October 2009 - Boost-users - lists.boost.org

Serialization, seg fault on "unregister key"
by dada＠lamef.bordeaux.ensam.fr 28 Oct '09

28 Oct '09

Hi, I'm using boost serialization. My program crash with a segmentation fault just before its end. A gdb's backtrace show that the last function's call is the unregister_key()'s function of boost serialization. Is there a way to fix it ? Thank you, Damien.

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[bind] Unable to pass method to simple function pointer
by Carlos 28 Oct '09

28 Oct '09

Hello, I am trying to make a wrapper for libxml's SAX api, for learning purpose, I am trying to use bind to wrap sax events in a class like this : namespace sax { class document { public: document(); ~document(); protected: virtual void start_node( void *user_data, const xmlChar *name, const xmlChar **attrs ); xmlSAXHandler m_evhdl; xmlParserCtxtPtr m_ctxt; }; } The start_node() function is intended to be pointed by the startElement member from xmlSAXHandler ( it has same definition than start_node ). I tried to use bind to copy function pointer in the constructor like this : document::document() { // binding here m_evhdl.startElement = boost::bind( &document::start_node, this, _1, _2, _3 ); // xml init m_ctxt = xmlCreateFileParserCtxt( "catalogue.xml" ); m_ctxt->sax = &m_evhdl; xmlParseDocument( m_ctxt ); } The issue is that I can't submit the binded function to startElement because bind submits "this" as a parameter to startElement, which is incompatible definition, so is there a solution to my binding ? Regards Carlos

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Problem with weak_ptr exception
by Jacob Carlborg 28 Oct '09

28 Oct '09

I'm having some problems with bad_weak_ptr exceptions. I have reduced my code into this test case: #include <boost/shared_ptr.hpp> #include <boost/weak_ptr.hpp> using boost::shared_ptr; using boost::weak_ptr; class A { weak_ptr<A> weakThis; public: virtual ~A(){} shared_ptr<A> a; shared_ptr<A> getThis () { shared_ptr<A> x(weakThis); return x; } void init () { a = getThis(); } static shared_ptr<A> create () { shared_ptr<A> x(new A); x->weakThis = x; x->init(); return x; } }; class B : public A { weak_ptr weakThis; public: virtual ~B(){} shared_ptr getThis () { shared_ptr b(weakThis); return b; } static shared_ptr create () { shared_ptr x(new B); x->weakThis = x; x->init(); return x; } }; int main (char** argv, int argc) { shared_ptr b = B::create(); return 0; } If I create an instance of A instead of B or doesn't call x->init() in the B's create function I don't get an exception. The problem is creating a shared_ptr from the weak_ptr in getThis.

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[statechart] Added triggering_event() to the trunk (will be in 1.42 release)
by Andreas Huber 28 Oct '09

28 Oct '09

Those in urgent need of this feature can get it from the trunk. Documentation isn't there yet, but the test should give you a pretty good idea of what it does: <http://svn.boost.org/svn/boost/trunk/libs/statechart/test/TriggeringEventTe…> As always, feedback is highly welcome. Regards, -- Andreas Huber When replying by private email, please remove the words spam and trap from the address shown in the header.

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BGL: cutting subgraph using more than one condition.
by Arman Khalatyan 28 Oct '09

28 Oct '09

Hello, I would like to cut my MST graph using several conditions on Edge. template<typename WMap> class Remover { public: Remover(const WMap& weights, MyFloat threshold) : m_weights(weights), m_threshold(threshold) {} template<typename ED> bool operator()(ED w) const { return m_weights[w] < m_threshold; }// here I would like to have set of conditions based on vertexes of the edge private: const WMap& m_weights; MyFloat m_threshold; }; Remover<weight_map_type> r(get(edge_weight, graphMST), Wthr ); remove_edge_if(r, graphMST); Is it possible to define instead of Wthr to define an array of properties? What is the proper way to do it? Thanks Arman.

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[Boost.Assign][doc] Question on a statement in the documentation
by Alexander Gutenev 28 Oct '09

28 Oct '09

Here http://www.boost.org/doc/libs/1_40_0/libs/assign/doc/index.html#extensions is stated "it is illegal to take the address of a function in the standard library" Is it correct? Where is it mentioned in the Standard? 17.4.4.4/2 says that a member function may be replaced with the version with other signature, but a) "a member function" != "a function" b) May be replaced with the version with other signature doesn't mean one cannot take its address, it only means taking its address doesn't make sense for portable code.

