed ..Bh6 in the analysis all the way up to 44 ply where it gives black +1.49 with 23. ... Bh6 24.Qa5 Be3 25.Qe1 Qxe1 26.Nxe1 Bxd4 27.Rc4 Rd8 28.Rxc7 Bxe5 etc.

white's 2nd blunder Rxc7?? is just unthinkable in lieu of the threat. What's that old saying? ... "He who grabs pawns sleeps in the streets!" Suicide!

Mar-06-19
Premium Chessgames Member
  whiteshark: Yet another <backrank mating tactic> ftw
Mar-06-19  TheaN: Wednesday 7 March

<24....?>

With a Queen on the second rank, sacs on f7 and f2 are quite common. Typically it wasn't the first I looked at, as it seems so counterproductive. In contrary:

<24....Qxf2+! 25.Rxf2 (Kh1 Qxg2#) Rb1+ 26.Rf1 (Rc1 Rcxc1+ 27.Ne1 Rxe1+ 28.Rf1 Rxf1#, Ne1 Rxe1+ 27.Rf1 Be3+ 28.Kh1 Rxf1#) Be3+ 27.Kh1 Rxf1+ 28.Ng1 Rxg1# 0-1> is entirely forced.

Mar-06-19
Premium Chessgames Member
  drollere: <After 24...Be3 25.Rxc8+ Kg7 White can distract the bishop with 26.Rcc1 Bxc1 27.d5 Rxa2 28.Qe7 Ra1 29.Qf6+ and get a draw by perpetual check after 29...Kg8 30.Qd8+>

24. .. Be3
25. Rxc8+ Kg7
26. Rcc1 Bxf2+
27. Kh1 Bxd4

(27. Rxf2 Qxf2+ and mate next)

28. Qxd4 Qxg2#

Mar-06-19
Premium Chessgames Member
  drollere: <24...Be3 25. Rxc8+ Kg7 26. h3 Bxf2+ 27. Kh2 Qxf1 now there is the threat Bg3+ folliwed by Qxg2>

i think 27. .. Bxd4 still works.

the B is really the key to all variations of the combination; Bh6 is the "tell" for the attack.

Mar-06-19
Premium Chessgames Member
  vonKrolock: I was fancying about 24...♗e3 25. ♖xc8+ ♔g7 26. ♖cc1 ♗xf2+ 27. ♔h1 ♗g3 28. ♖g1 ♕xf3 29.gxf3 ♖xh2#


click for larger view

or 29.♖cf1 ♖xg2


click for larger view

(Evidently cooked, the actual harsh mating attack was enough...)

Mar-06-19  bcokugras: Yusupov is the world champion of our hearts.
Mar-07-19
Premium Chessgames Member
  AylerKupp: <drollere>, <HeMateMe>, <saturn2>, <erixn>

I also thought that 24...Be3 would lead to mate but I overlooked <Yorkshire Fog>'s 24...Be3 25.Rxc8+ Kg7 26.Rcc1 protecting against the back rank mate.

<Yorkshire Fog> After 24...Be3 25.Rxc8+ Kg7 26.Rcc1 Bxc1 27.d5 Rxa2 28.Qe7 Ra1


click for larger view

Now, instead of 29.Qf6+ and the presumed perpetual check (but see below), Stockfish 10 at d=42 suggests 29.Qd7, evaluating the resulting position at [+2.58] (White has a winning advantage) after 29...exd5 30.Ng5 Bxg5 31.Rxa1 Qxe5 32.Rd1 Qe2 33.Qxd5 (White is now a clear exchange ahead and Black's attack is over, but there is no forced win) 33...h5 34.Qd3 Qe6 35.g3 h4 36.Qf3 hxg3 37.hxg3 Bf6 38.Kg2 Be7 39.Qa8 Qe5 40.Rh1 Bf8 41.Rh4 Qc3 42.Rf4 Bd6 43.Ra4 Qe5 44.Qc6 Qc5 45.Ra6 Qxc6+ 46.Rxc6 Bb4 47.Kf3 f5 48.Kf4 Bd2+ 49.Ke5 Be1 50.Rc2 Kh6 51.Kf4 Bb4 52.Ke3 Ba5 53.Rc6 Bb4 54.Ke2 Kg7 55.Rc7+ Kf6 56.Kf3 Be1


click for larger view

But I'm not sure how White makes progress, and Stockfish's last few moves does not give me confidence that it knows how to reach a definite winning position.

