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MatPlus.Net Forum Twomovers Mutate reconstruction
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(1) Posted by Michael McDowell [Wednesday, Jun 1, 2011 22:49]

Mutate reconstruction

A nicely keyed mutate:

2nd Prize Hlas l’udu 1969

(= 5+6 )

Mate in 2

Set 1…bS~ 2.Rxd4

1…Kc5 2.Qc6
1…Ke4 2.Qf5
1…bS~ 2.Qxd4 (dual 2.Rxd4 after 1…Sc5)
1…dS~ 2.Qe6

Comins Mansfield quoted the problem in The Problemist, September 1971, saying that he would have replaced the d8 knight with a bishop at d7, moved the white king to b2 and removed the pawn at g5. He overlooked that this allows a cook by 1.Bh2 (easily eliminated by moving the position to the right) and further duals by 1…dS various 2.Bc6.

A little reconstruction can save a pawn:

(= 5+5 )

Mate in 2

Unfortunately the dual after 1…Se5 seems inevitable.
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(2) Posted by seetharaman kalyan [Thursday, Jun 2, 2011 21:12]; edited by seetharaman kalyan [11-06-02]

Surprising that Mansfield missed the dual ! It seems moving the position to the right eliminates the pawn which is needed only to control the white king. Am I missing anything?
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(3) Posted by Joaquim Crusats [Friday, Jun 3, 2011 20:40]; edited by Joaquim Crusats [11-06-04]

The dual can be avoided, but then maybe something else essential is lost.

(= 5+5 )

Edit (June 4)
The following version keeps the original mates, but the wP to stop the set duals is still needed.

(= 6+3 )

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(4) Posted by Milan Velimirović (+) [Saturday, Jun 4, 2011 04:47]

A charming little position... pity for the dual! In theory it shouldn't be too harmfull (we could say "the BSc6 has 7 possible moves and only one causes a dual - not a big deal!"), but the fact is that one cannot neglect it - so it isn't quite harmless. My attempts to fix it led me to the conclusion that it cannot be succesfully done with 10 (probably neither with 11) pieces, although there is a position which "moves" the dual to a non-thematic set variation (i.e. the one without changed mate):

(= 6+4 )

The WPc6 is unpleasant, but if somebody insists it can be replaced by the WSb8 for pawnless white position.

I managed to get two dual-free phases only in a 12-men setting:

(= 7+5 )

Unfortunatelly there's again the white pawn which serves only to stop the set dual Qf3.
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MatPlus.Net Forum Twomovers Mutate reconstruction