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MatPlus.Net Forum Endgame studies Aftermath: Only one main line?
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(1) Posted by Milan Velimirović (+) [Thursday, Sep 1, 2011 11:23]

Aftermath: Only one main line?

The corrected distribution of points in the last endgame (No.9) from the WCSC 2011, Round 3:
Leopold Mitrofanov & Nikolay Ryabinin
cm Shakhmaty v SSSR 1990
(= 3+5 )

1.Rh6+! Kg8 2.Rg6+ Kf8 3.exd7 (1 point) Rc5+ 4.Kg4 Rc4+ 5.Kh3 Be7 6.Rd6 Rh4+ 7.Kg2 Rh2+! 8.Kg1! (1 point) Nf3+ 9.Kf1 Rd2/v 10.d8=Q+! Bxd8 11.Rf6+! (1 point) Bxf6 =
4... Bc7 5.Rd6 Rg5+ 6.Kh3 Rg3+ 7.Kh2 (1 point) Sf1+ 8.Kh1 Bd8 9.Rf6+ Bxf6 10.d8=Q+ (1 point) =

This marking was applied in the final WCSC table.

However, having analyzed the study once again I am almost sure that my first decision to grant the points only for the first line (4...Rc4+! etc.) was correct (3 points after 11.Rf6+!, no points at all for the second line). The play after 4...Bc7 ends with an obvious stalemate with the white king on h1 and the best chance for black is to drive the white king away of the h-file. The final "trap" 9...Rd2(!) 10.Rf6+?? Bxf6 11.d8=Q+ Rxd8! -+ (Bxd8??) makes this line clearly superior to the second one. Consequently there is only one main line and its weight should be all 5 available points.

I would like to hear the opinion of real endgame experts about this issue.
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(2) Posted by Evgeny Victorov [Friday, Sep 2, 2011 16:45]

I' m not the expert but I have my own opinion. 4...Rc4 is stronger then 4...Bc7 because it gives a choice to white (5.Kh5, Kf5,Kh4). So it's the main line. But I don't see a lot of difference between 9...Rd2 and 9...Bd8. Stalemates are the same and the trap Rd2 is not dangerous. So I think that one point should be given for 9...Rd2 10.d8Q 11.Rf6 and one point for 9...Bd8 10.Rf6 11.d8Q
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(3) Posted by Siegfried Hornecker [Monday, Sep 5, 2011 10:01]; edited by Siegfried Hornecker [11-09-05]

Source of publication, according to hhdbiv, is Shakhmaty v SSSR 2/1991

While the database gives 4...Rc4+ only as main line, the other one is also without duals. Personally, I don't see much difference between both lines. So I think one can have either opinion but I find the decision correct to don't glue on the actual solution and also award points for the almost equal sideline 4...Bc7.
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(4) Posted by Georgy Evseev [Friday, Sep 9, 2011 14:11]

In fact, in this study there is a secondary line, which is almost as good as a main line, but still looks secondary.

I once had a similar situation in one competittion I directed. I used (and intentionally prepared in advance) the following marking.

If a full main line is shown - 5 points.

If main line is missed, but secondary line is shown - 1 (IIRC) bonus point (plus the points given before reaching branching point).

In this case the solver does not need to write both lines to get full points, but those who had written secondary line receive more points than those who had not found any intended final position.
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MatPlus.Net Forum Endgame studies Aftermath: Only one main line?