Was Black right in allowing/encouraging the exchange of queens after 44...Qc5? Probably. Starting an analysis after 44...Qc5 45.Ra6 Qxc6+ 46.Rxc6


click for larger view

Stockfish at d=56 evaluates the resulting positions at [+2.79] (White has a winning advantage) after either 26...Be7, 46...Bb4, 46...Bf8, 46...Ba3, or 46...Bb5, with most of the moves transposing into the same line. Here is one of them:

46...Bb4 47.Rc7 Bd2 48.Kf3 Kf6 49.Ke4 Be1 50.Rc1 Bd2 (obviously not 49...Bxf2??, 50.Rf1 wins the bishop) 51.Rc4 Be1 52.Kf3 Bd2 53.g4 Ke6 54.Rc6+ Ke5 55.Rc5+ Ke6 56.Ke4 Be1 57.Rc6+ Ke7 58.f4 Kf8 59.Rc8+ Ke7 60.Rc7+ Kf6 61.Kd5 Bd2 62.g5+ Kg7 63.Rc4 Kf8 64.Ke5 Kg7 65.Rc6 Be3 66.Rc8 Bd2 67.Rb8 Be3 68.Rb7 Kf8 69.Ke4 Bc5 70.Kd5 (70.f5 gxf5 is a theoretical tablebase draw) 70...Be3 71.Ke5 Ke8 72.Rc7 Bb6 73.Rc8+ Ke7 74.Kd5 Kd7 75.Rc4 Ba5 76.Ra4


click for larger view

It seems that Black's control of the dark squares allows him to set up a fortress that Stockfish can't recognize. And since f4-f5 leads to a theoretical tablebase draw, White can't make any progress. So the theoretical outcome of the game is really a draw, although that's not easily realized OTB, particularly at Rapid time controls.

Note: If 29.Qf6+ instead of 29.Qd7 and if the latter is considered to be advantageous for White, then White can transpose into the 29.Qd7 line after 29...Kg8 30.Qd8+ Kg7 31.Qd7, reaching the same position as after 29.Qd7. So 29.Qf6+ can be considered to be the same line with 2 extra moves. To help in reaching the time control? :-)

And Stockfish evaluates any other reasonable (although not necessarily obvious) move (29.Qe8, 29.Qb7, 29.Nd2, 29.Nd1) as providing equal chances ([0.00]) for both sides.

Mar-07-19
Premium Chessgames Member
  AylerKupp: <Yorkshire Fog> So I tried Komodo 12.3 MCTS which supposedly plays "more human" moves (like AlphaZero) than "classic" engines using a hand-crafted evaluation functions, minimax position evaluation, alpha-beta pruning, and search tree pruning heuristics, even though its Elo rating is 91 points less (3295 vs. 3386) in the latest CCRL 40/4 engine tournament rating list). This is how it evaluated the position (top 5 moves) after 28.Qe7 Ra1 at d=32:


click for larger view

1. [+2.07]: 29.Qd7 exd5 30.Ng5 Bxg5 31.Rxa1 Qxe5 32.Rd1 Bd2 33.Qb5 h5 34.Qd3 Bc3 35.Qxd5 Qf6 36.g3 h4 37.g4 Be5 38.Rd3 Qf4 39.h3 Kh6

2. [+1.92]: 29.Qf6+ Kg8 30.Qd8+ Kg7 31.Qd7 exd5 32.Ng5 Bxg5 33.Rxa1 Qxe5 34.Rd1 h5 35.Qxd5 Qe2 36.Qd3 Qe6 37.Qc3+ Bf6

3. [+0.27]: 29.Qe8 Bb2 30.Rxa1 Bxa1 31.Qa4 Bxe5 32.dxe6 fxe6 33.Qd7+ Kh6 34.h3 Bf4 35.Qd8 Kg7 36.Qd4+ e5 37.Qd7+ Kh8 38.Qe8+ Kg7

4. [+0.18]: 29.Qb7 Bb2 30.Rxa1 Bxa1 31.Qb1 Bxe5 32.dxe6 fxe6 33.Qb7+ Kf6 34.Qd7 Bc7 35.Qd4+ e5 36.Qd5 Bb6 37.Qc6+ Kf5

5. [0.00]: 29.Ne1 Bd2 30.Qf6+ Kh6 31.Qh4+ Kg7 32.Qf6+

Komodo 12.3 MCTS agrees with Stockfish in considering 29.Qd7 to be White's best move, but it considers that there's more than a draw after 29.Qf6+ Kg8 30.Qd8+ since after 30...Kg7 31.Qd7 the line pretty much transposes to the 29.Qd7 line two moves behind after 31...exd5 32.Ng5, even when it transposes ...h5 and ....Bd2.

I should add that Komodo MCTS's evaluations and search depth are estimated since, without using an explicit evaluation function, MCTS evaluates positions probabilistically based on the expected scoring % (wins + draws/2) / total simulated games, and the "search depth" is based on the number of nodes evaluated in the current search tree.

