## Retrograde problems

### Retrograde problems

Are you interested by retrograde problems?

Let me first try to define what a retrograde problem is.

Stable position : a position is said stable if no pieces are in a capture position.

A retrograde problem generally start from an unstable position and the goal is to retrograde the position till a stable position but with a unique optimum suite of moves!

A suite of move is optimum (from the highest priority to the lowest) if

1) the number of plies used is minimum

2) the number of pieces added is minimum

3) the number of kings added is minimum

Just an example

The following position is a correct problem with a unique solution in 2 plies, 1 piece added and 0 king added

But this following one is not correct because there are two solutions in 2 plies, 1 piece added and 0 king added

Some problem can be extremely difficult but let me propose some "easy" ones, just to see if you are interested

Can you solve the five following ones (white to move):

Let me first try to define what a retrograde problem is.

Stable position : a position is said stable if no pieces are in a capture position.

A retrograde problem generally start from an unstable position and the goal is to retrograde the position till a stable position but with a unique optimum suite of moves!

A suite of move is optimum (from the highest priority to the lowest) if

1) the number of plies used is minimum

2) the number of pieces added is minimum

3) the number of kings added is minimum

Just an example

The following position is a correct problem with a unique solution in 2 plies, 1 piece added and 0 king added

But this following one is not correct because there are two solutions in 2 plies, 1 piece added and 0 king added

Some problem can be extremely difficult but let me propose some "easy" ones, just to see if you are interested

Can you solve the five following ones (white to move):

Gérard

### Re: Retrograde problems

The rules don't specify it but I assume that white has the move in all these diagrams?

The examples:
And the diagrams:

The examples:

**Spoiler:**

**Spoiler:**

Lasst die Maschinen verhungern, Ihr Narren...

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

### Re: Retrograde problems

Hi Iljarn,ildjarn wrote:The rules don't specify it but I assume that white has the move in all these diagrams?

The examples:And the diagrams:Spoiler:Spoiler:

To answer your first question, yes in each diagram it is white to move (as usual for a problem).

Concerning the five diagrams you already succeed in 3 of them.

For the reader who is not familiar with such problem I will give the complete solution for these 3 diagrams:

Diag.3

White to play

Diag3 solution

Black to play

1...10-15 2.34-29 15x24

The solution needs 3 plies and when you compare the initial and the final diagram you can see that 2 pieces have been added and 0 king have been added. The score is then 3.2.0. I will write this with the six digit number 030200 which is the best (smallest) number you can get.

Diag 4

White to play

Diag 4 solution

Black to play

1...20-25 2.33-28 25x23

score 030200

Diag 5

White to play

Diag 5 solution

Black to play

1...21-26 2.28-23 26x28

score 030200

Let me comment your proposals for the first two diagrams

Diag 1

White to play

If I understand correctly you propose the sequence

Black to play

1...20-25 2.21-16 25x21

score 030400

You have to note here that you could get the same score from the diagram

Black to play

Does that mean that it is a dual and the problem is not correct? NO because 030400 is not the best (smallest) score!

Diag2

White to play

It is exactly the same situation in this diagram. You proposed a sequence with a score 030400, you can get easily a dual with the same score, but this score is not the best one.

Of course, for the time being, I let you and the reader search the solution for these two last diagrams

Gérard

### Re: Retrograde problems

030201 is smaller than 030400.

Lasst die Maschinen verhungern, Ihr Narren...

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

### Re: Retrograde problems

Yes Ildjarn ... but it is not still the best score, and so the problem is always not solved.ildjarn wrote:

030201 is smaller than 030400.

I am fond of retrograde problem because you have to be very imaginative and skillful and, even with a very simple position (only three pieces here!), you can build quite interesting problems.

Gérard

### Re: Retrograde problems

For 16/11,21:

020601, 32-38 33x11

For 15/10,20:

020401, 4-31 36x20

020601, 32-38 33x11

For 15/10,20:

020401, 4-31 36x20

Lasst die Maschinen verhungern, Ihr Narren...

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

### Re: Retrograde problems

Almost perfect Ildjarn.ildjarn wrote:For 16/11,21:

020601, 32-38 33x11

For 15/10,20:

020401, 4-31 36x20

In the first diagram you can now very easily get the score 020501 which was what I had in mind.

Gérard

### Re: Retrograde problems

Oh, of course: 32-37 42x11.

Lasst die Maschinen verhungern, Ihr Narren...

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

### Re: Retrograde problems

Congratulation Ildjarn!ildjarn wrote:Oh, of course: 32-37 42x11.

Who will be interested if I post here some new retrograde problems?

Gérard

### Re: Retrograde problems

I like these kind of puzzles, but I doubt many people here would be interested, since you can't complain about the draw margin in these puzzles.

Lasst die Maschinen verhungern, Ihr Narren...

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

### Re: Retrograde problems

Thank you very much for your answer Ildjarn.ildjarn wrote:I like these kind of puzzles, but I doubt many people here would be interested, since you can't complain about the draw margin in these puzzles.

At least with one person interested I can continue proposing such kind of puzzles.

I think it is a good idea to wait some days between each problem. So I will post a new position in 3 or 4 days.

Do you yourself built positions to be retrograde (but not necessarily a problem with a unique solution) ?

Gérard

### Re: Retrograde problems

As promised I come back here to give you some more retrograde problems

Let me remind you and clarify how to calculate the score?

First of all you count the number of plies : pliesNumber

Then you compare the problem position (i.e. the final position!) and the solution position (i.e. the initial position you have to discover) and you count:

piecesAddedNumber = number of pieces in the solution position - number of pieces in the problem position

kingsAddedNumber = number of kings in the solution position - number of kings in the problem position

The calcultatio is quite simple:

score = (10000 * pliesNumber) + (100 * piecesAddedNumber) + kingsAddedNumber

Note1 : pliesNumber is always at least equal to 1

Note2 : piecesAddedNumber is null or positive

Note3 : kingsAddedNumber can be null, positive or negative

The goal is always to get the minimum score.

In all problems it is white to play

Two problems for beginners:

and two others a little more difficult

Let me remind you and clarify how to calculate the score?

First of all you count the number of plies : pliesNumber

Then you compare the problem position (i.e. the final position!) and the solution position (i.e. the initial position you have to discover) and you count:

piecesAddedNumber = number of pieces in the solution position - number of pieces in the problem position

kingsAddedNumber = number of kings in the solution position - number of kings in the problem position

The calcultatio is quite simple:

score = (10000 * pliesNumber) + (100 * piecesAddedNumber) + kingsAddedNumber

Note1 : pliesNumber is always at least equal to 1

Note2 : piecesAddedNumber is null or positive

Note3 : kingsAddedNumber can be null, positive or negative

The goal is always to get the minimum score.

In all problems it is white to play

Two problems for beginners:

and two others a little more difficult

Gérard

### Re: Retrograde problems

tries for diagram 1-3:
Still thinking about #4.

**Spoiler:**

Lasst die Maschinen verhungern, Ihr Narren...

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

### Re: Retrograde problems

Oops not so easy is it?ildjarn wrote:tries for diagram 1-3:Still thinking about #4.Spoiler:

#1 :OK

#2 : your proposal is not correct because your start position is not stable. If you put black man on 23 (instead of 28) and you begin by 23-28 then the score is not the best.

#3 herer you can still get a better score!

#4 is more difficult

Gérard

### Re: Retrograde problems

**Spoiler:**

Lasst die Maschinen verhungern, Ihr Narren...

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!

Lasst sie verrecken!

Schlagt sie tot -- die Maschinen!