January 2010 - Boost-users - lists.preview.boost.org

Problem iterating over vertices (Property Map!?)
by Pedram Pedarsani 11 Jan '10

11 Jan '10

I am kind of new to C++ and also BGL, so it'll be great if you can help me with this problem! I'm iterating over all the vertices of my graph, and each time I iterate, I want to *mark* a vertex (which has some specific degree for example, or some other property that I can calculate), so as not to iterate over it the next time. I'll do this process until all vertices are marked, so no more iteration. For now, what I'm doing is putting the marked vertices in a separate list, and each time I iterate over all vertices again and I check whether each vertex is in the marked list (which is very inefficient). Could you please help me with an efficient way of doing this? I was thinking to use Property Map but I have no idea how! Any small piece of code will be appreciated. Thanks a lot!

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BGL: shared_ptr as bundled properties > how to generate properties maps ???
by Damien Maupu 11 Jan '10

11 Jan '10

Dear all, I am using bundled properties when I define my graph. The bundled properties are smart pointers to my own class Edge and Vertex. I write something like: typedef boost::shared_ptr<Vertex> VertexPtr; typedef boost::shared_ptr<Edge> EdgePtr; typedef adjacency_list<vecS, vecS, directedS, VertexPtr, EdgePtr> Graph; Vertex and Edge being my own classes to store information on the vertices and the edges. For what I read in the doc, this is the correct, more modern way to do it. My problem is the following. I am trying to use the BGL algorithms and some of them require vertex/edge info to be provide as properties maps. From http://www.boost.org/doc/libs/1_41_0/libs/graph/doc/bundles.html I know it is possible to generate those maps from bundled properties. It works well if I don't use shared_ptr but cannot compile otherwise. When using shared_ptr, similarly to the doc, I wrote: typedef property_map<SearchGraph, float EdgePtr::*>::type WeightMap; WeightMap weightMap = get(&EdgePtr::m_cost, *_graph); m_cost being a public float member of my own class Edge. I have the following compilation error: 'm_cost' : is not a member of 'boost::shared_ptr<T>' Indeed it is not. My question is, I can let the shared_ptr access the member? In other world how to deal with bundled properties / properties maps and shared_ptr. Extra question, could 'm_cost' be a private member of my own class Edge? Thank you very much Sincerely, Damien

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can serialize multi-class into a single Archive?
by pengdw 11 Jan '10

11 Jan '10

I want to serialize multiple class into a single file. that's: class object {}; ofstream ofs; ofs.open("data.txt"); boost::archive::text_oarchive oa(ofs); while (get_next_object(object_t obj)) { oa << obj; } It is ok when I use text_iarchive to read back these objects. Now I want to append some objects to a Archive, I need to reopen the data file "data.txt" with (ios_base::app | ios_base::out), and serialize some object to the new-opend Archive. then when I use text_iarchive to load, I got error messages. I checked some manuals, and use boost::archive::no_header to skip the archive headers like "22 serialization::archive" when appending objects. but still I got error messages when loading. can anyone tell me how to store and append objects to a single Archive, and load correctly. tks.

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[Accumulators] Errors compiling the "Hello, World!" example
by Marco Guazzone 11 Jan '10

11 Jan '10

Hello! I'm new to Accumulators. I've tried to compile the "Hello, World!" example (found in the User Guide) but it fails: --- [error] --- $ g++ -ansi -Wall -o accumulators_test1 accumulators_test1.cpp /usr/include//boost/accumulators/statistics_fwd.hpp: In function ‘int main()’: /usr/include//boost/accumulators/statistics_fwd.hpp:87: error: ‘template<int N> struct boost::accumulators::tag::moment’ is not a function, /usr/include//boost/accumulators/statistics/moment.hpp:104: error: conflict with ‘template<int T2, class Arg1, class A0, class A1, class A2, class A3, class A4, class A5, class A6, class A7, class A8, class A9, class A10, class A11, class A12, class A13, class A14> typename boost::accumulators::detail::extractor_result<Arg1, boost::accumulators::tag::moment<T2> >::type boost::accumulators::extract::moment(const Arg1&, const A0&, const A1&, const A2&, const A3&, const A4&, const A5&, const A6&, const A7&, const A8&, const A9&, const A10&, const A11&, const A12&, const A13&, const A14&)’ accumulators_test1.cpp:22: error: in call to ‘moment’ --- [/error] --- My system is: Fedora 12 x86_64 -- GCC 4.4.2 20091222 (Red Hat 4.4.2-20) -- Boost 1.39 (also tried with the latest Boost trunk) Just for the sake of completeness, here below is the code stored in the "accumulators_test1.cpp" file --- [code] --- #include <iostream> #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/stats.hpp> #include <boost/accumulators/statistics/mean.hpp> #include <boost/accumulators/statistics/moment.hpp> using namespace boost::accumulators; int main() { // Define an accumulator set for calculating the mean and the // 2nd moment ... accumulator_set<double, stats<tag::mean, tag::moment<2> > > acc; // push in some data ... acc(1.2); acc(2.3); acc(3.4); acc(4.5); // Display the results ... std::cout << "Mean: " << mean(acc) << std::endl; std::cout << "Moment: " << moment<2>(acc) << std::endl; return 0; } --- [/code] --- Where I am wrong? Thank you very much for any help!! Best, -- Marco

