computer chess

Computer Chess

Tag and you will unmask!
Crazy name, real hobbies
[ Sign up | Log in | Guest ] (beta)
sf115 49 ( +1 | -1 )
Analysis In a reacent game (7th Jan 07) between sf115 and gammon007 an interesting postion came up:



After 15.bxc3 Nxe4 16. Qf4 Bxf3 17 Bxg7!!!

Black has some choices

17...Kxg7 18. Qxf3 Nd2 19. Qe3 Nxf1 20. Kxf1 b6 21. Re1 Re8 22. a4 is about even
OR
17...Kxg7 18.gxf3 Nf6 which is very unclear but I think it's about even
OR
17...Be2 18. Rfe1 Bd3 19 Red1 Bc2 20. Re1 Bd3 21. Rcd1 Bc2 22. Rc1 draw


Can anyone add to this analysis?
ionadowman 116 ( +1 | -1 )
17...Be2 doesn't look very eligible... But before I continue, just checking: At this point White is the Exchange ahead, yes?
After 17.Bxg7 Be2 18.Bxf8 seems to be indicated, and White comes out a whole rook ahead: 18...Bxf1 19.Kxf1 (or 19.Qxe4); or 18...Qxf8 19.Qxe4 Bxf1 20.Kxf1...
Though much less decisive for White is this intriguing possibility:
17.Bxg7 Be2 18.Bxf8 Bxf1 19.Qh6 (?) Qxf8 (forced) 20.Qxf8+ Kxf8 21.Kxf1... leaving White with a margin of R vs N+P. Probably White ought to win this, but Black's still in the game.
I think your assessments after 17.Bxg7 Kxg7 are about right. After 18.Qxf3 White has to give up the exchange and go into a major piece ending a pawn down. He's going to have to fight for the draw, though. I'd avoid it. 18.gxf3 keeps the exchange (for the pawn minus), but White's pawns are wrecked (4 pawn islands to 2). All the same, this is the line I'd choose for White. Although it looks fairly even, there's plenty of play in the position for both sides.
As for 17.Bxg7, I can't see any real improvement for White. At best 17.gxf3 leads to a position similar to 17.Bxg7 Kxg7 18.gxf3 line.
More: Chess
ganstaman 32 ( +1 | -1 )
I looked at the actual game. I think 15. Rxc3 was a wise choice. While I don't have analysis of my own to provide, that looks like it works out better.

Hmm, ok, two minor analytical notes. In the actual game, maybe 16...Nxc3 (I haven't played it out so I may be miscounting what pieces come off the board). Also, why not 17 or 18. Rxf3?
sf115 34 ( +1 | -1 )
16...Nxc3 transposes into the real game, while 17.Rxf3 is illegal because of a pawn on f2.

ionadowman, and anyone else, in the game I played 15. Rxc3 instead of 15. bxc3 was this correct?

the game continued:
15. Rxc3 Nxe4
16. Qf4 Bxf3
17. Bxg7 Kxg7
18. Qxf3 Nxc3
19. Qxc3+ f6
20. Qe3 b6
21. Qe6 f5
22. Re1 Draw agreed (white asked)
ganstaman 8 ( +1 | -1 )
As I said in my last paragraph, my suggestions of 16...Nxc3 and 17. or 18. Rxf3 are for the actual game.
ionadowman 261 ( +1 | -1 )
I agree with ganstaman's suggestions... ... They are at least worth a good look. This is one of those "string of captures" tactical situations that are quite hard to evaluate accurately, as different move orders lead to all sorts of permutations.
Personally, I would have recaptured with the pawn at move 15, the line sf115 made enquiries about in the first instance. After 15.Rxc3?! Nxe4, things look rather rocky: 16.Qf4 Nxc3 threatens ...Ne2+, which just about forces White's response. 17.bxc3 Bxh6 with a sizable edge for Black however White chooses to retake: a pawn extra, and I think the bishop will have the ascendancy over the knight in this sort of position (though indeed I would exchange of f3 if White chose to take the h6-bishop).

Later on in the game, it seems likely that 17.Rxf3 would have been a good choice, instead of 17.Bxg7!? But let's look at the game line first. Can Black improve on the immediate recapture on g7? What about 17.Bxg7 Nxc3!? That nasty fork is again threatened on e2, which rules out 18.Bxf8. So, try 18.Bxc3, now Black can't afford 18...Bxd5 on account of 19.Qd4! So 18...Be2 is indicated. 19.Qd4!? f6 20.Re1 Ba6. Black has to avoid ...Bh5 in these lines owing to the response g2-g4. White can restore the material deficit, but in any case looks comfortable enough, with "opposite coloured" bishops to widen the margin of draw. So there's nothing wrong, seemingly, with exchanging at once on g7.

Now let's look at the alternative, 17.Rc3xf3. White keeps his exchange, and Black has no fork available on d2, not even after exchanging bishops on h6. Now we see why 17.Rxf3 is an improvement on 17.Bxg7. It also suggests why, after the exchanges on g7 in the game continuation, 18.Rxf3 wasn't a bad idea either.

Having said that, Black seems to me to retain very good chances of holding the game even after 17.Rxf3 or 17.Bxg7 Bxg7?! 18.Rxf3. Black's position would have been nice and solid, with an extra pawn and an active minor piece for the exchange. He could, in the latter line, play 18.f4 to maintain the knight in its commanding post and making it a little harder for White to undertake operations down the e- and c-files.

The final draw offer was reasonable. Though Black could safely have played on to see if he couldn't extract some advantage from his extra pawn, there is no reason to criticise his acceptance, either.

