Hi guys, just using assign after branching on A doesn't work. Assign has a very different semantics, you can only use it if you are guaranteed to find a solution using the leftmost branch. What you need here is either the two-stage search Christian mentioned: for every solution to A, run a new search engine that finds a single solution for the rest of the variables. Or implement something like the "once" combinator. I think our radiotherapy example includes code for this. We can't provide a generic solution very easily, because it's a combinator that modifies another search heuristic (so it would have to be "wrapped around" the existing branchers).
Cheers, Guido -- Guido Tack On 28/01/2013, at 20:38, Christian Schulte <cschu...@kth.se> wrote: > Yes, that should do the trick as assign only creates a single alternative > (so there will be no branching on B). > > Christian > > -- > Christian Schulte, www.ict.kth.se/~cschulte/ > > > -----Original Message----- > From: users-boun...@gecode.org [mailto:users-boun...@gecode.org] On Behalf > Of Martin Mann > Sent: Monday, January 28, 2013 10:36 AM > To: 'gecode user list' > Subject: Re: [gecode-users] splitting branching in full enumeration and > first-fail check > > > Great! Thanks Christian! > > Had a look into MPG yesterday but somehow skipped it.. Thanks for the help > and exactly the piece of code I was looking for! :) > > If I am right the following statements at the end of my Space constructor > should do right? > > branch( *this, A, ..); > assign( *this, B, ..); > > So the overall reported solutions should show all valid assignments for A > but for each only one valid assignment for B, right? > > Please let me know if I am wrong and thanks again for the quick help! > > Cheers, > Martin > > > > Am 28.01.2013 10:00, schrieb Christian Schulte: >> That should be easy enough: set up a search engine with branching on A. >> Suppose you get a solution there (a space): then post the simple >> assignment branching on B on use a different search engine to find a > solution there. >> >> You might want to read about assignment branchings in MPG. >> >> Best >> Christian >> >> -- >> Christian Schulte, www.ict.kth.se/~cschulte/ >> >> >> -----Original Message----- >> From: users-boun...@gecode.org [mailto:users-boun...@gecode.org] On >> Behalf Of Martin Mann >> Sent: Sunday, January 27, 2013 12:09 PM >> To: gecode user list >> Subject: [gecode-users] splitting branching in full enumeration and >> first-fail check >> >> >> Dear Gecoders, >> >> I am working on a small problem where the CSP variables are split into >> two subsets A and B. >> >> For set A, a full enumeration of all valid assignments is wanted while >> for set B a single check for a valid assignment is sufficent. >> >> Some years ago with Gecode 1.3 I wrote my own branching that did the >> latter part. >> Thus, first normal branch on A followed by pseudo-branching on B. The >> latter stopped the subsearch for B after the first solution was found >> such that the search in A was continued and so on. >> >> So my question: is there a direct support for such a scheme in Gecode 3.7? >> Or do I have to find my old branching implementation and make it ready >> for the new version? I am crossing fingers you have something ready.. >> :/ >> >> Thanks for your help, >> Martin > > > _______________________________________________ > Gecode users mailing list > users@gecode.org > https://www.gecode.org/mailman/listinfo/gecode-users > > > _______________________________________________ > Gecode users mailing list > users@gecode.org > https://www.gecode.org/mailman/listinfo/gecode-users _______________________________________________ Gecode users mailing list users@gecode.org https://www.gecode.org/mailman/listinfo/gecode-users
