Re: [Boost-users] [BGL] question about connected_components()

Subject: Re: [Boost-users] [BGL] question about connected_components()
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2012-01-23 14:56:16

On Thu, 19 Jan 2012, Andriy Gapon wrote:

>
> This page:
> http://www.boost.org/doc/libs/1_48_0/libs/graph/doc/connected_components.html
> says "The connected_components() functions compute the connected components of
> an _undirected_ graph using a DFS-based approach." [emphasis mine]
>
> Looking here:
> http://www.boost.org/doc/libs/1_48_0/boost/graph/connected_components.hpp
> I see somewhat some unexpected things.
>
> o Only the first variant asserts that the graph is undirected, in the second
> variant the assert is commented out - why is that?

I don't know for sure, but the likely reason is to allow the use of a 
directed graph that has each edge inserted in both directions.

> o Both variants use depth_first_search() and not undirected_dfs(), which would
> seem to be more logical for the undirected case - why?

I don't know.

> Despite the above questions I actually want to use connected_components() [and
> not strong_components()] for a directed graph.  Should that be possible?  Does
> it make sense?

Do you want to compute the weak components of the graph?  I.e., do you 
want the connected components that would be present if you ignored edge 
directions?

-- Jeremiah Willcock