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[repost][serialization] version handling in {save|load}_construct_data
by JOAQUIN M. LOPEZ MUÑOZ 11 Jan '10

11 Jan '10

Hello, allow me to repost this message from a couple of weeks ago: I've taken a look at how the version number is dealt with in Boost.Serialization collection serialization code: * The relevant code at saving time is: if(3 < ar.get_library_version()){ const unsigned int item_version = version< BOOST_DEDUCED_TYPENAME Container::value_type >::value; ar << BOOST_SERIALIZATION_NVP(item_version); } * At loading time, the equivalent code is: unsigned int item_version; ar >> BOOST_SERIALIZATION_NVP(count); if(3 < ar.get_library_version()) ar >> BOOST_SERIALIZATION_NVP(item_version); else item_version = 0; Can someone (aka Robert :-) ) shed some light on this bit? Why the version number has to be given such manual processing when this is not needed if, for instance, serializating values via the simple ar&value? I'm trying to do the equivalent thing in Boost.MultiIndex. Thank you, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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Re: [Boost-users] boost.m4 checks correct header but detects wrong header version
by Peter Schueller 11 Jan '10

11 Jan '10

Hi Tsuna, On Mon, Jan 11, 2010 at 08:30, tsuna <tsunanet(a)gmail.com> wrote: > On Mon, Aug 24, 2009 at 1:57 AM, Peter Schueller <ps(a)kr.tuwien.ac.at> wrote: >> (posting to the boost-users list and to the boost.m4 maintainer) > > Hi Peter, > sorry for the belated reply. No problem at all. >> I have several boost installations, among others a 1.34.1 in >> /usr/include and several in my homedir in >> /home/staff/ps/include/boost-1_36/ >> /home/staff/ps/include/boost-1_37/ >> /home/staff/ps/include/boost-1_39/ >> >> Calling configure with --with-boost=/home/staff/ps/include/boost-1_37/ >> I get the following information: >> >> checking for Boost headers version >= 103300... >> /home/staff/ps/include/boost-1_37/include >> checking for Boost's header version... 1_34_1 >> >> The first check finds the correct headers, the second one uses the wrong ones. > > I believe this issue has been fixed by > http://github.com/tsuna/boost.m4/commit/93faeb67fbbc5d68a397c64ebc2dddf23a9… > > Can you retry with the latest version and let me know if it still > doesn't work for you? Thank you very much, this indeed resolves the issue! > Happy new year! Happy new year to you as well! Best Regards, Peter -- Peter Schüller Vienna University of Technology, Institute of Information Systems Favoritenstrasse 9-11/1843, 1040 Wien, Austria T: +43 1 58801 18470 E: ps(a)kr.tuwien.ac.at DVR: 0005886 http://www.kr.tuwien.ac.at/staff/ps

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Re: [Boost-users] [repost][serialization] version handling in{save|load}_construct_data
by JOAQUIN M. LOPEZ MUÑOZ 10 Jan '10

10 Jan '10

________________________________________ De: boost-users-bounces(a)lists.boost.org [boost-users-bounces(a)lists.boost.org] En nombre de Robert Ramey [ramey(a)rrsd.com] Enviado el: domingo, 10 de enero de 2010 20:22 Para: boost-users(a)lists.boost.org Asunto: Re: [Boost-users] [repost][serialization] version handling in{save|load}_construct_data > > I investigated a little bit more. Seems that save/load_construct data needs > the version # and there is no place else to get it. Why can't you directly use serialization::version<T>::value? This is for instance what you're doing at lines 51 and following of boost/serialization/hash_collections_save_imp.hpp. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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Re: [Boost-users] [repost][serialization] version handling in{save|load}_construct_data
by JOAQUIN M. LOPEZ MUÑOZ 10 Jan '10

10 Jan '10

________________________________________ De: boost-users-bounces(a)lists.boost.org [boost-users-bounces(a)lists.boost.org] En nombre de Robert Ramey [ramey(a)rrsd.com] Enviado el: sábado, 09 de enero de 2010 21:40 Para: boost-users(a)lists.boost.org Asunto: Re: [Boost-users] [repost][serialization] version handling in{save|load}_construct_data > I believe that this came about when error to the serialization of > collections was discovered. Previous library versions didn't > properly save the version of the collection item. When this > was corrected, this code was needed to permit the the loading > of archives created previously. > > If the type isn't versioned (e.g. some primitive type), then the > default version # would be zero. I suppose this could be > made more elaborate so that the version # wouldn't even > be in the archive in these cases - but that's not way we did it. > > I don't know if that answers your question, but that's what > I remember about it. I'm afraid that does not entirely answer my question. I understand what the "if(3 < ar.get_library_version()){" guard is for. What puzzles is me is why you need to explicitly save the type serialization version number when this info is seemingly recovered in other contexts without any explicit user operation. Let me put it another way: consider a user defined type my_type with associated serialization code: template<class Archive> void serialize(Archive& ar,my_type & m,const unsigned int version) { ... } When serialize() is called internally by Boost.Serialization, version is correctly passed without the user explicitly saving this info as it happens in the code for collection serialization. Why this difference? Am i making myself clear as to what the root of my puzzlement is? Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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BOOST_FUSION_ADAPT_STRUCT
by Hicham Mouline 09 Jan '10

