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MatPlus.Net Forum General Double check in a model mate

Double check in a model mate

Eugene Fomichev
1st Prize FIDE World Cup 2019

(= 8+11 )

Mate in 3

Set 1…Sxb6 2.Qxc7 Bd8 3.Bxb6

1.bxc7 (>2.dxc8S Bxd8 3.Bb6)
1…Bxd8 2.cxd8S > 3.Sxb7
1…Sb6 2.Bxb6+ Kxb6 3.c8S
1…Sd~ 2.Bc3+ Kb6 3.dxc8S

A nice problem. The judge, Igor Agapov, draws attention to the knight promotions on the 2nd and 3rd moves and says “The fact that play in both pairs ends with model mates is a considerable achievement. Such synthesis is presented for the first time in the history of chess composition!”

Is the mate after 1…Sb6 a model? I thought that a double check is only acceptable in a model if both checks are essential. Here the queen attack on b6 is not essential, since nothing is attacking the knight.

Is this correct?

Good question, don't know the answer.
A funny example for an ugly model mate is
http://pdb.dieschwalbe.de/search.jsp?expression=probid=%27P1234413%27

Queen check was essential to guard a5, c7

Which is totally irrelevant to the point I am making.

There is an unnecessary second guard on b6. Does that mean the mate is not a model?

But the queen is attacked by Be7, so the double check is necessary.

But the knight is not attacked, so the double attack on b6 is not necessary.

Maybe the point at issue is - so long as the squares around the mated king are blocked or guarded once (let's ignore pin-models for the moment) is it irrelevant if the king's square is attacked once or twice, or for the mate to be a model should both checks be essential (i.e. if either check wasn't there the other could be parried).

The redundant check by wQ clearly violates the principle of a model mate.
Of course, bureaucracy may impose rules without any underlying principles and still call it a 'model mate'.
And that would mean that such 'model mates' are simply not worth mentioning.

Cited from "Ideal-Mate Chess Problems" by Eugene Albert, published 1966:

"An ideal mate is a model mate in which every White man guards, king and pawns included, and every Black man blocks. ... For a mate by double check, both checks must be necessary."

It doesn't help much. This was the definition of an ideal mate.

Quite a lousy definition :-(

yes, the guarding of b6 by the queen is not strictly needed.
This kind of defect is generally accepted and it is legitimate to speak of model mate in such a case.

You have another kind of (similar ?) defect with some pin mates. If the pinned black piece is in the royal field
say :
white : Qh3, Rf1
black : Kh1, Bh2
The mate is usually called model, although h2 is both blocked by the bishop and guarded by the queen.

This being Milan's site, let's note that according to the Encyclopedia it is not a model mate:

"Mate is called pure when there is only one guard or block on each square in the (mated) ↑King's field. Double check is allowed if the mate could be parried without it. A pin-mate is allowed if pinning is needed in mate."

So this explicitly mentions that the pin in Jacques' example is a different thing.

The definition is very clear and an ideal mate is only a special case of a model mate.

(14) Posted by seetharaman kalyan [Friday, Sep 27, 2019 21:36]

"Double check is allowed if the mate could be parried without it". There is no mention of attack on the checking piece in the definition. In the given example there is no mate if either queen or knight is removed. Obviously model mate.

-"Obviously model mate."-
Very interesting view. So, even without Be7 it would be an OBVIOUSLY model mate - did I understand well?

QUOTE
Double check is allowed if the mate could be parried without it

The question is what does "it" in this definition really mean:
- either of the checking units (Seetharaman interpretation)
- either of the checks

@ Nikola "So, even without Be7 it would be an OBVIOUSLY model mate - did I understand well?"
Yes. the test for whether a double check is essential is to see if black can parry the mate without 'it'

@ Dmitri "The question is what does "it" in this definition really mean:
- either of the checking units (Seetharaman interpretation)
- either of the checks "

It is the same effect in either case. I understood "it" in the definition as 'double check' only. However i thought that one of the checks can be removed only by removing the checking piece.

'It' refers to the DOUBLE CHECK, what could be unclear about that?
Double check is an attack on the opponent's King's square by two pieces.
...could be parried without either of the checks..., means the same.

@Seetharaman
it is not the same effect.