April 2005 - Boost-users - lists.preview.boost.org

BGL example correction?
by Peter Kümmel 22 Apr '05

22 Apr '05

Hello, here maybe a small correction for boost_1_32_0\libs\graph\example\file_dependencies.cpp, line 176 : dijkstra_shortest_paths_no_init (g, *i, &pred[0], &time[0], weight, indexmap, - compare, combine, 0, // Since we are using > instead of >, we + compare, combine, //0, // Since we are using > instead of >, we (std::numeric_limits<int>::max)(), // flip 0 and inf. default_dijkstra_visitor()); And I don't understand the comment '> instead of >' or what means '>,' ??? If I compile with zero distance the program crashes, although the declaration is: dijkstra_shortest_paths_no_init (const VertexListGraph& g, typename graph_traits<VertexListGraph>::vertex_descriptor s, PredecessorMap predecessor, DistanceMap distance, WeightMap weight, IndexMap index_map, Compare compare, Combine combine, -> DistZero zero, DijkstraVisitor vis) Regrads, Peter

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graph type used in BGL function "connected_components()"
by Qiaofeng Yang 22 Apr '05

22 Apr '05

Hi, I have a question about the graph type used in BGL function "connected_components()". When I define the graph type to be: adjacency_list<vecS, vecS, undirectedS> Everything is OK. When I change the graph type to be: adjacency_list<listS, listS, undirectedS> I got a lot of compilation error messages. Anybody knows why is so? Was "connected_components()" only implemented on one particular implementaton of graphs like vecS? Best regards, Qiaofeng

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wrong library extension on HP-UX
by Oliver Kowalke 22 Apr '05

22 Apr '05

Hi, my previous 2 emails were silently droped - so I try it a 3thd time. I've compiled boost on HP/UX with gcc. The extension of the shared libraries is *.so. I think it should be *.sl ! how can I fix this? thx, Oliver

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recommended gcc for boost users on opteron (64-Bit)
by Michal Simecek 22 Apr '05

22 Apr '05

Hi all, Does somebody know, which gcc is recommended for boost users especially BGL users working on opterons, with linux on it, compiling with optimisation (-O2) and 64-bit mode. I run in some problems with gcc 3.2.2 thus I try to find out which compiler is the best choice for that system. Thanks

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(no subject)
by Sliwa, Przemyslaw (London) 22 Apr '05

22 Apr '05

All, I have found a very strange behaviour (for me at least!) in boost.Thread. The same dummy code: boost::mutex M; void functionA(int j) { for(int i=0; i<j; ++i) { boost::mutex::scoped_lock lock(M); sqrt(static_cast<double>(i)); } } void functionB(int j) { for(int i=0; i<j; ++i) { boost::mutex::scoped_lock lock(M); sqrt(static_cast<double>(i)); } } int main() { thread A(bind(&functionA, 1000000000)), AA(bind(&functionA, 1000000000)), B(bind(&functionB, 100000000)), BB(bind(&functionA, 100000000)); A.join(); B.join(); AA.join(); BB.join(); } executed on a two processor machine uses the resourced differently depending if the line boost::mutex::scoped_lock lock(M); is comennted or not. If we do not lock the mutex then both processors are used on 100%. However, in case the line is uncommented (we lock the mutex) only one processor is used. Can anyone explain me why? Thanks in advance Pshemek -------------------------------------------------------- If you are not an intended recipient of this e-mail, please notify the sender, delete it and do not read, act upon, print, disclose, copy, retain or redistribute it. Click here for important additional terms relating to this e-mail. http://www.ml.com/email_terms/ --------------------------------------------------------

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RE: [Boost-users] A Simple Problem: File Transfer...
by Sliwa, Przemyslaw (London) 22 Apr '05

22 Apr '05

Are there any plans to include the networking libraries into boost? I have heard about the Boost.Socket but I guess this project has been abandoned long time ago. Is it correct? Pshemek -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Ben Hutchings Sent: 18 April 2005 17:36 To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] A Simple Problem: File Transfer... Hossein Haeri wrote: > Dear all, > > If you were assigned to write a file transfer utitlity > "in C++", what would your suggestions be? More > specific, I've got two IP's (perhaps plus their > ports), I've got to send one file from one to the > other. Which parts of the Boost would you use, if any? Boost probably isn't going to help you much with file transfer, as it doesn't (yet) include any networking libraries. There are various Boost libraries that might be useful, though, such as smart_ptr and program_options. Ben. _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users -------------------------------------------------------- If you are not an intended recipient of this e-mail, please notify the sender, delete it and do not read, act upon, print, disclose, copy, retain or redistribute it. Click here for important additional terms relating to this e-mail. http://www.ml.com/email_terms/ --------------------------------------------------------

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[multi_index] FYI: Experiences with the Boost.MulitIndex container
by Jochen Hammann 22 Apr '05

