Re: [Boost-users] BGL new graph type implementation trouble

Subject: Re: [Boost-users] BGL new graph type implementation trouble
From: Sebastian Weber (sebastian.weber_at_[hidden])
Date: 2009-09-01 15:39:48

Hi!

I am currently trying to implement a new graph type which I want to use with
>> the BGL. The graph implements the Incidence Graph concept and should work
>> out of the box with DFS algorithm of the BGL. However, I had to find out
>> that the edge_descriptor must obey an EqualityComparison concept which keeps
>> DFS from compiling. My current edge_descriptor is just a typedef to
>> std::pair<vertex_descriptor, vertex_descriptor>. The vertex_descriptor
>> itself is a custom object I wrote myself.
>>
>
> This is actually documented in the quickbook version of the documents...
> which are incomplete and not distributed :)
>
> I am actually working on them today... A rare case of free time before I
> have to teach a class.
>

I found out that if vertex_descriptor is something like std::size_t for
which all sort of operators are defined, everything is ok. So I suppose it
is sufficient to supply equality operators and the like for my custom
vertex_descriptor and I will be fine, right? Can I get the newer quickbook
version documents somewhere? svn? What branch? Would be great as it looks
like graph documentation is rather out-dated, e.g. the parallel library is
now in boost, but nowhere documented.

>
>
>> Another problem turns out to appear with the copy-graph algorithm. This
>> algorithm tries to copy vertex_all-property maps and edge_all property maps
>> which I simply do not have defined in my custom graph as I only support the
>> vertex_index mechanism. So what to do here? How can I tell copy-graph that
>> these maps are not existent?
>>
>> Any help would be great here as I have the impression to hit limits of the
>> documentation (the Equality-thing is not mentioned in the docs, at least I
>> did not find it...).
>>
>
> I'm not particularly familiar with the inner workings of the algorithm. Do
> you actually need the algorithm? Most graph data structures are
> CopyConstructible and Assignable (Semiregular, I think). If your graphs are
> of the same type, you could probably use those features.
>

Well, yes I need it. I am using the same program with different underlying
graphs, depending on what I want to do. So I definetly would like to make
things work with copy_graph ... I looked into the definition of
adjacency_list, but this is a beast in my eyes and is not well readable to
me. So this vertex_all-property is still puzzling me...

Thanks a lot,

Sebastian

>
> Andrew Sutton
> andrew.n.sutton_at_[hidden]
>
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