August 2010 - Boost-users - lists.preview.boost.org

Using Boost.MPI with gather , data becomes overwritten after gather operation
by hgc-01134＠hkedcity.net wong 01 Sep '10

01 Sep '10

Hi, I am trying to use Boost.MPI to do a very simple program that 1. Processes from different ranks do a gather operation 2. The gather operation will gather the CoProcessInfo ( which is just a data structure of rank# and hostname) into a vector 3. After the gather operation, Rank 0 will print the CoProcessInfo one by one in the vector. ------------------------------------------------------------------------------------------------------------------------------------------------------ My testing environment consists of TWO virtual machine ( each of the machine has two cores ): Centos 5.5 mpich2 Boost.mpich2 Boost 1.41 mpiexec ------------------------------------------------------------------------------------------------------------------------------------------------------ The expected output of the program should be something like ( just an example order of ranks ): Host VM1, Rank 0 Host VM1, Rank 1 Host VM2, Rank 2 Host VM2, Rank 3 ---------------------------------------------------------------------------------------------------------------------------------------------------------- However, I got something like: ( just an example order of ranks ), the hostname is incorrect after gather operation ( three VM2 appears!) Host VM1, Rank 0 Host VM2, Rank 1 Host VM2, Rank 2 Host VM2, Rank 3 I found that each process CAN correctly found out the hostname and rank#, however, the data will become a bit like overwritten, after the gather operation. Thank you very much. ------------------------------------------- Source Code ------------------------------------------------------------------- #include <boost/asio/ip/host_name.hpp> #include <iostream> #include <vector> #include <string> #include <boost/mpi/environment.hpp> #include <boost/mpi/communicator.hpp> #include <boost/mpi.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <sstream> #include <fstream> using namespace std; namespace mpi = boost::mpi; class CoProcessInfo { private: string hostname; int rank; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int /* version */) { ar & hostname & rank; } public: CoProcessInfo() { hostname = boost::asio::ip::host_name(); rank = 0; } void setRank(int _rank) { rank = _rank; } string getHostname() const { return hostname; } int getRank() const { return rank; } }; int main(int argc, char* argv[]) { int myrank; mpi::environment env(argc, argv); mpi::communicator world; myrank = world.rank(); CoProcessInfo localInfo; localInfo.setRank( myrank ); std::vector<CoProcessInfo> coProcInfo; mpi::gather(world, localInfo, coProcInfo, 0); if( myrank == 0 ){ for (std::vector<CoProcessInfo>::const_iterator it = coProcInfo.begin(); it !=coProcInfo.end(); ++it) { cout << endl << " Host : " << it->getHostname() << " , Rank : " << it->getRank() << endl; } } return 0; } ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Regards, Joseph

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boost::addressof
by Stanisław Findeisen 31 Aug '10

31 Aug '10

Hi! In the latest boost release (1.44) boost::addressof is defined as follows (boost/utility/addressof.hpp): namespace detail { template<class T> struct addr_impl_ref { T & v_; inline addr_impl_ref( T & v ): v_( v ) {} inline operator T& () const { return v_; } private: addr_impl_ref & operator=(const addr_impl_ref &); }; template<class T> struct addressof_impl { static inline T * f( T & v, long ) { return reinterpret_cast<T*>( &const_cast<char&>(reinterpret_cast<const volatile char &>(v))); } static inline T * f( T * v, int ) { return v; } }; } // namespace detail template<class T> T * addressof( T & v ) { #if defined( __BORLANDC__ ) && BOOST_WORKAROUND( __BORLANDC__, BOOST_TESTED_AT( 0x610 ) ) return boost::detail::addressof_impl<T>::f( v, 0 ); #else return boost::detail::addressof_impl<T>::f( boost::detail::addr_impl_ref<T>( v ), 0 ); #endif } Q1: What is volatile in the cast needed for? Q2: Could anyone please explain to me what are the 2nd parameters in each of the f functions in struct addressof_impl for? Q3: What is struct addr_impl_ref::operator T& () const ??! I understand it is there to get called when passing addr_impl_ref<T>(v) instead of v to addressof_impl<T>::f, but I've never seen such a thing before. I would understand T& struct addr_impl_ref::operator(), or something, but this one is different. Sorry if this is a newbie question. Q4: I can see that in 1.34.1 boost::addressof was much more simple: // VC7 strips const from nested classes unless we add indirection here # if BOOST_WORKAROUND(BOOST_MSVC, == 1300) template<class T> struct _addp { typedef T * type; }; template <typename T> typename _addp<T>::type # else template <typename T> T* # endif addressof(T& v) { return reinterpret_cast<T*>( &const_cast<char&>(reinterpret_cast<const volatile char &>(v))); } so I wonder what was the problem with this design?... -- http://eisenbits.homelinux.net/~stf/ OpenPGP: DFD9 0146 3794 9CF6 17EA D63F DBF5 8AA8 3B31 FE8A Like Hardship, Risk & Challenge? --- Follow Jesus!!

