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boost graph pruning vertices (nodes)
by Brian Davis 14 Oct '16

14 Oct '16

In reading http://www.boost.org/doc/libs/1_62_0/libs/graph/doc/adjacency_list.html regarding Iterator and Descriptor Stability/Invalidation it leaves the impression that when using vecS there is no real good way to remove nodes. as example: typedef adjacency_list<listS, vecS> Graph; // VertexList=vecS all cases are wrong and typedef adjacency_list<listS, listS> Graph; // VertexList=listS where only one case is correct which leave the programmer walking the mine field. Of course same can be said for stl. My goal to remove graph vertices based on the value of the connected components. I currently have a method which uses connected components to generate a connected components list. I then generate a histogram of the connected components values thus giving me how many vertices are connected and what the connection property value is... assuming I understand connected components however I have thought I understood portions of boost only to find through some brain warp and folding my thought process back on itself like an origami master that I came to understand how certain parts work. vertid, component 0 0 1 0 2 0 3 0 4 1 5 1 6 2 7 2 8 2 9 2 10 2 11 2 12 3 13 3 so in this simple example vert ids [0-3] are connected in subnet 0 with a total of 4, [4-5] are connected in sub net 1 with a total of 2, [6-11] are connected in subnet 2 with a total of 6, and [12-13] is connected in subnet 3 with a total of 2. Histogram yields connected component value and number of vertices that have that value in the bin component : bin counts 0: #### 1: ## 2: ###### 3: ## etc for say subnet/subgraph less than 4 would yield the filtered histogram: 1: ## 3: ## using values 1, and 3 from filtered histogram I can then find the vertex ids to filter. Yielding vertices 4,5,12, and 15 to be removed which would remove subnets 1 and 3. 4 1 5 1 12 3 13 3 I tried to use boost::accumulators::density and maybe I have a different idea of what a histogram really is, but for a typical histogram density is just plane broken due to the seemingly use of count for number of bins (seems to ignore tag::density::num_bins) and associated logic. accumulator_t acc( tag::density::num_bins = n_bins, tag::density::cache_size = n_bins/2 ); Sure wish there was a boost::accumulators::histogram that just did what we need as programmers. I am unsure as to how much boost coolaid to drink before finding any use for density. I did find this relating to the seemingly not as advertised implementation of density http://lists.boost.org/Archives/boost/2008/01/132801.php. From http://www.boost.org/doc/libs/1_62_0/doc/html/accumulators/user_s_guide.html "The tag::density feature returns a histogram of the sample distribution. For more implementation details, see density_impl." err huh no it does not... at least in my testing. It would also be great if the abcicissas (intervals) were some how obtainable to compare to the ordinates (bin counts) . Note the histogram.hpp attached there. So I write by own histogram code using stl. I digress on that. So as I said I then filter the vertex vs connected components data based on a threshold say 4 to remove all vertices that are not connected to 4 or more vertices in a subnet/subgraph So I then have a list of vertices (subnets/subgraphs) that I wish to prune from the graph thus these questions: Question 1: if finding a list of vertices to erase, sorting them, and then using, a reverse iterator to remove(*itr, g) would this also not work? If this works why is it now shown as an example of vecS vertex removal working? Question 2: Should there not be a boost graph-ish way of doing this such as coloring vertices to be pruned by possibly adding property prune = true. then maybe a future call to prune(g) Question 3: Possibly there is a way to get filtered_graph to do the trick? Statement: it is unfortunate the use of the term vertex/vertices in stead of node(s) in boost graph. As some graphs have a vertex (euclidean geometry) such as a graph of the center-lines of the vascular network of a brain while other graphs do not. It is very confusing in this instance to keep the two strait in code. Ugh!

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Re: [Boost-users] [Serialization] Free-standing serialize function for "enum class"
by Bjorn Reese 13 Oct '16

13 Oct '16

On 10/13/2016 06:56 PM, Rüdiger Berlich wrote: > I have for a while suspected a problem with the serialization of an „enum class“ item (currently with Boost 1.61 on Ubuntu 16.04), and have written a small test program to further examine any potential problems. While the generated XML looks fine and I cannot see any problems with the enum class, my custom, free-standing „serialize“ function does not get called. Boost.Serialization automatically converts an enum into an int before it is serialized.

