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[BGL] dijkstra visitor for examine edge event
by Alejandro Marcos Aragón 08 Feb '07

08 Feb '07

Hi everyone, I am trying to store all the vertices with their respective distances from a source within the Dijkstra shortest path algorithm. For that I plan to use a std::vector<std::queue > >. I was able to have the visitor working but I don't know how to access to those values that are computed automatically by the algorithm (d_v, d_u, for example). The code I wrote is as follows: template <class Tag> struct vis : public default_dijkstra_visitor { vis() { } template <class Edge, class Graph> void edge_relaxed(Edge e, Graph& g){ cout<<"VISITOR!!!"<<endl; cout<<"Edge -> "<<e<<endl; } private: std::vector<std::queue<Vertex> > storage; }; template <class Tag> vis<Tag> target_visit(Tag) { return vis<Tag>(); } void Dijkstra() { // maps needed by the algorithm IndexMap indexmap = get(vertex_index, *gPtr); WeightMap weightmap = get(edge_weight, *gPtr); // define containers for the predecessor vertices and // for distances std::vector<Vertex> pred(num_vertices(*gPtr)); std::vector<double> dist(num_vertices(*gPtr)); // vertex to compute Dijkstra's algorithm on Vertex source = vertex(get_source(), *gPtr); // Dijkstra's algorithm dijkstra_shortest_paths(*gPtr, source, predecessor_map(&pred[0]).distance_map(&dist[0]).visitor(target_visit(on_examine_edge()))); ... Any help will be appreciated. aaragon

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serialization question
by Aljaz 07 Feb '07

07 Feb '07

Hello.. I have a derived class serialization: for instance: class client_request_base { public: client_request_base() : _type( 0 ) {} private: friend boost::serialization::access; template< class ARCHIVE > void serialize( ARCHIVE& ar, const unsigned int version ) { ar & _type; } unsigned int _type; }; class calc_skip_images_request : public client_request_base { public: calc_skip_images_request() : client_request_base( 1 ), _images_client( 0 ) {} private: friend boost::serialization::access; template< class ARCHIVE > void serialize( ARCHIVE& ar, const unsigned int version ) { ar & boost::serialization::base_object<client_request_base>( *this ); ar & _images_client; } unsigned int _images_client; }; Now I wonder.. If I want to use serialization do I have do EXPORT second class? Or set first class to abstract? Like: BOOST_IS_ABSTRACT( client_request_base ) BOOST_CLASS_EXPORT(calc_skip_images_request) Im confused which of these two things is needed? When should I use export and when is abstract macro?

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[signals] Automatic connection management and MT
by Timmo Stange 07 Feb '07

07 Feb '07

I'm working on a preliminary solution for an interface-compatible but thread-safe implementation of Signals for my project so that I will be able to switch to Boost.Signals should Doug Gregor find the time to add thread-safety there. While deciding what parts to include and which to leave out, I noticed that the automatic connection management is probably not usable in a multi-threaded context in the current form. Using a base class destructor (signals::trackable) to monitor an observer's lifetime is bound to result in race condition trouble with the order of destruction in a class hierarchy. Has that been discussed somewhere and are there any proposed solutions/alternatives? Regards Timmo Stange

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Re: [Boost-users] Boost.Thread contained within a class?
by Sohail Somani 07 Feb '07

07 Feb '07

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Joshua ChaitinPollak > > Hello, > > I have a question about Boost.Thread. I am trying to create a class > which upon instantiation creates a thread based upon itself, > and then > on destruction, stops the thread and cleans up after itself. > A simple > example is below. Is this possible, and if not, what alternatives do > I have? It should be possible the way you've outlined it except for the fact that you try to initialize a pointer with an unrelated type and also never initialize the background thread. Are there specific problems that you are having?