22 Apr '05

Hi, I am using the Boost MultiIndex container in conjunction with the Microsoft Visual C++ 7.1 compiler. I encountered an runtime exception during some tests of my application. I made the mistake, that I tried to construct an index as a separate object instead of using a reference to the respective index. The MultiIndex documentation highlights this issue: "Note that get returns a reference to the index, and not an index object. Indices cannot be constructed as separate objects from the container they belong to, so the following // Wrong: we forgot the & after employee_set::nth_index<1>::type const employee_set::nth_index<1>::type name_index=es.get<1>(); does not compile, since it is trying to construct the index object name_index. This is a common source of errors in user code." I could reproduce the exception by using the MultiIndex example basic.cpp from the Boost 1.32.0 release. Unfortunately, Microsoft Visual C++ 7.1 compiles the above mentioned line without an error or warning. During the execution of the example an exception will be thrown while processing the following line: std::copy(i.begin(),i.end(),std::ostream_iterator<value_type>(std::cout)); within the function template print_out_by(). Regards, Jochen.

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boost::serialization: how to BOOST_CLASS_VERSION a template class?
by Bo Peng 22 Apr '05

22 Apr '05

Dear list, I use boost::serialization to serialize my classes. They are template classes that are instantiated and wrapped by SWIG. Everything works fine until I decide to use BOOST_CLASS_VERSION to set version for the class. The first parameter of BOOST_CLASS_VERSION(class, version) is a class but my template will only be instantiated by SWIG. The syntax does not allow me to do something like template<class T> BOOST_CLASS_VERSION(class<T>, version) or BOOST_CLASS_VERSION( template<class T>class <T>, version). What should I do? Many thanks in advance. Bo

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Question about memory management and Serialization
by kauai 22 Apr '05

22 Apr '05

Hi folks, When I unserialize an object that has pointers in it (composite recursive structure), does boost unserialize take care of allocating them on the heap? I assume it does, however... I run a memory profiling tool call 'valgrind' and I on purpose decided not to cleanup my newly created serialized object. What happened after running through valgrind surprised me, it reported no memory leaks. Whats the magic here, smart pointers? Thanks for any help, Kauai __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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Re: potential bugs in BGL function "brandes_betweenness_centrality()"
by qyang＠cs.ucr.edu 22 Apr '05

22 Apr '05

Hi Doug, Thanks for the hint! I manually re-index all the vertices after the vertex removal(a for() loop) and put vertex_centrality(num_vertices(G)) outside the while() loop. The code works fine now :). I have another question concerning vertex and edge iterator. The problem is now that I want to remove the nth edge in the graph. I use the following code: ================================================== //typedef stuff ... EdgeDescriptor Edge; Edge = *(edges(G).first + n); //n is an int remove_edge(Edge, G); ================================================== I got compilation errors at line "Edge = *(edges(G).first + n);". I have to use the following code in order to compile the code and to run it correctly: ================================================== //typedef stuff ... EdgeDescriptor Edge; EdgeIterator edge_iter; edge_iter = edges(G).first; for(int i = 0; i < n; i++) { edge_iter++;} Edge = *edge_iter; remove_edge(Edge, G); ================================================== Basically, you have to use a for() loop to increment the edge_iterator varialbe. Is it possible just to use one addition(the first code) instead of n additions(the second code) to increment the iterator? Best regards, Qiaofeng >> while(num_vertices(G)>0) >> { >> int V = num_vertices(G); >> vector<double> vertex_centrality(V); >> >> brandes_betweenness_centrality(G, >> make_iterator_property_map(vertex_centrality.begin(), get(vertex_index, >> G), double())); >> >> //print the vertex betweenness centrality for all the vertices >> ... >> >> //find the index of the vertex with the highest betweenness centrality >> ... >> >> clear_vertex(...); >> remove_vertex(...); >> } > > After the call to remove_vertex, the vertex indices are no longer > valid, e.g., > > 1) The first time through the loop, V = 9. The vertices have indices 0, > 1, 2, 3, 4, 5, 6, 7, 8 > 2) We delete one vertex, so V = 8. Say it's the vertex with index 3. > The vertices have indices 0, 1, 2, 4, 5, 6, 7, 8 > > During the execution of brandes_betweenness_centrality in the second > iteration, we'll try to access vertex_centrality[8], which is an error. > vertex_centrality has been reallocated to only allow 8 elements, not 9. > > The easiest way to fix this is to remove the vertex_centrality vector > from the loop, then add: > > vector<double> vertex_centrality(num_vertices(G)); > > *before* the loop. This will speed up the computation because the > vector doesn't get reallocated each time. More importantly, it will > stay at the maximum number of vertices, so even though we delete vertex > index "3" there is still a vertex index "8". The vector will have some > "holes" in it where values aren't used after the first iteration, but > that's okay. > > Vertex and edge indices are a weak point in the BGL. It seems like they > should be automatically updated, but that can't be done efficiently. We > have a partial solution (a graph type that is reasonably good > all-around and does automatic (re-)indexing), but it's not ready for > release yet. > > Doug

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