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[Serialization] Free-standing serialize function for "enum class"
by Rüdiger Berlich 13 Oct '16

13 Oct '16

Hi there, I have for a while suspected a problem with the serialization of an „enum class“ item (currently with Boost 1.61 on Ubuntu 16.04), and have written a small test program to further examine any potential problems. While the generated XML looks fine and I cannot see any problems with the enum class, my custom, free-standing „serialize“ function does not get called. It is modelled after the examples for non-intrusive serialization, so I do not understand the reason behind this. Any idea ? /*************************************/ // Compile with g++ --std=c++14 -o enum_ser -I/opt/boost/include/ -L/opt/boost/lib enum_ser.cpp -lboost_serialization #include <boost/serialization/nvp.hpp> #include <boost/archive/xml_oarchive.hpp> #include <boost/archive/xml_iarchive.hpp> #include <iostream> #include <sstream> enum class test_enum : int {a=5,b=6}; namespace boost { namespace serialization { //----------------------------------------- template<typename Archive> void serialize(Archive &ar , test_enum &x, const unsigned int){ std::cout << "Serializing via custom serialize function" << std::endl; int t = 0; if (Archive::is_saving::value) { t = static_cast<int>(x); ar & t; } else { ar & t; x = static_cast<test_enum>(t); } } //----------------------------------------- } } int main(int argc, char **argv){ std::ostringstream oss; test_enum x = test_enum::a; { boost::archive::xml_oarchive oa(oss); oa << BOOST_SERIALIZATION_NVP(x); } std::cout << oss.str() << std::endl; } /*************************************/ Output of the program (note: the „Serializing via custom serialize function“ does not appear) : /*************************************/ <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="14"> <x>5</x> </boost_serialization> /*************************************/ Thanks and Kind Regards, Beet

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Boost test failures on arm platform
by Carlos Ferreira 13 Oct '16

13 Oct '16

Hello! I'm cross-compiling Boost to an arm platform and because of that, boost fails to execute the cxx11_* tests and then it outputs the information that the compiler does not support a series of cxx11_* capabilities. Is there a way to disable these library tests, when cross-compiling? -- 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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Announcing version 3 of the cxx_dual library
by Edward Diener 12 Oct '16

12 Oct '16

I have created version 3 of the cxx_dual library. version 3 is a large rewrite of the documentation to simplify the use of the library, as well as a change in the directory structure so that the basic usage of the library is through a single header file and the use of a namespace alias, and not through the macro interface. As in: #include <boost/cxx_dual/regex.hpp> void SomeFunction() { cxxd_regex_ns::regex re("A regular expression etc."); bool result(cxxd_regex_ns::regex_match("Some string...",re)); // etc. } What ! No macros ! Actually a few macros still exist for testing which dual library has been chosen and overriding the dual library chosen, but the basic functionality means almost no macros in user code. The library is available at https://github.com/eldiener/cxx_dual.git. What is it ? The Cxx Dual library, or CXXD for short, is a C++ macro header-only library which chooses between using a Boost library or its C++ standard equivalent library for a number of different C++ implementations, while allowing the end-user to use the same code to program either choice. An implementation is a Boost library which has a C++ standard library equivalent whose public interfaces are nearly the same in both cases. An 'implementation' is called a 'mod' for short and each of the possible Boost or C++ standard implementations for that mod are called a 'dual library'. The Cxx Dual library does this by automatically choosing either the Boost library or the C++ standard library for a particular mod, including the correct header file(s) needed for the dual library chosen, and creating a namespace alias for the namespace of the dual library chosen. CXXD also provides a macro-based solution for distinguishing between the Boost version and the C++ standard version of a dual library so that specific code for a particular dual library choice may be written in those cases where the public interfaces diverge.