That's as I see it so far. Maybe there are resources that I've overlooked that others might find...
Cheers,
ion
sf115 7 ( +1 | -1 )
I think this is good analysis but there are no conclusive answers
ionadowman 74 ( +1 | -1 )
None that give anything decisive either way, no.. ...but I think it is pretty clear that the pawn capture at move 15 (bxc3) is better than the rook capture (15.Rxc3), but even that leads to no particular advantage for White: a slight material edge (R for N+P) but with pawns so scattered it is hard to think of it as a structure, especially compared with Black's solid set up.
(The line I'm following is this one: 15.bxc3 Nxe4 16.Qf4 (Something like 16.Qd3 doesn't seem to change much) 16...Bxf3 17.Bxg7 Kxg7 18.gxf3 Nf6 or 18...Nc5.)
But is 15.Rxc3 a bad move? Maybe not. I wouldn't have played it, and I think it leads to a Black advantage after 15...Nxe4 (an extra pawn) but the activity of White's position after 16.Qf4 Nxc3 17.bxc3 Bxh6 18.Qxg4 might be enough for the pawn...
Cheers,
Ion
sf115 6 ( +1 | -1 )
That is what I had in mind when I played the move
wote 24 ( +1 | -1 )
if
15. bxc3 Nxe4
16. Qf4 Bxf3
17. Bxg7 Be2
18. Rf-e1 Bd3
19. Re-d1 Bc2
20. Rxc2

Better may have been
1. e4 c5
2. c3 g6
3. Nf3 Bg7
4. d4 cxd4
5. cxd4 d6
6. Be3 Nc6
7. Nc3 Nf6
8. Bb5 Bd7
9. O-O O-O
10. Bxc6 Bxc6
11. d5 Bd7
12. Qd2 Rc8
13. Ra-c1 Bg4
14. Bh6 Rxc3
15. Rxc3 Nxe4
16. Qf4 Bxf3
17. Rxf3


and if

17. Rxf3 Bxh6
18. Qxh6 f5
19. Re3
White still has a better game
ionadowman 80 ( +1 | -1 )
Welll... ... I still think Black is much better off playing 16...Nxc3 in the 15.Rxc3 line.
But even in the continuation 16...Bxf3?! 17.Rxf3 Bxh6 18.Qxh6 f5!? 19.Re3 ... has White really the better game? An immediate 19...Nf6 looks as though it might cause White some headaches: 20.Rd1? Ng4 (-+), or 20.Rd3 Qa5, say, or 20.Rh3 Qa5 ...
Hard to evaluate. If Black can pick up a pawn for nothing hereabouts (the d-pawn of one of the Q-side pawns) then I'd fancy Black's chances. If not, then White maybe has the edge - a very slight edge.
wote, you might not have noticed, in the 15.bxc3 line
(15. bxc3 Nxe4
16. Qf4 Bxf3
17. Bxg7 Be2)
that White can play 18.Bxf8 (instead of 18.Rfe1), and come away a whole rook ahead: 18.Bxf8 Bxf1 19.Kxf1 etc
Cheers,
Ion
wote 76 ( +1 | -1 )
there is also
15. bxc3 Bxh6
16. Qxh6 Bxf3
17. gxf3
white is still up. But yes black can still win or darw.
the pawns become a problem for white yet the half open G file is a gateway to mate.

but black has defences.
17. gxf3 Nh5
18. Kh1 f6
19. Rg1 Ng7

if
after witch balck and play

20. h4(or any) Qa5
21. Rc2 Rc8
bringing the battle to the queen side.
As long as black can keep pawns on the board
the Kninght is useful....
h4 Qa5
21. Rc2 Rc8
22. Qe3 b6
23. Rg-c1 Qb5
24. c4 Qd7
25. f4


Just another vertion after 15.


ionadowman 38 ( +1 | -1 )
An interesting line... ...Which suggests that Black would be ill-advised to play 15.(bxc3) Bxh6?!, or, if he does play it, then after 16.Qxh6, Nxe4 is indicated. After the suggested line, 16.Qxh6 Bxf3?! 17.gxf3 I reckon White really does have the better of it, on account of that impressive central pawn mass, to go with his exchange extra.
Cheers,
Ion
sf115 45 ( +1 | -1 )
I agree with ionadowman that after
15. bxc3 Bxh6
16. Qxh6 Bxf3
17. gxf3
I favour white

but I agree with wote that after
15. Rxc3 Nxe4
16. Qf4 Bxf3
17. Rxf3 Bxh6
18. Qxh6 f5
white is winning but I would add that instead of 19. Re3
19. Rh3!!! Nf6
20. Re1 Qa5
21. Rxe7 winning for white
sf115 8 ( +1 | -1 )
I'll just add that after 19...Rf7 white is a pawn up with a better position
ionadowman 79 ( +1 | -1 )
All of which... ... would indicate that Black is better off playing (15.Rxc3 Nxe4 16.Qf4) Nxc3.
But in the line under discussion:
15. Rxc3 Nxe4
16. Qf4 Bxf3?
17. Rxf3 Bxh6
18. Qxh6 f5 <snip>
19. Rh3!!! Nf6
20. Re1 Qa5
21. Rxe7 ...
19...Rf7 ought to be preferred, retaining the knight on its central square. White can't chase it away yet: 20.f3? Qb6+ recovers the exchange, whence Black ought to win. In fact, f3 doesn't look easy for White to arrange in a hurry, which means it won't be easy for White to shift that knight.

I presume that by "a pawn up" sf115 means the "equivalent of a pawn up" i.e. R vs N+P. I agree that White retains this material edge for the moment (i.e. after 19...Rf7), but it seems to me Black has at least some compensation for this slight material deficit. A difficult game ahead for both sides, methinks!
sf115 4 ( +1 | -1 )
I think white has an easier game