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system error 22
by pedro chaparro 28 Oct '09

28 Oct '09

hi, im trying the serialization examples in http://www.boost.org/doc/libs/1_40_0/doc/html/boost_asio/examples.html , the fact is that i'm getting and invalid argument error, i have examined deeply the code, and i found that the error comes from handle_read function in client.cpp which receive in its function parameter a system::error "e" that is equal to system 22; what is this error related with? thanks --

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[iterator] Automatic definition of transform_iterator reference_type
by Sebastian Theophil 28 Oct '09

28 Oct '09

[Posted once again with better subject] I've encountered a problem when using boost::mem_fn in transform_iterators. In the attached example, I've chained two transform_iterators. The first iterator returns an Obj by value and the second extracts a member of the temporary object. The example shows that the return value is not quite what is expected. boost::mem_fn(&Obj::m_member) returns an int const&. The transform_iterator uses the return value of the UnaryFunction template parameter to initialize his value_type. In the given example, this logic seems too simple. At least if the UnaryFunction is of type boost::_mfi::dm the transform_iterator could do better: If Reference is boost::use_default If UnaryFunction is boost::_mfi::dm && Iterator::value_type is not a reference itself reference = boost::remove_reference( result_of(UnaryFunction) ) Else reference = result_of(UnaryFunction) Else reference = Reference Is this too much of a special case to fix it in the transform_iterator? The same logic would apply to all (unknown) functors that returned references to member variables. In general, the transform_iterator can probably not decide if a reference returned from a UnaryFunction will cease to exist when the temporary is destroyed. It could have been a global object. On the other hand, transform_iterators should work correctly if only boost objects are used, shouldn't they? I'd like to hear what you think, Sebastian #include "boost/iterator/transform_iterator.hpp" #include <vector> struct Obj { Obj(int n) : m_member(n) {} Obj(Obj const& obj) : m_member(obj.m_member) {} ~Obj() { m_member=INT_MIN; } int m_member; }; static Obj GetObjByValue( int n ) { return Obj(n); } void main() { std::vector<int> v(1, 5); int n=*boost::make_transform_iterator( boost::make_transform_iterator( v.begin(), GetObjByValue ), boost::mem_fn(&Obj::m_member) ); _ASSERT(n==INT_MIN); } -- Sebastian Theophil . stheophil(a)think-cell.com Software Engineer think-cell Software GmbH . Invalidenstr. 34 . 10115 Berlin, Germany http://www.think-cell.com . phone +49-30-666473-10 . toll-free (US) +1-800-891-8091 Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl . Amtsgericht Berlin-Charlottenburg, HRB 85229

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[mpi] - why this code hangs on gather?
by tomasz jankowski 28 Oct '09

