[Lemon-user] Copy constructors

[D Haley]

Péter:
Ah Thanks, I was doing (a), which I felt was messy but had not thought about (b) -- I think (b) is a lot cleaner.

Alpár:
The vector<> statement is not entirely valid. I utilise ::reserve() to advise the vector in advance of the size that I will require, as for my application all this information is known a-priori. The vector<> length never actually changes after the initial push_back().

In my current application I have  many small graphs with 8-15 nodes and ~20-30 edges, so the copying overhead should be minimal.

Thanks for the help, again.

Cheers.

--- On Wed, 2/24/10, Kovács Péter <kpeter at inf.elte.hu> wrote:

> From: Kovács Péter <kpeter at inf.elte.hu>
> Subject: Re: [Lemon-user] Copy constructors
> To: "D Haley" <mycae at yahoo.com>
> Cc: "lemon-user at lemon.cs.elte.hu" <lemon-user at lemon.cs.elte.hu>
> Date: Wednesday, February 24, 2010, 5:08 AM
> Hi All,
> 
> In LEMON, the maps don't have default constructors nor copy
> constructors. The first one is clear: the graph has to be
> given for the map. The second one is because there is a
> long-standing discussion between the developers whether the
> maps should be copied by value or by a reference-counted
> solution. For more details, see these tickets:
> http://lemon.cs.elte.hu/trac/lemon/ticket/137
> http://lemon.cs.elte.hu/trac/lemon/ticket/146
> 
> So the copy constructors are decided to set to 'private'.
> In LEMON 1.1, the maps can only be copied by hand. However,
> a mapCopy() function is intorduced in the development
> verison, which will be present in the upcomming release
> 1.2.
> 
> Therefore I suggest to
>     (a) create the maps dynimcally or
>     (b) couple each graph and its map(s) into a
> class/struct.
> 
> See the details below. If I were you, I would use (b).
> 
> Regards,
> Peter
> 
> 
> (a):
>     using namespace lemon;
> 
>     vector<ListGraph> g;
>    
> vector<ListGraph::EdgeMap<float>*> edgeCostVec;
> 
>     makeSomeGraphs(g); //pass-by-ref (non-const)
> 
>     edgeCostVec[ui].resize(g.size());
>     for(unsigned int ui=0;ui<g.size(); ui++)
>         edgeCostVec[ui] = new
> ListGraph::EdgeMap<float>(g[ui]);
> 
>     // use g[i] with (*edgeCostMap[i])
> 
>     for(unsigned int ui=0;ui<g.size(); ui++)
>         delete edgeCostVec[ui];
> 
> 
> (b):
>     using namespace lemon;
> 
>     struct GraphWithCostMap {
>       ListGraph g;
>       ListGraph::EdgeMap<float> cost;
>       GraphWithCostMap() : g(), cost(g) {}
>     };
> 
>     vector<GraphWithCostMap> graphs;
> 
>     makeSomeGraphs(graphs); //pass-by-ref
> (non-const)
> 
>     // use graphs.g[i] with graphs.cost[i]
> 
> 
> 
> 
> 
> > Hello again,
> > 
> > I am having more troubles with edgemaps (thanks for
> the prev. help,
> worked a treat). Due to the library interface, the copy
> constructors are
> private for edgemaps, which seem to prevent me assigning or
> dupliating
> them in any way. Is there a way I can do something like the
> following?
> I'm currently dropping to pointer semantics, but it feels
> like a kludge.
> > 
> >         
> vector<lemon::ListGraph>  g;
> >         
> vector<lemon::ListGraph::EdgeMap<float> 
> >  edgeCostVec;
> > 
> >          makeSomeGraphs(g);
> //pass-by-ref (non-const)
> > 
> >         
> edgeCostVec[ui].resize(g.size());
> >          for(unsigned int
> ui=0;ui<g.size(); ui++)
> >               
>   edgeCostVec[ui] =
> (lemon::ListGraph::EdgeMap<float>(g[ui]));
> > 
> > _______________________________________________
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> > Lemon-user at lemon.cs.elte.hu
> > http://lemon.cs.elte.hu/mailman/listinfo/lemon-user
>