March 2013 - Boost-users - lists.preview.boost.org

[Thread] Constructing a move-only object asyncronously
by Alexander Lamaison 20 Mar '13

20 Mar '13

I'm trying to create a move-only object asyncronously using Boost.Thread unique_future but I'm running into trouble: error C2248: 'A::A' : cannot access private member declared in class 'A' c:\users\awl03\documents\visual studio 2005\projects\boost_1_51_0\boost\thread\future.hpp 493 I've tried all sorts of ways to work around this but always end up with some variation or other of this error message. What am I doing wrong? The code is below. The setup is: Visual Studio 2005 Boost 1.51 Thanks, Alex #include <boost/noncopyable.hpp> #include <boost/move/move.hpp> #include <boost/thread/future.hpp> #include <boost/thread/thread.hpp> using namespace boost; class A : public noncopyable { BOOST_MOVABLE_BUT_NOT_COPYABLE(A) public: A(int i) {} A(BOOST_RV_REF(A) other) {} A& operator=(BOOST_RV_REF(A) other) {} }; A create_a() { return A(42); } unique_future<A> async_create_a() { packaged_task<A> task(create_a); unique_future<A> result = task.get_future(); thread(move(task)).detach(); return move(result); } int main() { A a = async_create_a().get(); return 0; } -- Swish - Easy SFTP for Windows Explorer (http://www.swish-sftp.org)

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Re: [Boost-users] [graph] problem with weight_map ? (brandes_betweenness_centrality)
by The Maschine 20 Mar '13

20 Mar '13

Hi, ## > EdgeWeightProperty weight = getWeight(a, b); // 0f ... 2.0f Can you just assign a double to a boost::property<...> object? That should probably not be allowed. ## I found the example here and made my code: http://programmingexamples.net/wiki/CPP/Boost/BGL/DijkstraUndirected ### What happens if you write an explicit loop over all of the edges and use put(edge_weight, g, e) directly? Does that change any of the results? -- Jeremiah Willcock ### In not sure what you mean? Im not a super expert, can you please explain your thought more? Best, Tasos

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Boost Geometry Compilation Errors
by Joel Markham 20 Mar '13

20 Mar '13

Trying to use the boost geometry library. Have a very simple example from the boost geometry home page int main(int argc, const char * argv[]) { double points[][2] = {{2.0, 1.3}, {4.1, 3.0}, {5.3, 2.6}, {2.9, 0.7}, {2.0, 1.3}}; bgm::polygon<bgm::d2::point_xy<double> > poly; bg::append(poly, points); boost::tuple<double, double> p = boost::make_tuple(3.7, 2.0); std::cout << "Point p is in polygon? " << std::boolalpha << bg::within(p, poly) << std::endl; … } When trying to build on my Mac I get compiler warnings: point_type.hpp No matching function for call to 'assertion_failed" coordinate_type.hpp No matching function for call to 'assertion_failed" convert_point_to_point.hpp Call to function 'get that is neither visible in the template definition or found… access.hpp Nom member named 'get in boost::geometry::core_dispatch… Is there something wrong with the boost libraries installed via macports?

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[BGL] Dijkstra/A* with large graph
by Nicholas Mario Wardhana 20 Mar '13

20 Mar '13

Hi all, I am wondering if with Boost Graph Library, I can do either of these two things: 1) Merge several small graphs into one large graph 2) Save and load only a portion of a large graph at a time? So the background is as follows. I have a large geometric graph (i.e. a graph with 3D coordinate custom vertex properties), which I want to use for path planning. The graph can be too large to be stored in the memory (if I understand correctly, BGL uses STL data structures, which have limits for the number of elements), so I implement the large graph as multiple small graphs (let's just call them mini-graphs). This way, I can save the mini-graphs to hard-disk, and load only the necessary mini-graphs to plan the path (I have cost function to determine the mini-graphs using Dijkstra). The problem is, this breaks the connectivity of the original graph, and I also have to add some points to two mini-graphs. Running Dijkstra/A* is consequently not straightforward, since the starting and the goal nodes can be in different mini-graphs. The two aforementioned solutions can be used as a workaround. Using approach #1, I can combine the chosen mini-graphs into one, on which I can directly run Dijkstra/A*. In approach #2, I just have one variable of graph, while the mini-graphs can just be implemented as extra properties of the nodes and edges. This way, I can select which nodes and edges to load from the files (e.g. if a node has a mini-graph ID of 1, load the node). Having said that, I don't know how to implement those approaches with BGL. It seems to me that subgraph provides a hierarchically structured graph, but is it possible to just load a subgraph without loading the whole graph? BTW, I am wondering if BGL has an external memory variant, like Parallel BGL for multi-core environment? If not, is anybody aware if there is such library (preferrably free to use for research purpose)? Thank you! Best regards, Nicholas Mario Wardhana

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accessing last element in boost multi-index
by Mahmood Naderan 19 Mar '13

19 Mar '13

Hi Using boost::multiindex, I am looking for a method to retrieve the the last element. Something like rbegin(). As I looked in to the manual page, http://www.boost.org/doc/libs/1_53_0/libs/multi_index/doc/tutorial/basics.h…, I could not find such function. Problem with end() is that it points to the last_element+1 which is null. Regards, Mahmood

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[graph] problem with weight_map ? (brandes_betweenness_centrality)
by The Maschine 19 Mar '13