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Creating a thread and blocking its execution
by Jean-Sebastien Stoezel 31 Aug '10

31 Aug '10

Hello, I use boost::thread as follow: mp_Thread = new boost::thread(boost::bind(CSubsystem::TaskWrapper, this)); to create a thread in an initialization method. I observe that this thread gets to run before my initialization method has completed its execution. I would like to create a thread from this initialization method, and wait for it to execute until the whole initialization process it done. Is it possible to create a thread in suspended mode, and then release it once the system is ready? Or do I need to use a synchronization mechanism like a semaphore to release it? Jean-Sebastien

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Does BOOST ASIO HTTP support 1.1
by Manna Patri 31 Aug '10

31 Aug '10

Hi, Looking at the boost::asio:: http server I am very much interested to have it in my application server.However before proceeding further I would like to know does HTTP server implmentation supports HTTP 1.1 ? Looking at the example available under HTTP client it seems "HTTP 1.0" is sent across in header as part of HTTP message. And to my curoisity when I modifeid the client code to send "HTTP 1.1" that also worked. Reply in this regard is appreciated. Thanks. Manna

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Re: [Boost-users] Boost.Serialization: Restoring object state(preventcreation of a new object)?
by ray＠maya-studio.com 31 Aug '10

31 Aug '10

> That's likely something else entirely. We'd have to see more code. Forget my previous post, the exception was due to mixed up ofstream and ifstream... Just to resume - if I have a list of pointers to the objects (all derived from the same base class) and I'd like to serialize them through a reference, a code like this would be needed: // List of pointers A a; B b; // Derived from A C c; // Derived from C std::list<A*> list; list.push_back(&a); // Base list.push_back(&b); // Derived list.push_back(&c); // Derived ... // Save std::ofstream ofs("c:/test.xml"); boost::archive::xml_oarchive oa(ofs); BOOST_FOREACH(A* pA, list) { if (dynamic_cast<B*>(pA)) { B& b = *static_cast<B*>(pA); oa & BOOST_SERIALIZATION_NVP(b); } else if (dynamic_cast<C*>(pA)) { C& c = *pA; BOOST_SERIALIZATION_NVP(c); } else { A& a = *pA; BOOST_SERIALIZATION_NVP(a); } } Am I right?

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multi_array: error: expected primary-expression before ‘)’
by Valmor de Almeida 31 Aug '10

31 Aug '10

Hello, I am trying from the multi_array web site doc: typedef boost::multi_array<double,3> array_type; array_type A(boost::extents[3][4][2],boost::fortran_storage_order); and getting the following compile-time error: g++ img2hermes2dmsh.cpp In function ‘int main()’: error: expected primary-expression before ‘)’ token Any insights? I am using boost-1.41 on gentoo linux. Thanks, -- Valmor

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download question
by Stanisław Findeisen 31 Aug '10

31 Aug '10

Hi What are the file checksums? -- http://eisenbits.homelinux.net/~stf/ OpenPGP: DFD9 0146 3794 9CF6 17EA D63F DBF5 8AA8 3B31 FE8A Like Hardship, Risk & Challenge? --- Follow Jesus!!

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Comparing boost bind object with a pointer to member function
by jej 31 Aug '10

31 Aug '10

Hello, Is is possible to compare a pointer to member function with a function object returned by boost bind? I have a class with several different functions; for each member function I use boost bind to bind the function object to several args. At the point where I want call the function object, I would like to check which member function it's been bound to, and decide whether or no it should be executed. For example, I would like the second comparison in the code snippet below to return "Bind match." For any other member function of foo it should return "Bind not match." Thanks. int main(int, char**) { Data d(1, 2); Foo fx, fy; //typedef void (Foo::*foofunctwo_t)(const Data&); //foofunctwo_t del1 = &Foo::FuncTwo; boost::function<void (Foo*, const Data&)> bf(&Foo::FuncTwo); if(bf == &Foo::FuncTwo) { cout << "match" <<endl; } else { cout << "no match" << endl; } boost::function<void (const Data&)> boundfunc = boost::bind(&Foo::FuncTwo, &fx, _1); if(boundfunc == &Foo::FuncTwo) { cout << "Bind match" << endl; } else { cout << "Bind not match" << endl; } return 0; }; -- View this message in context: http://old.nabble.com/Comparing-boost-bind-object-with-a-pointer-to-member-… Sent from the Boost - Users mailing list archive at Nabble.com.

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Overloading boost::for_each()
by Jeremiah Willcock 31 Aug '10

31 Aug '10

There are several container types (such as typical deque implementations, if you have access to their internals) that can have for_each() implemented for them in a way that is faster than using iterators and a generic for_each() function. Is there a way to take advantage of that in Boost.Range, such as by overloading boost::for_each()? Is there some kind of Iterable concept that doesn't require actual iterators or allows them to be slow? Would it be worthwhile to add one? Are there any other techniques that would be useful instead, such as always calling for_each() unqualified in my code and using ADL to find custom versions (like is done for swap)? I am not interested in making Boost.Range algorithms use this new concept, but there are places in my own code that could use for_each() rather than explicit loops if that was faster. Thank you for any answers or advice. -- Jeremiah Willcock

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asio HTTP client example always returns error 400
by G S 31 Aug '10

31 Aug '10

Hi all. I copied the boost::asio HTTP client example code: http://live.boost.org/doc/libs/1_39_0/doc/html/boost_asio/example/http/clie… and just replaced the argv stuff with a hard-coded domain name and "index.html". It appears to make the socket connection OK, but the response to the request is 400 ("bad request"). Is there something wrong with this request? boost::asio::streambuf request; std::ostream request_stream(&request); request_stream << "GET " << "index.html" << " HTTP/1.0\r\n"; request_stream << "Host: " << "musicobsession.com" << "\r\n"; request_stream << "Accept: */*\r\n"; request_stream << "Connection: close\r\n\r\n"; It doesn't matter what host I use (as long is it's real). Thanks for any insight!

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