May 2016 - Boost-users - lists.preview.boost.org

udp::endpoint - port change
by Alexander Carôt 04 May '16

04 May '16

Hello all, probably trivial but I am currently stuck with this: I create a UDP endpoint via udp::resolver::query query(udp::v4(),IP,port); destinationEndpoint = new udp::endpoint(*resolver.resolve(query)); but after the creation I want to change the port without deleting and recreating it with different parameters. How can I do this ? Thanks in advance, best Alex

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Re: [Boost-users] Extending boost graph edge class
by Rafael Gasperetti 03 May '16

03 May '16

Hi, The third option fit in my case. I haver a class that I need to be the edge of the graph, and i have another one that I need to be the vertex. Using this way, My classes Can be used inside the graph to calculate distance, scc, etc. Thanks,Rafael -------- Mensagem original -------- De : Daniel Hofmann <daniel(a)trvx.org> Data: 03/05/2016 19:23 (GMT-03:00) Para: boost-users(a)lists.boost.org Assunto: Re: [Boost-users] Extending boost graph edge class Can you elaborate on "extend the edge class"? Here are some possible interpretations: 1/ You want to optimize the memory consumption for large graphs. The edges and vertices still fit into uint32_t: using graph_t = compressed_sparse_row_graph<directedS, no_property, no_property, no_property, uint32_t /* Vertex */, uint32_t /* EdgeIndex */>; 2/ You want to store arbitrary metadata on your edges and retrieve this edge data based on your graph and a specific edge descriptor: struct edge_data_t { int distance = 0; }; using graph_t = compressed_sparse_row_graph<directedS, no_property, edge_data_t>; // .. auto duration = [&graph](auto edge) { return graph[edge].duration; }; auto total = accumulate(edges(graph) | transformed(duration), 0); This example is using "bundled properties". There is also the possibility to store edge data external to the graph and not couple the edge data's lifetime with the graph (e.g. if you need edge weights for a particular algorithm in your use-case). 3/ You want to provide your own graph representation and make it a model for the BGL graph concepts: http://www.boost.org/doc/libs/1_60_0/libs/graph/doc/leda_conversion.html http://www.boost.org/doc/libs/1_60_0/libs/graph/doc/graph_concepts.html Here are some more BGL examples that should get you started: https://github.com/daniel-j-h/cppnow2016 Cheers, Daniel J H On 05/03/2016 08:37 AM, Rafael Gasperetti wrote: > > > Hi, > My name is Rafael and I need to extend the edge class of de graph part > of the boost lib, but I always find problems trying to do this. Can you > help me with examples and explanations about how to do this? > I read a lotação of places trying to do this but no help was found, > please help me. > > Thanks a lot, > Rafael > > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Extending boost graph edge class
by Rafael Gasperetti 03 May '16

03 May '16

Hi,My name is Rafael and I need to extend the edge class of de graph part of the boost lib, but I always find problems trying to do this. Can you help me with examples and explanations about how to do this?I read a lotação of places trying to do this but no help was found, please help me. Thanks a lot,Rafael

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[boost.multiprecision] print cpp_int with a thousands separator
by Tassilo Glander 03 May '16

03 May '16

Dear List, how can I control the thousands separator behavior when streaming a cpp_int to std::cout? I think it is not possible without changing the global locale, as cpp_int.str uses lexical_cast, which uses the global locale object to read the thousands separator character. This prevents me from having a custom formatting like below. Is there another way? Best, Tassilo #include <iostream> #include <locale> #include <iomanip> int main() { struct my_numpunct : std::numpunct<char> { protected : virtual char do_thousands_sep() const override { return '.' ; } virtual std::string do_grouping() const override { return "\03" ; } }; cpp_int testNum(1000); std::cout.imbue( std::locale( std::cout.getloc(), new my_numpunct ) ) ; std::cout << testNum << '\n' ; // still get 1000, desired is 1.000 }

