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 Post subject: Re: Retrograde problems
PostPosted: Sat Jul 28, 2018 20:21 
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ildjarn wrote:
Sorry, I haven't been able to find anything. Can you give the exact last move (capture over which pieces exactly)?


Of course Ildjarn.
As I suspected a retrograde problem with more then 3 plies may be quite difficult.
Here the first problem needs 4 plies which are very difficult to find.

Position before the last move:
Image

It remains 3 plies to find, for a final score = 040703

The second problem needs 5 plies but, surprisingly, I feel it is far easier than the first problem.

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 Post subject: Re: Retrograde problems
PostPosted: Sat Jul 28, 2018 21:03 
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Real name: Joost de Heer
Image
I was constantly starting with 9x24 3x19, I just never got the idea for a king on the 46-23 line.

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 Post subject: Re: Retrograde problems
PostPosted: Sat Jul 28, 2018 21:53 
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ildjarn wrote:
Image
I was constantly starting with 9x24 3x19, I just never got the idea for a king on the 46-23 line.

Oops you are now very good on 3 plies problem!

Image

here is the score of this problem
Spoiler:
score = 050701

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 Post subject: Re: Retrograde problems
PostPosted: Sun Jul 29, 2018 16:01 
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Real name: Joost de Heer
Apart from 'last move is probably by piece 32 or 14', I haven't got a clue how to start....

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 Post subject: Re: Retrograde problems
PostPosted: Sun Jul 29, 2018 16:23 
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ildjarn wrote:
Apart from 'last move is probably by piece 32 or 14', I haven't got a clue how to start....


Yes Ildjarn, the last move is done by 32 or 14 but one of this two pieces is obviously far better than the other!

The key idea:
Spoiler:
With the first retrograde ply (the mast move) you put a white king on the rectangle 3-25-48-26 by avoiding to put any other piece on this rectangle.
That way, with the second retrograde ply you do a capture along this rectangle by decreasing as far as possible the number of unstable pieces.
After that the problem is almost solved because there are no other capture move!

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 Post subject: Re: Retrograde problems
PostPosted: Sun Jul 29, 2018 19:15 
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Real name: Joost de Heer
Image
13-19 32-28 26-31 42x39 45x32

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 Post subject: Re: Retrograde problems
PostPosted: Sun Jul 29, 2018 23:05 
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ildjarn wrote:
Image
13-19 32-28 26-31 42x39 45x32


Congratulations for having solved this 5 plies problem!

Before showing you other problems I would like to discuss with you the criterias I used here to find the best solution.
The idea is to find a solution as simple as possible and I took for grant that the number of plies was the best criteria for measuring the simplicity of a solution.
After having seen your different proposals I am now not quite sure it is the correct approach.

First example:
Image

In order to limit as far as possible the number of plies we have seen the following solution:
Image

but if you search the solution with the minimum number of pieces you find your proposal
Image

which appear to me far simpler!


Second example:
Image

In order to limit as far as possible the number of plies we have seen the following solution:
Image

but you search to find the solution with the minimum number of pieces you find the solution
Image

which appear also simpler with only 4 pieces added instead of 6.

What is your feeling?

Isn't it better to define the priorities as follows:
from the highest priority to the lowest:
1) the number of pieces added is minimum
2) the number of kings added is minimum
3) the number of plies used is minimum

Note: for the two last problems I proposed the solution is the same (they do not depend of the order of priorities).

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Gérard


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 Post subject: Re: Retrograde problems
PostPosted: Wed Aug 08, 2018 22:26 
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This time I would like to propose some problems by adding the following contraint : you are not allowed to use kings!

Two problems for beginners (2 plies):

Diag 1
Image

Diag 2
Image


Three rather easy problems (3 plies)

Diag 3
Image

Diag 4
Image

Diag 5
Image


Four difficult problems (5 or 6 plies)

Diag 6
Image

Diag 7
Image

Diag 8
Image

Diag 9
Image


One very difficult problem (10 plies)

Diag 10
Image

Take pleasure studiing such problems !

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 Post subject: Re: Retrograde problems
PostPosted: Thu Aug 09, 2018 17:58 
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Attempts for the first 5 ones:
Spoiler:
1: 19.24.33.35.43.44/9.30 1. 19-14 9x40
2: 29.34.39.45/35.40 1. 34-30 35x44
3: 8.9.17.27.37.46.47.49 / 24.25.33.38.43 1... 38-42 2. 49x20 25x41
4: 6.16.36 / 1.2.12.21.22.27 1... 27-31 2. 36x7 2x11
5: 18.27.36.46.47 / 4.14.24.33.37.41 1... 37-42 2. 47x9 4x31

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 Post subject: Re: Retrograde problems
PostPosted: Thu Aug 09, 2018 18:19 
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ildjarn wrote:
Attempts for the first 5 ones:
Spoiler:
1: 19.24.33.35.43.44/9.30 1. 19-14 9x40
2: 29.34.39.45/35.40 1. 34-30 35x44
3: 8.9.17.27.37.46.47.49 / 24.25.33.38.43 1... 38-42 2. 49x20 25x41
4: 6.16.36 / 1.2.12.21.22.27 1... 27-31 2. 36x7 2x11
5: 18.27.36.46.47 / 4.14.24.33.37.41 1... 37-42 2. 47x9 4x31


Fine Ildjarn, three optimum solutions
Spoiler:
diag3: your score is 030900 and you can reach 030200 !!!

diag4: your score is 030400 and you can reach 030300

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 Post subject: Re: Retrograde problems
PostPosted: Thu Aug 09, 2018 18:25 
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Spoiler:
4. 16.37 / 1.7.11.21.22.27 1... 27-32 2. 37x6 7-11

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 Post subject: Re: Retrograde problems
PostPosted: Thu Aug 09, 2018 18:27 
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ildjarn wrote:
Spoiler:
4. 16.37 / 1.7.11.21.22.27 1... 27-32 2. 37x6 7-11


diag 4 : very good Ildjarn

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 Post subject: Re: Retrograde problems
PostPosted: Thu Aug 09, 2018 18:29 
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Spoiler:
3. 26.47 / 31.36.37.41 1... 37-42 2. 26x46 36-41

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 Post subject: Re: Retrograde problems
PostPosted: Thu Aug 09, 2018 18:34 
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ildjarn wrote:
Spoiler:
3. 26.47 / 31.36.37.41 1... 37-42 2. 26x46 36-41


Here again very good.
The first 5 diag are solved.

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 Post subject: Re: Retrograde problems
PostPosted: Sun Aug 19, 2018 09:58 
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#7, first attempt:
Spoiler:
21, 27, 37, 47, 48, 49 / 4, 11, 12, 14, 24, 33, 38, 39, 43; 1. 21-16 39-44 2. 16x18 38-42 3. 47x9 4x42

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