Re: [eclipse-clp-users] How to implement a sudoku explainer

Marcos Müller wrote:
> Hi,
> I'm trying to define a soduku solver and i did it... I also find one at (
> http://87.230.22.228/examples/sudoku.ecl.txt)  but i wanna to show to the
> user how i got to the result...
> "explain better" - i wanna to show how many and what tentatives my solver
> took to solve this sudoku and then i will try to improve it. Someone has an
> idea on how to do that? I think that i have to put some (printf) inside the
> labeling or the alldifferent procedures. Rigth?
> Ty....
> 
> 
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Hi Marcos,

The visualisation tools (as described in the Visualisation tools manual) 
will let you see the effect of propagation on the variable domains, i.e. 
you can see how the domain for the other variables are affected by 
labelling of a variable to a value (which I think is what you mean by 
"what tentative my solver took").

Note however that for many instances, ECLiPSe's lib(ic) does not require 
much search to find the solution, i.e. just by posting the constraints, 
it is sufficent to find the solution, or to nearly do so, so you may not 
see much. [Sudoku puzzles are supposed to have a single unique solution, 
so the constraints alone are sufficient to determine what the solution 
should be without any search. The reason that search may be done is 
because the `resoning' performed by the constraints are not powerful 
enough. There is a tradeoff between the amount of reasoning done and the 
time to perform this reasoning, and for the alldifferent constraint used 
  in Sodoku, you currently have a choice of two implementations that 
perform different amount of reasoning, and the example code you refer to 
above uses the alldifferent from ic_global, which does more reasoning 
(and hence less search).

Cheers,

Kish


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