[Retros] Retractor (was Re: Programs for Solving Retro Problems)

[Alain BROBECKER]

> Maybe we can also use this discussion to define the

> requirements

> for a retrograde analysis program.

> 

> I'll start with my personal experiences when using

> 'Retractor':

> 

> On the 'plus' side:

> + the only publically available RA program

> + free usage (you do not have to pay for it)

> + graphical user interface

> + good and fast for 'Last n moves' problems

> + FEN input configurable (so I can use 'N' for

> knight

>   and am not forced to use 'S' for knight as popeye

> does)

> + has a rather strong pawn capture analysis

> + a lot of non-trivial cages are detected 

> + allows at least some user intervention:

>   * w/b 'peacefulness'

>   * specification of w/b promotions

> 

> On the 'minus' side (please have in mind, that the

> program

> is from 1998, so some points can be simply explained by

> the limitations of HW and SW of that time!):

> - some trivial king cages are not detected

> - some simple illegalities are not detected

> - the number of variations is limited to 30

> - the above mentioned parameter settings

> (promotions/peacefulness)

>   are not permanently visible

> - no warning, that the program is limited to

>   approx. 99 last single moves (after saving a longer

> retractions

>   at least some information gets lost, sometimes the

> program

>   hangs up totally, if such a *.ret file is reloaded)

> - if one first makes some retromoves by pointing and

> clicking,

>   and than calls the Resolve function, the moves so far are

> lost

>   (the help therefore gives the advice to always save the

> game

>    before starting a reosultion. O.k. - but I'm often

> forgetting

>    it - so in this case an on/off-switchable message

> "Resolving

>    will destroy the game so far" would be nice ...)

> - no explanation (= the reason), why e.g. a position

>   has a 'Bad pawn structure'

> 

> -- most severe (and at least to some extent a k.o.

> criteria):

>    some *legal* positions are judged by 'Retractor'

> as *illegal*.

> 

> Regards,

> 

>   mario


I was not aware of the 99 moves limitation, and this
may explain some sad experiences i had while using it.

Concerning illegalities, i was pleased at Retractor
handling them until i tried to solve Dragan Petrovic's
Circe RA. ;)

What i would really look forward is not a program that
can handle retro analysis, only a program that allows
the user to unplay a position. It would even be better
if one could try different lines (as in forward chess).

But of course the analysis of Mario is really valuable,
it will make me look a bit deeper at Retractor.
Thank you Ted for writing it and giving it to the
RA community!