[gecode-users] How to stop a branching?

[Martin Mann]

Hi,

I would like to know, if it is possible to stop a branching (when 
multiple ones are present). Thus, to ignore all remaining branches for 
this specific one.

Maybe an example to make my question clear.

I have two sets of variables X_1, X_2 linked via several constraints. 
Within my Space I post two brachning B_1(X_1) and B_2(X_2) such that 
first all variables of X_1 are assigned before B_2 is considered.

My final goal is to enumerate solutions with different X_1 assignments!

My current solution (was implemented for Gecode 1.3.* and I am going to 
reimplement in 3.*) is to formulate a COP instead of a CSP and to 
implement the *constrain* function and to post a constraint that ensures 
that the next solution is at least in one X_1 assignment different from 
the current solution.

Thus, I get a new constraint per solution ... and I dont like that! ;)

But when looking at the problem, it would be sufficient to stop the 
branching on X_2! I dont need to post new constraints but to cancel the 
remaining branching of B_2 on X_2. This will lead to a backtracking in 
B_1 and therefore ensures that the next solution differs in the X_1 
assignment in at least one solution...

This seems to be much more efficient to me. Btw. I would end up with a 
CSP instead of this strange COP hack.

So my question: Is it possible to stop the remaining branching on B_2 
out of the (Gecode 3.*) box? Or do I have to implement/subclass my own 
branching?

Thanks for your help,

Martin


-- 
Martin Mann, Dipl. Bioinf.
Bioinformatics - Inst. of Computer Science
Albert-Ludwigs-University Freiburg
Tel: ++49-761-203-8259
Fax: ++49-761-203-7462
http://www.bioinf.uni-freiburg.de/~mmann/