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MatPlus.Net Forum Twomovers Who is gonna explain me Twomovers?
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(1) Posted by Sven Hendrik Lossin [Friday, Jan 20, 2012 23:05]

Who is gonna explain me Twomovers?

I always love to solve and comment problems in Die Schwalbe with one exception: After all I still think that I dont know anything about twomovers. That there are a lot of things that I dont know after two yrs of interest in problem chess is okay but then something happened that really embarassed me:

In Schwalbe 247 there were these two twomovers:
14710 D. Shire
(= 11+11 )

and 14711 G. Mosiashvili
(= 10+13 )

Of course I didnt understand anything what was going on there but I was sure that in 14710 the wPa2, bPh2, bQh1 and in 14711 the bPb2 and the bPc2 are nightwatchmen (afterwards I came to the conclusion that this was also the case with bPe4). I wrote that to the editor and in the solutions and comments six months later these two works were praised by the community despite these flaws that I thought were obvious. Moreover the editor did not even mention it. Also in the tries I simply see no function for these pieces. It is okay that every author has its own style but I think idle pieces of that kind are not a matter of style. So what is wrong with me?
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(2) Posted by Jacques Rotenberg [Sunday, Jan 22, 2012 07:25]

Well... nowadays, it is usual to consider some tries as being part of the solution.
It also usual not to be afraid to add black pieces in order to obtain more accurate play, such as
- precise (or good) variations in actual or try play
- precise (or good) refutation of tries

The aim of these additional pieces may be to add black (or white) moves, or to eliminate black (or white) moves, depending on the intention of the author.
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(3) Posted by Eugene Rosner [Sunday, Jan 22, 2012 19:13]

In 14710, the bQ is necessary to attack b1 when 1....Sg3 in the try 1.Sc6? the wp crystallizes the matrix to prevent an unwanted wS move. This looks like a beautiful threat correction, a specialty of the composer with 1.Sc6/Sc2? (2.Qb1/Rf4#) Sd2/Rxf5! and 1.Sxd5!! (2.Sc3#!), a beautiful flight giving key, with changed play for 1...Rc7 in set and transferred play for 2.Rf4# (different defenses, same mate
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(4) Posted by Sven Hendrik Lossin [Monday, Jan 23, 2012 10:59]; edited by Sven Hendrik Lossin [12-01-23]

Dear Eugene,

did I understand you right that the bQh1 and bPh2 exist for that reason that the mating move after 1.Sc6 Sg3 is unique? That seems quite expensive to me but is certainly alright because it strengthens the try 1.Sc6?.

So I have a good explanation for these two pieces. Now I need to find a variation where Sa2 is possible to have an explanation for the wPa2. I suppose that the wPa2 was needed in older versions in which 1.Sa2 was also possible. In 14711 I am still clueless.
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(5) Posted by Eugene Rosner [Monday, Jan 23, 2012 17:52]

the wPa2 is a plug to stop the unwanted 1.Sa2, which blurs the intention...
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(6) Posted by Eugene Rosner [Monday, Jan 23, 2012 17:53]

it also looks like a cook!
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(7) Posted by Jacques Rotenberg [Monday, Jan 23, 2012 19:04]

1.Sa2? Rc7!
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(8) Posted by Eugene Rosner [Monday, Jan 23, 2012 19:44]

so the try is unwanted because of the double threat....
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(9) Posted by Joost de Heer [Monday, Jan 23, 2012 20:39]

In the second problem, bPb2 and bPc2 are necessary to avoid multiple refutations to 1. Qd2?
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(10) Posted by Sven Hendrik Lossin [Tuesday, Jan 24, 2012 14:33]

Well I think it is okay to spend some material on having a single refutation for a try. I can understand as well that an author wants a unique mating move c after 1.a? 1.-b? 2.c. But that somebody might spend material on suppressing a try because it has double threats is something I was not aware of.

So there is only the bPe4 in 14711 left to be explained and after that I will know some more about twomovers ;)
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(11) Posted by Jacques Rotenberg [Tuesday, Jan 24, 2012 16:57]

bPe4 in 14711 forbids a double refutation after 1.Qh2?

Now, about the wPa2 in 14710.... I don't really understand it
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(12) Posted by Hauke Reddmann [Tuesday, Jan 24, 2012 17:26]

If the unwanted try tends to obscure the theme (and boy, is this easily
the case in letteromania :-), the author did good to spend a mere pawn.

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(13) Posted by Jacques Rotenberg [Tuesday, Jan 24, 2012 17:40]

here what exactly is the idea that need do avoid the try 1.Sa2 ?
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(14) Posted by Eugene Rosner [Tuesday, Jan 24, 2012 21:49]

I think the coposer simply doesn't want you to consider it. All he wants is the threat correction sequence. this additional try has a refutation that already appears in one of the thematic phases, and the double threat is a real distraction. I'm with Shire on adding the wP, all the way!
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(15) Posted by Sven Hendrik Lossin [Wednesday, Jan 25, 2012 11:47]; edited by Sven Hendrik Lossin [12-01-25]

Okay, now everything is clear.

Thanks to Jacques who showed me that I am not the only one to pose these questions.

In my selfmates I always avoided extra material to enrich the virtual play - perhaps I will change my mind in that matter. I see that it is allowed in orthodox problems so it should be okay with selfmates as well.

