[gecode-users] Limiting the number of solutions of a search's subtree

[Andrea Peano]

Hello,
thank you for your suggestion.

Taking a cue from this discussion:
http://www.gecode.org/pipermail/users/2013-January/003765.html

I've implemented this system:
once installed branchers for variables x and y, I install a brancher that
takes in input a function (nested_search()). This function installs the
brancher for variable z, instantiates a new search engine, calls the next()
method, then kills the brancher on z.
Here the code:
*void MyModel::nested_search()*
*{*
* IntVarArgs z;*

* z << get_z();*
* BrancherHandle b = branch(*this, z, INT_VAR_SIZE_MIN(), INT_VAL_MIN(),
NULL, &printZ);*

* DFS<MyModel> dfs_first_sol(this);*
* if( MyModel *sol = dfs_first_sol.next() ) {*
* sol->print(cout);*
* delete sol;*
* }*

* b.kill(*this);*
* done();*

*}*

This works pretty well, unless the fact that Gist "can't see" the nested
search tree, and I can't use inspectors for the nested solution. Moreover
the current solution space is the calling one, so it's a bit hard to use
for example a B&B search over the entire search tree. In fact, I've a
search engine for each leaf of the upper search tree, and they can't share
information, as it is.
Am I right?

Should I design a new search engine in order to achieve a more flexible
behaviour?

Best regards,
Andrea


On Wed, Nov 20, 2013 at 8:22 PM, Christian Schulte <cschulte at kth.se> wrote:

> There has been a similar discussion along these lines (for only two
> branchers) on this mailing list (using more than one search engine to get
> the desired behavior). Please try to find it in the mailing list archives.
>
>
>
> Christian
>
>
>
> --
>
> Christian Schulte, www.ict.kth.se/~cschulte/
>
>
>
> *From:* users-bounces at gecode.org [mailto:users-bounces at gecode.org] *On
> Behalf Of *Andrea Peano
> *Sent:* Wednesday, November 20, 2013 8:08 PM
> *To:* users at gecode.org
> *Subject:* [gecode-users] Limiting the number of solutions of a search's
> subtree
>
>
>
> Hello all,
>
> I've installed 4 branchers in order to solve my model.
>
> Although I need to compute the entire search tree of the first three
> branchers, It would be very effective to limit the number of solutions of
> the remaining subtrees.
>
>
>
> In other words, given a leaf of the search three produced by the first
> three branchers, I would compute only the first solution of the last one.
>
>
>
> I read section 8.1 of the guide, named "Executing code between branchers",
> and this behaviour seems to be achievable by posting some contraints,
> somehow...
>
> Is it the right way?
>
>
>
> Do you have any suggestion?
>
>
>
> Thank you,
>
> Andrea
>



-- 

Andrea Peano - PhD student
Department of Engineering - University of Ferrara
Tel: +39 0532 97 4827
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