Re: [Boost-users] Boost-users Digest, Vol 2928, Issue 3

Subject: Re: [Boost-users] Boost-users Digest, Vol 2928, Issue 3
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2011-12-07 15:31:28

On Wed, 7 Dec 2011, Nicolas Saunier wrote:

> Hi,
>
> On 11-12-07 02:21 PM, boost-users-request_at_[hidden] wrote:
>> Message: 6
>> Date: Wed, 7 Dec 2011 14:19:46 -0500 (EST)
>> From: Jeremiah Willcock<jewillco_at_[hidden]>
>> To:boost-users_at_[hidden]
>> Subject: Re: [Boost-users] [BGL] Issue using connected_components
>> Message-ID:<alpine.LRH.2.00.1112071418120.25335_at_[hidden]>
>> Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
>> 
>> On Wed, 7 Dec 2011, Nicolas Saunier wrote:
>> 
>>> >  Hi,
>>> >
>>> >  here is a simplified code sample that I cannot get to work. I use 
>>> bundled
>>> >  properties for an undirected graph and I do not find what should be the 
>>> type
>>> >  of the component map (or property map) that should be passed as the 
>>> second
>>> >  argument of the connected_components function. The sample is useless 
>>> since
>>> >  only integers are for vertices.
>> The normal vector_property_map class does not work for adjacency_list
>> graphs with a listS vertex container unless you define a vertex_index_map.
>> Is there a reason you can't use vecS as the vertex container in your
>> graph?  If you truly need listS, you will need to create a vertex index
>> map, fill it in before you create the property map, and pass it to the
>> vector_property_map constructor (and as a type argument to that class).
>> 
>> -- Jeremiah Willcock
>
> Thanks for replying. The problem, and that may seem too simple or silly to 
> people familiar with the library, is that I have no idea what should be the 
> type of the component map to pass. I tried to declare the components variable 
> as:
>
> vector< graph_traits<FeatureGraph>::vertices_size_type > 
> components(num_vertices(g));
>
> And it does not work either. What is the type of the component map, the 
> second argument of connected_components? Can you give me an example of a type 
> that would work (compile and return the correct results)?

Try:

shared_array_property_map<
   ...::vertices_size_type,
   property_map<FeatureGraph, vertex_index_t>::const_type
> 
components(num_vertices(g), get(vertex_index, g));

This requires a vecS vertex container, though.

-- Jeremiah Willcock