Most importantly the ranking of the top 5 moves is almost identical between Stockfish and Komodo MCTS, and with effectively equal evaluations; Stockfish ranked its top 5 moves at (29.Qd7, 29.Qf6+, 29.Qe8, 29.Ne1, 29.Qb7) and Komodo MCTS ranked its top 5 moves at (29.Qd7, 29.Qf6+, 29.Qe8, 29.Qb7, 29.Ne1). And since Stockfish evaluated 29.Qe8, 29.Qb7, 29.Ne1 all at [0.00] and Komodo MCTS evaluated 29.Qe8 at [+0.27], 29.Qb7 at [+0.18], and 29.Ne1 at [0.00], their evaluations are essentially the same; i.e. even chances for both sides.

Of course I couldn't resist comparing the analysis done by Komodo 12.3 MCTS with the analysis done by "regular" Komodo 12.3, i.e. Komodo 12.3 with alpha-beta pruning (ABP). At d=29 Komodo ABP evaluated its top 5 moves to be 29.Qf6+ at [+2.19], 29.Qd7 at [+1.86], 29.Qe8 at [+0.20], 29.Qb7 at [+0.07], and 29.Nd2 instead of 29.Nd1 also at [0.00]. So Komodo ABP's evaluations and move rankings were very similar to both Stockfish and Komodo MCTS. And, no, I have no idea why at d=29 Komodo ABP evaluated 29.Qf6+ higher than 29.Qd7 other than to point out that since d=8 (the lowest search depth that I have the engines report an evaluation) 29.Qf6+ and 29.Qd7 were always ranked #1 and #2 and most of the time they were given the same evaluations. And whenever one move was evaluated higher than the other the evaluation differences were small, effectively indicating that both moves were equally good. Which, of course, they are.

Possibly of interest is that Komodo MCTS evaluated 4,938,772 nodes in about 4:20 <hours> of calculation and Komodo ABP evaluated 5,136,617 nodes in about 3:53 <minutes> of calculation. This is consistent with the results described with AlphaZero and Leela Chess Zero (which both use MCTS) when comparing their performance against Stockfish. But why their author think that this is somehow better is beyond me.

One irrelevant observation is perhaps worth noting. Komodo ABP reached d=29 after less than 4 minutes calculation time on my rather archaic 4-core, 32-bit computer and it then stopped increasing its search depth. I let it run overnight and after more than 14 hours of calculation it didn't advance even one search ply even though the number of nodes it calculated was > 20 times more. But that's not consistent behavior, I've seen all the most recent versions of Komodo behave similarly on occasion, with sometimes being stuck at one search ply for > 8 hours and then advancing several search plies within the next hour. And sometimes it doesn't get stuck at one search depth at all. No idea why.

Mar-07-19
Premium Chessgames Member
  AylerKupp: <Sally Simpson> We've had this discussion before so I thought that you might be interested in the following excerpts form the Komodo 12.3 readme file as they pertain to MCTS:

"Its playing style and move choices are more like Alpha-Zero than like normal engines, meaning that it is generally less materialistic than normal Komodo, in the style of the spectacular World Champion Mikhail Tal. In general, the MCTS moves are more human-like and more tricky for humans to meet than normal Komodo, <because Komodo MCTS does not assume that its opponent will always play the move that Komodo would play>." (emphasis mine)

"MCTS is different from traditional chess engine search techniques in that the search is guided by win probabilities [actually it's technically scoring probabilities; i.e. (wins + draws/2) / total simulated games] instead of a traditional alpha-beta search and evaluation. <The result is a more human-like way of playing, since humans, like MCTS, are normally concerned with what move will give them the best chance to win (or draw if in inferior position) against an imperfect opponent, not what move is best against perfect play, which is what alpha-beta search tries to do. <MCTS often gives very different move choices than normal Komodo."> (emphasis mine)

So, unlike a classic chess engine using minimax position evaluation following alpha-beta pruning which assumes best play by both sides, Komodo MCTS will play the move that gives it the best chance to win or draw against an imperfect opponent. And isn't that what you were wishing for?

However, "best chance against an imperfect opponent" to me implies that the opponent is either a human (even if a very, very strong one) or a relatively weak engine. And though that may give a better result in some games, overall it will result in weaker play if all other things are equal. This is reflected in the relative ratings and rankings of the same version of Komodo in alpha-beta pruning (ADP) and MCTS versions:

Komodo Version ADP <MCTS> Diff

12.3 (1CPU) 3323 <3237> 86

12.2.2 (1CPU) 3326 <3214> 112

Maybe the MCTS versions will improve, particularly in multi-core configurations (which the last CCRL engine vs. engine tournament I looked at (Feb 27) didn't have, that they will equal or exceed the performance of the ADP versions. The Komodo developers seem to think so. Or, if all else fails, Komodo could automatically switch to trying an MCTS-based analysis if the best that a classic ADP-based analysis can do is detect a likely lost position (evaluation > [ ±2.00]). After all, as you've said, what does it have to lose?

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