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Issues trying to use boost::unordered_map
by Ram 12 Oct '16

12 Oct '16

Hi, I am trying to use a boost::unordered_map as a member of my class. The unordered_map is defined as, boost::unordered_map<int, int> a; as a private member in the class. I have included #include "boost/unordered_map.hpp" using namespace boost; This is the compilation error I get, x_objs.cpp c:\codeworks\common\lib\boost\boost\unordered\detail\buckets.hpp(767) : error C2059: syntax error : '(' c:\codeworks\common\lib\boost\boost\unordered\detail\buckets.hpp(766) : while compiling class template member function 'void boost::unordered::detail::functions<H,P>::construct(bool,const H &,const P &)' with [ H=boost::hash<int>, P=std::equal_to<int> ] c:\codeworks\common\lib\boost\boost\unordered\detail\table.hpp(152) : see reference to class template instantiation 'boost::unordered::detail::functions<H,P>' being compiled with [ H=boost::hash<int>, P=std::equal_to<int> ] c:\codeworks\common\lib\boost\boost\unordered\detail\unique.hpp(179) : see reference to class template instantiation 'boost::unordered::detail::table<Types>' being compiled with [ Types=boost::unordered::detail::map<std::allocator<std::pair<const int,int>>,int,int,boost::hash<int>,std::equal_to<int>> ] c:\codeworks\common\lib\boost\boost\unordered\unordered_map.hpp(74) : see reference to class template instantiation 'boost::unordered::detail::table_impl<Types>' being compiled with [ Types=boost::unordered::detail::map<std::allocator<std::pair<const int,int>>,int,int,boost::hash<int>,std::equal_to<int>> ] c:\codeworks\sample_issue.h(276) : see reference to class template instantiation 'boost::unordered::unordered_map<K,T>' being compiled with [ K=int, T=int ] li_pip.cpp ld_pip.cpp pip.cpp . . . Can someone please help me? Thanks, Ram

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[fiber] Asio autoecho example crashes (VS 2015 u3)
by DePizzottri 11 Oct '16

11 Oct '16

Hi all, I'm found that asio autoecho example crashes after main's return statement. Debugger shows write access from the fiber scheduler to the already destroed io_service. Substitution reference to io_service: boost::asio::io_service & io_svc_; in round_robin algo to the shared_ptr: boost::shared_ptr<boost::asio::io_service> io_svc_; with approprieate correction of the other code solves the problem. Maybe I misunderstood something in the descrition from documentation? Or its some kind of feature? -- View this message in context: http://boost.2283326.n4.nabble.com/fiber-Asio-autoecho-example-crashes-VS-2… Sent from the Boost - Users mailing list archive at Nabble.com.

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Re: [Boost-users] [ASIO] Do coroutines allow serving multiple clients at once?
by mmarkd9＠libero.it 11 Oct '16

11 Oct '16

Thanks, does spawning a coroutine also spawn a new thread? I'd be inclined to think so from what you told me

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R: Re: [ASIO] Do coroutines allow serving multiple clients at once?
by mmarkd9＠libero.it 10 Oct '16

10 Oct '16

Thanks, does spawning a coroutine also spawn a new thread? I'd be inclined to think so from what you told me ----Messaggio originale---- Da: "Oliver Kowalke" <oliver.kowalke(a)gmail.com> Data: 10-ott-2016 15.19 A: "boost-users"<boost-users(a)lists.boost.org> Ogg: Re: [Boost-users] [ASIO] Do coroutines allow serving multiple clients at once? 2016-10-10 9:44 GMT+02:00 mmarkd9(a)libero.it <mmarkd9(a)libero.it>: I'd like to know if this code is able to serve multiple clients connecting at the same time to the server. I would say no. You spawn only one coroutine that calls in the for-loop async. operations of accept(), read() and write() in a sequence. No other client is able to connect to your server, e.g. connect() on the client side returns, until you enter accept() again. In order to serve multiple clients at the same time you need to spawn a coroutine that accepts new connections and for each client request (read()/write() operations) you need to spawn a new coroutine.

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Re: [Boost-users] [ASIO] Do coroutines allow serving multiple clients at once?
by mmarkd9＠libero.it 10 Oct '16

10 Oct '16

Thanks, does spawning a coroutine also spawn a new thread? I'd be inclined to think so from what you told me

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