[gecode-users] Adding restart-based search to ECLiPSe's interface to Gecode

[Kish Shen]

Hi Christian,

Thanks for the code. This code looks to be more C++ like than what I 
have now, where my GecodeSearch class (equivalent to EngineBase here) 
has several private engine pointers for the different engine types, and 
the functions like next() switch on the search methods to call the 
function of the correct engine type. I will change my code to be more 
like what you are doing here. Thanks again.

My next question is now about doing the restart: are there any 
alternatives to doing restart based on the number of failures? One 
alternative is to do restart only with a new solution. I assume this is 
what the old RESTART engine did. As the current gfd interface supports 
this engine, I would like to continue to support it. As I said in my 
previous posting, I am not sure if the next solution is done via restart 
in RBS, because it seem to use DFS or BAB as the "actual" search engine, 
and these engines don't restart (as far as I can tell) with the next 
solution.

Thanks and cheers,

Kish

On 27/08/2013 09:51, Christian Schulte wrote:
> Hi Kish,
>
> Here is a solution built on top of Gecode. It defines a type
> Kish::EngineBase that can be passed around irrespective of which engine it
> actual is. The other stuff is just for illustration and how to recast
> Gecode's engines as engines of type Kish::EngineBase.
>
> Hope this helps.
>
> Best
> Christian
>
>
> namespace Kish {
>
>    class EngineBase {
>    public:
>      EngineBase(void) {}
>      virtual Gecode::Space* next(void) = 0;
>      virtual Gecode::Search::Statistics statistics(void) const = 0;
>      virtual bool stopped(void) const = 0;
>      virtual ~EngineBase(void) {}
>    };
>
>    class DFS : public EngineBase {
>    protected:
>      Gecode::DFS<Gecode::Space> e;
>    public:
>      DFS(Gecode::Space* s, const Gecode::Search::Options& o)
>        : e(s,o) {}
>      virtual Gecode::Space* next(void) {
>        return e.next();
>      }
>      virtual Gecode::Search::Statistics statistics(void) const {
>        return e.statistics();
>      }
>      virtual bool stopped(void) const {
>        return e.stopped();
>      }
>      virtual ~DFS(void) {}
>    };
>
>    class BAB : public EngineBase {
>    protected:
>      Gecode::BAB<Gecode::Space> e;
>    public:
>      BAB(Gecode::Space* s, const Gecode::Search::Options& o)
>        : e(s,o) {}
>      virtual Gecode::Space* next(void) {
>        return e.next();
>      }
>      virtual Gecode::Search::Statistics statistics(void) const {
>        return e.statistics();
>      }
>      virtual bool stopped(void) const {
>        return e.stopped();
>      }
>      virtual ~BAB(void) {}
>    };
>
>    template<template<class> class E>
>    class RBS : public EngineBase {
>    protected:
>      Gecode::RBS<E,Gecode::Space> e;
>    public:
>      RBS(Gecode::Space* s, const Gecode::Search::Options& o)
>        : e(s,o) {}
>      virtual Gecode::Space* next(void) {
>        return e.next();
>      }
>      virtual Gecode::Search::Statistics statistics(void) const {
>        return e.statistics();
>      }
>      virtual bool stopped(void) const {
>        return e.stopped();
>      }
>      virtual ~RBS(void) {}
>    };
>
>    enum WhichEngine {
>      WE_DFS, WE_BAB,
>      WE_RBS_DFS, WE_RBS_BAB
>    };
>
>    EngineBase* engine(WhichEngine we,
>                       Gecode::Space* s,
>                       const Gecode::Search::Options& o) {
>      switch (we) {
>      case WE_DFS: return new DFS(s,o);
>      case WE_BAB: return new BAB(s,o);
>      case WE_RBS_DFS: return new RBS<Gecode::DFS>(s,o);
>      case WE_RBS_BAB: return new RBS<Gecode::BAB>(s,o);
>      }
>    }
> }
>
>
> --
> Christian Schulte, Professor of Computer Science, KTH,
> www.ict.kth.se/~cschulte/
>
>
> -----Original Message-----
> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
> Of Christian Schulte
> Sent: Thursday, August 22, 2013 9:50 AM
> To: 'Kish Shen'
> Cc: users at gecode.org
> Subject: Re: [gecode-users] Adding restart-based search to ECLiPSe's
> interface to Gecode
>
> Hi Kish,
>
> My bad... There is really no common basetype for search engines, the type I
> mentioned is actually for the implementations and not the interfaces...
>
> I think you will have to wait until I have added a common basetype (there is
> a basetype, but it is not powerful enough), I might be able to do it until
> the end of the week.
>
> Sorry for the confusion!
>
> Cheers
> Christian
>
> --
> Christian Schulte, Professor of Computer Science, KTH,
> www.ict.kth.se/~cschulte/
>
>
>
> -----Original Message-----
> From: Kish Shen [mailto:kisshen at cisco.com]
> Sent: Thursday, August 22, 2013 9:45 AM
> To: cschulte at kth.se
> Cc: users at gecode.org
> Subject: Re: [gecode-users] Adding restart-based search to ECLiPSe's
> interface to Gecode
>
> Hi Christian,
>
> Thanks again!
>
> On 21/08/2013 19:17, Christian Schulte wrote:
>> Try to avoid the Gecode::Search::bab .... functions. Just create as
> follows:
>> 	Gecode::Search::Engine* e = new Gecode::BAB(...) Then it also will
>> work for RBS, and you do not have to create a second engine yourself,
>> this will the RBS class do for you.
>>
>> And do not forget to delete e eventually!
>>
>
> This is the part that I don't know how to do correct -- probably because of
> my lack of C++ knowledge, but as far as I can tell, Gecode::DFS etc are not
> of class Engine*, according to the doc:
>
> template<class T>
> class Gecode::DFS<T>
>
> for subclasses T of Space
>
> T is GecodeSpace in my case, I assume. I am not sure what class DFS is, but
> I can't see how it could be Engine*.
>
> Anway, I tried to do the assignment as you suggested:
>
>
> Search::Engine* segine;
> ...
> sengine = new DFS<GecodeSpace>(solver, o); and indeed I get the error
>
> cannot convert 'Gecode::DFS<GecodeSpace>*' to 'Gecode::Search::Engine*'
>
> (I first tried sengine = new DFS(solver, o) but got an error 'expected
> type-specifier')
>
> So I am not sure what to do -- do I need to change the type of sengine,
> and/or the way I assign an engine to sengine?
>
> Cheers,
>
> Kish
>
>
>
>
>
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