Re: [Boost-users] [BGL] Writing an edge_iterator for add_edges in CSR graph

Subject: Re: [Boost-users] [BGL] Writing an edge_iterator for add_edges in CSR graph
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2011-04-08 10:48:03

On Fri, 8 Apr 2011, Johan Oudinet wrote:

> On Fri, Apr 8, 2011 at 1:50 PM, Johan Oudinet <johan.oudinet_at_[hidden]> wrote:
>> Hi,
>>
>> I'm trying to write an edge_iterator in order to load a CSR graph from
>> a GraphViz by using the add_edges method.

Could you use one of the iterator-based constructors instead of add_edges?

>>
>> So far, I successfully write a edge_iterator so you can iterate on it
>> and dereference it to get either a pair of vertex_descriptor or a edge
>> label.
>>
>> However, if it try to use this iterator as arguments for the method
>> add_edges of CSR graph, I got cryptic errors and I don't know how to
>> solve them :-/
>
> Problem solved. My input_iterator must be copy constructible and was
> not due to the std::ifstream attribute.
> Now, I use a boost::shared_ptr and it solves the compilation errors.
>
> Thanks anyway.
>
> P.S.: It could be a good idea to add an example in CSR documentation
> that uses this new add_edges method instead of the old add_edge
> method, which is more difficult to use I think.
>
> P.P.S.: Do you plan to adapt the Graphviz reader in order to load CSR graphs?

I didn't realize it was broken, but it doesn't seem too hard to fix (sort 
the edges and use add_edges to put them into the graph when possible). 
Could you please file a bug report for that?  For now, you can need to 
read the graph into an adjacency_list and then copy it from there to CSR. 
You won't need custom iterators for that copy (there is a CSR constructor 
from arbitrary graphs).

-- Jeremiah Willcock