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cheesehead 2014-06-28 20:39

White 34
 
I rediscovered the resource for Black that I couldn't recall before.

[QUOTE=cheesehead;376803][QUOTE=cheesehead;376494]I just found that in my favorite [B]33 Nxc8 Kxe6 34 Bh3+[/B] line, Black does have at least one defensive sequence that avoids losing his a5-pawn, so I retract my claim that we have a forced win of material there.[/QUOTE]Now I've discovered how to tighten the sequence that Black has to tread in order not to lose material.

[quote][B]33 Nxc8 Kxe6 34 Bh3+ Kf6 35 Rb6+ Kf7 36 Rb7 Bb4 37 Nxe7 Bxe7 38 Ra7[/B][/quote]If [B]38 ... Nb3 or Nc4[/B] then[B]
39 Ra6[/B] threatening 40 Be6+ winning the knight (on either b3 or c4)

< snip >

If [B]39 ... Bc5+ 40 Kg2[/B] (NOT Kf1 Nd2+ 41 K-move Bb4 protecting both knight and pawn) and now we still have [strike]the same threats to capture pawn or knight as we did before.[/strike][/QUOTE]... [I]almost[/I] the same threats, [I]but not quite[/I].

Now Black has a way to prevent losing either his a-pawn or his knight, by playing
[B]40 ... Ke7[/B] (note that 39 ... Bc5+ was necessary to vacate the e7 square).

If [B]41 Be6[/B] attacking the knight, it's not a check, so Black can move the knight. But if then 42 Rxa5 Kxe6.
In particular,
If (with knight on b3) [B]41 ... Nd4[/B] attacking the bishop, and there aren't any Black targets that our B can threaten when it moves.
If [B]42 B-move Bb4[/B]. Of course, then we can start nabbing king-side pawns with [B]43 Rxg6[/B], but Black retains his a-pawn threat.
If (with knight on c4) [B]41 ... Ne3+[/B] 42 Kf3 does prevent 42 ... Bb4 because of 43 Kxe3, but Black can simply move the knight again to a safe square, and because our bishop is still next to his king, we can't afford 43 Rxa5 yet, giving Black a tempo for ... Bb4.
If (with knight on c4) [B]41 ... Na3 or Nb2 or Nd2 or Ne5 or Nd6[/B] (not ... Nb6, where Black's bishop has to protect it and thus can't play ... Bb4) [B]42 Bb3 Bb4[/B] and again we've been thwarted in attempting to capture the a-pawn, but we can proceed to clean out Black's king-side with 43 Rxg6.

WMHalsdorf 2014-06-28 23:05

33 Nxc8 Kxe6 34 Bh3+ Kf6 35 Rb6+ Kf7 36 Rb7 Bb4 37 Nxe7 Bxe7 38 Ra7
If 38 ... Nb3 or Nc4 then 39. Bf1 Should be able to pick up another pawn.

cheesehead 2014-06-29 00:14

[QUOTE=WMHalsdorf;376961]33 Nxc8 Kxe6 34 Bh3+ Kf6 35 Rb6+ Kf7 36 Rb7 Bb4 37 Nxe7 Bxe7 38 Ra7
If 38 ... Nb3 or Nc4 then 39. Bf1 Should be able to pick up another pawn.[/QUOTE]Yes, but not the a-pawn anytime soon.

One problem with Bf1 is that the square from which the bishop will attack the knight, c4, is vulnerable to counterattack by the knight, thus deterring our rook from taking on a5 before Black can play ... Bb4. The other is that the Black king can un-pin itself so as to allow Bc5+ threats, and we can't stop the unpinning without getting into repetition of position:

If [B]38 ... Nb3 39 Bf1 Kf8 40 Bc4 Nd2[/B]
If [B]41 B-moves Bc5+[/B]
If [B]41 Rc7[/B] now the rook isn't threatening to capture the a-pawn.
If [B]40 Ra8+ Kg7[/B]
If [B]41 Bc4 Nd2[/B]
If [B]42 B-moves Bb4[/B] and the a-pawn is protected.
If [B]41 Ra7 Kf8[/B] leads to repetition of position, or else White stops checking the king, allowing Black to get in Bc5+ or Bb4.

If [B]38 ... Nc4 39 Bf1 Kf8[/B]
If [B]40 Bxc4 Bc5+[/B]
If [B]40 Kg2 Ne3+ and 41... Nxf1 and 42... Bb4[/B] and the a-pawn is protected.
If [B]40 Kh1 Nd2 41 Bd3 Bb4[/B] and the a-pawn is protected. (Sure, 42 Bxg6, but we were going to get the king-side pawns eventually anyway. The point of this analysis is that we don't have a forced capture of the a-pawn as I'd originally thought.)

- - -

Now for why I came here:
[QUOTE=cheesehead;376956]
If [B]41 Be6[/B] attacking the knight, it's not a check, so Black can move the knight. But if then 42 Rxa5 Kxe6.
In particular,
If (with knight on b3) [B]41 ... Nd4[/B] attacking the bishop, and there aren't any Black targets that our B can threaten when it moves.[/QUOTE]and
If [B]42 Rxa5[/B]
If [B]42 ... Kxe6 43 Rxc5[/B] we've won the pawn, but
If [B]42 ... Nxe6[/B] we've lost a bishop for a pawn.

