Re: [Boost-users] [BGL] bundled GraphProperties

Subject: Re: [Boost-users] [BGL] bundled GraphProperties
From: Damien Maupu (damien.maupu_at_[hidden])
Date: 2010-01-22 12:34:02

Hi,

I ran in a case where it could be useful or at least make the code more 
clear.

I am searching an implicit graph that is generate as the search proceed.
I am using A* but I guess this applies to other search algorithms.
Therefore it might happen that you don't know the goal vertex in advance 
and you discover it when the search proceed.

Not knowing the goal means that the end test in examine_vertex() is not 
done on the vertex descriptor anymore but on some other variable for 
example the distance of a vertex to be below some threshold.

Once the goal is reached the search stops but we need to save the vertex 
descriptor of the goal vertex in order to retrieve the path we search 
for (from a predecessor list for example).

The best place (and the only one I found intuitive) is to save such 
information in the graph properties.
I think it is impossible to save that info in the visitor because the 
visitor passed by copy to the algorithm and not by reference.

So far I am using property<graph_name_t, int> to save that vertex 
descriptor (I am using adjacency list so I assumed vertex descriptor are 
int, otherwise I don't know how to do it because vertex descriptor are 
only defined once the graph is defined which is done after the graph 
property is defined. If anyone know how to do it more properly please 
tell me so).

Instead of using graph_name property I could create one of my own with a 
more intuitive name.
Bundled graph property would be even better for clarity reason.

Sincerely,

Damien

Jeremiah Willcock a écrit :
> On Thu, 21 Jan 2010, Damien Maupu wrote:
>
>   
>> Dear all,
>>
>> Are bundled properties available for GraphProperties (for adjacency list)?
>> If no, why?
>>     
>
> No, they are not; I do not believe there is a particular reason.  There is 
> a bug report on the issue, but no plan or schedule for adding them.
>
> -- Jeremiah Willcock
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