Thank you to the community for providing me an insight into the dangerous minds of twomovers authors ;o)
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(16) Posted by Hartmut Laue [Friday, Jan 27, 2012 17:24]

The topic of this thread is not a simple one! In any case it would be preferred to have a presentation without idle units in the solution if such a construction could be found without loss of thematic clarity. This last "if" clause, however, is the crucial addition: Rather than risk a lack of clarity, one finally gives in and adds a pawn after all attempts to avoid this last way out have shown that one can't do without it. There must be REALLY STRONG thematic reasons for employing extra material which plays no role in the solution. It should never be seen as a legitimate and standard method! In letter themes, for example, it is generally viewed as a major weakness if moves which are constitutive for the theme also occur in by-play, thus making it hard to recognize the theme. Then, if there is no other possibility, the use of an extra pawn may be justified. Other examples are themes in the area of changed play. In the (good old) "New German School", the logical clearness is so utterly important, even characteristic for the whole category, that an extra pawn to achieve this can be a must while the eventual observation that, technically, the solution would work without that pawn would be just a remark of little importance.

If a problem has a thematic try which may be "seductive" or "neat", even rich of contents, but otherwise has no strict significance for the thematic aim of the problem, it is by far less convincing to use extra material in order to "give it more polish". On the contrary, if there are tries which have no convincingly close connection with the thematic object of the problem, there is always the risk that they disturb the artistic qualities. In this case it would be a step into the wrong direction to employ extra material for such a variation/try play which has too much weight anyway! From the artistic point of view, a (serious) try should be part of a harmonious unity with the solution. A try which is a mere seduction deserves considerations of the above kind only if the author's aim is to produce a puzzle for solvers, to make an attempt more likely because it apparently explains the use of some unit which in reality is an idle one in the solution. There may be acceptable reasons to pursue such aims, for example, when constructing a problem for a solvers' competition. But generally discussions about chess problems have principles of art in mind, not those of how to puzzle solvers.

Therefore I would not agree that it is "allowed" in orthodox problems to use extra material "to enrich the virtual play". It is the thematical cleanness (where that virtual play plays a decisive role) which may require some extra pawn - and is then more of a constructional defeat than an acknowledged method (to put it in rough terms). Rather than throwing away the problem, one would accept an extra unit as a compromise.

In many cases it is a delicate decision if an author considers the gain in cleanness as such an improvement that it is worth a pawn or even two. Apart from a number of clear cases (like those mentioned above - in particular, problems in two or three moves have reached a sophisticated level of discussion in that respect) such a decision will contain the risk of provoking criticism.

If, in a main variation, two black moves are equivalent in the sense that they both open the way to the same white continuation (and further variation), this is frequently seen as a weakness (the severeness of which may differ by the circumstances). An author may wish to exclude such a "black dual" (as, among others, Hans Peter Rehm calls it), and this may be worth extra material. But there is no fixed rule for this. For example, if a bQb1 moves to b2 or to a1 (say, to guard h8) and both moves lead to the same continuation, would one really add a bRa1 to make the move Qb2 unique? Or a wPb2? Maybe not, but still one would try to shift the whole position to the left so that (then) only the black move Qa2 (replacing the old Qb2) remains. This feeling shows: Yes, the double possibility Qb2,a1 is a nuisance so that one should try to find a way to exclude it - but if a simple shift to the left does not work (for other reasons), it is by no way clear that one would employ an extra unit!

A thematic try must fail to a unique black move as we all know. Certainly, two refutations which are very different or even contain different ideas of defence are a most serious flaw. But if there is a bQb1 and a try fails to 1. - Qb2! and 1. - Qa1! (say, both because now h8 is guarded), is this such a damage that it justifies an additional bRa1? Depends on the whole position, but again - a shift to the left, if possible, would help without harm. And if not possible, there would be no automatism to use a plug on a1 now instead of enduring the not quite unique refutation 1. - Qb2,a1.
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(17) Posted by Eugene Rosner [Friday, Jan 27, 2012 18:00]

Hartmut's reply is really excellent. It truly tackles an example where thematic/aesthetic qualities have to be weighed. What is interesting here is that there are often situations where the decision to be made is very clear and others where it is not. I think, the more someone composes or solves other problems, the easier the decision making process becomes.

Again, a really wonderful contribution by Hartmut!
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(18) Posted by Jacques Rotenberg [Sunday, Jan 29, 2012 02:19]

To my taste, the language used by Hartmut is a little bit limitative.
More or less everyone may put his own "may" "should" "must" "could" where he wants.

On one hand chess problem is a sport where general technical limitations or rules are acceptable.
On the other hand chess problem is also an art where personal will and taste is the rule.

To speak of "rules of art..." sounds a bit like an oxymoron.
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(19) Posted by Hartmut Laue [Sunday, Jan 29, 2012 04:15]

Just a hint: While I read the word "rule" three times in Jacques' post, I find it just once in my foregoing contribution. May I quote that sentence: "But there is no fixed rule for this." Jacques' "oxymoron remark" obviously does not refer to my post. By the way - and this, as easily seen, is the spirit of my post - I likewise object when attempts are made to force art into a Procrustean bed. Even the widest spread convictions cannot be viewed as "laws" or "rules" of an art.
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(20) Posted by Jacques Rotenberg [Sunday, Jan 29, 2012 09:04]; edited by Jacques Rotenberg [12-01-29]

OK Hartmut your humor is nice :
let's quote some of the verbs or terms you use :

"There must be REALLY STRONG thematic reasons for..."
"It should never be seen as a legitimate and standard..."
"...In this case it would be a step into the wrong direction..."
"But generally discussions about chess problems have principles of art..."
"Therefore I would not agree that it is "allowed" in orthodox problems..."
"Rather than throwing away the problem, one would accept an extra unit as a compromise..."

In any case, I don't fully disagree with your purpose, I just give a little criticism about what may appear as a lack of pliability

It is interesting that you speak of "Procrustean bed". It is exactly what frightens me.
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MatPlus.Net Forum Twomovers Who is gonna explain me Twomovers?