WMHalsdorf 2014-06-29 02:58

[B]33 Nxc8 Kxe6 34 Bh3+ Kf6 35 Rb6+ Kf7 36 Rb7 Bb4 37 Nxe7 Bxe7 38 Ra7[/B]
If [B]38 ... Nb3 39 Bf1 Kf8 40 Ra6[/B]
If [B]38 ... Nc3 39 Bf1 Kf8 40 Ra8+[/B] wins knight
If [B]38 ... Nc3 39 Bf1 Nd2 40 Be2[/B] wins the a pawn
If [B]38 ... Nc3 39 Bf1 Ne3 40 Bd3[/B] wins the a pawn
If [B]38 ... Nc3 39 Bf1[/B] Other N-moves [B]40 Rxa5[/B]

LaurV 2014-06-29 15:25

They replied [B]Kxe6[/B] as expected. I spent few of the Sunday afternoon hours with the position, nothing else to do :wink: and I can't get rid of that feeling that we just gave away a clear victory, with the last move. Now, after [B]34 Bh3+ [STRIKE]Kf6[/STRIKE] Nf5[/B], we might be in for a long "rook against horse" final, which we may either be unable to win, if they play well. I mean, it still seems we are winning, at least we are able to clear the king's pawns with the rook, in about 8-10 moves, but you never know...

cheesehead 2014-06-29 19:12

[QUOTE=LaurV;376999]Now, after [B]34 Bh3+ [STRIKE]Kf6[/STRIKE] Nf5[/B][/QUOTE]I just noticed a few minutes ago that I'd been blind to that possibility, and came here to confess! Oh, well, we have lots of tricks and traps left.

- - -

[URL="http://www.mersenneforum.org/showpost.php?p=376982&postcount=155"]33...Kxe6[/URL] timestamp is 29 Jun 14, 05:48.
Our deadline (with one-hour margin) is Sunday, July 6 4:48 GMT
= Sunday, July 6 11:48 Thai time
= Sunday, July 6 0:48 EDT
= Saturday, July 5 23:48 CDT

cheesehead 2014-06-29 19:35

[QUOTE=LaurV;376999]I can't get rid of that feeling that we just gave away a clear victory, with the last move.[/QUOTE]

You've been having that sort of fear periodically throughout this game :-) So far, none have come to pass. :-) We still have all the advantages we had before.

Get some sleep. :-)

- - -

If [B]34 Bh3+ Nf5[/B], we _do_ have that Black knight pinned, after all -- just on a different square.
Possibilities for us after that include:

If [B]35 Rb6+ ????[/B]

If [B]35 Rb5 ????[/B]

If [B]35 Kg2[/B] (eliminating the Bc5+ threat) [B]35 ... ????[/B]

If [B]35 Bxf5+[/B]
If [B]35 ... Kxf5 36 ????[/B]
If [B]35 ... gxf5 36 ????[/B]
- - -

[QUOTE=LaurV;376999]we might be in for a long &quot;rook against horse&quot; final[/QUOTE]

With opposite-color bishops, I expect rook-and-bishop vs. knight-and-bishop.

cheesehead 2014-06-30 01:40

Hmmm ...

[B]34 Bh3+ Nf5 35 Rb6+[/B] can get us a piece-swap and K-side pawns.
If [B] 35 ... Kd7 36 Rxg6[/B] (getting R off the a7-g1 diagonal) [B]36 ...Kxc8 37 Bxf5+ K-moves 38 Rxh6[/B] and now we're ready to roll our K-side passers. I think we ought to be able to delay Black's capture of our a-pawn long enough to advance our g/h-pawns to the point where we queen one of them before Black queens his a-pawn - but that's not based on hard calculation,

-

[B]34 Rb6+[/B] I'd been avoiding doing this before Bh3+ because ... Kd7 ruins the pin set-up the other move aimed at. (And, as usual, we must keep in mind that this puts rook and king on same a7-g1 diagonal.)) But I'm taking a second look, and this has possibilities such as:
If [B]34 ...Kd7 35 Bh3+[/B]
But if [B]35 ... Kc7[/B], we mustn't fall for the trap of trying to win two pieces for our rook with 36 Nxe7 Kxb6 37 Nd5+, because Black would play 36 ... Bd4+ instead, and we'll have given away our material advantage.
However, in this position Black is threatening to win a piece with Nxc8 because our B/c8 is double-attacked and single-defended ... and our rook must flee.
Although 36 Rb5 threatens 37 Rc5+ after 36 ...Nxc8, Black can strike first with 36 ... Bd4+ and if 37 Kg2 Nxc8 38 Rxa5 Black has two knights for our rook+pawn.

