Thanks for your reply. I tried to simplify my real architecture, maybe too much!
I create a "backup" space before starting the search, that is a copy of the original space used during the search, and it is a global variable of the code. Within the ::post function I create a copy of the backup model, I update this space by passing the current (partial) solution, and then I search the first sol, like that: MyModel *inner_model=static_cast<MyModel *>(backup->clone(true)); inner_model->update_variables(this->partial_sol_values()); inner_model->status(); ... inner_dfs.next(); Scary stuff again, I guess! In general, I need of a partial solution before starting the second step in order to run some scary heuristics :) You refer to this discussion: http://www.gecode.org/pipermail/users/2013-January/003769.html don't you? Thanks, Andrea On Tue, Apr 15, 2014 at 4:27 PM, Christian Schulte <cschu...@kth.se> wrote: > Hi Andrea, > > > > Whoa! Scary stuff ;-) That's not possible to clone a space that is > currently in use for propagation (because that is what is still going on > when the ::post function is executed). > > > > However it should work much much easier: there has been a discussion in > this users group a while ago on how to split search into two parts. Then > you can parallelize each one. Just go through the archive (or maybe one of > the users who took part in the discussion can help here). > > > > Cheers > > Christian > > > > -- > > Christian Schulte, Professor of Computer Science, KTH, > www.ict.kth.se/~cschulte/ > > > > *From:* users-boun...@gecode.org [mailto:users-boun...@gecode.org] *On > Behalf Of *Andrea Peano > *Sent:* Tuesday, April 15, 2014 2:35 PM > *To:* users@gecode.org > *Subject:* [gecode-users] Multithreading executions crash > > > > Hello everyone, > > my model is solved by a two-steps search. The first step can be a DFS as > well as a BAB search, the second step is always a DFS. > > > > I implemented this search by following the section "Executing code between > branchers" of the Gecode's guide, like this: > > branch(*this, MyModel::post) > > > > The function "post" copies the current space into a local variable, then > instantiates a new DFS engine and finally calls the method "next", in order > to compute only the first solution. > > > > MyModel *inner_model=static_cast<MyModel *>(this->clone(true)); > > inner_model->status(); > > ... > > inner_dfs.next(); > > > > The idea is to parallelize the first level of the search... but if I use > only one thread everything works fine, otherwise every time the execution > crashes on a different instruction of the function "post". > > > > Do you have any clue about this behavior? > > The worst scenario I see is that this solving architecture is totally > incompatible with the multithreading system implemented in Gecode. > > > > Thanks, > > Andrea > -- Andrea Peano - PhD student Department of Engineering - University of Ferrara Tel: +39 0532 97 4827
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