19 Mar '13

Hi all, I think I've got a problem with the way I use the weight property map in my betweenness_centrality (and maybe other locations too). I've got a graph like that: typedef boost::property<boost::edge_weight_t, double> EdgeWeightProperty; typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, VertexProperties, EdgeWeightProperty> unGraph; And I add edges with weights like that (simplified): EdgeWeightProperty weight = getWeight(a, b); // 0f ... 2.0f std::pair<unGraph::edge_descriptor, bool> e = boost::add_edge(a, b, weight, m_ugraph); Than I try to do the brandes_centrality_betweenness: std::vector< double > v_centrality_vec(boost::num_vertices(m_ugraph), 0.0); boost::brandes_betweenness_centrality(m_ugraph , boost::centrality_map(boost::make_iterator_property_map(v_centrality_vec.begin(),boost::get(boost::vertex_index, m_ugraph),double())).vertex_index_map(get(boost::vertex_index, m_ugraph)).weight_map(get(boost::edge_weight, m_ugraph)) ); But I get crazy results... 1) I have checked by hand that my "getWeight" (my weights) are OK. 2) I have set _ALL_ weights to 1.0 (almost as if brandes was using BFS internally), Again I get the _SAME_ crazy results! So there is something wrong with the way Im using the weight_map. What am I missing?? Best, Tasos

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[regex] using partial_match?
by Armel Asselin 19 Mar '13

19 Mar '13

[boost 1.53.0] Hello, I'd like to find in a stream of text either "abcd" or "ab". The text is not bounded in size, so I think I should use partial_match. However I present it the following text: "hello abc<cut_here>d, how are you?" it reports to find "ab" and does not wait for the second block to be appended. #include "boost/regex.hpp" int main(int argc, char* argv[]) { boost::regex re ("abcd|ab"); std::string str ("hello abc"); boost::match_results<std::string::const_iterator> results; bool found = boost::regex_search (str.cbegin(), str.cend(), results, re, boost::regex_constants::match_partial); if (!found || results[0].matched) printf("problem...\n"); return 0; } Am I doing something wrong? I see in the specification that "Specifies that if no match can be found, then ....", isn't this specification flowed? should not it be "if the regular expression engine needs to check past the end of the block of text, and the start matches partially, ...." ? I hope I am wrong and there are good flags to pass.... Regards Armel

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[range] contiguous iterators
by Stefan Strasser 19 Mar '13

19 Mar '13

Hi everyone, is there any way to generically determine at compiletime whether an iterator or a boost range refers to contiguous memory? i.e. &*(it+1) == (&*it)+1 some type trait like is_contiguous<T *>::value == true is_contiguous<vector<T>::iterator>::value == true is_contiguous<std::list<T>::iterator>::value == false ?

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Android: segfault while writing to archive during Serialization
by wespaugh 18 Mar '13

18 Mar '13

Greetings! New to discussion, apologies in advance for any inadvertent misuse of terminology / standards. (also, I tried e-mailing this post directly last night, but it doesn't appear to have shown up, yet. double-apologies if double-post). I'm trying to port my project, which involves some serialization code, to Android. I followed instructions to build boost 1.49 found here: https://github.com/MysticTreeGames/Boost-for-Android and can successfully compile my application using crystax NDK r7 (gcc 4.5.3) , and link it to the Serialization library. Unfortunately! When my application calls the serialization code to send my object to the archive, it crashes. I've reduced my actual code to try and isolate the crash in a way I can post here. std::ofstream outStream(MAP_SAVE_FILE, std::ios_base::binary); boost::archive::text_oarchive outputArchive(outStream, 1); Classroom *c = new Classroom(); CCLog("Outputting archive"); // outputArchive << mapInstance; outputArchive << c; The crash occurs at outputArchive << c; "Fatal signal 11 (SIGEGV) at 0xdeadbaad (code=1), thread 1870 (Thread-97)" which is a segfault, in Androidvania. Ideally I want to be outputting that mapInstance variable that's commented out to archive, but for sanity's sake I made a silly little Classroom class, which I'll include for sanity's sake: class Classroom { friend class boost::serialization::access; template <class Archive> void serialize( Archive &ar, const unsigned int version ) { ar & studentCount; } int studentCount; public: Classroom() { studentCount = 1; } ~Classroom(){} }; I've run across several red flags about wchar support in Android or on gcc versions, so I'm inclined to think that's related. Then again, it appears as though my boost configuration files were aware of the compiler version when it built (that Mystic Tree link at the top really does seem to be on top of things, if anyone's interested), which is how the program was able to compile and run, at all. I'm almost 100% certain this is related to the Android NDK, either the gcc version or the gnu-stl, because I can compile and run this code on Windows through Visual studio with no problem, but it crashes on Android. I've made sure that my app has write permissions to the internal storage being used. I can even write out text files using basic std::ostreams without a crash. I am not at all familiar with dealing with these sorts of compiler- or platform-specific issues; I have a bachelor's in SE which taught me design patterns, architecture, and project management, but nothing like this. I'd greatly appreciate some direction in learning how to work through these kinds of problems, (although I'd even more greatly appreciate an actual solution to the problem I'm seeing). Thanks in advance for any assistance. -- View this message in context: http://boost.2283326.n4.nabble.com/Android-segfault-while-writing-to-archiv… Sent from the Boost - Users mailing list archive at Nabble.com.

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boost serialization of std::pair
by Andrew Smith 18 Mar '13

18 Mar '13

Hi, Is there any way of customizing the element names given to serialization of std::pair via xml_oarchive. Im think of something like the|||BOOST_SERIALIZATION_NVP mechanism. In particular Im looking to serialize std::map with custom elemnet names to replace '<first>' and '<second>' Thanks Andy |

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