I'm sorry for multiple replies, but I want to ask this in a more general fashion.
Consider I planned to perform a quite burdensome heuristic in a particular point of the search (that's why I'm splitting the search). Obviously this heuristics helps to prune the search space. How can I be sure that this heuristic is not recomputed more and more? Thanks, Andrea Peano On Tue, Sep 23, 2014 at 2:24 PM, Andrea Peano <andrea.pe...@unife.it> wrote: > On Tue, Sep 23, 2014 at 2:09 PM, Christian Schulte <cschu...@kth.se> > wrote: > >> You can disable recomputation but this is not a good idea as it degrades >> performance seriously and increases memory consumption considerably. >> > Yes, I see. > > >> >> >> What you could do (also not good) is call status() yourself. >> > I'm already doing it, but this does not seem enough to prevent > recomputation on those nodes. I call it within second_level and third_level > but it's not enough. Do you mean somewhere else? > > >> >> >> The real (but tough) thing to do is to implement your own brancher. >> > >> >> And just checking: do you know that multiple branchers are executed in >> the order they are created? But maybe that is not enough for you. >> > Yes, I know, I tried to make the search as simple as possible, but there > are some aspects of the problem a bit difficult to manage. > Anyway, I'll find a way. > > Thanks for giving me a halping hand. > > Andrea > > >> >> >> Cheers >> >> Christian >> >> >> >> -- >> >> Christian Schulte, Professor of Computer Science, KTH, >> www.gecode.org/~schulte/ >> >> >> >> *From:* users-boun...@gecode.org [mailto:users-boun...@gecode.org] *On >> Behalf Of *Andrea Peano >> *Sent:* Tuesday, September 23, 2014 2:00 PM >> *To:* users@gecode.org >> *Subject:* Re: [gecode-users] Strange branching behaviour when using >> FunctionBrancher >> >> >> >> I was just reading on the Gecode guide that this behaviour is due to the >> "recomputation". >> >> So I have two more questions: can I completely prevent this behaviour by >> disabling recomputation? >> >> Has recomputation a direct effect on parallel search? >> >> >> >> Thanks, >> >> Andrea >> >> >> >> On Tue, Sep 23, 2014 at 1:22 PM, Andrea Peano <andrea.pe...@unife.it> >> wrote: >> >> Hello, >> >> >> >> I've implemented a search strategy by splitting the search into three >> levels. I think the code may explain better this strategy. >> >> >> >> >> >> void MyModel::post(Space& home) >> >> { >> >> static_cast<MyModel&>(home).second_level(); >> >> } >> >> >> >> void MyModel::second_level() >> >> { >> >> status(); >> >> >> >> //do something with the partial solution >> //print "second level" >> >> branch(*this, BoolBranchDirection, INT_VAL_MIN()); >> >> branch(*this, post2); >> >> } >> >> >> >> void MyModel::post2(Space& home) >> >> { >> >> static_cast<MyModel&>(home).third_level(); >> >> } >> >> >> >> void MyModel::third_level() >> >> { >> >> if(BoolBranchDirection.val()==0) >> { >> //print third level left >> //left branch behaviour (install further branches) >> } >> else >> { >> //print third level right >> //right branch behaviour (install further branches) >> } >> >> } >> >> >> >> Imagine now we are fixing the partial solution before the "post" calling, >> so the solver goes only once into the "post" function (and it's confirmed >> by GIST). >> >> >> >> The strange fact is that "second_level" is called more than once! Instead >> I expect one call for "second_level" and two calls for "third_level", which >> executes two different paths of the code. >> >> >> >> These are the prints I read: >> >> second level >> >> third level left >> >> second level >> >> third level right >> >> second level >> >> third level right >> >> >> >> But I expected: >> >> second level >> >> third level left >> >> third level right >> >> >> >> Can you clarify this behaviour please? >> >> >> >> Furthermore, I experienced that I need to call "status()" within the >> second level, to ground some variables I expected to be already ground. Is >> this normal? >> >> >> >> I'm using Gecode 4.2.1 >> >> >> >> Thanks, >> >> Andrea >> >> >> >> >> >> -- >> >> >> >> Andrea Peano - PhD student >> >> Department of Engineering - University of Ferrara >> >> Tel: +39 0532 97 4827 >> >> >> >> >> >> -- >> >> >> >> Andrea Peano - PhD student >> >> Department of Engineering - University of Ferrara >> >> Tel: +39 0532 97 4827 >> > > > > -- > > Andrea Peano - PhD student > Department of Engineering - University of Ferrara > Tel: +39 0532 97 4827 > -- Andrea Peano - PhD student Department of Engineering - University of Ferrara Tel: +39 0532 97 4827
_______________________________________________ Gecode users mailing list users@gecode.org https://www.gecode.org/mailman/listinfo/gecode-users
