Re: [Boost-users] Parallel BGL status in Boost

Subject: Re: [Boost-users] Parallel BGL status in Boost
From: Mathieu Malaterre (mathieu.malaterre_at_[hidden])
Date: 2009-09-04 08:24:25

On Thu, Sep 3, 2009 at 10:37 PM, Nick Edmonds<ngedmond_at_[hidden]> wrote:
> Yep, PBGL as in the distributed data structures, MPI infrastructure, and
> distributed algorithms is now in Boost.

Cool, I did not see it in the changelog, so I was confused.

> Yep, that webpage is desperately out of date, I'm a terrible webmaster.
>  Updating it (and the attendant performance numbers) has been on my todo
> list for ages.  I'd make more promises, but they'd probably sound hollow
> now.  So when I actually do it, it will be a pleasant surprise.

So that it serve as reference to anyone reading this. The
documentation have been updated, simply not uploaded neither on
boost.org page nor on the old PBGL page. It is available locally as:

file:///path/to/boost/libs/graph_parallel/doc/html/index.html

> Structural information about the graph is only available on the process that
> owns that portion of the graph.  Currently PBGL distributes the graph using
> a row-wise decomposition of the adjacency matrix.  This means that calling
> vertices(g) returns the local vertex set owned by the calling process.  The
> result of calling edges(g) depends on the directed category of the edge, but
> basically iterates over incident edges.  Attempting to access structural
> information that is not local to the calling process, i.e. calling
> out_edges(v, g) where 'v' is not owned by the calling process is invalid and
> results in undefined behavior.

ok that clears things quite a bit !

> If you want more details, to know why things work the way they do now, or
> how they might work in the future, feel free to ask away.

'in the future', what do you mean ? What are the actual plans ?

Thanks again,
-- 
Mathieu