December 2013 - Boost-users

[graph] boykov_kolmogorov_max_flow and reverse edges capacity
by Olivier Tournaire 21 Dec '13

21 Dec '13

Hi, I am trying to use boykov_kolmogorov_max_flow algorithm to find a minimum cut of some graph. To build the graph, I first create source and sink vertices. I then add some vertices, and connect them. Each time I create and edge, I also create the reverse edge: edge_descriptor_bool e01 = add_edge(v0, v1, _graph); edge_descriptor_bool e10 = add_edge(v1, v0, _graph); reverse[e01.first] = e10.first; reverse[e10.first] = e01.first; where reverse is: boost::property_map<Graph, boost::edge_reverse_t>::type reverse = get(boost::edge_reverse , _graph); I then fill edge capacity: capacity[e10.first] = this->getEnergy(fh, fh_v0); // Use policy to compute energy capacity[e01.first] = this->getEnergy(fh, fh_v0); // Use policy to compute energy My question is how capacity of reverse edge has to be computed. The doc states that reverse edge can carry capacities different than 0, but should they be the same as their parallel edge? Note that I use the algorithm with this method: _minEnergy = boykov_kolmogorov_max_flow(_graph, _source, _sink); Any help would be appreciated. Regards, Olivier

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BGL: using short integer as vertex_descriptor
by Adam Celick 21 Dec '13

21 Dec '13

Hi, I am using the graph library in a memory constrained environment. By default vertex_descriptor for an adjacency_list (of vectors, i.e. vecS, vecS) seems to be std::size_t. I was wondering if there's a way to use say uint16_t for the vertex_descriptor? Thanks, -Adam

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[boost.test] Unable to perform init at startup
by Adam Nielsen 21 Dec '13

21 Dec '13

Hi all, I'm having a bit of a problem trying to figure out how to perform some class init while manually registering my tests.

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[boost.asio] Concurrently Ping 1000+ Hosts
by Kyle Ketterer 21 Dec '13

21 Dec '13

Hello, So the subject line pretty much says it all. Basically, I am trying to expand off of the icmp ping example given by the boost library documentation. I would like to ping 1000+ hosts in say, a matter of minutes rather than a matter of hours. I have already expanded the class shown here: http://www.boost.org/doc/libs/1_40_0/doc/html/boost_asio/example/icmp/ping.… Before I start posting code, I would like to discuss the strategy of trying to do this. In my Main thread, I was thinking about creating a vector of PingX objects. In the PingX class, I would have a separate io_service as well as wrap the async() functions in strands. I set the deadline timer at 800ms that way the io_service should return in less than a second. I would then call io_service run() in separate threads to *concurrently* ping these hosts. The problem appears to be that even through the async handers are wrapped in strands, there is data corruption. Is it true that when async handlers are wrapped in strands, they still cannot be executed *concurrently* ? My understanding of strand was that it serializes the handler functions to allow for thread safe access. However, I think that because I am accessing the same resources in multiple threads (such as the socket() object ), it is corrupting my expected output as well as occasionally throwing some exceptions. Are there any suggestions for the logic surrounding this or if this can be done in a multithreaded environment? Thanks! -- Kyle Ketterer

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Boost.Coroutine and Object Inheritance
by Carlos Ferreira 20 Dec '13

20 Dec '13

Hello to all. I need some help using the Boost.Coroutine lib. I wanted to use the coroutines as objects and for that, I tried to build a simple object and inherit the boost::coroutines::coroutine template. ex: class SimpleObj : public boost::coroutines::coroutine<SimpleObj>{ private: std::unique_ptr<boost::asio::ip::tcp::socket> tcpSkt_uPtr; std::unique_ptr<boost::asio::ip::tcp::acceptor> acc_uPtr; public: SimpleObj(std::shared_ptr<boost::asio::io_service> ioService_ptr, boost::asio::ip::tcp::endpoint &endPoint); ~SimpleObj(); void run(); }; Is this right? Can I actually inherit from the boost::coroutines::coroutine template ? If yes, how can I proceed from here, to use the run() object method as the coroutine itself, with an io_service provided through the constructor ? Thanks for any assistance! -- Carlos Miguel Ferreira Researcher at Telecommunications Institute Aveiro - Portugal Work E-mail - cmf(a)av.it.pt Skype & GTalk -> carlosmf.pt(a)gmail.com LinkedIn -> http://www.linkedin.com/in/carlosmferreira

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[git][testing] regression testing?
by Joaquín Mª López Muñoz 19 Dec '13

