Re: [Boost-users] Confused with Depth-First-Searchmethod,forwardorcross edge found on a undirected graph ?

Subject: Re: [Boost-users] Confused with Depth-First-Searchmethod,forwardorcross edge found on a undirected graph ?
From: lizy10b (lizy10b_at_[hidden])
Date: 2013-06-27 03:44:20

Hi Jeremiah Willcock,
Thanks for your reply.
Sad to say the pararallel version BFS example file (\boost_1_53_0_\libs\graph_parallel\example\breadth_first_search.cpp) can not be compiled with VS2010 on my end. It complains an unresolved external symbol "void _cdecl boost::bfs_helper....". And I found a similar report on http://boost.2283326.n4.nabble.com/LINK-Error-while-building-PBGL-example-breadth-first-search-cpp-td3799909.html. but with no result.
I also tried to build the boost with MinGW, but it seems the Boost.MPI cannot be compiled correctly upon MPICH2, so the parallel BGL library will not be built either. 
Any sugguestions will be appreciated.
Thanks.

Zhiyu Li
Student

2013-06-27 



lizy10b 



发件人： Jeremiah Willcock 
发送时间： 2013-06-26  22:54:58 
收件人： lizy10b 
抄送： boost-users 
主题： Re: Re: Re: [Boost-users] Confused with Depth-First-Searchmethod,forwardorcross edge found on a undirected graph ? 
 
On Wed, 26 Jun 2013, lizy10b wrote:
>  
> Hi Jeremiah Willcock,
> Thanks for your reply.
> As maybe there are some problems when invoke depth_first_visit() on an undirected graph, the undirected_dfs()
> could be a very good substitution.
> So I continue to test the parallel version of the DFS function -- tsin_depth_first_visit(), and the test file comes
> from  \boost_1_53_0\libs\graph_parallel\test\distributed_dfs_test.cpp.
> The test file invokes the tsin_depth_first_visit() on a distributed undirected graph, and the visitor print all
> events,  the "forward_or_cross_edge" appears four times. So maybe there are some problems in
> tsin_depth_first_visit() too. 
> Does the parallel tsin_depth_first_visit() base on the serial depth_first_visit(), so they appear similiar problem
> when work with undirected graph?
It looks like it's similar to the directed DFS, so it would likely return 
the same results.
> My final target is to find a parallel version DFS works with undirected graph, in order to find all cycles
> parallelly.  Could you please give me some advices on that? I am stucked.
It doesn't look like there is one, but you can use breadth-first search to 
find cycles as well.  Would that work for you?
-- Jeremiah Willcock
> 
> ____________________________________________________________________________________________________________________
> lizy10b
> 
> ____________________________________________________________________________________________________________________
> 发件人： Jeremiah Willcock
> 发送时间： 2013-06-26  03:34:37
> 收件人： lizy10b
> 抄送： boost-users
> 主题： Re: Re: Re: [Boost-users] Confused with Depth-First-Searchmethod,forwardor cross edge found on a undirected
> graph ?
> On Tue, 25 Jun 2013, lizy10b wrote:
> > Hi Jeremiah Willcock,
> >    Can I use the predecessor_map in undirected_dfs() like in dijkstra_shortest_paths()?
> > undirected_dfs(g, predecessor_map(&p[0]).root_vertex(vertex_descriptor(0)).visitor(vis)
> >                  .edge_color_map(get(edge_color, g)).vertex_color_map(get(vertex_color, g)));
> > It does not work on my end, all elements in predecessor remain 0 after invoke the undirected_dfs() .
> If that parameter isn't in the documentation for undirected_dfs, the 
> argument will just be ignored.
> > In the last section (Extending Algorithms with Visitors) of http://www.boost.org/doc/libs/1_53_0/libs/graph/doc/q

> uick_tour.html,
> > an example shows how to write a predecessor_map using visitor,
> > and the "event point" is edge_relaxed().
> > But as the undirected_dfs document shows there is no edge_relaxed() for DFS.
> > So is there any way to save predecessors in DFS?
> > For example an edge (u,v) and start at vertex u
> > When the discover_vertex(Vertex, Graph&) is invoked at vertex v, then 
> > inside the discover_vertex() how could I know the previous discovered 
> > vertex is u?
> I believe you would want to hook tree_edge() instead of edge_relaxed().
> -- Jeremiah Willcock
> > 
> > _________________________________________________________________________________________________________________
> ________________________________________
> > 发件人： Jeremiah Willcock
> > 发送时间： 2013-06-25  00:44:05
> > 收件人： lizy10b
> > 抄送： boost-users
> > 主题： Re: Re: [Boost-users] Confused with Depth-First-Search method,forwardor cross edge found on a undirected g
> raph ?
> > On Tue, 25 Jun 2013, lizy10b wrote:
> > > Hi Jeremiah Willcock ,
> > > ?
> > > It seems undirected_dfs() works. I have not燾heck the result according to the graph, but at least there is no
> > > forward edge or cross edge output.
> > > Attached is the revised cpp file using undirected_dfs() .
> > > My question is why edge_color_map(get(edge_color,爂))?is required when calling the undirected_dfs() .
> > > Thanks
> > It looks like what is going wrong with using directed DFS is that edges 
> > are examined twice (once in each direction), and so you can have forward 
> > edges even in a symmetric graph (which is how undirected graphs are 
> > treated in directed-graph algorithms in BGL).  An example is the triangle 
> > 0 -- 1 -- 2 -- 0: starting at 0 and processing the edges out of a vertex 
> > in numerical order, 0 -> 1 is a tree edge, 1 -> 0 is a back edge, 1 -> 2 
> > is a tree edge, 2 -> 0 is a back edge, 2 -> 1 is a back edge, then 0 -> 2 
> > is a forward edge.  An undirected DFS would mark 2 -> 0 as a back edge 
> > then ignore 0 -> 2 since it is the same as 2 -> 0.  The edge colors in 
> > undirected_dfs are used to do this filtering-out of multiple directions 
> > for the same edge.
> > -- Jeremiah Willcock
> > 
> >
> 
>