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Multiprecision vector pass to function by reference
by Cooper, Bridgette R D 02 May '16

02 May '16

Hi, I am having some difficulties passing a vector of type std::vector<float128> to a function. I'm getting multiple errors out. The first few of which are: tql2.cpp:13:50: error: 'float128' was not declared in this scope void tql2(const int nm, int n, const std::vector<float128> & d, const std::vector<float128> & e, const std::vector< std::vector<float128> > & z, int ierr) ^ tql2.cpp:13:50: note: suggested alternative: In file included from tql2.cpp:1:0: /home/bcooper/Tarballs/boost_1_57_0/boost/multiprecision/float128.hpp:124:42: note: 'boost::multiprecision::float128' typedef number<float128_backend, et_off> float128; ^ tql2.cpp:13:58: error: template argument 1 is invalid void tql2(const int nm, int n, const std::vector<float128> & d, const std::vector<float128> & e, const std::vector< std::vector<float128> > & z, int ierr) ^ tql2.cpp:13:58: error: template argument 2 is invalid tql2.cpp:13:83: error: 'float128' was not declared in this scope void tql2(const int nm, int n, const std::vector<float128> & d, const std::vector<float128> & e, const std::vector< std::vector<float128> > & z, int ierr) ^ tql2.cpp:13:83: note: suggested alternative: In file included from tql2.cpp:1:0: /home/bcooper/Tarballs/boost_1_57_0/boost/multiprecision/float128.hpp:124:42: note: 'boost::multiprecision::float128' typedef number<float128_backend, et_off> float128; ^ The first few lines of my code are: #include <boost/multiprecision/float128.hpp> #include <boost/math/cstdfloat/cstdfloat_types.hpp> #include <boost/math/cstdfloat/cstdfloat_limits.hpp> #include <boost/math/cstdfloat/cstdfloat_cmath.hpp> #include <boost/math/cstdfloat/cstdfloat_iostream.hpp> extern "C"{ #include <quadmath.h> } #include <iostream> #include <vector> #include <iterator> void tql2(const int nm, int n, const std::vector<float128> & d, const std::vector<float128> & e, const std::vector< std::vector<float128> > & z, int ierr) { using namespace boost::multiprecision; ... } Not sure where I am going wrong? Any advice? Thanks,

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Re: [Boost-users] [boost.multiprecision] export_bits throws on a negative
by Tassilo Glander 02 May '16

02 May '16

Hi John, I opened tickets to track both issues: - Ticket #12170 (new Bugs) boost::multiprecision::export_bits throws on a negative cpp_int number - Ticket #12171 (new Feature Requests) boost::multiprecision should provide a hash function Best, Tassilo

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boost log facility multithreading issue
by David Frank 01 May '16

01 May '16

Greetings,I have 4 threads, in each thread, I created its own log file using boost log facility, different from the ones in other thread.The problem is that the log entries I put into one file in one thread, got into all other log files in other threads, though the boost log instances are not shared among threads. Anyone know how to avoid this? Thanks, David

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boost/multiprecision/float128
by Cooper, Bridgette R D 01 May '16

01 May '16

I'm new to boost. I am trying to use the float128 type for calculating sqrts as a larger part of code, however I am not sure the values obtained are accurate to float128 precision. I have tried running the example for printing log(2) found here, I find the same for sqrt: http://www.boost.org/doc/libs/1_57_0/libs/multiprecision/doc/html/boost_mul… However, the value printed log(2) only agrees to 16 decimal places, i.e. double precision. The value I obtain is 0.693147180559945286226763982995180413 rather than 0.693147180559945309417232121458176575 I'm using: g++ (GCC) 4.8.2 20140120 (Red Hat 4.8.2-15) with boost 1.57.0. Any advice as to what I am doing incorrectly? My compile line is: g++ -I ~/$BOOSTLIB new.cpp -lquadmath -o new Thanks,

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