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using filesystem on Solaris 9 and 10
by Polder, Matthew J 07 Feb '07

07 Feb '07

Hi, I'm using the boost library filesystem on Windows XP and Solaris 9 and 10. I haven't had any problems with Windows so far. When linking my executable on Solaris 9, the linker warned me that the filesystem library I linked wanted to be linked with libm.so.2, which isn't on my Solaris 9 system. The executable still runs but when I use filesystem to list the files in a directory it doesn't list all of them. I was able to link on Solaris 10, but there I am getting a core dump when I run. Has anyone ever had similar problems on Solaris? thanks, matthew

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Boost.Thread contained within a class?
by Joshua ChaitinPollak 07 Feb '07

07 Feb '07

Hello, I have a question about Boost.Thread. I am trying to create a class which upon instantiation creates a thread based upon itself, and then on destruction, stops the thread and cleans up after itself. A simple example is below. Is this possible, and if not, what alternatives do I have? The reason for this is to create a single external API (actually defined in a base class), and still have a background thread (hidden from the API) which can share that object's internal member variables. I'm looking to do something like this: class my_handler { public: boost::thread* background_thread; my_hander() : background_thread(NULL) { background_thread(*this); } ~my_hander() { if (background_thread != NULL) { running = false; background_thread.join(); } operator()() { while(running) { // do something } } }; -Thanks, Josh -- Joshua ChaitinPollak Software Engineer Kiva Systems

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[thread_safe_signals] postconstructors and predestructors
by Frank Mori Hess 07 Feb '07

07 Feb '07

> Actually, I've realized there's no reason it has to be tied so closely to > enable_shared_from_this. There could be a completely independent base > class called boost::postconstructible which is treated similarly to > enable_shared_from_this in shared_ptr.hpp. Similarly, there could be a > boost::predestructible base class that gets its hook called before the > shared_ptr deletes its pointer (perhaps only in the default deleter). I > believe the hooks would compile to nothing if the shared_ptr isn't > holding a pointer derived from one of these classes, just like (I assume) > they do for enable_shared_from_this. > > > I think you're better off writing a specialized smart pointer if you > > want that kind of functionality. > > I'm no so keen on a specialized smart pointer, for reasons that you've > already brought up earlier. But I suppose that's what I'll do if it comes > to it. It shouldn't be too bad to come up with a new name and do a search > and replace on shared_ptr.hpp. > > My point is, enable_shared_from_this was deemed important enough for > special hooks to be put into shared_ptr.hpp for it. So there is > precedent. And postconstructors/predestructors aren't peculiar ideas that > I just came up with myself. I'm sure they could be useful in other > contexts. > Now I realize I don't need any changes to shared_ptr at all, I can do it all in a wrapper function inserted between the raw pointer and shared_ptr. I can't think of a name, so call it ptr_wrapper(): shared_ptr<MyClass>(signalslib::ptr_wrapper(new MyClass)); ptr_wrapper would call postconstruct() if its input pointer is derived from postconstructible, and return a shared_ptr. The deleter for the returned shared pointer would be (by default) customized to call the predestructor if the input pointer is derived from predestructible. A custom deleter could be accepted as a second argument to ptr_wrapper. -- Frank

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[Serialization] Undefined reference to... (header or compilation problem)
by misha＠gildia.pl 07 Feb '07

