[gecode-users] branching and copy in Gecode

[Jun He]

Hi,

Thank you for your explanation.

I want all the instances of my propagator to share the data structure 
instead of making a copy, as storing the data structure needs too much 
memory.  Hence I want my propagator to rollback the data structure when 
a backtracking happens.  Is there an event to notify the propagator (or 
some policy to make the propagator detects) when a backtracking happens?

Best regards,
Jun


On 28/10/12 01:24, Guido Tack wrote:
> Hi,
>
> backtracking always jumps back to a copy and then recomputes the node 
> that it actually wants to jump to.  So you can maintain your 
> propagator data structures incrementally, as long as they're copied 
> (or marked for recomputation) during cloning.  See chapter 7.2 in MPG 
> for a more detailed explanation of recomputation.
>
> Cheers,
> Guido
>
> On 28/10/2012, at 2:23 , Jun He <hejunnudt at gmail.com 
> <mailto:hejunnudt at gmail.com>> wrote:
>
>> Hi,
>>
>> In Gecode, copy doesn't happen for every branching of the search 
>> tree, and whenever a failure happens it just backtracks to a node 
>> between the current failure node and the previous copied node.  If a 
>> propagator works dependent on some data structure, and the backtrack 
>> jumps to a node that is not copied, then the data structure should be 
>> recomputed.  My question is how to maintain the data structure 
>> incrementally for the propagator?  Is there an easy setting to make 
>> Gecode copy at each branching, so that a simple undo policy can be 
>> used to maintain the data structure?
>>
>> Best regards,
>> Jun
>>
>> _______________________________________________
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>
> -- 
> Guido Tack,
> http://www.csse.monash.edu/~guidot/ 
> <http://www.csse.monash.edu/%7Eguidot/>
>
>
>

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