19 Dec '13

There's been some unanswered questions around this. I understand that regression tests, which are critical to ensure clean develop->master merges, will be eventually updated to work against git rather than the abandoned SVN, but I can't find any info on the progress of this. FWIW, I see some authors are going ahead and merging their libs anyway, which will bring breakages etc if changes are not properly validated through regression testing. Any indication on how this is progressing much appreciated. Best, Joaquín M López Muñoz Telefónica Digital ________________________________ Este mensaje se dirige exclusivamente a su destinatario. Puede consultar nuestra política de envío y recepción de correo electrónico en el enlace situado más abajo. This message is intended exclusively for its addressee. We only send and receive email on the basis of the terms set out at: http://www.tid.es/ES/PAGINAS/disclaimer.aspx

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How to use the optional with property_tree‏
by 王郁槐 19 Dec '13

19 Dec '13

Could anyone help? Why the below code will crash on the below line? I'm using the boost property_tree. Thanks. child1.get().put(sub_field, strValue); ========================================================= #include <fstream> #include <boost/filesystem.hpp> #include <boost/property_tree/ptree.hpp> #include <boost/property_tree/ini_parser.hpp> #include <boost/any.hpp> #include <boost/optional.hpp> void writeConfig(const std::string &field, const std::string &sub_field, const std::string & strValue) { if (!boost::filesystem::exists(prog_cfg_file)) { std::ofstream ofIniConfig(prog_cfg_file, std::ofstream::out|std::ofstream::app); ofIniConfig.close(); } boost::property_tree::ptree pt; boost::property_tree::ini_parser::read_ini(prog_cfg_file, pt); boost::optional<boost::property_tree::ptree&> child1 = pt.get_child_optional(field); if (child1) { boost::optional<boost::property_tree::ptree&> child2 = child1.get().get_child_optional(sub_field); if (child2) { child2.get().put_value(strValue); }else { child2.get().put_value(strValue); } }else { child1.get().put(sub_field, strValue); } boost::property_tree::ini_parser::write_ini(prog_cfg_file, pt); } int main() { writeConfig("test", "a", "OK"); return 0; } -- 兰生幽谷, 不以无人而不芳...

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Caching the iterator of async_resolve()?
by Kaspar Fischer 18 Dec '13

18 Dec '13

Hi everybody, Just to be on the safe side: I assume that I can cache the iterator returned by async_resolve<http://www.boost.org/doc/libs/1_49_0/doc/html/boost_asio/reference/ip__basi…>'s handler, correct? The fact that it's a forward iterator suggests so... Thanks! Kaspar

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[MPL] How to generate pre-generated header files for a mpl::list containing more than 50 entries?
by Klaus.Kempf＠industronic.de 18 Dec '13

18 Dec '13

Hello MPL experts, I want to code a state machine which has a reaction list containing more than 50 entries. I found here [http://svn.boost.org/svn/boost/trunk/libs/mpl/preprocessed/] some python scripts to generate header files for a mpl::list containing more than 50 entries. But I cannot manage to generate a single header file. Can someone please explain to me how to use these scripts? I also didn't find any help in boost documention. Command line messages of the related script were also not helpful for me: preprocess_list.py Usage: preprocess_list.py <mode> <boost_root> [<source_file>] Purpose: updates preprocessed version(s) of the header(s) in "boost\mpl\list\aux_\preprocessed" directory Example: the following command will re-generate and update all 'apply.hpp' headers: preprocess_list.py all f:\cvs\boost apply.cpp What is the meaning of [<source_file>] here? And how/where do I have to specify the count of list entries in order to generate the header files "list60.hpp", "list70.hpp" and so on? Many thanks for any help you could provide. Best regards, Klaus

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async_send handler problem
by Alexander Carôt 17 Dec '13

17 Dec '13

Hello all, I am new to boost and asio in particular. For now I am implementing a simple UDP sender. The sending process itself works fine but for some reason the send handler does not execute. The call itself looks like this: In my class sender.cpp I have a functions called void sender::sendIt(){ sj->dFC->s->async_send_to(boost::asio::buffer( this->charBuffer,sendBytes), *sj->dFC->e, boost::bind(&sender::sendHandler,this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred); } and the corresponding handler is this: void sender::sendHandler(const boost::system::error_code& error,std::size_t bytes_transferred){ cout << "TRIGGER" << endl; } Can anyone give me a hint what the reason for the not-working handler might be ? Thanks in advance, best Alex

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