28 Oct '09

hello boost users please look (if you find few minutes) code bellow first i'm declaring molecule class (with needed serialization) in main() first I'm building vector of data (which are molecules) then vector is divided to chunks and send in point to point nonblocking communication model to rest of mpi processes. after that some calculation on molecules are done. at the end I want gather all data but the program hangs on gather in proces with rank 0 does anyone has idea what is wrong in this code? tom #include <vector> #include <algorithm> #include <boost/mpi.hpp> #include <boost/serialization/string.hpp> #include <boost/serialization/vector.hpp> #include <boost/lexical_cast.hpp> #include <iostream> #include <cstdlib> #include <string> #include <boost/random/linear_congruential.hpp> #include <boost/random/uniform_real.hpp> #include <boost/random/variate_generator.hpp> #include <boost/format.hpp> namespace mpi = boost::mpi; class molecule { friend std::ostream & operator<<(std::ostream &os, const molecule &prot); friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int){ ar & x_ & y_ & z_ & number_ & message_; } public: // constructor molecule(){x_=0; y_=0; z_=0; number_= 0; message_ = "";}; molecule(double x, double y, double z, unsigned int n, std::string m) : x_(x), y_(y), z_(z), number_(n), message_(m) {} void print(){ std::cout << (boost::format("%.6f") % x_) << " | "<< (boost::format("%.6f") % y_) << " | " << (boost::format("%.6f") % z_) << " | " << number_ << "\t| " << message_ << std::endl; } double x_; double y_; double z_; unsigned int number_; std::string message_; }; int main(int argc, char* argv[]) { //generator boost::minstd_rand generator_real(42u); //distribution boost::uniform_real<> uni_dist_real(0,1); //functor boost::variate_generator<boost::minstd_rand, boost::uniform_real<> > uni_real(generator_real, uni_dist_real); mpi::environment env(argc, argv); mpi::communicator world; // data construction std::vector<molecule> data; if (world.rank() == 0) { for(unsigned int i=0;i<8020;++i){ std::string txt("see you later aligator"); molecule tmp(1,1,1,i,txt); data.push_back(tmp); } } //broadcast(world,data,0); //we could do it by broadcast (line above) - but lets do it by point to point with only amount of data we need //work vectors std::vector<molecule> res; std::vector<std::vector<molecule> > allRes; // we need to divide our data between processes unsigned int nProcs=world.size(); unsigned int chunkSize=data.size() / nProcs; unsigned int extraBits=data.size() % nProcs; // extra bits we will do in root process if( world.rank() == 0 ){ mpi::request reqs[nProcs-1]; for(unsigned int i=1;i<nProcs;++i){ std::vector<molecule> sendmol; unsigned int pos=extraBits+i*chunkSize; for(unsigned int j=0;j<chunkSize;++j){ sendmol.push_back(data[pos]); pos++; } reqs[i-1] = world.isend(i, 0, sendmol); std::cout<<"msg sended to "<< i <<std::endl;std::cout.flush(); } for(unsigned int i=0;i<chunkSize + extraBits;++i){ molecule tmp = data[i]; tmp.x_ *= uni_real(); tmp.y_ *= uni_real(); tmp.z_ *= uni_real(); tmp.message_ = "from process: " + boost::lexical_cast<std::string>(world.rank()); res.push_back(tmp); } mpi::wait_all(reqs, reqs + nProcs - 1); std::cout<<"calculation finished in 0 "<<std::endl;std::cout.flush(); } std::vector<molecule> recvmol; mpi::request recv; recv = world.irecv(0, 0, recvmol); recv.wait(); std::cout<<"receiving finished "<<world.rank()<<std::endl;std::cout.flush(); for(unsigned int i=0;i<recvmol.size();++i){ molecule tmp = recvmol[i]; tmp.x_ *= uni_real(); tmp.y_ *= uni_real(); tmp.z_ *= uni_real(); tmp.print(); tmp.message_ = "from process: " + boost::lexical_cast<std::string>(world.rank()); res.push_back(tmp); } std::cout<<"calculation finished in "<<world.rank()<<std::endl;std::cout.flush(); //wysylanie wynikow ze wszystkich procesow mpi do procesu 0 if( world.rank() == 0 ){ gather(world,res,allRes,0); std::cout<<"gather finished "<<world.rank()<<std::endl;std::cout.flush(); } else { gather(world,res,0); std::cout<<"gather finished"<<world.rank()<<std::endl;std::cout.flush(); } // output if(world.rank()==0){ for(unsigned int i=0;i<static_cast<unsigned int>(world.size());++i){ std::cout<<"results from process "<<i<<": "<<std::endl; for(int k=0; k<allRes[i].size();k++){ allRes[i][k].print(); } std::cout<<std::endl; } std::cout<<"making output finished "<<world.rank()<<std::endl;std::cout.flush(); } return 0; } ---------------------------------------------------- Kabaret Łowcy.B atakuje! Wygraj płytę DVD. Weź udział w konkursie: http://klik.wp.pl/?adr=http%3A%2F%2Fcorto.www.wp.pl%2Fas%2Fkonkurs_lowcy.ht…

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[spirit][regex] rxstrlit/regex_p with wchar_t strings
by Adam Badura 28 Oct '09

28 Oct '09

Is it possible to use rxstrlit/regex_p with wide character strings (wchar_t based)? Or even better, with arbitrary char type/char traits pair? I tried this with suggested example (http://www.boost.org/doc/libs/1_40_0/libs/spirit/classic/example/fundamenta…) and after converting to wchar_t what was required and compiling it run successfully. But it generated a lot of warnings about converting wchar_t to char in headers that looked like regex headers. So I guess it worked only because the wchar_ts in the example are actually chars. If I changed the example to use wchar_t which have no corresponding char values the example would likely fail. In the end I have a string with templated char type and traits type (just like with string and iostream library). And I want to match it against grammar build from (among others) strings with the same char type and traits type. Can I force regex in Spirit to do that? Adam Badura

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