But after [B]34 Rb6+ Kd7[/B], there's another forcing move:
[B]35 R[U][B]d[/B][/U]6+[/B]

If [B]35 ... Kxc8 36 Bh3+[/B]
If [B]36 ... Kb7 or Kc7 37 Rd7+[/B] restores our material edge.
If [B]36 ... Kb8 37 Rd8+[/B]
If [B]37 ... Ka7 or Kb7 or Kc7 38 Rd7+[/B] again restores our material edge.
If [B]37 ... Nc8 38 Rxc8+[/B] and [B]39 Rxc3[/B] - we're up a whole rook!
If [B]36 ... Nf5 37 Rc6+[/B] and [B]38 Rxc3[/B] - we traded our knight for their strong bishop and remain the Exchange up!

If [B]35 ... Kc7[/B] Is there any advantage to this strange choice? [B][B]36 ????[/B]

If [B]35 ... Ke8[/B][/B] Is there any advantage to this strange choice? [B]36 ????[/B]

LaurV 2014-06-30 07:58

[QUOTE=cheesehead;377006]You've been having that sort of fear periodically throughout this game :-)[/QUOTE]
Yes, usually (and only) after my move is outvoted :-P

Now, if you are optimistic about it, I don't mind we being playing any other version, you convinced me over the game that you know your stuff. This is your final, and I am convinced you can play it and win it.

Right now is clear that we can't do better than [B]34 Bh3+[/B], so, we can play it and see what they come out with. I think it doesn't really make sense to argue about move 35, they may still play 34...Kf6, or 34...Kf7 directly (why waste a move? :-P). So, we see after that how we go.

cheesehead 2014-06-30 18:32

[QUOTE=LaurV;377044]Yes, usually (and only) after my move is outvoted :-P[/QUOTE]Oh ... that makes sense,

[quote]Now, if you are optimistic about it, I don't mind we being playing any other version, you convinced me over the game that you know your stuff. This is your final, and I am convinced you can play it and win it.

Right now is clear that we can't do better than [B]34 Bh3+[/B][/quote]... and that's just why I came here! A few minutes ago, I discovered a great continuation if they respond with 34 ... Nf5. (And we know that if they play 34 ... K-moves, we give them a great hassle!)

If [B]34 Bh3+[/B]
If [B]34 ... Nf5[/B]

Now, something I glanced at previously, but didn't follow through earlier is:
*** ==> [B]35 g4[/B].

If Black doesn't move the N/f5, we get it. If they _do_ move the knight, we get a lovely little discovered check, and then an instant passed pawn on the sixth rank to cause Black headaches!

[I] Note: This is just my hurried first-draft analysis tree for [B]35 g4[/B], but I wanted to get it posted so you guys can start on it! This tree is going to get very big, because Black has such a wide variety of possibilities that listing _many_ legal moves at certain points will be necessary.
[/I]
If [B]35 ... Bd4+[/B]
If [B]36 Kh1 ????[/B] (NOT 36 Kg2 Nh4+ 37 Kg3 g5)

If [B]35 ... Nd6 36 ????

[/B]If [B]35 ... Ng3 36 hxg3 ????

[/B]If [B]35 ... Ne3 or or Ne7 or Ng7 or Nh4 36 g5+[/B] and now we have two branches, depending on Black's king move:

If [B]36 ... Kd5 or Ke5 or Ke7 37 gxh6[/B] and?

If [B]36 ... Kf7 37 gxh6[/B]
If [B]37 ... Kg8[/B]
If [B]38 Rb7[/B] and now Black has a wide variety of possibilities, so I'll just list every legal move:
If [B]38 ... Ba1 or [/B][B]Bb2 39 ????[/B]
If [B]38 ... Bd4+ 39 Kh1 ????[/B]
If [B]38 ... Be5 39 ????[/B]
If [B]38 ... Bf6 39 ????[/B]
If [B]38 ... Bg7 39 Rxg7+ ????[/B]
If [B]38 ... Bh8 39 ????[/B]

If [B]38 ... Nb1 39 ????[/B]
If [B]38 ... Nb3 39 ????[/B]
If [B]38 ... Nc4 39 ????[/B]
If [B]38 ... Ne4 39 ????[/B]
If [B]38 ... Nf1 39 ????[/B]
If [B]38 ... Ndf3+ 39 ????[/B]
If [B]38 ... g5[/B] threatening ... Ng8 [B]39 ????[/B]
If [B]38 ... Kf8 39 ????[/B]
If [B]38 ... Kh8 39 ????[/B]
If [B]38 ... Nhf3+ 39 ????[/B]
If [B]38 ... Nf5 39 ????[/B]
If [B]38 ... Ng2 39 ????
[/B]
- - -

I have to go to an appointment soon, so I'll leave this messy tree as is for right now.

cheesehead 2014-07-01 10:15

Speculative scenario:

34 Bh3+ Nf5 35 g4 Nf3+ 36 Kh1 (not Kg2) Nh4 37 g5+ Kf7 38 gxh6 Kg8 39 Rb7 Nf5 40 Bxf5 gxf5 41 Nd6 f4 42 h7+ Kh8 43 Nf7+ Kxh7 44 Ng5+ K-moves 45 Nxf3


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