07 Feb '07

Hello, I wonder if anyone could help me with my problem. I'm trying to serialize my project's data. Beeing new to the boost libs I started with simple tutorial example. Today is the 3rd day I'm unable to launch a serialization of an object of the simpliest Vertex class containing 2 double values. The errors I get follow this patern: [mack/.../]$ g++ -Wall -o main test3.cpp /tmp/ccQkfdAS.o (.gnu.linkonce.t._ZN5boost7archive18text_oarchive_implINS0_13text_oarchiveEED2Ev+0x31): In function `boost::archive::text_oarchive_impl<boost::archive::text_oarchive>::~text_oarchive_impl()': : undefined reference to `boost::archive::basic_text_oprimitive<std::basic_ostream<char, std::char_traits<char> > >::~basic_text_oprimitive()' The problem is in line : boost::archive::text_oarchive oa (ofs); Any ideas? IMHO it's either compilation issue ( should I include any additional libs to cmd line?) or header order/lacking. To be sure I didn't miss anything else let me include the whole code: //CODE #include <iostream> #include <vector> #include <functional> #include <algorithm> #include <fstream> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/vector.hpp> //using namespace std; //using namespace boost::serialization; class Vertex { private: friend class boost::serialization::access; public: double x; double y; Vertex() {} // Serialization requires a default constructor Vertex(double newX, double newY) : x(newX), y(newY) {} double getX() const { return x; } double getY() const { return y; } void dump() { std::cout << x << " " << y << std::endl; } }; BOOST_IS_ABSTRACT(Vertex) namespace boost { namespace archive { template<class Archive> void serialize(Archive & ar, Vertex & vtx, const unsigned int version) { ar & vtx.x; ar & vtx.y; } } // namespace serialization } // namespace boost int main() { Vertex v1(1.5, 2.5); std::ofstream ofs("myfile.vtx"); boost::archive::text_oarchive oa(ofs); oa << v1; ofs.close(); return 0; } // END CODE I use g++ (GCC) 3.4.4 20050721 (Red Hat 3.4.4-2) Fedora Core Boost ver. 1.32 Thanks in advance for any feedback. Regards Misha

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Error from boost
by gopal.reddy＠wipro.com 07 Feb '07

07 Feb '07

Hi All , I am using boost in Opendiameter code using boost libraray, but i am not running into problems! Details: Tool(compiler) : MSVC60 OS : Windows XP Boost Library Version: boost_1_33_1 Error : :\projects\diameter\opendiameter-1.0.7-h\include\framework.h(255) : error C2352: 'boost::shared_ptr<class AAA_GroupedJob>::get' : illegal call of non-static member function d:\projects\diameter\supporting softwares\boost_1_33_1\boost\shared_ptr.hpp(257) : see declaration of 'get' d:\projects\diameter\opendiameter-1.0.7-h\include\framework.h(255) : while compiling class-template member function 'class AAA_GroupedJob &__thiscall AAA_JobHandle<class AAA_GroupedJob>::Job(void)' memory_manager.cxx How it is used in framework.cpp (file) : template <class JOB> class AAA_JobHandle : public boost::shared_ptr<JOB> { public: AAA_JobHandle(JOB* job) : boost::shared_ptr<JOB>(job, AAA_JobDeleter()) {} JOB& Job() { return (JOB&)*boost::shared_ptr<JOB>::get(); } }; I seem to be doing some thing wrong with the above. Any help on how to go about resolving the problem would be appreciated! Thanks, Gopal The information contained in this electronic message and any attachments to this message are intended for the exclusive use of the addressee(s) and may contain proprietary, confidential or privileged information. If you are not the intended recipient, you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately and destroy all copies of this message and any attachments. WARNING: Computer viruses can be transmitted via email. The recipient should check this email and any attachments for the presence of viruses. The company accepts no liability for any damage caused by any virus transmitted by this email. www.wipro.com

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Re: [Boost-users] [statechart] : asynchronous_state_machine - access member functions
by Oliver.Kowalke＠qimonda.com 07 Feb '07

07 Feb '07

Hi Andreas, Your solution will not work in my application. I use an io-framework which has some requirements that could not be fullfilled with the creation process of an asynchronous_state_machine. asynchronous_state_machine is derived from state_machine - does this mean that asynchronous_state_machine provides only a thread-safe access to state_machine (acts as a wrapper)? In my application I've three event sources (io-device, UNIX-signal handler, trigger which periodically produces events). Each event source runs in ist own thread. I could use a state_machine and synchronize the insertion of events (process_event() function) via a mutex. Would asynchronous_state-machine provide a preformance benfit in this case? Would it be an adequat solution to queue the events from the three event sources in a thread-safe queue (producer-consumer pattern)? The threads providing events act as producer threads) and should not be blocked and the processing of the events (calling state_machine::process_event()) will be done snychronous (maybe by one consumer thread). Regards,Oliver

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