09 Jan '10

Hello, Can I use this macro with specialized templates as well? template <typename T> struct range { T min ; T max ; } ; BOOST_FUSION_ADAPT_STRUCT( range<double>, (double, min) (double, max) } Rds,

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[BGL] dijkstra_shortest_paths with listS
by gast128 09 Jan '10

09 Jan '10

Hello all, BGL supports a lot of graph algorithms, and lots of stuff get default filled in when using vecS as container type of vertices. However things become pretty ugly when not using this container. Below I used a listS for both edges and vertices. Maybe it can help other people (and maybe somebody can cross check me). Note that some constructs could be bundled, but for clearity I explicitly wrote all things out. I use the graph from the BGL book as example (figure 13.3). void TestgraphDijkstra() { typedef boost::adjacency_list<boost::listS, boost::listS, boost::bidirectionalS, std::string> Graph; typedef boost::graph_traits<Graph>::vertex_descriptor VertexDescriptor; typedef boost::graph_traits<Graph>::edge_descriptor EdgeDescriptor; typedef int Weight; typedef std::map<EdgeDescriptor, Weight> WeightMap; typedef std::map<VertexDescriptor, size_t> VertexIndexMap; typedef std::map<VertexDescriptor, Weight> DistanceMap; typedef std::map<VertexDescriptor, VertexDescriptor> PredecessorMap; Graph graph; WeightMap mapWeigth; VertexIndexMap mapVertexIndex; DistanceMap mapDistance; PredecessorMap mapPredecessor; boost::associative_property_map<WeightMap> pmWeigth(mapWeigth); boost::associative_property_map<VertexIndexMap> pmVertexIndex (mapVertexIndex); boost::associative_property_map<DistanceMap> pmDistance(mapDistance); boost::associative_property_map<PredecessorMap> pmPredecessor (mapPredecessor); //build a graph according to figure 13.3 //add vertices const VertexDescriptor vA = boost::add_vertex(graph); const VertexDescriptor vB = boost::add_vertex(graph); const VertexDescriptor vC = boost::add_vertex(graph); const VertexDescriptor vD = boost::add_vertex(graph); const VertexDescriptor vE = boost::add_vertex(graph); //set vertex names graph[vA] = "A"; graph[vB] = "B"; graph[vC] = "C"; graph[vD] = "D"; graph[vE] = "E"; //add edges const EdgeDescriptor eAC = boost::add_edge(vA, vC, graph).first; const EdgeDescriptor eBB = boost::add_edge(vB, vB, graph).first; const EdgeDescriptor eBD = boost::add_edge(vB, vD, graph).first; const EdgeDescriptor eBE = boost::add_edge(vB, vE, graph).first; const EdgeDescriptor eCB = boost::add_edge(vC, vB, graph).first; const EdgeDescriptor eCD = boost::add_edge(vC, vD, graph).first; const EdgeDescriptor eDE = boost::add_edge(vD, vE, graph).first; const EdgeDescriptor eEB = boost::add_edge(vE, vB, graph).first; const EdgeDescriptor eEA = boost::add_edge(vE, vA, graph).first; //set edge weights boost::put(pmWeigth, eAC, 1); boost::put(pmWeigth, eBB, 2); boost::put(pmWeigth, eBD, 1); boost::put(pmWeigth, eBE, 2); boost::put(pmWeigth, eCB, 7); boost::put(pmWeigth, eCD, 3); boost::put(pmWeigth, eDE, 1); boost::put(pmWeigth, eEB, 1); boost::put(pmWeigth, eEA, 1); //build index map boost::put(pmVertexIndex, vA, 0); boost::put(pmVertexIndex, vB, 1); boost::put(pmVertexIndex, vC, 2); boost::put(pmVertexIndex, vD, 3); boost::put(pmVertexIndex, vE, 4); //note: color map not needed, because of index map? boost::dijkstra_shortest_paths(graph, vA, boost::weight_map (pmWeigth).vertex_index_map(pmVertexIndex).distance_map (pmDistance).predecessor_map(pmPredecessor)); for (DistanceMap::const_iterator itDist = mapDistance.begin(); itDist != mapDistance.end(); ++itDist) { //dump const VertexDescriptor v = itDist->first; const VertexDescriptor vPrev = mapPredecessor[v]; std::cout << "Distance(" << graph[v] << ") = " << itDist->second << ", " << "Parent(" << graph[v] << ") = " << graph[vPrev] << std::endl; } }

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