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 12:34:37

 Hi Jeremiah Willcock,
Good news, the parallal version BFS example (\graph_parallel\example\breadth_first_search.cpp) could be built now.
I followed your suggestion to locate the boost::detail::bfs_helper(), there are two declarartions of this function, A and B.
 A is in \graph\breadth_first_search.hpp for the serial version, with another definition for the parallel version of this function (B) which is wrapped inside a macro (#ifdef BOOST_GRAPH_USE_MPI... #endif).
And the delcaration of B is in \graph\distributed\breadth_first_search.hpp.
I just comment out the delcaration of B and copy it to overwrite the definition inside the above macro.
and append "* = 0" at the end of the last parameter just like function A.
And then the example cpp built successfully.

As for the build error of Boost.MPI with MinGW, I will redo it and save the ouput to a file.

Thanks.
Zhiyu Li


2013-06-28 



lizy10b 



发件人： Jeremiah Willcock 
发送时间： 2013-06-27  22:47:02 
收件人： boost-users 
抄送： 
主题： Re: [Boost-users] Confused with Depth-First-Searchmethod,forwardorcross edge found on a undirected graph ? 
 
On Thu, 27 Jun 2013, lizy10b wrote:
> 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.
Is it boost::bfs_helper or boost::detail::bfs_helper?  Are there any 
symbols in the object file for breadth_first_search that are defined and 
demangle to names involving bfs_helper?
> 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. 
What is the issue with that version?
-- Jeremiah Willcock
>  
> 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
> > > 
> > >
> > 
> >
> 
>
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