[gecode-users] saving the way to one of the solution in a file

[Mikael De Bie]

Thanks for your answer !

nevertheless I wonder why the webpage http://www.gecode.org/gecodej/
indicates that Gecode/J allows to implement search engines using copying
and recomputation.

Don't you think I could program a new search engine totally in java as
it's done for Gist ?

cheers,
Mikael


On Mon, 2006-12-04 at 09:07 +0100, Guido Tack wrote:
> Hi.
> 
> > I'm using gecode/J 1.0.1-1 and wonder what's the best way to save the
> > position in the search tree in a file in order to be able to  
> > compute the
> > next solution later. Here's some details about what I want to do:
> >
> > * launch my program the first time :
> > 	- find the first solution of a CSP
> > 	- save the way to this solution in the search tree in a file
> > 	- quit
> >
> > * relaunch my program with arguments to indicate I want the next
> > solution :
> > 	- load the state (go to the node)
> > 	- find the next solution
> > 	- save the state (way to this solution)
> > 	- quit
> >
> >
> > I haven't found how to do that in the documentation...
> 
> This is not possible with the search engines we provide, but quite  
> easy to implement yourself. One slight complication is that you use  
> Gecode/J. In Java, we just use an interface to the C++ search  
> engines, so you don't have a Java implementation to start with.
> 
> If you know some C++, I would suggest you have a look at how search  
> is implemented there. The most interesting files are gecode/search/ 
> reco-stack.icc and gecode/search/dfs.icc. Basically, you have a stack  
> that stores branching descriptions and (in some stack cells) copies  
> of spaces. To save the state, you will just have to traverse the  
> stack and save the number of the alternative that has to be explored  
> next from each stack cell. To load the state, recreate the original  
> problem, and then recreate the stack by recomputation. Note, however,  
> that you cannot save the branching descriptions (they are completely  
> abstract anyway), just save the number of the alternative at each point.
> 
> I hope this helps getting you started. If anything is not clear to  
> you, just ask.
> 
> Cheers,
> 	Guido
> 
> 
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